Skeptic Papers 2015

Updated 27 March 2016

Reader Kenneth Richard presents 282 peer-reviewed papers published in 2015 supporting the skeptical position that natural factors are in fact a dominant climate driver:

Feel free to send this list to a political leader.
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Papers Supporting a Skeptical-of-the-Consensus Position for 2015

Solar Influence on Climate (95 papers)

http://link.springer.com/article/10.1007/s00024-014-0929-1

We have reconstructed the temperature time series using the second to tenth oscillatory principal components of all the eight regions and computed their power spectral density using MTM. Our analyses indicate that there is a strong spectral power in the period range of 2–7 years and 53 years, which are matched respectively with the known El Niño–Southern oscillation (ENSO) periods and ocean circulation cycles. Further, the spectral analysis also revealed a statistically significant but riven cycle in a period range of 9.8–13 years corresponding to the Schwabe cycle in all Indiaian maximum and minimum temperature records and almost all the zonal records except in the NE data. In some of the cases, the 22 year double sunspot (Hale cycle) cycle was also identified here. Invariably the splitting of spectral peaks corresponding to solar signal indicated nonlinear characteristics of the data and; therefore, even small variations in the solar output may help in catalyzing the coupled El Niño-atmospheric ENSO cycles by altering the solar heat input to the oceans. We, therefore, conclude that the Indian temperature variability is probably driven by the nonlinear coupling of ENSO and solar activity.

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http://geology.gsapubs.org/content/43/3/203

Mounting evidence from proxy records suggests that variations in solar activity have played a significant role in triggering past climate changes. However, the mechanisms for sun-climate links remain a topic of debate. Here we present a high-resolution summer sea-surface temperature (SST) record covering the past 9300 yr from a site located at the present-day boundary between polar and Atlantic surface-water masses. The record is age constrained via the identification of 15 independently dated tephra markers from terrestrial archives, circumventing marine reservoir age variability problems. Our results indicate a close link between solar activity and SSTs in the northern North Atlantic during the past 4000 yr; they suggest that the climate system in this area is more susceptible to the influence of solar variations during cool periods with less vigorous ocean circulation. Furthermore, the high-resolution SST record indicates that climate in the North Atlantic regions follows solar activity variations on multidecadal to centennial time scales.

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http://www.nonlin-processes-geophys-discuss.net/2/1447/2015/npgd-2-1447-2015.pdf

Introduction: Several recent studies of solar–geomagnetic effects on climate have been examined on both global as well as on regional scales. The Sun’s long-term magnetic variability is the primary driver of climatic changes. The magnetic variability (mostly short-term components) is due to the disturbances in Earth’s magnetic fields caused by the solar activity, which is usually indicated by indices of geomagnetic activity. The Sun’s magnetic variability modulates the magnetic and particulate fluxes in the heliosphere. This determines the interplanetary conditions and imposes significant electromagnetic forces and effects upon planetary atmospheres. All these effects are due to the changing solar-magnetic fields which are relevant for planetary climates, including the climate of the Earth. The Sun–Earth relationship varies on different time scales of days to years bringing a drastic influence on the climatic patterns. The ultimate cause of solar variability, at time scales from decadal to cen tennial to millennial or even longer scales, has its origin in the solar dynamo mechanism. During the solar maxima, huge amounts of solar energy particles are released, thereby causing the geomagnetic disturbances. The 11 years solar cycle acts an important driving force for variations in the space weather, ultimately giving rise to climatic changes. Therefore, it is very important to understand the origin of space climate by analyzing the different proxies of solar magnetic variability. The another most important climate variation is El Niño–Southern Oscillation (ENSO) events, which impact the global oceanic and atmospheric circulations which thereby produce droughts, floods and intense rainfall in certain regions. The strong coupling and interactions between the Tropical Ocean and atmosphere play a major role in the development of global climatic system. The El Niño events generally recur approximately every 3–5 years with large events spaced around 3–7 years apart. The El Niño–Southern Oscillation (ENSO) phenomena has shown huge impact on the Asian monsoon (Cole et al., 1993), Indian monsoon (Chowdary et al., 2006, 2014) as well as globally (Horel and Wallance, 1981; Barnett, 1989; Yasunari, 1985; Nicholson, 1997). In particular, the El Niño, solar, geomagnetic activities are the major affecting forces on the decadal and interdecadal temperature variability on global and regional scales in a direct/indirect way. …. The 11 year solar cyclic variations observed from the several temperature climate records also suggest the impact of solar irradiance variability on terrestrial temperature …These findings suggest that there is possible strong coupling between temperature–ENSO and solar–geomagnetic signals.

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http://www.ann-geophys.net/33/207/2015/angeo-33-207-2015.pdf

We concentrate on the Northern Hemisphere and North Atlantic in the period 1948–2012. Composite and correlation analyses point to a strengthening of the North Atlantic Oscillation and weakening (i.e. becoming more zonal) of the Pacific/North American pattern. The locations of points with lowest and highest sea level pressure in the North Atlantic change their positions between low and high solar activity. …  The solar effect on atmospheric circulation in the North Atlantic can be described as a tripole mechanism. During solar maximum conditions the differences between the Icelandic Low and Azores High increase, while the Greenland High decreases. Solar minimum conditions reinforce the high pressure above Greenland together with a weakening of the other two North Atlantic pressure centres.

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http://www.sciencedirect.com/science/article/pii/S0012825215300349#FCANote

[I]n order to account for the problem of urbanization bias, we compile a new estimate of Northern Hemisphere surface air temperature trends since 1881, using records from predominantly rural stations in the monthly Global Historical Climatology Network dataset. Like previous weather station-based estimates, our new estimate suggests that surface air temperatures warmed during the 1880s–1940s and 1980s–2000s. However, this new estimate suggests these two warming periods were separated by a pronounced cooling period during the 1950s–1970s and that the relative warmth of the mid-20th century warm period was comparable to the recent warm period. … We compare our new composite to one of the solar variability datasets not considered by the CMIP5 climate models, i.e., Scafetta and Willson, 2014’s update to the Hoyt and Schatten, 1993 dataset. A strong correlation is found between these two datasets, implying that solar variability has been the dominant influence on Northern Hemisphere temperature trends since at least 1881. We discuss the significance of this apparent correlation, and its implications for previous studies which have instead suggested that increasing atmospheric carbon dioxide has been the dominant influence.

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http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2473140

We discuss the issues of primary importance for understanding the nature of climate changes in the 20th century and main physical processes responsible for them. Special attention is paid to climate changes which occurred in 1943–1976 and 2000–2014. These periods exhibit the maximum increase in CO2 in the atmosphere, with virtually unchanged global temperature and its reduction in some regions. We study atmospheric and sea surface temperature effects of solar activity. The paper deals with results of the analysis of regularities and peculiarities of a tropospheric and sea surface temperature response to separate heliogeophysical disturbances as well as to long-term solar and geomagnetic activity variations. We also present results of the analysis of a change in sea surface temperature covering the time period 1854–2012 and their relation to solar activity variations. We find further evidence for the solar effect on climatic processes in the troposphere and ocean. We reveal a significant response in the major climatic characteristics, namely, surface air temperature and sea surface temperature (SST). It is established that the climatic response is characterized by significant space-time inhomogeneity, is regional and depends on the climate epoch. We discuss a role of wind stress and thermohaline circulation in the observable climate changes.

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http://www.sciencedirect.com/science/article/pii/S0377026515300051

Modulation of decadal ENSO-like variation by effective solar radiation

Here, we show that the effective solar radiation (ESR), which includes the net solar radiation and the effects of volcanic eruption, has modulated this decadal ENSO-like oscillation. The eastern Pacific warming (cooling) associated with this decadal ENSO-like oscillation over the past 139 years is significantly related to weak (strong) ESR [effective solar radiation]. The weak ESR with strong volcanic eruption is found to strengthen the El Niño, resulting in an El Niño-like SST anomaly on the decadal time scale. The strong eruptions of the El Chicho’n (1982) and Pinatubo (1991) volcanoes reduced the ESR [effective solar radiation] during the 1980s and 1990s, respectively. The radiation reduction weakened the Walker circulation due to the “ocean thermostat” mechanism that generates eastern Pacific warming associated with a decadal El Niño-like SST anomaly. This mechanism has been confirmed by the millennium run of ECHO-G model, in which the positive eastward gradient of SST over the equatorial Pacific was simulated under the weak ESR forcing on the decadal time scale. We now experience a reversal of the trend in the ESR. The strong solar radiation and lack of strong volcanic eruptions over the past 15 years have resulted in strong ESR [effective solar radiation], which should enhance the Walker circulation, leading to a La Niña-like SST anomaly.

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http://www.nature.com/articles/srep15689

The longest direct observation of solar activity is the 400-year sunspot-number series, which depicts a dramatic contrast between the almost spotless Maunder and Dalton minima, and the period of very high activity in the most recent 5 cycles [1950s – 2000s], prior to cycle 24. … The records show that solar activity in the current cycle 24 is much lower than in the previous three cycles 21–23 revealing more than a two-year minimum period between cycles 23 and 24. This reduced activity in cycle 24 was very surprising because the previous five cycles were extremely active and sunspot productive forming the Modern Maximum. … We predict correctly many features from the past, such as: 1) an increase in solar activity during the Medieval Warm period; 2) a clear decrease in the activity during the Little Ice Age, the Maunder Minimum and the Dalton Minimum; 3) an increase in solar activity during a modern maximum in 20th century. .. We note, in particular, a decreasing activity for solar cycles 25 and 26 coinciding with the end of the previous 350–400-year grand cycle and then increase of the solar activity again from cycle 27 onwards as the start of a new grand cycle with an unusually weak cycle 30. Hence, cycles 25–27 marks a clear end of the modern grand period that can have significant implications for many aspects of solar activity in human lives including the current debate on climate change.

http://www.nature.com/articles/srep15689/figures/3

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http://www.researchgate.net/publication/281267447_Cosmic_Theories_and_Greenhouse_Gases_as_Explanations_of_Global_Warming

According to the IPCC’s simplest model based on the anthropogenic driving forcing factors, the temperature increase up to 2011 from 1750 is 1.15 °C, which is 35 % greater than the observed temperature 0.85 °C. In this study three other models have been analysed. The first model is a cosmic model, which is based on the galactic cosmic rays (GCR) changes and space dust amount. This model gives correlation r2=0.972. The second model is the combination of space dust changes, the calculated warming impacts of greenhouse gases and the Total Solar Irradiance (TSI) changes giving correlation r2=0.971. The third model is the combination of space dust and TSI changes giving correlation r2=0.948. All these models have negligible error in 2010. The atmospheric water has a decisive role in the real impacts of greenhouse gases. It remains uncertain, because the first global humidity measurements start from 1948. The final conclusion of this study is: the greenhouse gases cannot explain the ups and downs of the Earth’s temperature trend since 1750 and the temperature pause since 1998, but the space dust changes can do it extremely well.

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http://www.nature.com/ncomms/2015/150915/ncomms9268/full/ncomms9268.html

Solar forcing synchronizes decadal North Atlantic climate variability

Introduction: There is increasing evidence that variations in solar irradiance at different time scales are an important source of regional climate variability. For instance, observational analyses of sea level pressure (SLP) in winter revealed positive anomalies in the Gulf of Alaska for sunspot peak years since the beginning of the twentieth century. In the North Atlantic region, a link between the 11-year solar cycle and the winter phase of patterns resembling the North Atlantic oscillation (NAO) or Arctic oscillation (AO) has been found by observational —–and modelling studies. Some of these studies particularly showed that the transfer mechanism leading to the North Atlantic solar signal was consistent with the polar route of the so-called ‘top–down’ mechanism related to solar ultraviolet irradiance variability. According to this mechanism, the solar signal is initially transferred from the upper stratosphere to the lower stratosphere by modulation of the polar night jet and the stratospheric meridional overturning circulation (or Brewer-Dobson circulation), through Rossby wave-mean flow interactions. Dynamical coupling processes between the stratosphere and the troposphere then transmit the solar signal to the Earth’s surface, projecting onto AO/NAO-like patterns

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http://iopscience.iop.org/1748-9326/10/5/054022/pdf/1748-9326_10_5_054022.pdf

Numerous studies have suggested an impact of the 11 year solar cycle on the winter North Atlantic Oscillation (NAO), with an increased tendency for positive (negative) NAO signals to occur at maxima (minima) of the solar cycle. Climate models have successfully reproduced this solar cycle modulation of the NAO, although the magnitude of the effect is often considerably weaker than implied by observations. A leading candidate for the mechanism of solar influence is via the impact of ultraviolet radiation variability on heating rates in the tropical upper stratosphere, and consequently on the meridional temperature gradient and zonal winds. … Recent analyses of observations have shown that solar cycle–NAO link becomes clearer approximately three years after solar maximum and minimum. … In this study, the impact of solar cycle on the NAO is investigated using an atmosphere–ocean coupled climate model. Simulations that include climate forcings are performed over the period 1960–2009 for two solar forcing scenarios: constant solar irradiance, and time-varying solar irradiance. We show that the model produces significant NAO responses peaking several years after extrema of the solar cycle, persisting even when the solar forcing becomes neutral. This confirms suggestions of a further component to the solar influence on the NAO beyond direct atmospheric heating and its dynamical response. Analysis of simulated upper ocean temperature anomalies confirms that the North Atlantic Ocean provides the memory of the solar forcing required to produce the lagged NAO response. These results have implications for improving skill in decadal predictions of the European and North American winter climate.

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http://onlinelibrary.wiley.com/doi/10.1002/2014JA020732/abstract

Abstract: With satellite altimetry data accumulating over the past two decades, the mean sea level (MSL) can now be measured to unprecedented accuracy. We search for physical processes which can explain the sea level variations and find that at least 70% of the variance in the annually smoothed detrended altimetry data can be explained as the combined effect of both the solar forcing and the El Niño-Southern Oscillation (ENSO). 

 

Introduction: Several global climate variables appear to vary in sync with the solar cycle. These include average air temperatures and pressures [Douglass and Clader2002Shaviv2005van Loon and Labitzke2000], the sea surface temperature [White et al.1997], and the ocean heat content and sea level [Shaviv2008]. On longer time scales, there are additional correlations between solar activity and climate [e.g.,Neff et al.2001Bond et al.2001Wang et al.2005]. These observed climate variations could be the result of a climate which is sensitive to any changes in the radiative forcing, including the small variations associated with the total solar irradiance. Alternatively, the large nonthermal solar activity variations could be amplified by a mechanism unrelated to the solar irradiance and inducing a large radiative forcing on the climate.

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http://www.sciencedirect.com/science/article/pii/S0277379115000451

10,000-year-long varved sediment records from lakes Nautajärvi and Korttajärvi, Finland provide evidence of climate and environment oscillations at multi-decadal to millennial timescales. … Results indicate that the Holocene winter climate in continental Scandinavia was forced by a combination of several factors, at least by solar variability and the North Atlantic ocean–atmosphere circulation-patterns [NAO], with varying influences through time.

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http://www.clim-past-discuss.net/11/4751/2015/cpd-11-4751-2015.pdf

Conclusion: Overall, the EAWM [East Asian Winter Monsoon] is broadly in-phase with the ISM [Indian Summer Monsoon], both of which decrease in strength from the early to the late Holocene, which is caused by the interplay of solar insolation between the winter and summer seasons and ENSO strength in the tropical Pacific.

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http://www.clim-past-discuss.net/11/2341/2015/cpd-11-2341-2015.pdf

Between 1920 and 1940 AD, there was a major warming period in the Arctic, known as ETCW [Early Twentieth Century Warming] and observed in all shown records here. Chylek et al. (2006) determined from meteorological data that the 1920–1930 warming was stronger than the 1995–2005 warming. For the NG-stack and Akademii Nauk record, the ETCW [early twentieth century warming] was warmer than the second half of the 20th century …  In general, higher solar activity causes higher temperatures (as during the MCA) whereas cold periods (e.g. LIA) are dominated by lower solar activity (Ammann 15 et al., 2007). … Fischer et al. (1998c) explained most of the long-term variation in northern Greenland by changes in solar activity

 

Conclusion: The solar activity and internal Arctic climate dynamics are likely the main factors influencing the temperature in northern Greenland.

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http://www.earth-syst-dynam-discuss.net/6/1237/2015/esdd-6-1237-2015.pdf

Solar activity (SA) has non-linear characteristics that influence multiple scales in solar processes (Vlahos and Georgoulis, 2004). For instance, millennia-scale solar oscillations have been recently detected, like those of about 6000 and 2400 years, by Xapsos and Burke (2009) and Charvátová (2000), respectively, with important and interesting influences in the near past and future climate. These millennial-scale patterns of reconstructed solar activity variability could justify epochs of low activity, such as the Maunder Minimum, as well as epochs of enhanced activity, such as the current Modern Maximum, and the Medieval Maximum in the 12th century. Although the reason for these solar activity oscillations is unclear, it has been proposed that they are due to chaotic behavior of non-linear dynamo equations (Ruzmaikin, 1983), or stochastic instabilities forcing the solar dynamo, leading to on-off intermittency (Schmittet al., 1996), or planetary gravitational forcing with recurrent multi-decadal, multi-centennial and longer patterns (Fairbridge and Sanders, 1987; Fairbridge and Shirley,1987; Charvátová, 2000; Duhau and Jager, 2010; Perry and Hsu, 2000). It should be noted that all proponents of planetary forcing have forecasted a solar Grand Minimum for the upcoming decades, but one of them has also forecasted a Super Minimum for the next centuries (Perry and Hsu, 2000). In addition, during recent decades, statistical forecasts (with physically-based spectral information of reconstructed records) of solar magnetic activity predict a clear decrease in solar activity, reaching a minimum around AD 2100 (Steinhilber et al., 2013; S13, hereafter, Velasco et al., 2015)

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http://www.clim-past-discuss.net/11/5401/2015/cpd-11-5401-2015.html

Due to its sensitivity to climate changes, south Greenland is a particularly suitable area to study past global climate changes and their influence on locale Human settlements. … Flood events showed similar trend in both records: they mainly occurred during cooler and wetter periods characterized by weaker Greenlandic paleo-temperatures, substantial glacier advances, and a high precipitation on the Greenlandic Ice Sheet and North Atlantic ice-rafting events. They can therefore be interpreted as a result of ice and snow-melting episodes. They occurred especially during rapid climate changes (RCC) such as the Middle to Late Holocene transition around 2250 BC, the Sub-boreal/Sub-atlantic transition around 700 BC and the Little Ice Age (LIA) between AD 1300 and AD 1900, separated by cycles of 1500 years and driven by solar forcing. These global RCC revealed by QAL-2011 and LKG-2011 flood events may have influenced Human settlements in south Greenland, especially the paleo-Eskimo cultures and the Norse settlement, and have been mainly responsible for their demise.

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http://www.sciencedirect.com/science/article/pii/S0273117714007340

Time evolution of growing season temperatures in the Northern Hemisphere was analyzed using both wavelet and Fourier approaches.  A comparison of the secular variation in the Northern Hemisphere temperature proxies with the corresponding variations in sunspot numbers and the fluxes of cosmogenic 10Be in Greenland ice shows that a probable cause of this variability is the modulation of temperature by the century-scale solar cycle of Gleissberg. This is consistent with the results obtained previously for Northern Fennoscandia (67°–70° N, 19°–33° E). Thus, evidence for a connection between century-long variations in solar activity and climate was obtained for the entire boreal zone of the Northern Hemisphere.

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http://www.sciencedirect.com/science/article/pii/S0375960114012201

Equatorial Pacific Ocean temperature time series data contain segments showing both a phase-locked annual signal and a phase-locked signal of period two years or three years, both locked to the annual solar cycle. Three such segments are observed between 1990 and 2014. It is asserted that these are caused by a solar forcing at a frequency of 1.0 cycle/yr. These periodic features are also found in global climate data (following paper). The analysis makes use of a twelve-month filter that cleanly separates seasonal effects from data. This is found to be significant for understanding the El Niño/La Niña phenomenon.

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http://hol.sagepub.com/content/25/12/1935.abstract?rss=1

Solar irradiance changes are thought to play an important role in natural climate variability. How the hydrological conditions were affected by solar irradiance in westerly-controlled arid central Asia (ACA) on decadal/centennial timescales remains poorly understood because of the lack of high-quality records. … Besides the generally confirmed cool-wet/warm-dry climate pattern in ACA, our data also consistently show frequent and substantial lake level fluctuations, resembling solar activity changes, especially during the ‘Little Ice Age’. Wavelet spectral analyses of our XRF data indicate strong 8- to 16-year, 64- to 128-year and 128- to 256-year cycles, coinciding with the ~11-year Schwabe cycle, ~70- to 100-year Gleissberg cycle, and the ~200-year Suess-de Vries cycle. We therefore suggest the existence of solar imprints on effective moisture fluctuations in ACA over the last millennium, and the potential occurrence of the Schwabe cycle even during the solar minima.

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http://onlinelibrary.wiley.com/doi/10.1111/bor.12130/full

We explored the sources and characteristics of each pigment, reconstructed an 800-year record of ultraviolet radiation (UVR) and total incoming light intensity, and identified the possible factors that may have influenced historical UVR changes in this region. The results indicated at least four UVR peaks during the past 800 years, corresponding to c. AD 1950–2000, 1720–1790, 1560–1630 and 1350–1480, with the intensity from the most recent sediments [1950-2000] being the highest.

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http://hol.sagepub.com/content/25/4/677

An important feature is that the ISM [Indian Summer Monsoon] failures inferred from the Lake Xihu proxy indices synchronize well with abrupt changes in solar activity. We argue that changes in solar activity play a primary role in producing most of these millennial ISM [Indian Summer Monsoon] failures

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http://www.ocean-sci-discuss.net/12/103/2015/osd-12-103-2015.pdf

Relationships between solar activity and climate in the North Atlantic region have long been reported and, more recently, mechanisms have been proposed to explain these. Normally such relationships are tested over decadal time scales. Here, daily sea surface temperature fields bridging the period of exceptionally low solar activity between solar cycles 23 and 24 have been analysed. The day-to-day variability of the fields has been measured and the fields have been classified, using cluster analysis. The main water masses are clearly expressed, together with detail of their interactions. Three features relate to the level of solar activity. First, there is a statistically significant difference in the day-to-day variability of the sea surface temperature field between the period of lowest solar activity and the remaining periods. Second, during the transition from summer to winter, there are systematic, inter-annual changes in the day-to-day variability of the sea surface temperature field. Third, the forms of the late summer temperature fields exhibit symmetry about the years of lowest solar activity. These features are attributable to variability in the passage of weather systems. The influence on North Atlantic surface climate of variations in the solar ultraviolet band acting through the stratosphere has been reported in a number of studies. This provides a credible mechanism for solar activity influencing sea surface temperatures in the Greenland Sea.

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http://onlinelibrary.wiley.com/doi/10.1002/2014JD022022/full

It has been suggested that the Sun may evolve into a period of lower activity over the 21st century. This study examines the potential climate impacts of the onset of an extreme ‘Maunder Minimum like’ grand solar minimum using a comprehensive global climate model. Over the second half of the 21st century, the scenario assumes a decrease in total solar irradiance of 0.12% compared to a reference RCP8.5 experiment. The decrease in solar irradiance cools the stratopause (c. 1 hPa) in the annual and global mean by 1.4 K. The impact on global mean near-surface temperature is small (c. -0.1 K), but larger changes in regional climate occur during the stratospheric dynamically active seasons. In Northern hemisphere (NH) winter-time, there is a weakening of the stratospheric westerly jet by up to c. 3-4 m s1, with the largest changes occurring in January-February. This is accompanied by a deepening of the Aleutian low at the surface and an increase in blocking over northern Europe and the north Pacific. There is also an equatorward shift in the Southern hemisphere (SH) midlatitude eddy-driven jet in austral spring. The occurrence of an amplified regional response during winter and spring suggests a contribution froma top-down pathway for solar-climate coupling; this is tested using an experiment in which ultraviolet (200-320 nm) radiation is decreased in isolation of other changes. The results show that a large decline in solar activity over the 21st century could have important impacts on the stratosphere and regional surface climate.

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http://www.hydrol-earth-syst-sci.net/19/465/2015/hess-19-465-2015.pdf

Abstract: Solar activity has some impact on changes in catastrophic floods, with cycles related to the quasi-biennial oscillation (QBO) and the Gleissberg solar cycle. In addition, anomalous periods of high flood frequency in autumn generally occurred during periods of increased solar activity. The physical influence of the latter in general circulation patterns, the high troposphere and the stratosphere, has been analysed in order to ascertain its role in causing floods.

Conclusion: Significant changes in flood occurrence could be associated with transient periods between solar maxima and minima. Recent studies (Martín-Puertas et al., 2012; Moffa-Sánchez et al., 2014) have revealed the possible influence of solar activity through changes to solar irradiance (mainly in the ultraviolet) and changes in cosmic rays and solar particles as they arrive in the stratosphere. Although these studies mainly refer to winter–early spring North Atlantic circulation (both atmospheric and ocean circulations), and floods in Catalonia are mainly produced in autumn, they provide a departure point for future research on this possible “top-down” mechanism. Changes in solar irradiance over the North Atlantic would be amplified through atmospheric feedbacks including the Atlantic meridional overturning circulation, which would in turn affect the formation of persistent atmospheric blocking events. The latter factor would also affect the predominant circulation patterns (i.e. NAO), with the consequent differential regional influence for heavy precipitation. Less interaction between cosmic rays and the ozone in the stratosphere during periods of maximum solar activity would increase ozone presence, diminish UV radiation arriving on the Earth’s surface, and increase the stratospheric temperature in some regions, with a consequent impact on the dynamics of the high atmosphere.

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http://www.sciencedirect.com/science/article/pii/S0273117715002562

Abstract: The upper atmosphere changes significantly in temperature, density and composition as a result of solar cycle variations, which causes severe storms and flares, and increases in the amount of absorbed solar radiation from solar energetic events.

Introduction:  There is a significant heating and consequent expansion of the upper atmosphere during solar and geomagnetic activities. Studies have shown that solar EUV and thermospheric temperature could increase by a factor of two (or more), and thermospheric density by a factor of up to ten from solar minimum to solar maximum.

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http://www.sciencedirect.com/science/article/pii/S027737911530007X

T]he ASM [Asian Summer Monsoon] varies at a periodicity of ∼220 years, concordant with a dominant cycle of solar activity. … Our findings suggest that variations in low-latitude monsoon precipitation are probably driven by shifts in the mean position of the intertropical convergence zone (ITCZ), which is further mediated by solar activity and tropical SSTs.

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http://www.tellusa.net/index.php/tellusa/article/view/25313

The incoming solar irradiance, which is absorbed by the upper ocean, is the main energy source in the ocean heat budget, and hence strongly impacts the oceanic thermal structure, heat transport and the global circulations. Shortwave radiation is attenuated exponentially with depth. The attenuation depth (e-folding depth) depends on the wavelength and biogenic components of the water. Traditionally, the water types are classified Jerlov I, IA, IB, II and III (Jerlov, 1976). The shortwave attenuation depth (SWAD) in open oceans (almost Jerlov I) is about 20–30 m, and it decreases with increasing water turbidity, particularly in coastal regions.

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http://www.sciencedirect.com/science/article/pii/S1364682615300778

Ocean heat content anomaly (OHCa) time series in some areas of the Pacific are significantly correlated with the total solar irradiance (TSI). Using the composite mean-difference method, we determined the mean response of OHCa in the upper-700 m of the ocean to the TSI. Among the high solar response areas, we figure out two regions, one in the tropical mid-Pacific and the other in the western Pacific, where the OHCa present decadal variations, but different phases. The variation in phase of the solar response indicates that there exists an agency for the OHCa’s response to TSI.

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http://www.sciencedirect.com/science/article/pii/S0277379115300299

We hypothesize that orbital induced weakening of the summer solar insolation and associated reorganization of the general atmospheric circulation, as a possible southward displacement of the tropical rainbelt, led to an unstable hydroclimate in central India between 4.8 and 4 ka. … Our findings shed light onto the sequence of changes during mean state changes of the monsoonal system, once an insolation driven threshold has been passed, and show that small changes in solar insolation can be associated with major hydroclimate changes on the continents, a scenario that may be relevant with respect to future changes in the ISM system.

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http://www.clim-past-discuss.net/cp-2015-164/

Introduction: The Holocene appears to be a steady climatic period in comparison with older glacial episodes, as climate evolution was not linear but showed several oscillations (O’Brien et al., 1995; Mayewski et al., 2004; D’Andrea et al., 2011; Larsen et al., 2012), resulting from various forcing mechanisms such as solar activity (Bond et al., 2001; Magny, 2013) volcano emissions (Miller et al., 2012; Sigl et al., 2013) and/or ocean/atmosphere interactions (Hurrell and Denser, 2010; Knudsen et al., 2011). It is of prime importance to establish their spatial influence and phasing in order to understand natural climate oscillations and their influence on past Human societies and thus to create better predictive climatic models. Indeed, even if current global warming is mainly the result of an anthropogenic pressure, the contribution of natural climate variability cannot be excluded and may explain the recent rapid rise in temperatures (Chylek et al., 2004; Solanki et al., 2004).

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http://www.pnas.org/content/112/34/E4640.extract

Here, we demonstrate that the CR [cosmic ray] effect on ΔGT [global temperature] is robust to reasonable measures of global temperature, and clarify technical details for determining significance with CCM.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JD023415/abstract

Solar influences on spatial patterns of Eurasian winter climate and possible mechanisms are investigated based on a multiple linear regression method and multisource observational and reanalysis data. Robust and significant solar signals are detected in Eurasian surface air temperature (SAT), and strong solar activity evidently warms most area of the continent. The spatial pattern of sea level pressure (SLP) responses to solar activity is similar but not identical to that of the North Atlantic Oscillation (NAO). Compared to the NAO, geographic distribution of solar-induced SLP anomalies shifts eastward, with significantly enhanced influences over northern Eurasia. Relatively weaker solar signals were also found in mid-to-upper troposphere. The spatial pattern of 500 hPa geopotential anomalies resembles a negative Scandinavia teleconnection pattern, and the 200 hPa subtropical jet is weakened, while zonal wind at high latitudes is enhanced due to strong solar activity. The anomalous zonal circulations can be attributed to the “top-down” mechanism. During high solar activity winters, an enhanced stratospheric zonal wind anomaly propagates downward, causing zonal wind anomalies in the troposphere. However, the “bottom-up” mechanisms may provide more reasonable explanations of the distinct solar influences on Eurasian climate. Solar-induced strong warm advection in lower atmosphere tends to increase SAT but decrease SLP, resulting in enhanced solar influences over northern Eurasia. Meanwhile, change in the land-ocean thermal contrast (LOTC) could also amplify the circulation anomaly. Inhomogeneous surface heating caused by anomalous solar activity modifies LOTC, which probably enhances the solar-induced circulation patterns. Such a positive feedback may potentially strengthen the solar influences.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JA022104/full

We found a high and statistically significant correspondence of temperature and zonal wind fluctuations in the stratosphere and troposphere with geomagnetic ULF power fluctuations at the ~27 day periodicity, with a substantial reduction at the tropopause height. A similar, clear relationship between the meteorological parameters and the polar cap potential difference was also observed. The results suggest that the changes in the atmospheric conductivity, due to energetic electrons precipitation driven by the ULF waves, as well as the high latitude potential variations, both associated to high geomagnetic activity, can affect the atmospheric dynamics.

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http://www.sciencedirect.com/science/article/pii/S0277379115301682

Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

Here, we use diatom assemblages from a marine sediment core collected from the West Greenland shelf to reconstruct changes in sea-ice cover over the last millennium. The proxy-based reconstruction demonstrates a generally strong link between changes in sea-ice cover and solar variability during the last millennium. Weaker (or stronger) solar forcing may result in the increase (or decrease) in sea-ice cover west of Greenland. In addition, model simulations show that variations in solar activity not only affect local sea-ice formation, but also control the sea-ice transport from the Arctic Ocean through a sea-ice–ocean–atmosphere feedback mechanism.

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http://www.earth.huji.ac.il/data/File/chaimg/GSetal15.pdf

Conclusions: A robust connection exists between intraseasonal solar variability and temperatures in the stratosphere in the reanalysis record. Decreasing solar flux leads to a cooling of the tropical upper stratosphere, while increasing solar flux leads to a warming of the tropical upper stratosphere, consistent with Hood[1986] and Chen et al., [1997, among others]. Subtropical zonal winds respond in order to maintain thermal wind balance. While the magnitude of the responses is consistent with previous work (1 K warming in the tropics and 2 m/s anomalies in subtropical zonal wind), future work using other reanalysis products is needed to confirm the magnitude of the responses, as reanalyses products differ as to the magnitude of the upper stratospheric response to the solar cycle on the 11 year timescale [Mitchell et al., 2015b]. Arctic stratospheric temperatures also change in response to changing incoming solar flux on intraseasonal timescales: during EQBO, a decrease in solar flux leads to a warming of the pole, while during WQBO, a decrease in solar flux leads to cooling of the pole. These changes in polar temperature are consistent with the changes in wave driving entering the stratosphere: more EP flux enters the stratosphere during EQBO, while less EP flux enters the stratosphere during WQBO, as solar flux is decreasing. Equatorward EP flux propagation within the stratosphere acts to modulate the impact of upward wave propagation entering the stratosphere…. All of these changes are consistent with those seen on the 11 year timescale, which enhances our confidence that they are robust and real.

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http://www.clim-past-discuss.net/11/279/2015/cpd-11-279-2015.pdf

The global picture emerges of a  200 year period climate oscillation which correlates highly with the De Vries/Suess oscillation of solar activity. This would indicate that the dominant forcing of the paleoclimate is the solar activity. For different records and different times, however, we find frequencies differing slightly from the main ∼ 200 year periodicity. The solar influence is modified by the 25 response of the Earth system and its inherent forcings such as volcanic activity.

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http://www.rxiv.org/pdf/1504.0124v1.pdf

Energy Non-Conservation and Climate Science: There have been many studies noting correlations between solar cycles and changes in the Earth temperature. The most notable being the Maunder minimum 1645-1715, during which there was no sunspot activity, and which coincided with the “little ice age”. However correlations do not provide causal relations. The assumption has always been that increased sunspot activity results in increased solar irradiance which subsequently causes increased Earth temperatures, although no convincing mechanism has been accepted. However the variation in irradiation is too small to cause the observed Earth temperature fluctuations. Fig.9 shows strong correlations between sea temperature and solar flare counts, and solar flare counts are simply a proxy for 3-space turbulence, as shown in [8]. Various data are thus implying that increased 3-space turbulence is responsible for the heating of the ocean. The mechanism is again coming from the _____ with increased [velocity] leading to maximum energy generation for water molecules moving in the direction of [velocity]. This energy is subsequently dissipated to other less energetic water molecules, resulting in an overall heating effect. This heating then explains why the earth’s temperature record so closely tracks solar flare counts. Fundamentally then it is implied that the Earth’s climate is controlled by a non-conservation of energy process.

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http://www.hydrol-earth-syst-sci-discuss.net/12/3391/2015/hessd-12-3391-2015.html

The composite floodplain record illustrates that periods of organic soil formation and deposition of phyllosilicates (from the medium high catchment area) match those of Total Solar Irradiance maxima, suggesting reduced flood activity during warmer climate pulses. Aggradation of clusters of flood layers with increased contribution of siliciclasts from the highest catchment area (plutonic bedrock) (e.g., 1300–1350, 1420–1480, 1550–1620, 1650–1720 and 1811–1851 cal yr AD) occurred predominantly during periods with reduced solar irradiance, lower δ18O anomalies, cooler summer temperatures and phases of drier spring climate in the Alps. 

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http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-14-0228.1?af=R&

The demands for water in agricultural regions depend on the rate of evapotranspiration (ET). Daily records of potential ET (pET) are available from the late 1980s through the present for five stations in eastern Washington state (George, Harrah, LeGrow, Lind and Odessa) through the Pacific Northwest Cooperative Agricultural Weather Network (AgriMet) under the auspices of the Bureau of Reclamation. These records reveal a secular increase in the summer (June-August) mean pET [potential evapotranspiration] over the period 1987-2014. This increase can be attributed largely to an increase in solar irradiance of 20-30 W m-2 over the same period. The seasonal mean solar irradiance accounts for approximately 35 to 50% of the variance in the interannual variations in seasonal mean pET at the individual stations, and about 60% of the variance from a 5-station average perspective. The period of analysis includes a mean increase of temperature of about 0.3°C per decade, and the variability in temperature relates more to the year-to-year fluctuations in pET than to the overall increase in pET.

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http://cc.oulu.fi/~usoskin/personal/riley_ApJ_2015.pdf

[W]e suggest that the Sun evolved from a 2008/2009-like configuration at the start of the Maunder Minimum toward an ephemeral-only configuration by the end of it, supporting a prediction that we may be on the cusp of a new grand solar minimum.

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http://www.sciencedirect.com/science/article/pii/S0277379115001997

Highlights: Evidence for a direct sun-climate connection during the early mid-Holocene

Abstract :Climate during the early Holocene was highly variable due to the complex interplay of external and internal forcing mechanisms. … The most striking feature of the δ18O record is the recurrence of centennial-scale oscillations, especially during the annually-counted period (8.8–6.1 ka BP). Cross-wavelet analyses between the δ18O record and solar proxies show strong coherence at 200-yr cycle, suggesting that solar output was actively involved as a primary contributor.

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http://www.sciencedirect.com/science/article/pii/S0273117715005712

Abstract: Our analysis revealed that GMATs [Global Mean Annual near-surface Temperatures] of rocky planets [Venus, Earth, Mars] can accurately be predicted over a broad range of atmospheric conditions and radiative regimes only using two forcing variables: top-of-the-atmosphere solar irradiance and total surface atmospheric pressure. The new model displays characteristics of an emergent macro-level thermodynamic relationship heretofore unbeknown to science that deserves further investigation and possibly a theoretical interpretation.

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http://m.pnas.org/content/112/28/8543.short?rss=1

We use optically stimulated luminescence dating of dunes, shorelines, and fluviolacustrine deposits to reconstruct the fluctuations of Lake Mega-Chad, which was the largest pluvial lake in Africa. Humid conditions first occur at ∼15 ka, and by 11.5 ka, Lake Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake levels fell rapidly at ∼5 ka, indicating abrupt aridification across the entire Lake Mega-Chad Basin. This record provides strong terrestrial evidence that the African Humid Period ended abruptly, supporting the hypothesis that the African monsoon responds to insolation [solar] forcing in a markedly nonlinear manner. 

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http://www.mdpi.com/2073-4433/6/7/942

During nucleation events, particle deposition increased markedly (i.e., downward fluxes), but no significant changes in CO2 concentrations and fluxes were observed. This is compatible with new particle formation above the measurement height and a consequent net transport towards the surface. Correlation with meteorology shows that the formation of new particles is correlated with solar radiation and favored at high wind velocity.

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http://www.sciencedirect.com/science/article/pii/S0277379115300202

Highlights: Insolation change [changes in solar activity] plus NAV [North Atlantic variability] account for most SA [South American) monsoon variability of the past [125,000 years].

 

Abstract: To further evaluate climate forcing over the last glacial cycle (∼125 ka), we developed a climate forcing model that combines summer insolation forcing and a proxy for North Atlantic SST forcing to reconstruct long-term precipitation variation in the SASM domain. The success of this model reinforces our confidence in assigning causation to observed reconstructions of precipitation.

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http://www.sciencedirect.com/science/article/pii/S0277379115301657

The results suggest storminess increased after 1000 cal yrs BP, with higher storminess during the Medieval Climate Anomaly (MCA) than the LIA, supporting the hypothesis that the NAO-storminess relationship was consistent with the instrumental period. However the shift from a predominantly negative to positive NAO at c.2000 cal yrs BP preceded the increased storminess by 1000 years. We suggest that the long-term trends in storminess were caused by insolation changes, while oceanic forcing may have influenced millennial variability.

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http://www.clim-past-discuss.net/11/2159/2015/cpd-11-2159-2015.pdf

Conclusion: Spectral analysis identifies a robust 250 yr periodicity, with evidence of stronger westerly airflow between 2000 and 1000 calendar yrs [before present]. Along with other records, this periodicity strongly suggests solar forcing plays a significant role in modulating the strength of the Southern Hemisphere westerlies, something hitherto not recognised, and will form the focus of future research.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0287.1?af=R

Southern Hemisphere mid-to-upper tropospheric planetary wave activity is characterized by the superposition of two zonally-oriented, quasi-stationary waveforms: zonal wavenumber one (ZW1) and zonal wavenumber three (ZW3). Previous studies have tended to consider these waveforms in isolation and with the exception of those studies relating to sea ice, little is known about their impact on regional climate variability. … While ZW1 and ZW3 are both prominent features of the climatological circulation, the defining feature of highly meridional hemispheric states is an enhancement of the ZW3 component. Composites of the mean surface conditions during these highly meridional, ZW3-like anomalous states (i.e. months of strong planetary wave activity) reveal large sea ice anomalies over the Amundsen and Bellingshausen Seas during autumn and along much of the East Antarctic coastline throughout the year. Large precipitation anomalies in regions of significant topography (e.g. New Zealand, Patagonia, coastal Antarctica) and anomalously warm temperatures over much of the Antarctic continent were also associated with strong planetary wave activity. The latter has potentially important implications for the interpretation of recent warming over West Antarctica and the Antarctic Peninsula.

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http://onlinelibrary.wiley.com/doi/10.1002/2014JD022497/full

Finally, we inspected dimming and brightening for the period 1979–2010 [China] with an indication for dimming early in the time series (i.e., 1979–1987) and brightening after, which agrees with surface-based observations. After 2000, however, a decrease in the brightening by more than 1 order of magnitude was evident which is in contrast to the continued brightening [after 2000] found in surface records and satellite-derived estimates.

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http://www.nonlin-processes-geophys-discuss.net/2/1275/2015/npgd-2-1275-2015.pdf

Conclusion: The theory is applied to decompose the Wolf [sunspot] numbers and temperature series from 818 weather stations of the Northern Hemisphere from 1955 to 2010. We obtained the following results. The CS- or NS-components [components with coincident or non-coincident signs] of the Wolf [sunspot] numbers and temperature series have significant correlation coefficients in the range from weak to strong values for small samples, typical for the minimum period of stability of the climate.

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http://www.sciencedirect.com/science/article/pii/S0033589415000137

Decadal to millennial-scale solar forcing of Last Glacial Maximum climate in the Estancia Basin of central New Mexico

Dominant periods of ~ 900, ~ 375, and ~ 265 yr are similar to cycles in Holocene 14C production reported for a variety of tree ring records, suggesting that the Lake Estancia sediments record variations in solar activity during LGM time. A prominent spectral peak with a period of ~ 88 yr appears to reflect the solar Gleissberg cycle and may help, along with the ~ 265 yr cycle, to explain an ongoing mystery about how Lake Estancia was able to undergo abrupt expansions without overflowing its drainage basin.

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http://www.sciencedirect.com/science/article/pii/S1364682615300638

Introduction: Atmospheric oscillations with periods of a few years have been observed and frequently discussed in the literature. Undoubtedly, the most prominent of such oscillations is the Quasi-Biennial Oscillation in the tropical stratosphere. Much longer periods near 11 years and 5.5 years are occasionally seen at higher altitudes in the upper mesosphere and lower thermosphere, and have been attributed to influences of the solar cycle and its harmonics. Solar cycle signals are also seen in the stratosphere and troposphere.

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http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2473162

This paper deals with possible causes of broken relationships between geomagnetic activity (GA) and sea surface temperature (SST) in the regions where it is most prominent. We analyze data of 0/700 m ocean heat content, SST, and wind stress for the period 1948–2013. The aa index is used to describe geomagnetic activity. The zonal wind stress is demonstrated to have a significant effect on sea surface temperature in the regions under consideration. Increased fluctuations of heat content anomalies and change in wind stress structure have been noted since the 1976 climate shift.

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http://hol.sagepub.com/content/early/2015/08/04/0959683615596839

Solar irradiance changes are thought to play an important role in natural climate variability. How the hydrological conditions were affected by solar irradiance in westerly-controlled arid central Asia (ACA) on decadal/centennial timescales remains poorly understood because of the lack of high-quality records. Here, we integrate 1.2-year-resolution x-ray fluorescence (XRF) scanner-derived carbonate accumulation estimates with 6-year-resolution biomarker and magnetic records in a well-preserved shoreline core from Lake Manas, northwestern China, to reconstruct lake level fluctuations and potential solar imprints over the last millennium. Besides the generally confirmed cool-wet/warm-dry climate pattern in ACA, our data also consistently show frequent and substantial lake level fluctuations, resembling solar activity changes, especially during the ‘Little Ice Age’. Wavelet spectral analyses of our XRF data indicate strong 8- to 16-year, 64- to 128-year and 128- to 256-year cycles, coinciding with the ~11-year Schwabe cycle, ~70- to 100-year Gleissberg cycle, and the ~200-year Suess-de Vries cycle. We therefore suggest the existence of solar imprints on effective moisture fluctuations in ACA over the last millennium, and the potential occurrence of the Schwabe cycle even during the solar minima.

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http://link.springer.com/chapter/10.1007/978-3-319-00693-2_13

[A] good data-model agreement exists when investigating the potential impact of solar variability on the SWW [southern westerly wind belt] at centennial time-scales during the latest Holocene with periods of lower (higher) solar activity causing equatorward (southward) shifts of the SWW.

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http://www.clim-past.net/11/283/2015/cp-11-283-2015.html

For the first time, short-term climate variability on a decadal to centennial scale is resolved in Lower Miocene shallow marine laminated sediments in a land-based section. The results hint at a close relationship between climate variability and solar forcing during the Late Burdigalian. Moreover, accepting that these cyclicities are indeed of solar origin, this would indicate that precipitation was driven by the two Gleissberg cycles, while upwelling was driven by the Suess cycle. Furthermore, proxies for primary productivity were influenced by both cycles, although the Suess cycle exerts dominant control, reflecting a stronger influence of upwelling on primary productivity.

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http://www.sciencedirect.com/science/article/pii/S0273117715008686

Variations in the annual radial growth of fossil trees (a palaeoclimatic indicator of the environment) that grew in the Gobi Desert (Mongolia) about 100 – 150 million years ago are considered. By using the method of combined spectral periodograms of variations in the ring widths of fossil samples, quasi-harmonic components with the periods similar to basic solar activity cycles of our days have been revealed. This suggests that the Earth’s climate is influenced by the solar activity over large time scales.

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http://www.doiserbia.nb.rs/img/doi/0354-9836/2015%20OnLine-First/0354-98361500018A.pdf

A long-term negative deviation of the Earth’s average annual energy balance from the equilibrium state is

corresponding with variations in its energy state. As a result, the Earth will have a negative average annual energy balance also in the future. This will lead to the beginning of the decreasing in the Earth’s temperature and of the epoch of the Little Ice Age after the maximum phase of the 24-th solar cycle approximately since the end of 2014. The influence of the consecutive chain of the secondary feedback effects (the increase in the Bond albedo and the decrease in the concentration of greenhouse gases in the atmosphere due to cooling) will lead to an additional reduction of the absorbed solar energy and reduce the greenhouse effect. The start of the TSI’s Grand Minimum is anticipated in the solar cycle 27±1 in 2043±11 and the beginning of the phase of deep cooling of the 19th Little Ice Age for the past 7,500 years around 2060±11.

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http://www.sciencedirect.com/science/article/pii/S003101821500108X

The seasonal monsoon cycle with winds from the southwest (SW) in summer and from the northeast (NE) in winter strongly impacts on modern regional sea surface temperature (SST) patterns in the Arabian Sea (northern Indian Ocean). Superimposed over the long-term trend are variations in northeast monsoon wind strength at time scales of centuries that were synchronous with late Holocene climate variations recorded on the Asian continent and in the high-latitude Northern Hemisphere. Their likely driving forces are insolation [solar radiation] changes associated with sunspot cycles. Enhanced by feedback mechanisms (e.g. land-sea thermal contrast) they enforced centennial scale fluctuations in wind strength and temperature in the northern Arabian Sea monsoon system.

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2375.html

Precipitation in low latitudes is primarily controlled by the position of the intertropical convergence zone, which migrates from south to north seasonally. The Little Ice Age (defined as AD 1400–1850) was associated with low solar irradiance and high atmospheric aerosol concentrations as a result of several large volcanic eruptions. The mean position of the intertropical convergence zone over the western Pacific has been proposed to have shifted southwards during this interval, which would lead to relatively dry Little Ice Age conditions in the northern extent of the intertropical convergence zone and wet conditions around its southern limit. However, here we present a synthesis of palaeo-hydrology records from the Asian–Australian monsoon area that documents a rainfall distribution that distinctly violates the expected pattern. Our synthesis instead documents a synchronous retreat of the East Asian Summer Monsoon and the Australian Summer Monsoon into the tropics during the Little Ice Age, a pattern supported by the results of our climate model simulation of tropical precipitation over the past millennium. We suggest that this pattern over the western Pacific is best explained by a contraction in the latitudinal range over which the intertropical convergence zone seasonally migrates during the Little Ice Age. We therefore propose that rather than a strict north–south migration, the intertropical convergence zone in this region may instead expand and contract over decadal to centennial timescales in response to external forcing.

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http://link.springer.com/article/10.1007%2Fs00704-015-1388-z

This paper investigates the monthly, winter, and annual temperature time series obtained from the instrumental records in Zagreb, Croatia, for the period 1864–2010. Using wavelet analysis, the dominant modes of variability in these temperature series are identified, and the time intervals over which these modes may persist are delineated. The results reveal that all three temperature records exhibit low-frequency variability with a dominant periodicity at around 7.7 years. The 7.7-year cycle has also been observed in the temperature data recorded at several other stations in Europe, especially in Northern and Western Europe, and may be linked to the North Atlantic Oscillation (NAO) and/or solar/geomagnetic activity.

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http://www.sciencedirect.com/science/article/pii/S0273117715004901

The recent extended, deep minimum of solar variability and the extended minima in the 19th and 20th centuries (1810–1830 and 1900–1920) are consistent with minima of the Centennial Gleissberg Cycle (CGC), a 90–100 year variation of the amplitude of the 11-year sunspot cycle observed on the Sun and at the Earth. The Earth’s climate response to these prolonged low solar radiation inputs involves heat transfer to the deep ocean causing a time lag longer than a decade. The spatial pattern of the climate response, which allows distinguishing the CGC forcing from other climate forcings, is dominated by the Pacific North American pattern (PNA). The CGC minima, sometimes coincidently in combination with volcanic forcing, are associated with severe weather extremes. Thus the 19th century CGC minimum, coexisted with volcanic eruptions, led to especially cold conditions in United States, Canada and Western Europe.

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http://www.sciencedirect.com/science/article/pii/S0031018215001297

The study of long-chain alkenones in the Ocean Drilling Program (ODP) core 1202B reveals a sub-centennial resolution record of sea surface temperature (SST) in the southern Okinawa Trough for the past 15 thousand years (kyr). From the Deglaciation to Holocene, SST varied from 21.1 to 26.5 °C. The presence of Bølling (15.0–14.2 kyr BP) and Allerød (13.7–13.4 kyr BP) warming phases, Older Dryas (14.2–13.7 kyr BP) and Younger Dryas (12.8–11.6 kyr BP) cold periods reflects a tight teleconnection of climate between the Okinawa Trough and the North Atlantic region in the last Deglaciation. After rapidly increased and reached the maximum at ~ 7.4 kyr BP, SST in the southern OT gradually decreased, corresponding with the lowering of northern hemisphere summer solar insolation. However, a series of abrupt SST drops were identified at ca. 8.6–8.1, 5.8–4.8, 4.1–3.9, 3.0–2.5, 1.6–1.3 and 0.6–0.5 kyr BP, which cannot be explained by solar insolation changes alone, and instead are mediated by a complex sun–ocean–atmosphere coupling.

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http://www.atmos-chem-phys.net/15/9851/2015/acp-15-9851-2015.html

Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. … We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the “water vapour conundrum” of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

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http://www.sciencedirect.com/science/article/pii/S0375960114012213

In part I, equatorial Pacific Ocean temperature index SST3.4 was found to have segments during 1990–2014 showing a phase-locked annual signal and phase-locked signals of 2- or 3-year periods. Phase locking is to an inferred solar forcing of 1.0 cycle/yr. Here the study extends to the global ocean, from surface to 700 and 2000 m. The same phase-locking phenomena are found. The El Niño/La Niña effect diffuses into the world oceans with a delay of about two months.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062773/abstract

China experiencing the recent warming hiatus

Based on the homogenized data set, we analyze changes in mean temperature and some extreme temperature indices over China since 1961 and especially during the recent warming hiatus period (1998–2012) in a global average context. The result shows that the decrease of annual mean maximum has contributed most to the decreases in overall mean temperature and in diurnal temperature range (DTR) during the warming hiatus period. In most parts of China except the southwest, the summer mean maximum temperature (TxS) shows the largest increase, while the winter mean minimum temperature (TnW) indicates slight cooling trends. These changes have augmented the seasonal cycle and increased the likelihood of extreme warm and cold events. Further analyses reveal that the increases in TxS [maximum temperature] are significantly correlated with concurrent increases in solar radiation. In southwest China, the annual mean temperature, TxS, TnW, and DTR increased during 1998–2012, possibly related to increased dryness in this region during the hiatus period.

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http://www.sciencedirect.com/science/article/pii/S0277379115000451

Results indicate that the Holocene winter climate in continental Scandinavia was forced by a combination of several factors, at least by solar variability and the North Atlantic ocean–atmosphere circulation-patterns, with varying influences through time.

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http://www.scirp.org/journal/PaperInformation.aspx?paperID=61284

By about 2030-2040, the Sun will experience a new grand solar minimum. This is evident from multiple studies of quite different characteristics: the phasing of sunspot cycles, the cyclic observations of North Atlantic behaviour over the past millennium, the cyclic pattern of cosmogenic radionuclides in natural terrestrial archives, the motions of the Sun with respect to the centre of mass, the planetary spin-orbit coupling, the planetary conjunction history and the general planetary-solar-terrestrial interaction. During the previous grand solar minima—i.e. the Sporer Minimum (ca 1440-1460), the Maunder Minimum (ca 1687-1703) and the Dalton Minimum (ca 1809-1821)—the climatic conditions deteriorated into Little Ice Age periods.

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http://www.sciencedirect.com/science/article/pii/S0926985115001160

It appears that monsoonal rainfall in the region is influenced by solar activity, with periods of high total solar irradiance being characterised by high rainfall and vice versa; it was relatively low during the Little Ice Age and high during the Medieval Warm Period. The magnetic susceptibility (Xlf) data exhibit a number of periodicities which might have a solar origin. The Xlf record exhibits similarities with other continental and marine palaeoclimatic records from the region, indicating that regional trends in the monsoon during the Late Holocene are broadly similar.

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http://iopscience.iop.org/article/10.1088/0004-637X/802/1/67/meta

Solar cycle (SC) 23 was extraordinarily long with remarkably low magnetic activity. We have investigated whether this is a common behavior of solar-type stars. From the Ca II H and K line intensities of 111 stars observed at Mount Wilson Observatory from 1966 to 1991, we have retrieved data of all 23 G-type stars and recalculated their cycle lengths using the damped least-squares method for the chromospheric activity index S as a function of time. A regression analysis was performed to find relations between the derived cycle length, Pavg, and the index for excess chromospheric emission, RHK. As a noteworthy result, we found a segregation between young and old solar-type stars in the cycle length-activity correlation. We incorporated the relation for the solar-type stars into the previously known rule for stellar chromospheric activity and brightness to estimate the variation of solar brightness from SC 22 to SC 23 as (0.12 ± 0.06)%, much higher than the actual variation of total solar irradiance (TSI) &l;&l; 0.02%. We have then examined solar spectral irradiance (SSI) to find a good phase correlation with a sunspot number in the wavelength range of 170-260 nm, which is close to the spectral range effective in heating the Earth’s atmosphere. Therefore, it appears that SSI rather than TSI is a good indicator of the chromospheric activity, and its cycle length dependent variation would be more relevant to the possible role of the Sun in the cyclic variation of the Earth’s atmosphere.

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http://www.sciencedirect.com/science/article/pii/S0033589415000745

A comparison to potential climatic forcings implicates a combination of changing summer – winter insolation and tropical and N Pacific sea-surface temperature dynamics as the primary drivers of Holocene climate in the central Mojave Desert.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0082.1?af=R

This paper examines recent southern New York State climate changes as reflected in a detailed hourly climate record collected ~110 km due north of New York City since 1988, including comprehensive surface radiation data. Comparing 1988–2000 and 2001–2014 means, the area has warmed, dominated by a 0.5–0.7 K summer warming. Daytime warming exceeds night-time’s. Warming is not due to enhanced downward longwave flux, but arises from increased incident solar fluxes accompanying declining aerosol loads. Local warming is shown to stem from a large scale response to increased solar forcing, the key element of which is accelerated summer hydrological cycle: increased precipitation, with smaller evaporation increases leading to large, significant soil moisture and runoff increases. Much of the accelerated summer hydrological cycle is shown to arise due to an anomalous low level cyclonic motion centered on the mid-Atlantic U.S. coast, rendering the results regional rather than local. Analyzing the stability and CAPE budgets of mean and individual summer profiles over the studied site provides a diagnostic explanation of the observed warming and accelerated hydrometeorology due to enhanced solar fluxes. The study reveals a complex suite of (thermo)dynamic feedbacks to radiative forcing of which surface warming is but one element, reiterating and re-emphasizing that surface temperature trends may be embedded in far richer physics than greenhouse gas induced radiative forcing alone.

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http://onlinelibrary.wiley.com/doi/10.1002/jqs.2776/abstract

A variety of palaeoclimatic records show a shift towards cooler, wetter and windier conditions in Europe around 2800 cal a BP. The shift broadly coincides with an increase of the atmospheric 14C concentration, suggesting a connection between solar activity variations and climate change. … Based on the new chronology, a shift to a Sphagnum-dominated bog, representing wetter conditions, and the onset of a period with increased storminess occurred around 2700 cal a BP. These changes are, within age model uncertainties, synchronous with climatic changes inferred from other sites in Europe, suggesting a shift in the larger scale atmospheric circulation, possibly triggered by decreased solar activity.

 

Solar-Cloud Influence on Climate

http://rd.springer.com/article/10.1007%2Fs00382-015-2862-0

One of the main sources of uncertainty in climate projections is represented by clouds, which have a profound influence on the Earth’s radiation budget through the feedbacks in which they are involved. The improvement of clouds representation in General Circulation Models relies largely on constraints derived from observations and on correct identification of processes that influence cloud formation or lifetime. Here we identify solar forced high cloud cover (HCC) patterns in reanalysis and observed data extending over the 1871–2009 period, based on their associations with known fingerprints of the same forcing on surface air temperature, sea surface temperature (SST) and sea level pressure fields. The solar influence on HCC has maximum amplitudes over the Pacific basin, where HCC anomalies are distributed in bands of alternating polarities. The colocation of the HCC and SST anomalies bands indicates a thermal influence on high clouds through convection and an amplification of the HCC anomalies by a positive feedback of long-wave fluxes, which increases the solar signal. Consistent with numerical simulations, the solar forced HCC [high cloud cover] pattern appears to be generated through a constructive interference between the so-called “top-down” and “bottom-up” mechanisms of solar influence on climate and is amplified by ocean–atmosphere positive feedbacks.

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http://onlinelibrary.wiley.com/doi/10.1002/joc.4540/abstract

At low latitudes, strong seasonal changes in cloud cover and precipitation largely control the mass balance of glaciers. Measurements of shortwave and longwave radiation fluxes reaching Zongo glacier, Bolivia (16°S, 5060 m asl), were analysed from 2005 to 2013 to investigate cloud radiative properties. Cloud shortwave attenuation and longwave emission were greater in the wet summer season (DJF) than in the dry winter season (JJA) probably because most DJF clouds were low warm cumulus associated with local convection, whereas JJA clouds were frequently altostratus associated with extra-tropical perturbations. Solar irradiance was high all year round and cloud radiative forcing on down-welling fluxes was strongly negative, with monthly averages ranging from -60 to -110 W m−2 from the dry to the wet season, respectively. In the wet season, high extraterrestrial solar irradiance and low shortwave transmissivity caused very negative cloud forcing despite the high longwave emissivity of convective clouds.

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http://webster.eas.gatech.edu/Papers/albedo2015.pdf

Abstract: The fraction of the incoming solar energy scattered by Earth back to space is referred to as the planetary albedo. This reflected energy is a fundamental component of the Earth’s energy balance, and the processes that govern its magnitude, distribution, and variability shape Earth’s climate and climate change.

Summary: [T]he amount of solar energy reflected from each hemisphere is essentially identical. This symmetry appears in broadband data but not in spectral radiances, thus hinting at the importance of such spectral data as a diagnostic tool for studying Earth’s climate system. Again, the cloudiness of the planet is the principal regulatory agent that maintains this symmetry with the increased energy reflected from SH clouds precisely balancing the larger reflections from NH land masses.

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http://search.proquest.com/openview/d32a3c1292edadbcc8a7d21d1eb54625/1

Climate variability is a hot topic not only for scientists and policy-makers, but also for each and every one of us. The anthropogenic activities are considered to be responsible for most climate change, however there are large uncertainties about the magnitude of effects of solar variability and other extraterrestrial influences, such as galactic cosmic rays on terrestrial climate. Clouds play an important role due to feedbacks of the radiation budget: variation of cloud cover/composition affects climate, which, in turn, affects cloud cover via atmospheric dynamics and sea temperature variations. Cloud formation and evolution are still under scientific scrutiny, since their microphysics is still not understood. Besides atmospheric dynamics and other internal climatic parameters, extraterrestrial sources of cloud cover variation are considered. One of these is the solar wind, whose effect on cloud cover might be modulated by the global atmospheric electrical circuit. Clouds height and composition, their seasonal variation and latitudinal distribution should be considered when trying to identify possible mechanisms by which solar energy is transferred to clouds. The influence of the solar wind on cloud formation can be assessed also through the ap index – the geomagnetic storm index, which can be readily connected with interplanetary magnetic field, IMF structure. This paper proposes to assess the possible relationship between both cloud cover and solar wind proxies, as the ap index, function of cloud height and composition and also through seasonal studies. The data covers almost three solar cycles (1984-2009). Mechanisms are looked for by investigating observed trends or correlation at local/seasonal scale

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064410/abstract

Mountain waters, glaciers, hazards and biodiversity are vulnerable to the impacts of global warming. Warming is projected to amplify over mountains by global climate models, yet meteorological records do not show a uniform acceleration of warming with elevation. Here, we explore warming-elevation relationships using records from 2660 meteorological stations, and determine that the vertical gradient of warming rate varies with location. The warming is faster at higher altitudes in Asia and Western North America, but the opposite is observed over Central Europe and Eastern North America which have received more short-wave radiation (brightening) associated with a decrease of aerosols and clouds since the 1980s. We found that altitudinal differences in air pollution (brightening), with observations showing more short-wave radiation received at low altitudes than at mountains, modulate the warming-elevation relationships. The advance in understanding of the drivers of regional climate change will contribute to the formulation of strategies for climate change mitigation at high elevations.

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http://iopscience.iop.org/1748-9326/10/4/044006/pdf/1748-9326_10_4_044006.pdf

Shallow cumulus clouds play a key role in the Earth’s radiation budget. Due to their low-altitude location in the atmospheric column, their emitted thermal radiation is comparable to the surface blackbody emission. Therefore, their radiative effect is determined mainly by the reflection of shortwave radiation and it is usually considered to be cooling, although the exact radiative effect is still uncertain. Ramanathan et al (1989) estimated the global radiative effect of all clouds to be −13.2 W m−2 , whereas recent estimations based on satellite data and models stand at −21 W m−2 (Allan 2011).

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www.sciencedirect.com/science/article/pii/S003442571530016X

Highlights: Four representative global satellite Rs [incident solar radiation] products were evaluated at 1151 sites. Incident solar radiation (Rs) over the Earth’s surface is important for studying our climate and environment. Global observation networks have been established, but many land surfaces are under-represented. Satellite remote sensing is the only way to estimate Rs [incident solar radiation] at both global and regional scales…. A significant dimming was found between 1984 and 1991, followed by brightening from 1992 to 2000, and then by a significant dimming over 2001–2007. The CERES-EBAF product showed a brightening trend, but not significantly since 2000. … [C]louds contribute more to the long-term variations of Rs [incident solar radiation] derived from satellite observations than aerosols.

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http://webster.eas.gatech.edu/Papers/albedo2015.pdf

We show how clouds provide the necessary degrees of freedom to modulate the Earth’s albedo setting the hemispheric symmetry. We also show that current climate models lack this same degree of hemispheric symmetry and regulation by clouds.

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http://www.sciencedirect.com/science/article/pii/S136468261530081X

Solar wind-atmospheric electricity-cloud microphysics connections to weather and climate

Highlights

  • Large-scale troposphere responses to changes in global atmospheric electric current.
  • Review Jz-related observed meteorological effects and proposed associated pathways.
  • Energy flow can be modulated by cloud microphysical responses to Jz changes.
  • One way is amplification by storm invigoration.
  • The second way is by changes in cloud albedo, cloud cover, and infrared opacity.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0076.1

The surface energy budget plays a critical role in determining the mass balance of the Greenland Ice Sheet, which in turn has significant implications for global sea levels. Nearly three years of data (January 2011–October 2013) are used to characterize the annual cycle of surface radiative fluxes and cloud radiative forcing (CRF) from the central Greenland Ice Sheet at Summit Station. The annual average CRF [cloud radiative forcing] is 33 W m−2, representing a substantial net cloud warming of the central Greenland surface. Unlike at other Arctic sites, clouds warm the surface during the summer. The surface albedo is high at Summit throughout the year, limiting the cooling effect of the shortwave CRF and thus the total CRF is dominated by cloud longwave warming effects in all months. All monthly mean CRF [cloud radiativer forcing] values are positive (warming), as are 98.5% of 3-hourly cases. The annual cycle of CRF is largely driven by the occurrence of liquid-bearing clouds, with a minimum in spring and maximum in late summer. Optically thick liquid-bearing clouds [liquid water path (LWP) > 30 g m−2] produce an average longwave CRF of 85 W m−2. Shortwave CRF is sensitive to solar zenith angle and LWP. When the sun is well above the horizon (solar zenith angle < 65°), a maximum cloud surface warming occurs in the presence of optically thin liquid-bearing clouds. Ice clouds occur frequently above Summit and have mean longwave CRF values ranging from 10 to 60 W m−2, dependent on cloud thickness.

Orbital – Solar Climate Forcing

http://www.clim-past.net/11/1271/2015/cp-11-1271-2015.html

Orbital forcing is a key climate driver over multi-millennial timescales. In particular, monsoon systems are thought to be driven by orbital cyclicity, especially by precession. Here, we analyse the impact of orbital forcing on global climate with a particular focus on the North African monsoon, by carrying out an ensemble of 22 equally spaced (one every 1000 years) atmosphere–ocean–vegetation simulations using the HadCM3L model, covering one full late Miocene precession-driven insolation cycle with varying obliquity (between 6.568 and 6.589 Ma). The simulations only differ in their prescribed orbital parameters, which vary realistically for the selected time period. We have also carried out two modern-orbit control experiments, one with late Miocene and one with present-day palaeogeography, and two additional sensitivity experiments for the orbital extremes with varying CO2 forcing. Our results highlight the high sensitivity of the North African summer monsoon to orbital forcing, with strongly intensified precipitation during the precession minimum, leading to a northward penetration of vegetation up to ~ 21° N. The modelled summer monsoon is also moderately sensitive to palaeogeography changes, but it has a low sensitivity to atmospheric CO2 concentration between 280 and 400 ppm.

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http://www.sciencedirect.com/science/article/pii/S0277379115300160

There is strong proxy and model evidence of precession- and obliquity-induced [solar] changes in the freshwater budget over the Mediterranean Sea and its borderlands, yet explanations for these changes vary greatly. We investigate the separate precession and obliquity forcing of the freshwater budget over the Mediterranean using a high-resolution coupled climate model, EC-Earth. At times of enhanced insolation seasonality, i.e. minimum precession and maximum obliquity, the area was wetter and the Mediterranean Sea surface was less saline. The latter has been attributed to increased runoff from the south as a consequence of a strengthened North African monsoon, as well as to increased precipitation over the Mediterranean Sea itself. Our results show that both mechanisms [precession and obliquity, or solar forcing] play a role in changing the freshwater budget. Increased monsoon runoff occurs in summer during times of enhanced insolation seasonality, especially minimum precession, while increased precipitation is important in winter for both precession and obliquity. We relate changes in winter precipitation to changes in the air-sea temperature difference and subsequently, convective precipitation. The freshening in the minimum precession and maximum obliquity experiments has a strong effect on Mediterranean sea surface salinity and mixed layer depth, thereby likely influencing deep sea circulation and sedimentation at the ocean

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http://www.clim-past.net/11/1335/2015/cp-11-1335-2015.pdf

The influence of obliquity, the tilt of the Earth’s rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity [orbital] signal.

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http://www.nature.com/nature/journal/v520/n7549/full/nature14401.html

The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

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http://www.nature.com/ncomms/2015/150122/ncomms7159/full/ncomms7159.html

The relatively stable SST [sea surface temperatures] seasonality in the tropical North Atlantic Ocean at the end of the last interglacial and its inferred orbital [solar radiation] control is remarkable as this period was characterized by large-scale perturbations of ocean circulation and climate resulting from instabilities of polar ice sheets. Results from Western Australia suggest that, after a prolonged period of stable sea level at ~3–4 m above present sea level between 127 and 119 kyr ago, eustatic sea level rose rapidly to ~8 m above present at the end of the last interglacial, peaking at 118.1±1.4 kyr ago.

 

Our findings based on combining coral proxy records with climate model simulations indicate that northern tropical Atlantic SST seasonality at 118 kyr ago was similar to today and controlled mainly by orbital insolation [solar radiation] changes, despite dramatic ocean circulation and climate perturbations resulting from instabilities of polar ice sheets that characterized the end of the last interglacial. Today, tropical Atlantic SST plays a major role in seasonal climate extremes, such as hurricanes, flashfloods and droughts, which cause severe socioeconomic damage on the adjacent continents. Our results indicate that SST seasonality in the tropical Atlantic did not substantially change during a period of abrupt high-latitude ice sheet, ocean and climate perturbations at the end of the last interglacial, and, thus, suggest that tropical SST seasonality is controlled mainly by orbital insolation [solar radiation] changes during interglacials. However, more seasonally resolved proxy records of SST are needed to better constrain both the climate sensitivity of the tropical ocean in the past and the seasonal response in model-based scenarios of past and future climate change.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00639.1

The δ18O of calcite (δ18Oc) in speleothems from South America is fairly well correlated with austral summer [December–February (DJF)] insolation, indicating the role of orbitally paced changes in insolation in changing the climate of South America. Using an isotope-enabled atmospheric general circulation model (ECHAM4.6) coupled to a slab ocean model, the authors study how orbitally paced variations in insolation change climate and the isotopic composition of precipitation (δ18Op) of South America. Compared with times of high summertime insolation, times of low insolation feature (i) a decrease in precipitation inland of tropical South America as a result of an anomalous cooling of the South American continent and hence a weakening of the South American summer monsoon and (ii) an increase in precipitation in eastern Brazil that is associated with the intensification and southward movement of the Atlantic intertropical convergence zone

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0125.1?af=R

We demonstrate that a significant September trend towards increased convection (reduced OLR) in the poleward portion of the South Pacific Convergence Zone (SPCZ) is statistically related to [natural] Rossby wave-like circulation changes across the southern oceans. The wave response is strongest over the South Pacific in September and propagates eastward to the South Atlantic in October. OLR-related changes are linearly congruent with around half of the observed total changes in circulation during September and October, and are consistent with observed trends in South Pacific sea ice concentration and surface temperature over western West Antarctica and the western Antarctic Peninsula. These results suggest SPCZ variability in early spring, especially on the poleward side of the SPCZ, is an important contributor to circulation and surface temperature trends across the South Pacific / Atlantic and West Antarctica.

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http://www.sciencedirect.com/science/article/pii/S0277379115300457

Our results suggest that a transition occurred from dry and dusty conditions during the Younger Dryas (YD) to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early Holocene (9000–6000 Yr BP). This period was followed by relatively drier and dustier conditions during middle to late Holocene, which is consistent with orbital changes in insolation that affected much of the northern hemisphere.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00639.1

The δ18O of calcite (δ18Oc) in speleothems from South America is fairly well correlated with austral summer [December–February (DJF)] insolation, indicating the role of orbitally paced changes in insolation in changing the climate of South America. Using an isotope-enabled atmospheric general circulation model (ECHAM4.6) coupled to a slab ocean model, the authors study how orbitally paced variations in insolation change climate and the isotopic composition of precipitation (δ18Op) of South America. Compared with times of high summertime insolation, times of low insolation feature (i) a decrease in precipitation inland of tropical South America as a result of an anomalous cooling of the South American continent and hence a weakening of the South American summer monsoon and (ii) an increase in precipitation in eastern Brazil that is associated with the intensification and southward movement of the Atlantic intertropical convergence zone, which is caused by the strengthening of African winter monsoon that is induced by the anomalous cooling of northern Africa. Finally, reduced DJF insolation over southern Africa causes cooling and the generation of a tropically trapped Rossby wave that intensifies and shifts the South Atlantic convergence zone northward.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JC010713/abstract

In a transient accelerated simulation of a coupled climate model, we identified a zonal dipole-like pattern of sea surface temperature (SST) anomalies in the tropical Indian Ocean, which is forced by precessional insolation [solar radiation] changes since 300 ka and named as the paleo-IOD. A positive paleo-IOD mean state at 23-kyr’s precessional band exhibits warmer and wetter conditions over the western Indian Ocean and cooler and drier conditions over the eastern tropical Indian Ocean from August to October. The zonal thermal seesaw at the sea surface can extend downward to the subsurface ocean between 60 m and 80 m and accompanies stronger oceanic upwelling in the eastern tropical Indian Ocean.

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http://www.sciencedirect.com/science/article/pii/S0277379115000554

A review of the bipolar see–saw from synchronized and high resolution ice core water stable isotope records from Greenland and East Antarctica

Numerous ice core records are now available that cover the Last Glacial cycle both in Greenland and in Antarctica. Recent developments in coherent ice core chronologies now enable us to depict with a precision of a few centuries the relationship between climate records in Greenland and Antarctica over the millennial scale variability of the Last Glacial period. Stacks of Greenland and Antarctic water isotopic records nicely illustrate a seesaw pattern with the abrupt warming in Greenland being concomitant with the beginning of the cooling in Antarctica at the Antarctic Isotopic Maximum (AIM).

Natural Oceanic/Atmospheric Oscillation Influence on Climate (29)

http://www.nature.com/nature/journal/v521/n7553/full/nature14491.html

Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062451/full

Multidecadal variability of the continental precipitation annual amplitude driven by AMO and ENSO

As the water vapor content in the atmosphere scales with temperature, a warmer world is expected to feature an intensification of the hydrological cycle. Work to date has mainly focused on mean precipitation changes, whose connection to climatic modes is elusive at a global scale. Here we show that continental precipitation annual amplitude, which represents the annual range between minimum and maximum (monthly) rainfall, covaries with a linear combination of the Atlantic Multidecadal Oscillation and low-frequency variations in the El Niño–Southern Oscillation on a decadal to multidecadal scale with a correlation coefficient of 0.92 (P < 0.01). The teleconnection is a result of changes in moisture transport in key regions. Reported trends in the annual amplitude of global precipitation in recent decades need to be assessed in light of this substantial low-frequency variability, which could mask or enhance an anthropogenic signal in hydrological cycle changes.

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http://rd.springer.com/article/10.1007%2Fs00382-015-2866-9

By performing a new adaptive time series decomposition on the composite average of multiple ice core records obtained from the Arctic and Greenland, we extracted a robust quasi-oscillatory signal with a period of ~70 years throughout the preceding millennium, and showed that it is strongly connected to the Atlantic Multidecadal Oscillation (AMO). In the same decomposition there exists the Greenland signature of the Little Ice Age and Medieval Warm Period. Throughout the warm and cold periods the AMO properties remained robust. It implies that the evolution of the AMO has its own coherent mechanism and was little affected by these large climatic excursions.

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http://link.springer.com/article/10.1007/s00382-014-2143-3

The results show a strong link between ENSO and droughts (SPEI) over Southern Africa. The link is owing to the influence of ENSO on both rainfall and temperature fields, but the correlation between ENSO and temperature is stronger than the correlation between ENSO and rainfall. Hence, using only rainfall to monitor droughts in Southern Africa may underestimate the influence of ENSO on the droughts.

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http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL064764/full

Abstract: The abrupt Northern Hemispheric warming at the end of the twentieth century has been attributed to an enhanced greenhouse effect. Yet Greenland and surrounding subpolar North Atlantic remained anomalously cold in 1970s to early 1990s. Here we reconstructed robust Greenland temperature records (North Greenland Ice Core Project and Greenland Ice Sheet Project 2) over the past 2100 years using argon and nitrogen isotopes in air trapped within ice cores and show that this cold anomaly was part of a recursive pattern of antiphase Greenland temperature responses to solar variability with a possible multidecadal lag. We hypothesize that high solar activity during the modern solar maximum (approximately 1950s-1980s) resulted in a cooling over Greenland and surrounding subpolar North Atlantic through the slowdown of Atlantic Meridional Overturning Circulation with atmospheric feedback processes.

 

Introduction: Greenland and the surrounding subpolar North Atlantic experienced anomalously low temperatures amid rising Northern Hemispheric average temperatures [during the “1970s to early 1990s”]. This cooling and subsequent warming since 1995 is a regional pattern attributed to the Atlantic Multidecadal Oscillation (AMO). Recent studies indicate that temperature changes in the North Atlantic before and after 1995 were induced by changes in the frequency of atmospheric blocking activity and associated changes in warmer and more saline seawater in the subpolar North Atlantic, and Atlantic Meridional Overturning Circulation (AMOC) likely played an important role for these changes. However, the underlying causes of the multidecadal variations remain unknown.

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http://www.sciencedirect.com/science/article/pii/S0277379115301372

Holocene climatic change is driven by a plethora of forcing mechanisms acting on different time scales, including: insolation, internal ocean (e.g. Atlantic Meridional Overturning Circulation; AMOC) and atmospheric (e.g. North Atlantic Oscillation; NAO) variability. … We demonstrate that an observed modern link between Icelandic precipitation variability during different NAO phases, may have existed from ∼7.5 kyrs BP. A simultaneous decoupling of both air, and sea surface temperature records from declining insolation at ∼3.2 kyrs BP may indicate a threshold, after which internal feedback mechanisms, namely the NAO evolved to be the primary drivers of Icelandic climate on centennial time-scales.

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http://www.nature.com/srep/2015/150310/srep08909/full/srep08909.html?WT.ec_id=SREP-20150317

A prominent feature of recent climatic change is the strong Arctic surface warming that is contemporaneous with broad cooling over much of Antarctica and the Southern Ocean. Longer global surface temperature observations suggest that this contrasting pole-to-pole change could be a manifestation of a multi-decadal interhemispheric or bipolar seesaw pattern, which is well correlated with the North Atlantic sea surface temperature variability, and thus generally hypothesized to originate from Atlantic meridional overturning circulation oscillations. Here, we show that there is an atmospheric origin for this seesaw pattern. The results indicate that the Southern Ocean surface cooling (warming) associated with the seesaw pattern is attributable to the strengthening (weakening) of the Southern Hemisphere westerlies, which can be traced to Northern Hemisphere and tropical tropospheric warming (cooling). Antarctic ozone depletion has been suggested to be an important driving force behind the recently observed increase in the Southern Hemisphere’s summer westerly winds; our results imply that Northern Hemisphere and tropical warming may have played a triggering role at an stage earlier than the first detectable Antarctic ozone depletion, and enhanced Antarctic ozone depletion through decreasing the lower stratospheric temperature.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00297.1

The patterns of atmospheric circulation and air temperatures are similar to those of the annually integrated Arctic Oscillation (AO). The negative annual AO forms colder anomalies in autumn sea surface temperatures both over the East Siberian Sea and the Okhotsk Sea, which causes heavy sea-ice conditions in both seas through season-to-season persistence.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00424.1

The SST [sea surface temperature] influence is dominated by the Atlantic multidecadal oscillation (AMO), which also has a horseshoe shape, but with larger amplitude in the subpolar basin. A warm AMO phase leads to an atmospheric warming limited to the lower troposphere in summer, while it leads to a negative phase of the NAO in winter. The winter influence of the AMO is suggested to be primarily forced by the Atlantic SSTs in the northern subtropics. Such influence of the AMO is found in winter instead of early winter because the winter SST anomalies have a larger persistence, presumably because of SST reemergence.

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http://www.sciencedirect.com/science/article/pii/S1674927815000532

The decadal changes in EASM [East Asian Summer Monsoon] and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover, Arctic sea ice, sea surface temperatures in tropical Pacific and Indian Ocean, ocean–atmospheric coupled systems of the Pacific Decadal Oscillation (PDO) and Asian–Pacific Oscillation (APO), and uneven thermal forcing over the Asian continent. Up to now, the roles of anthropogenic factors, such as greenhouse gases, aerosols, and land usage/cover changes, on existing decadal variations of EASM and summer rainfall in this region remain uncertain.

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http://link.springer.com/article/10.1007/s00382-014-2283-5

Australia experienced much above average rainfall in association with strong, extended La Niña conditions during 2010–2012. Was the heavy Australian rainfall influenced by La Niña conditions and/or anthropogenic greenhouse gases? … Overall, the attribution of seasonal-scale heavy Australia rainfall to a particular cause is likely more complicated than for temperature extremes. As estimates of the greenhouse gas attributable change in rainfall risk may depend on the model datasets considered, it is also useful to consider model outputs from several datasets and using various estimates of counterfactual surface conditions to establish robust attribution statements for extreme rainfall events. In contrast, comparing the likelihoods of heavy rainfall during simulated La Niña years with El Niño/neutral years reveals a substantial La Niña influence on Australian rainfall during 2010–2012 that is robust to changes in the attribution framework

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00521.1?af=R

We report here that the North Atlantic Oscillation (NAO), which has been known to directly affect winter weather conditions in western Europe and the eastern United States of America, is also linked to surface air temperature over the broad southwestern United States (SWUS) region encompassing California, Nevada, Arizona, New Mexico, Utah, and Colorado in the early warm season. We have performed monthly timescale correlations and composite analyses using three different multi-decadal temperature datasets. Results from these analyses reveal that NAO-related upstream circulation positively affects not only the means, but also the extremes of the daily maximum and minimum temperatures in SWUS. This NAO effect is primarily linked with the positioning of upper-tropospheric anti-cyclones over the western US that are associated with development of the positive NAO phase, through changes in low-tropospheric wind directions as well as suppression of precipitation and enhanced short-wave radiation at the surface. The effect is observed in SWUS only during the March-June period because the monthly migration of anti-cyclones over the western US follows the migration of the NAO center over the subtropical Atlantic Ocean. The link between the SWUS temperatures and NAO has been strengthened in the last 30-year period (1980-2009) compared to the previous 30-year period (1950-1979). In contrast to the NAO-SWUS temperature relationship, the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) show only marginal correlation strengths in several limited regions for the same 60-year period.

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http://onlinelibrary.wiley.com/doi/10.1002/wea.2543/abstract

The influence of the ocean circulation on the climate of Ireland is more subtle than it first appears. Temperatures in Ireland are warmer than similar Pacific maritime climates. It is heat – carried primarily in the Atlantic overturning circulation – released over the Atlantic that provides this additional warmth. We investigate variations in Irish climate using long-term station-based time series. The Atlantic multidecadal oscillation (AMO) explains over 90% of the pronounced decadal temperature and summer precipitation variation. Understanding the impact of these ocean variations when interpreting long climate records, particularly in the context of a changing climate, is crucial.

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http://link.springer.com/article/10.1007/s00382-015-2535-z/fulltext.html

Introduction: The climate in the extra-tropical SH (Southern Hemisphere) is dominated by two primary modes of variability: the high-latitude response to El Niño–Southern Oscillation (ENSO); and variations in the Southern Annular Mode (SAM). …ENSO is the most prominent coupled mode involving atmospheric and oceanic variability over the tropical Pacific and exerts strong impacts on the climate over the extra-tropics through the excitation of a large-scale atmospheric wave train. … The ENSO-induced atmospheric teleconnection, in turn, modulates Antarctic sea ice as well as sea surface temperature (SST) in the Southern Ocean through alteration of the surface energy fluxes. … Climate in the extra-tropical SH is also strongly influenced by the SAM, which is a dominant mode of the SH atmospheric circulation. …. The positive phase of the SAM is associated with a positive atmospheric pressur e anomaly in the mid-latitudes together with a negative anomaly in Antarctica and vice versa for the negative phase of the SAM. Previous studies have shown that the SAM has a profound impact on SH climate variability. In particular, changes in surface westerly winds by the SAM directly affect Ekman flow as well as air–sea fluxes, which drive SH SST anomalies. … SAM yields a clear local impact on the SH climate. For example, locally enhanced low-pressure anomaly to the west of the Antarctic Peninsula during a positive SAM phase results in advection of warm air and subsequent warming in the Antarctic Peninsula.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00372.1?journalCode=clim

The time series of twentieth-century subtropical eastern Australian rainfall (SEAR) shows evident fluctuations over decadal to multidecadal time scales. Using observations from the period 1900–2013, it was found that SEAR is connected to the North Atlantic Oscillation (NAO) over decadal time scales, with the NAO leading by around 15 yr. The physical mechanism underlying this relationship was investigated. The NAO [North Atlantic Oscillation] can have a delayed impact on sea surface temperature (SST) fluctuations in the subpolar Southern Ocean (SO), and these SST changes could in turn contribute to the decadal variability in SEAR [subtropical eastern Australian rainfall] through their impacts on the Southern Hemisphere atmospheric circulation. This observed lead of the NAO relative to SO SST and the interhemispheric SST seesaw mechanism are reasonably reproduced in a long-term control simulation of an ocean–atmosphere coupled model. The NAO exerts a delayed effect on the variation of Atlantic meridional overturning circulation that further induces seesaw SST anomalies in the subpolar North Atlantic and SO. With evidence that the NAO precedes SEAR decadal variability via a delayed SO bridge, a linear model for SEAR decadal variability was developed by combination of the NAO and Pacific decadal oscillation (PDO). The observed SEAR decadal variability is considerably well simulated by the linear model, and the relationship between the simulation and observation is stable. SEAR over the coming decade may increase slightly, because of the recent NAO weakening and the return of negative PDO phase.

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http://m.pnas.org/content/112/45/13784.short?rss=1

Impacts of high-latitude volcanic eruptions on ENSO and AMOC

Large volcanic eruptions can have major impacts on global climate, affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is roughly 2–3 y. … Here, we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere cause strong hemispheric cooling, which could induce an El Niño-like anomaly, in the equatorial Pacific during the first 8–9 mo after the start of the eruption. The hemispherically asymmetric cooling shifts the Intertropical Convergence Zone southward, triggering a weakening of the trade winds over the western and central equatorial Pacific that favors the development of an El Niño-like anomaly. In the model used here, the specified high-latitude eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first 25 y after the eruption, followed by a weakening lasting at least 35 y. The long-lived changes in the AMOC strength also alter the variability of the El Niño–Southern Oscillation (ENSO).

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http://link.springer.com/article/10.1007%2Fs00704-015-1565-0

The anti-phase relationship of the hydroclimatic variations between western and eastern modes at the interdecadal variations occurs during the periods with the enhanced El Nino Southern Oscillation (ENSO) variance. Similarly, the multidecadal hydroclimate variations are anti-phase when the Pacific Decadal Oscillation (PDO) is in its warm phases. The inverse relationship between western and eastern modes is stable for the centennial scale.

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http://onlinelibrary.wiley.com/doi/10.1002/joc.4440/abstract

A multiple linear regression analysis reveals that interannual variability in extreme blocking and the Atlantic Multidecadal Oscillation (AMO) are the two predominant drivers of surface meltwater production across the entire Greenland ice sheet (GrIS), but Arctic sea ice extent and North Atlantic cyclone activity can also influence the extent of summer melting over portions of the GrIS.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0396.1?af=R

The impact of the North Atlantic Oscillation on climate through its influence on the Atlantic Meridional Overturning Circulation

A positive phase of the NAO strengthens the AMOC by extracting heat from the subpolar gyre, thereby increasing deepwater formation, horizontal density gradients, and the AMOC. The flux forcings have the spatial structure of the observed NAO, but the amplitude of the forcing varies in time with distinct periods varying from 2 to 100 years. The response of the AMOC to NAO variations is small at short time scales, but increases up to the dominant time scale of internal AMOC variability (20-30 years for the models used). … We show that NAO fluctuations, similar in amplitude to those observed over the last century, can modulate hemispheric temperature by several tenths of a degree.

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http://en.cnki.com.cn/Article_en/CJFDTOTAL-ZNTB201501038.htm

(4) El Nino event caused precipitation decrease and temperature increase, while La Nina event caused precipitation increase and temperature decrease, and had a certain degree of lagging; (5) El Nino and La Nina events had significant relationship with the drought and waterlog in Anhui Province, the drought and flood disaster occurred mostly in ENSO events years, the next year or the year before ENSO events, and the risk of drought was higher in the continuous El Nino years.

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http://link.springer.com/article/10.1007/s00704-014-1248-2

Evaluation of Labrador air temperatures over the past century (1881–2011) shows multi-scale climate variability and strong linkages with ocean-atmospheric modes of variability and external forcings. The Arctic Oscillation, Atlantic Multidecadal Oscillation, and El Nino Southern Oscillation are shown to be the dominant seasonal and interannual drivers of regional air temperature variability for most of the past century. Several global climate models show disagreement with observations on the rate of recent warming which suggests that models are currently unable to reproduce regional climate variability in Labrador air temperature. Using a combination of empirical statistical modeling and global climate models, we show that 33 % of the variability in annual Labrador air temperatures over the period 1881–2011 can be explained by natural factors alone; however, the inclusion of anthropogenic forcing increases the explained variance to 65 %. Rapid warming over the past 17 years is shown to be linked to both natural and anthropogenic factors with several anomalously warm years being primarily linked to recent anomalies in the Arctic Oscillation and North Atlantic sea surface temperatures. Evidence is also presented that both empirical statistical models and global climate models underestimate the regional air temperature response to ocean salinity anomalies and volcanic eruptions. These results provide important insight into the predictability of future regional climate impacts for the Labrador region.

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http://onlinelibrary.wiley.com/doi/10.1002/qj.2633/abstract;jsessionid=654489B51B0A28D945F90FCEB781CA3F.f03t03

We begin by providing observational evidence that the probability of encountering very high and very low annual tropical rainfall has increased significantly in the recent decade (1998-present) as compared to the preceding warming era (1979–1997). These changes over land and ocean are spatially coherent and comprise of a rearrangement of very wet regions and a systematic expansion of dry zones. While the increased likelihood of extremes is consistent with a higher average temperature during the [1998-present] pause (as compared to 1979–1997), it is important to note that the periods considered are also characterized by a transition from a relatively warm to cold phase of the El Niño Southern Oscillation (ENSO). To further probe the relation between contrasting phases of ENSO and extremes in accumulation, a similar comparison is performed between 1960–1978 (another extended cold phase of ENSO) and the aforementioned warming era. Though limited by land-only observations, in this cold-to-warm transition, remarkably, a near-exact reversal of extremes is noted both statistically and geographically. This is despite the average temperature being higher in 1979–1997 as compared to 1960–1978. Taken together, we propose that there is a fundamental mode of natural variability, involving the waxing and waning of extremes in accumulation of global tropical rainfall with different phases of ENSO.

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http://adsabs.harvard.edu/abs/2015EGUGA..17.2379M

The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability affecting the North Sea with amplitudes comparable to the climate change signal. Here we investigate in the fully coupled scenario run how the NAO impact the surface heat fluxes, which comprises the sum of the four components: net surface solar radiation, net surface thermal radiation, sensible heat flux, and latent heat flux. In particular, we analyzed NAO+ and NAO- composites. The results show that the largest contributions to the net radiation balance are attributed to the sensible heat flux and the latent heat fluxes. The highest anomalies in both variables are found over the Norwegian Trench which are related to mixed layer dynamics, circulation changes, and changing in the mean wind field. This modification in the mixed layer dynamics, and mean wind fields will be further investigated.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JD023583/full

The interdecadal change in the relationship between the winter mean surface air temperature (SAT) over East Asia (EA) and the El Niño–Southern Oscillation (ENSO) is investigated using both observational data and a simple general circulation model. The positive phase of the first empirical orthogonal function (EOF) of SAT [surface air temperature] over EA [East Asia] is characterized by significant warming over midlatitude to high-latitude EA and is linked to the Arctic Oscillation. The second EOF (SAT-EOF2) is represented by significant cooling extending from 55°N to the tropics and abnormal warming over high-latitude EA. Focus is given to SAT-EOF2 which has a close relationship with the La Niña-type sea surface temperature (SST) anomalies. A clear shift in SAT-EOF2 is observed in the mid-1980s.

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http://link.springer.com/article/10.1007/s00382-014-2173-x

The most intense El Niño episodes in more than a century occurred after the 1970s climate shift. Previous studies show that the characteristics of the El Niño-Southern Oscillation (ENSO) phenomenon changed synchronously with the shift, but the associated causes are not fully understood. An analysis of the observed tropical Pacific sea surface temperature (SST) anomalies shows that their increase in the eastern part of the basin after the 1970s is not related to the canonical ENSO pattern, but to the tropical Pacific meridional mode (TPMM). We present observational evidence which supports the hypothesis that the change in the TPMM was triggered by the great salinity anomaly (GSA), which manifested in the North Atlantic during the late 1960s. The GSA induced a weak Labrador convection and a SST dipole south of Greenland. The associated atmospheric structure includes a North Pacific Oscillation sea level pressure dipole in the Pacific sector. This excites the TPMM which contributes to the intense El Niño events and to the enhanced ENSO’s asymmetry, observed after the shift. Our results imply that, if the GSA has not an anthropic origin, as was suggested, then the tropical Pacific climate shift has a natural origin. This is supported by the end of the North Atlantic regime in the 1990s and by the rebound of the tropical Pacific after 1998.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL066281/full

Pacific low-frequency variability (timescale > 8 years) exhibits a well-known El Niño-like pattern of basin-scale sea surface temperature, which is found in all the major modes of Pacific decadal climate. Using a set of climate model experiments and observations, we decompose the mechanisms contributing to the growth, peak, and decay of the Pacific low-frequency spatial variance. We find that the El Niño-like interdecadal pattern is established through the combined actions of Pacific meridional modes (MM) and the El Niño–Southern Oscillation (ENSO).

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http://onlinelibrary.wiley.com/doi/10.1002/2014JD022888/full

This study examines multiyear climate variability associated with sea salt aerosols and their contribution to the variability of shortwave cloud forcing (SWCF) using a 150 year simulation for preindustrial conditions of the Community Earth System Model version 1.0. The results suggest that changes in sea salt and related cloud and radiative properties on interannual timescales are dominated by the El Niño–Southern Oscillation cycle.

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http://link.springer.com/article/10.1007/s00382-014-2319-x

El Niño phenomenon is the main oceanic driver of the interannual atmospheric variability and a determinant source of predictability in the tropics and extratropics. Several studies have found a consistent and statistically significant impact of El Niño over the North Atlantic European Sector, which could lead to an improvement of the skill of current seasonal forecast systems over Europe. ….The results obtained suggest, for both hypotheses, an important role of the natural internal variability of the ocean at multidecadal timescales.

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http://link.springer.com/article/10.1007/s00382-014-2233-2

Although the climate is highly expected to change due to global warming, it is unclear whether the El Nino-Southern Oscillation (ENSO) will be more or less active in the future. One may argue that this uncertainty is due to the intrinsic uncertainties in current climate models or the strong natural long-term modulation of ENSO. Here, we propose that the global warming trend cannot significantly modify ENSO amplitude due to weak feedback between the global warming induced tropical climate change and ENSO. By analyzing Coupled Model Intercomparison Project Phase 5 and observation data, we found that the zonal dipole pattern of sea surface temperature [SST; warming in the eastern Pacific and cooling in the western Pacific or vice versa; ‘Pacific zonal mode’ (PZM)] is highly correlated to change in ENSO amplitude.

Do Humans,CO2, Drive Climate? (10)

https://www.researchgate.net/profile/David_Vares/publication/281612324_Earths_Diminishing_Magnetic_Dipole_Moment_is_Driving_Global_Carbon_Dioxide_Levels_and_Global_Warming/links/562fa89f08ae8e12568770a4.pdf

Earth’s Diminishing Magnetic Dipole Moment is Driving Global Carbon Dioxide Levels and Global Warming

Introduction: The consensus of opinion regarding the increases in global temperature as causally connected to anthropogenic sources of CO2 is primarily based upon models rather than quantitative or multivariate analyses of actual data. Because the variables are not experimentally manipulated, even a strong association is still a correlation with the possibility that a third factor produces both changes. Several authors have shown that during the same period as the slow increase in global temperature, the solar corona has expanded and related interplanetary parameters have changed. The global warming apparently occurring on Mars (0.7˚C over 20 years) that is concurrent with terrestrial increases in temperature is more consistent with sources within the solar system than human activities.

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http://www.seipub.org/des/paperInfo.aspx?ID=21810

This paper presents observed atmospheric thermal and humidity structures and global scale simulations of the infrared absorption properties of the Earth’s atmosphere. These data show that the global average clear sky greenhouse effect has remained unchanged with time. A theoretically predicted infrared optical thickness is fully consistent with, and supports the observed value. It also facilitates the theoretical determination of the planetary radiative equilibrium cloud cover, cloud altitude and Bond albedo. In steady state, the planetary surface (as seen from space) shows no greenhouse effect: the all-sky surface upward radiation is equal to the available solar radiation. The all-sky climatological greenhouse effect (the difference of the all-sky surface upward flux and absorbed solar flux) at this surface is equal to the reflected solar radiation. The plane-tary radiative balance is maintained by the equilibrium cloud cover which is equal to the theoretical equilibrium clear sky transfer function. The Wien temperature of the all-sky emission spectrum is locked closely to the thermo-dynamic triple point of the water assuring the maximum radiation entropy. The stability and natural fluctuations of the global average surface temperature of the heterogeneous system are ultimately determined by the phase changes of water. Many authors have proposed a greenhouse effect due to anthropogenic carbon dioxide emissions. The present analysis shows that such an effect is impossible.

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http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0448.1

Conclusion: Changes in heat content are found to be caused mainly by anomalous ocean heat transport convergence (Fig. 6). Variations in ocean heat convergence largely originate in the inflow from the Atlantic proper, and a temporal decomposition of the Atlantic heat transport shows that volume transport anomalies dominate (Fig. 8). Simulated ocean heat anomalies in the northern seas are thus driven mainly by changes in the strength of the northward flowing Atlantic water. A similar decadal-scale oscillation in the strength of the subpolar gyre (Fig. 9b) further supports the close coupling, observed and modeled, between the subpolar North Atlantic and Nordic seas/Arctic Ocean (e.g., Hátún et al. 2005; Glessmer et al. 2014; Jungclaus et al. 2014). A potentially predictable relation between anomalous ocean heat and climate in the northern seas region is furthermore identified. Ocean heat anomalies in the northern seas are reflected in regional sea ice extent and found to influence the atmosphere by driving changes in surface air temperatures through anomalous air–sea fluxes (Fig. 10).

[CO2 not mentioned as a factor influencing ocean heat content changes, or anywhere in the paper.]

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL066749/fullAbstract: For this region [central Antarctica], the emission to space is higher than the surface emission; and the greenhouse effect of CO2 is around zero or even negative, which has not been discussed so far. We investigated this in detail and show that for central Antarctica an increase in CO2 concentration leads to an increased long-wave energy loss to space, which cools the Earth-atmosphere system.

For most of the Antarctic Plateau, GHE-TES [greenhouse effect as measured by the Tropospheric Emission Spectrometer] is close to zero or even slightly negative; i.e., the presence of CO2 increases radiative cooling. Over Greenland, the greenhouse effect of CO2 is also comparatively weak but invariably positive. An evaluation of monthly averages of GHE-TES shows that the increased cooling due to CO2 of Antarctica is strongest during austral spring and autumn. … Central Antarctica is the only place on the planet where increased CO2 concentrations lead to an increased LW energy loss to space [cooling]. In the Northern Hemisphere the lowest, but invariably positive, [CO2] forcing values are seen over Greenland and Eastern Siberia.

[Graph from the paper below indicates that the observed CO2 greenhouse warming effect is weak, close to zero W m-2, for both Antarctica and Greenland relative to the rest of the globe]

http://onlinelibrary.wiley.com/store/10.1002/2015GL066749/asset/image_n/grl53769-fig-0004.png?v=1&s=e020fff98b6acf78d73242ddc49a2603806b7158

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http://onlinelibrary.wiley.com/doi/10.1002/qj.2628/abstract

https://drive.google.com/file/d/0B74u5vgGLaWoSEx0R2c1bGJfUVU/view

Abstract: We find that surface fluxes and radiative heating act as positive feedbacks, favoring self-aggregation, but advection of moist static energy acts as a negative feedback [causes cooling], opposing self-aggregation, for nearly all temperatures and times. Early in the process of self-aggregation, surface fluxes are a positive feedback at all temperatures, shortwave radiation is a strong positive feedback at low surface temperatures but weakens at higher temperatures, and longwave radiation [from greenhouse gases] is a negative feedback [causes cooling] at low temperatures but becomes a positive feedback [causes warming] for temperatures greater than 295–300 K [current Earth temperature is 288 K]. Clouds contribute strongly to the radiative feedbacks, especially at low temperatures [less than 295 K].

5.3 Physical Mechanisms: In the four coldest simulations, (TS = 280K, 285K, 290K, 295K), the longwave radiation [from greenhouse gases] is at first a negative feedback, but in the warmer simulations [>295K], it is an important positive feedback. 7.3 Temperature Dependence of Aggregation: Aggregation occurs in spite of an initially negative longwave feedback at Ts <= 295 K, because this negative feedback is overridden by the combination of a positive surface flux and shortwave feedbacks; recall that the increasing strength of the shortwave feedback with decreasing temperature is largely due to clouds.

[At Earth’s current temperature, CO2/GHG/LW radiation is associated with cooling/negative feedback.]

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http://www.researchgate.net/publication/281111296_RESPONSIVENESS_OF_ATMOSPHERIC_CO2_TO_ANTHROPOGENIC_EMISSIONS_A_NOTE

A statistically significant correlation between annual anthropogenic CO2 emissions and the annual rate of accumulation of CO2 in the atmosphere over a 53-year sample period from 1959-2011 is likely to be spurious because it vanishes when the two series are detrended. The results do not indicate a measurable year to year effect of annual anthropogenic emissions on the annual rate of CO2 accumulation in the atmosphere.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL066942/abstract

Correct representation of the SSTs changes is important for the Northern Hemisphere, while correct representation of stratospheric ozone changes is important for the Southern Hemisphere. The ensemble-mean trend (which captures only the forced response) is nearly always much weaker than trends in reanalyses. This suggests that a large fraction of the recently observed changes [in sea surface temperatures, ozone] may, in fact, be a consequence of natural variability and not a response of the climate system to anthropogenic forcings.

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https://www.researchgate.net/profile/Tongren_Xu2/publication/275036378_A_New_Perspective_about_Climate_Change/links/553078e50cf2f2a588ab233c.pdf

Introduction: What is the leading cause of climate change? In modern times, with continuous development of science and technology, humans are still incapable of controlling climate change, and even fail to know its causes. Climate change has been subject to much attention from politicians, economists, scientists, etc. worldwide. The Earth is an extremely complicated ecosystem. Its climate continuously changes over its long history, including changes induced by solar radiation, volcanic eruptions, etc. Most scholars consider that it is humans that cause global warming. In their point of view, by burning fossil fuel and deforesting, humans caused the increase in greenhouse gas concentration, the changes in sulphide aerosol concentrations, continental surface coverage and land-use changes, etc. Humans have not found the real reasons for climate change mainly because of the limitation of observational data and our research methods. The changes in atmosphere and ocean circulations are widely considered to be main cause leading to natural climate change and influence the climate on land accordingly: these circulatory changes are the primary cause of key climate factor changes at a regional scale. However, why do atmosphere and ocean circulations happen and what are earthquakes and volcanic eruptions caused by? Climate change cannot be comprehended further before answering the above questions. …. [C]elestial bodies regulate themselves continually to achieve a new dynamic equilibrium by absorbing or releasing energy. Regarding the Earth, it regulates its energy in the forms of atmosphere and ocean current cycles, earthquakes, volcanic eruptions, etc. during its high-speed movement. This research proposed that the changes in weather and climate (even the appearance and disappearance of species) are caused by the periodic changes in celestial body orbits. Due to exerting only small effects on climate change, humans have to adapt to climate change passively in most situations.

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http://www.researchgate.net/publication/276276180_An_Estimate_of_The_Centennial_Variability_of_Global_Temperatures

There has been widespread investigation of the drivers of changes in global temperatures. However, there has been remarkably little consideration of the magnitude of the changes to be expected over a period of a few decades or even a century. To address this question, the Holocene records up to 8000 years before present, from several ice cores were examined. The differences in temperatures between all records which are approximately a century apart were determined, after any trends in the data had been removed. The differences were close to normally  distributed. The average standard deviation of temperature was 0.98 ± 0.27 ° C. This suggests that while some portion of the temperature change observed in the 20th century was probably caused by greenhouse gases, there is a strong likelihood that the major portion was due to natural variations.

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http://onlinelibrary.wiley.com/doi/10.1002/jqs.2775/abstract

Research on Quaternary climate change is reviewed from the perspective of the real or potential contribution to improving our ability to predict the climate of the future. For convenience the literature is divided into four timescales: orbital, sub-Milankovitch, Holocene and the last 2000 years. Four ‘challenges’ provide a framework for discussion: better understanding of the way the climate system works, better forecasting of the drivers of climate change, improved estimates of climate sensitivity (change in global mean annual temperature per unit increase in forcing) and evaluation of the models used to predict the climate of the future. Although a great deal of progress has been made, it is concluded that there are some aspects of our scientific culture that limit our potential. These include our tradition of storytelling rather than critical hypothesis testing, an over-emphasis on the role of surface water sinking in the far north Atlantic as a driver of ocean circulation and an attendant under-emphasis on the critical importance of changes in atmospheric circulation, and a lack of rigour in testing the hypothesis that changes in solar irradiance are an important driver of climate change.

Sea Level (22)

http://iopscience.iop.org/article/10.1088/1748-9326/10/8/084024

Sea level rates up to three times the global mean rate are being observed in the western tropical Pacific since 1993 by satellite altimetry. From recently published studies, it is not yet clear whether the sea level spatial trend patterns of the Pacific Ocean observed by satellite altimetry are mostly due to internal climate variability or if some anthropogenic fingerprint is already detectable. We show that subtraction of the IPO contribution to sea level trends through the method of linear regression does not totally remove the internal variability, leaving significant signal related to the non-linear response of sea level to El Niño Southern Oscillation (ENSO). In addition, by making use of 21 CMIP5 coupled climate models, we study the contribution of external forcing to the Pacific Ocean regional sea level variability over 1993–2013, and show that according to climate models, externally forced and thereby the anthropogenic sea level fingerprint on regional sea level trends in the tropical Pacific is still too small to be observable by satellite altimetry.

Furthermore, regressed CMIP5 MME-based sea level spatial trend pattern in the tropical Pacific over the altimetry period do not display any positive sea level trend values that are comparable to the altimetry based sea level signal after having removed the contribution of the decadal natural climate mode. This suggests that the residual positive trend pattern observed in the western tropical Pacific is not externally forced and thereby not anthropogenic in origin. In addition the amplitude of the sea level spatial trend pattern from regressed CMIP5 MME is low over the altimetry period in the tropical Pacific. This amplitude is significantly lower than the expected error in trend patterns from satellite altimetry (in the order of 2 mm yr-1 to 3 mm yr−1, Ablain et al 2015, Couhert et al 2015) and suggest that satellite altimetry measurement is still not accurate enough to detect the anthropogenic signal in the 20 year tropical Pacific sea level trends.

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http://link.springer.com/article/10.1007/s12665-015-4050-2

The worldwide average tide gauge data show that sea level is consistently slowly rising, without any acceleration component over the last decades as it is in North Carolina. Here, we review the relevant data, both worldwide and for the specific area of North Carolina. The acceleration-free long-term tide gauge results reported here show that relative sea levels are only oscillating worldwide. … If we want to study the changes in the rate of sea levels over the satellite altimeter era, we have to consider only the tide gauges that were already satisfying the minimum 60 years length requirement 20 years ago. There are 100 tide gauges of PSMSL [Permanent Service for Mean Sea Level] having length more than 80 years at the present time, and the average rate of rise for them is 0.24 ± 0.15 mm/year [~1 inch per century]. For these 100 tide gauges, the rate of rise has been moving up and down over the last 20 years without any sign of positive or negative accelerations.   If the ice caps are melting at an increased rate and the ocean waters are expanding because they are warming at a faster rate, then the sea level rise should be accelerating, but this is not the case.

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http://geology.gsapubs.org/content/early/2015/04/27/G36555.1.abstract?papetoc

The geological stability and existence of low-lying atoll nations is threatened by sea-level rise and climate change. Funafuti Atoll, in the tropical Pacific Ocean, has experienced some of the highest rates of sea-level rise (∼5.1 ± 0.7 mm/yr), totaling ∼0.30 ± 0.04 m over the past 60 yr. We analyzed six time slices of shoreline position over the past 118 yr at 29 islands of Funafuti Atoll to determine their physical response to recent sea-level rise. Despite the magnitude of this rise, no islands have been lost, the majority have enlarged, and there has been a 7.3% increase in net island area over the past century (A.D. 1897–2013). There is no evidence of heightened erosion over the past half-century as sea-level rise accelerated. Reef islands in Funafuti continually adjust their size, shape, and position in response to variations in boundary conditions, including storms, sediment supply, as well as sea level. Results suggest a more optimistic prognosis for the habitability of atoll nations and demonstrate the importance of resolving recent rates and styles of island change to inform adaptation strategies.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JC010716/full

Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. This has motivated a number of authors to search for already existing accelerations in observations, which would be, if present, vital for coastal protection planning purposes. No scientific consensus has been reached yet as to how a possible acceleration could be separated from intrinsic climate variability in sea level records. This has led to an intensive debate on its existence and, if absent, also on the general validity of current future projections.

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http://onlinelibrary.wiley.com/doi/10.1002/2015JC011139/full

According to long-term sea level reconstruction and steric sea level data, regional sea levels in the tropical Pacific have oscillated between east and west on a decadal time scale over the past 60 years, but the oscillation has been intensified significantly in the last three decades. Using conditional composite analysis, we show that the recent intensification in sea level variability is caused by modulation between the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO), i.e., an El Niño in a positive PDO or a La Niña in a negative PDO phase. Our analysis of meteorological fields indicates that atmospheric circulation associated with the changes in ENSO-PDO phase relationship plays a positive role in enhancing the decadal sea level oscillation. The intensified sea level oscillation, when superimposed on the global trend of sea level rise, will have profound implications for coastal communities, therefore, the combined effect of PDO and ENSO should be taken into account in the decadal sea level prediction in the tropical Pacific.

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http://link.springer.com/article/10.1007/s10236-014-0805-7

We show that it is essentially the vertical movement of the thermocline that governs most of the observed sea level changes and trends in the tropical Pacific. Furthermore, we also show that in the equatorial band, the changes in the upper ocean thermal structure are in direct response to the zonal wind stress. Away from the equatorial band (say, within 5°–15° latitude), the changes in the upper ocean thermal structure are consistent with the wind stress-generated Rossby waves. We also estimate the contribution of the Interdecadal Pacific Oscillation (IPO) on the vertical thermal structure of the tropical Pacific Ocean. Removing the IPO contribution to the upper layer steric sea level provides a non-negligible residual pattern, suggesting that IPO-related internal ocean variability alone cannot account for the observed trend patterns in the Pacific sea level. It is likely that the residual signal may also reflect non-linear interactions between different natural modes like El Niño Southern Oscillation (ENSO), IPO, etc.

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http://www.geosociety.org/gsatoday/archive/25/8/pdf/i1052-5173-25-8-4.pdf

Today, relative sea-level rise (3.4 mm/yr) is faster in the Chesapeake Bay region than any other location on the Atlantic coast of North America, and twice the global average eustatic rate (1.7 mm/yr). Dated interglacial deposits suggest that relative sea levels in the Chesapeake Bay region deviate from global trends over a range of timescales. Glacio-isostatic adjustment of the land surface from loading and unloading of continental ice is likely responsible for these deviations, but our understanding of the scale and timeframe over which isostatic response operates in this region remains incomplete because dated sea-level proxies are mostly limited to the Holocene and to deposits 80 ka or older.

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http://tsijournals.com/upload/ESAIJ_3873/Ereprint_ESAIJ_3873.pdf

Because of the quasi-60 years oscillations, sea level records longer than 60 years are required to identify any long-term trends that might appear in the data and properly assess velocities and accelerations. Cherry picking of short time windows in selected locations may support almost any statement, from sharply accelerating to sharply decelerating sea level rise, or even falling sea level. … The latest PSMSL Table of Relative Mean Sea Level Secular Trends update 14-Feb-2014 (www.psmsl.org) proposes the relative rates of rise computed for 2133 tide gauges of variable record length (maximum 183, minimum 21, average 56.5 years) with the more recent, shortest readings collected mostly in areas of subsidence and a strongly non uniform geographical coverage. The average relative rate of rise of the 2133 tide gauges is 1.04±0.45 mm/year, but this number has very little significance. By using only the 170 tide gauges of PSMSL extending over more s than 60 years at the present time, Parker (2014b) computed an average relative rate of rise of 0.25±0.19 mm/year. … The relative rate of rise of sea levels in these latter tide gauges is on average about the same now as 20 years ago. The average rate of rise for them is now 0.24±0.15 mm/year. In addition, for these 100 tide gauges, the rate of rise has been rising and falling over the last 20 years without any sign of positive or negative accelerations. The average rate of rise for them was about the same in 1993. Therefore, the world wide average relative sea level result derived from tide gauge of sufficient quality and length shows slow rising with no acceleration since 1993. [T]he absolute sea level rise velocity determined from the worldwide average tide gauge is probably smaller than 0.24 mm/year, not accelerating, and at least partly due to subsidence at the tide gauge. This result is in striking contrast to the global mean sea level determined from satellite altimeter-based computations and they cannot both be true.

The nominal satellite altimeter-based determination of the absolute global mean sea level is actually a computational result rather than a direct observation. It is obtained by correcting the satellite altimeter raw signal with algorithms having many features in common with the climate models. Regardless of any modeling problems, Carter et al. (2014) pointed out that estimates of sea-level change from satellite-collected data remain problematic, because of the many uncertainties in data collection and processing. In particular, there is inconsistency between the results derived by different research groups, with all results depending upon the accuracy of complex adjustments, some of which lack in- dependent verification, plus the severe problem that the signal being sought may be less than the noise level of the data being used. Many corrections applied to all satellite altimeter measurements of sea-level since 2003 had the effect of changing a sea-level record that showed no trend or a gentle rise into one that projects high rates of rise. The trend 1992 to 2000 was +0 mm/year. This trend was increased by 2.3 mm/year in 2003 and then by another 0.8 mm/year introduced in 2008 to make the present 3.1 mm/year. … Even without the corrections, the satellite altimeter results are unreliable. Processing of all satellite altimeter data takes place against the background of known errors that at least match, if not exceed, the sea-level signal being sought.

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http://link.springer.com/article/10.1007%2Fs12517-014-1739-6#page-2

Abstract: The global mean sea level (GMSL) changes derived from modelling do not match actual measurements of sea level and should not be trusted. Compilations of individual tide gauges of sufficient quality and length provide much more reliable information. The present work is a contribution towards a better understanding of the observed of sea levels in India and its relation to worldwide observations. The latest average relative rate of rise of worldwide sea levels from a compilation of 170 stations with more than 60 years of data returns an average relative rate of rise +0.25 mm/year. The individual rates of rise are about constant in between subsequent updates suggesting the absence of any acceleration. Observation in key sites suggests a similarly stable pattern. Along the coastline of India, the average rate of rise of sea level is +1.06 mm/year computed by considering the 11 longest tide gauges of average length 51 years. Shorter records may overrate the sea level rate of rise because of the local phasing of the quasi-60-year oscillation. In the longest records, the rates of rise are decreasing since 1955.

 

Introduction: The reconstructed global temperatures roughly follow the anthropogenic carbon dioxide emission only during the last phase of a quasi-60-year natural oscillation between 1970 and 2000. The similarity is lost prior of 1970 and since 2000.  The carbon dioxide content of the atmosphere rose throughout this period.  There is no correlation between the temperature record and atmospheric carbon dioxide. The anthropogenic in carbon dioxide is said to have started in 1945, and this also shows no correlation to temperature.

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http://www.degruyter.com/view/j/quageo.2015.34.issue-1/quageo-2015-0003/quageo-2015-0003.xml

The paper revisits the Isle of the Dead benchmark and the Sydney, Fort Denison tide gauge to confirm that long term, high quality tide gauges are acceleration free, consistently to the analysis of key sites suggesting the sea levels are not sharply raising following the carbon dioxide emissions. The paper also discusses the flaws of the IPCC AR5 Chapter13 Sea levels. The time history of the relative rate of rise computed by linear fitting of the data locally collected by tide gauges is the best parameter to assess the effect of global warming providing length and quality requirements are satisfied. There is no reason to search for less reliable alternative methods because the climate models predicted different trends. The Global Positioning System (GPS) inferred vertical tide gauge velocity suffers of significant inaccuracies. Larger inaccuracies are provided by the satellite altimetry Global Mean Sea Level (GMSL) that is a computation and not a measurement.

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http://link.springer.com/article/10.1007/s10651-014-0293-4

The location of tide gauges is not random. If their locations are positively (negatively) correlated with sea level rise (SLR), estimates of global SLR will be biased upwards (downwards). Using individual tide gauges obtained from the Permanent Service for Mean Sea Level during 1807–2010, we show that tide gauge locations in 2000 were independent of SLR as measured by satellite altimetry. Therefore these tide gauges constitute a quasi-random sample, and inferences about global SLR obtained from them are unbiased. Using recently developed methods for nonstationary time series, we find that sea levels rose in 7 % of tide gauge locations and fell in 4 %. The global mean increase is 0.39–1.03 mm/year. However, the mean increase for locations where sea levels are rising is 3.55–4.42 mm/year. These findings are much lower than estimates of global sea level (2.2 mm/year) reported in the literature and adopted by IPCC (2014), and which make widespread use of imputed data for locations which do not have tide gauges. We show that although tide gauge locations in 2000 are uncorrelated with SLR, the global diffusion of tide gauges during the 20th century was negatively correlated with SLR. This phenomenon induces positive imputation bias in estimates of global mean sea levels because tide gauges installed in the 19th century happened to be in locations where sea levels happened to be rising.

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http://link.springer.com/article/10.1007%2Fs10584-015-1346-x?utm_content=bufferc4771&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

In a recent paper Bamber and Aspinall (Nat Clim Change 3:424–427, 2013) (BA13) investigated the sea-level rise that may result from the Greenland and Antarctic ice sheets during the 21st century. Using data from an expert judgment elicitation, they obtained a final high-end (P95) value of +84 cm integrated sea-level change from the ice sheets for the 2010–2100 period. However, one key message was left largely undiscussed: The experts had strongly diverging opinions about the ice-sheet contributions to sea-level rise. We argue that such (lack of) consensus should form an essential and integral part of the subsequent analysis of the data. By employing a method that keeps the level of consensus included, and that is also more robust to outliers and less dependent on the choice of the underlying distributions, we obtain on the basis of the same data a considerably lower high-end estimate for the ice-sheet contribution, +53 cm (+38-77 cm interquartile range of “expert consensus”). The method compares favourably with another recent study on expert judgement derived sea-level rise by Horton et al. (Q Sci Rev 84:1–6, 2014). Furthermore we show that the BA13 results are sensitive to a number of assumptions, such as the shape and minimum of the underlying distribution that were not part of the expert elicitation itself. Our analysis therefore demonstrates that one should be careful in considering high-end sea-level rise estimates as being well-determined and fixed numbers.

Higher Sea Levels with Low CO2 (Late Holocene)

http://www.sciencedirect.com/science/article/pii/S0033589415000642

In northeastern Kuwait, ancient beach ridges and associated berms are separated from the present shoreline by a 4–6 km-wide sabkha. A diverse mollusk fauna in the beach ridges attests to a former open marine environment. A total of 21 AMS dates were obtained in this study. Thirteen mollusk samples from beach ridges yielded AMS dates ranging from ~ 6990 cal yr BP in the southeast to ~ 3370 cal yr BP in the northwest, suggesting a southeast to northwest age progression during the Holocene transgression. In contrast, four samples from berms throughout the study area yielded AMS dates of 5195–3350 cal yr BP showing no age progression; these berms consist largely of Conomurex persicus gastropods that aggregated by storms during a [sea level] highstand at ~ 5000–3500 cal yr BP [before present]. The berms are presently at ~ + 6 m above sea level, 2–3 m above the beach ridges. Human settlements were common on the ridge crests before and after the highstand [~6 m above present levels]. Regression to present-day sea level commenced after the highstand, which is when the sabkha began forming.

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http://onlinelibrary.wiley.com/doi/10.1111/ter.12187/full

Results: The data shows a period of RSL[relative sea level] highstand at c. 2.2 m above present MSL [mean sea level] between c. 5.0 and 4.0 ka BP [5,000 to 4,000 years before present] .After that, RSL drops by c. 1.3 m between c. 4.0 and 3.4 ka BP to an elevation roughly 1 m above present MSL. Since then, RSL has been falling at more or less even rates.

Discussion: Yu et al. (2007) present evidence for a sea-level ‘jump’ of several meters occurring at 7.6 ka bp in SE Sweden, and data suggesting RSL changes with a similar timing and magnitude were obtained for a field site in the southern Gulf of Finland (Rosentau et al., 2013). The suddenness of the RSL change has been attributed to the collapse of parts of the Laurentide Ice Sheet (Blanchon and Shaw, 1995; Carlson et al., 2007), though the global indications and the potential triggers of such a eustatic event remain inconclusive (Törnqvist and Hijma, 2012).

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http://www.sciencedirect.com/science/article/pii/S0025322715000869

A rapid sea-level rise, at an averaged rate of approximately 6.1 mm/yr− 1, occurred between 8300 and 7000 cal. yr BP. Since then, the pace of relative sea-level rise slowed and non-eustatic factors, namely terrigenous sediment supply and coastal dynamics, became dominant in the evolution of the estuary.

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http://www.sciencedirect.com/science/article/pii/S0033589415000381

Late Quaternary reflooding of the Persian Gulf climaxed with the mid-Holocene highstand previously variously dated between 6 and 3.4 ka. Examination of the stratigraphic and paleoenvironmental context of a mid-Holocene whale beaching allows us to accurately constrain the timing of the transgressive, highstand and regressive phases of the mid- to late Holocene sea-level highstand in the Persian Gulf.  Mid-Holocene transgression of the Gulf surpassed today’s sea level by 7100–6890 cal yr BP, attaining a highstand of > 1 m above current sea level shortly after 5290–4570 cal yr BP before falling back to current levels by 1440–1170 cal yr BP.  These new ages refine previously reported timings for the mid- to late Holocene sea-level highstand published for other regions. By so doing, they allow us to constrain the timing of this correlatable global eustatic event more accurately.

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http://onlinelibrary.wiley.com/doi/10.1002/esp.3663/abstract

The foredunes overlie upper beach deposits located up to >2 m above the present upper beach level and provide evidence for a higher mid-Holocene RSL [relative sea level].

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http://www.vims.edu/research/units/labgroups/coastal_geology/_Publication_PDFs/Brazil%20Coastal%20Seds%20Paper%202015.pdf

Introduction: In southern Brazil, falling RSL [relative sea level] following a 2–4 m [above present sea level] highstand at 5 to 6 ka [5,000 to 6,000 years ago] forced coastal progradation. This reworked abundant shelf and fluvial sediment, smoothing the irregular, headland-dominated coastline, filling coastal embayments, and developing 2–7-km wide strandplains (mainland-connected parallel / semiparallel beach and/or dune ridges separated by shallow swales; Roy et al. 1994).

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http://www.sciencedirect.com/science/article/pii/S0277379114004843

Highlights: Isostatic response to deglaciation continues in the late Holocene.

Formerly glaciated areas show variable RSL [relative sea level] change; where data are present, highstands of RSL occur immediately post-deglaciation and in the mid to late Holocene. Sites at the periphery and distant to formerly glaciated areas demonstrate a continuous rise in RSL [relative sea level] with a decreasing rate through time due to the collapse of the peripheral forebulge and the reduction in meltwater input during deglaciation. Late Holocene RSL [relative sea level] change varies spatially from falling at 0.7 ± 0.8 mm a−1 in southern British Columbia to rising at 1.5 ± 0.3 mm a−1 in California. The different sea-level histories are an ongoing isostatic response to deglaciation of the Cordilleran and Laurentide Ice Sheets.

Rapidly Fluctuating Sea Levels with Stable CO2

http://www.sciencedirect.com/science/article/pii/S0025322715300281

Episodic, rapid sea-level rises on the central Mediterranean shelves after the Last Glacial Maximum: A review

The evidence presented here confirms drowned shorelines documented elsewhere at similar water depths and shows that melt-water pulses have punctuated the post-glacial relative sea-level rise with rates up to 60 mm/yr. [6 meters per century] for a few centuries. 

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http://www.sciencedirect.com/science/article/pii/S0025322715300402

A fast-paced post-glacial sea-level rise and subsequent mid-Holocene sea-level highstand are well documented at several far field locations away from the presence of former ice sheets but sea-level development during the late Holocene remains ambiguous. … Thick (> 10 cm) fossil oyster visors above the equivalent modern growth suggest higher relative sea-levels in the past (i.e. > 1200 cal. yr BP [prior to 1,200 years before present]). Radiocarbon analyses of the modern oyster visors suggest continuous lateral accumulation over the past ~ 800 yr which implies relatively stable sea-level over this period. The modern and fossil dataset defines a distinct and rapid relative ~ 1 m sea-level fall between 1200 and 800 cal. yr BP. Whether the sea-level fall was stepped or followed a broader smooth/monotonic pattern is unclear. The timing coincides with the initiation of some inshore fringing coral reefs in the Great Barrier Reef region and other major geomorphological changes along the coastal zone. A combination of various factors may have been the driving mechanism behind this relative sea-level fall with rates between 1.0 to 5.2 mm yr− 1.

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http://www.sciencedirect.com/science/article/pii/S0277379114004144

Relative sea-level fell at −0.7 to −0.9 mm yr−1 over the past 3300 years in NW Norway

Erroneous Climate Models and the Pause (25)

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2605.html

Despite a steady increase in atmospheric greenhouse gases (GHGs), global-mean surface temperature (T) has shown no discernible warming since about 2000, in sharp contrast to model simulations, which on average project strong warming. The recent slowdown in observed surface warming has been attributed to decadal cooling in the tropical Pacific, intensifying trade winds,  changes in El Niño activity, increasing volcanic activity and decreasing solar irradiance. Earlier periods of arrested warming have been observed but received much less attention than the recent period, and their causes are poorly understood. Here we analyse observed and model-simulated global T fields to quantify the contributions of internal climate variability (ICV) to decadal changes in global-mean T since 1920. We show that the Interdecadal Pacific Oscillation (IPO) has been associated with large T anomalies over both ocean and land. Combined with another leading mode of ICV, the IPO explains most of the difference between observed and model-simulated rates of decadal change in global-mean T since 1920, and particularly over the so-called ‘hiatus’ period since about 2000. We conclude that ICV, mainly through the IPO, was largely responsible for the recent slowdown, as well as for earlier slowdowns and accelerations in global-mean T since 1920, with preferred spatial patterns different from those associated with GHG-induced warming or aerosol-induced cooling. Recent history suggests that the IPO could reverse course and lead to accelerated global warming in the coming decades

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL063299/full

Introduction: There is significant decadal variability in OHC, which complicates the view of a simple linear trend, and this makes discussion of mechanisms and pathways of warming difficult. The most recent decade has seen the global warming signal (from surface air temperatures) undergoing a hiatus, which has been explained by some authors as increased uptake of heat by the deep ocean [Meehl et al., 2011; Balmaseda et al., 2013a; Kosaka and Xie, 2013; England et al., 2014]. These authors attribute the hiatus to La Niña and Pacific decadal variability enhancing subduction of warm waters and upwelling of cold waters, but the Atlantic Ocean also shows similar behavior of increased deep ocean heat uptake during hiatus periods [Meehl et al., 2011; Balmaseda et al., 2013a].

Discussion: Below 700 m, agreement among reanalyses is poor. This is particularly important in view of arguments suggesting that extensive deep ocean warming may compensate for the “hiatus” in global warming of surface air temperature since 2000 [Balmaseda et al., 2013a]. In the North Atlantic, all our reanalyses and objectively analyzed data show a hiatus with zero warming in 0–700 m during 2005–2013.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064458/full

The recent warming “hiatus” is subject to intense interest, with proposed causes including natural forcing and internal variability. Here we derive samples of all natural and internal variability from observations and a recent proxy reconstruction to investigate the likelihood that these two sources of variability could produce a hiatus or rapid warming in surface temperature. The likelihood is found to be consistent with that calculated previously for models and exhibits a similar spatial pattern, with an Interdecadal Pacific Oscillation-like structure, although with more signal in the Atlantic than in model patterns. The number and length of events increases if natural forcing is also considered, particularly in the models. From the reconstruction it can be seen that large eruptions, such as Mount Tambora in 1815, or clusters of eruptions, may result in a hiatus of over 20 years, a finding supported by model results.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062669/abstract

Observational analyses of running 5-year ocean heat content trends (Ht) and net downward top of atmosphere radiation (N) are significantly correlated (r~0.6) from 1960 to 1999, but a spike in Ht [ocean heat content trends] in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations. Variations in N between 1960 and 2000 were dominated by volcanic eruptions, and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5). We find an observation-based reduction in N of -0.31±0.21 Wm-2 between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear. While present-day anomalies of N in the CMIP5 ensemble mean and observations agree, this may be due to a cancellation of errors in outgoing longwave and absorbed solar radiation.

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2608.html

The El Niño/Southern Oscillation (ENSO) is the leading mode of interannual climate variability. However, it is unclear how ENSO has responded to external forcing, particularly orbitally induced changes in the amplitude of the seasonal cycle during the Holocene. Here we present a reconstruction of seasonal and interannual surface conditions in the tropical Pacific Ocean from a network of high-resolution coral and mollusc records that span discrete intervals of the Holocene. We identify several intervals of reduced variance in the 2 to 7 yr ENSO band that are not in phase with orbital changes in equatorial insolation, with a notable 64% reduction between 5,000 and 3,000 years ago. We compare the reconstructed ENSO variance and seasonal cycle with that simulated by nine climate models that include orbital forcing, and find that the models do not capture the timing or amplitude of ENSO variability, nor the mid-Holocene increase in seasonality seen in the observations; moreover, a simulated inverse relationship between the amplitude of the seasonal cycle and ENSO-related variance in sea surface temperatures is not found in our reconstructions. We conclude that the tropical Pacific climate is highly variable and subject to millennial scale quiescent periods. These periods harbour no simple link to orbital forcing, and are not adequately simulated by the current generation of models.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062775/abstract

The observed global mean surface air temperature (GMST) has not risen over the last 15 years, spurring outbreaks of skepticism regarding the nature of global warming and challenging the upper range transient response of the current-generation global climate models. Recent numerical studies have, however, tempered the relevance of the observed pause in global warming by highlighting the key role of tropical Pacific internal variability. Here we first show that many climate models overestimate the influence of the El Niño–Southern Oscillation on GMST, thereby shedding doubt on their ability to capture the tropical Pacific contribution to the hiatus. Moreover, we highlight that model results can be quite sensitive to the experimental design. We argue that overriding the surface wind stress is more suitable than nudging the sea surface temperature for controlling the tropical Pacific ocean heat uptake and, thereby, the multidecadal variability of GMST. Using the former technique, our model captures several aspects of the recent climate evolution, including the weaker slowdown of global warming over land and the transition toward a negative phase of the Pacific Decadal Oscillation. Yet the observed global warming is still overestimated not only over the recent 1998–2012 hiatus period but also over former decades, thereby suggesting that the model might be too sensitive to the prescribed radiative forcings.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062773/abstract

China experiencing the recent warming hiatus

Based on the homogenized data set, we analyze changes in mean temperature and some extreme temperature indices over China since 1961 and especially during the recent warming hiatus period (1998–2012) in a global average context. The result shows that the decrease of annual mean maximum has contributed most to the decreases in overall mean temperature and in diurnal temperature range (DTR) during the warming hiatus period. In most parts of China except the southwest, the summer mean maximum temperature (TxS) shows the largest increase, while the winter mean minimum temperature (TnW) indicates slight cooling trends. These changes have augmented the seasonal cycle and increased the likelihood of extreme warm and cold events. Further analyses reveal that the increases in TxS [maximum temperature] are significantly correlated with concurrent increases in solar radiation. In southwest China, the annual mean temperature, TxS, TnW, and DTR increased during 1998–2012, possibly related to increased dryness in this region during the hiatus period.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064884/abstract

Our study examined the recent global warming hiatus on the land surface using an area-weighted summary of a scale-dependent phenomenon with substantial spatiotemporal heterogeneity, and revealed the winter cooling in the Northern Hemisphere low-mid latitudes in 1999-2008 as the major contributor to the global warming hiatus on land surface in 2005.

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http://link.springer.com/article/10.1007%2Fs00376-015-5016-8

The climatological mean state, seasonal variation and long-term upward trend of 1979–2005 latent heat flux (LHF) in historical runs of 14 coupled general circulation models from CMIP5 (Coupled Model Intercomparison Project Phase 5) are evaluated against OAFlux (Objectively Analyzed air–sea Fluxes) data. Inter-model diversity of these models in simulating the annual mean climatological LHF is discussed. Results show that the models can capture the climatological LHF [latent heat flux] fairly well, but the amplitudes are generally overestimated. Model-simulated seasonal variations of LHF match well with observations with overestimated amplitudes. The possible origins of these biases are wind speed biases in the CMIP5 models. Inter-model diversity analysis shows that the overall stronger or weaker LHF over the tropical and subtropical Pacific region, and the meridional variability of LHF, are the two most notable diversities of the CMIP5 models. Regression analysis indicates that the inter-model diversity may come from the diversity of simulated SST and near-surface atmospheric specific humidity. Comparing the observed long-term upward trend, the trends of LHF and wind speed are largely underestimated, while trends of SST and air specific humidity are grossly overestimated, which may be the origins of the model biases in reproducing the trend of LHF.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0099.1

Compared to precipitation extremes calculated from a high-resolution daily observational dataset in China during 1960–2005, simulations in 31 climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) have been quantitatively assessed using skill-score metrics. Four extreme precipitation indices, including the total precipitation (PRCPTOT), maximum consecutive dry days (CDD), precipitation intensity (SDII), and fraction of total rainfall from heavy events (R95T) are analyzed. Results show that CMIP5 models still have wet biases in western and northern China. Especially in western China, the models’ median relative error is about 120% for PRCPTOT; the 25th and 75th percentile errors are of 70% and 220%, respectively. However, there are dry biases in southeastern China, where the underestimation of PRCPTOT reach 200 mm.

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http://www.sciencemag.org/content/early/2015/07/08/science.aaa4521.abstract

“Recent hiatus caused by decadal shift in Indo-Pacific heating”

Recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature in the most recent decade. Some of these studies seem to support the idea of internal variability and/or rearrangement of heat between the surface and the ocean interior. Others suggest that radiative forcing might also play a role. Our examination of observational data over the past two decades shows some significant differences compared to model results from reanalyses, and provides the most definitive explanation of how the heat was redistributed. We find that cooling in the top 100-meter layer of the Pacific Ocean was mainly compensated by warming in the 100- to 300-meter layer of the Indian and Pacific Oceans in the past decade since 2003.

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http://www.ocean-sci-discuss.net/12/1471/2015/osd-12-1471-2015.html

The northern limb of the Atlantic thermohaline circulation and its transport of heat and salt towards the Arctic strongly modulates the climate of the Northern Hemisphere. Presence of warm surface waters prevents ice formation in parts of the Arctic Mediterranean and ocean heat is in critical regions directly available for sea-ice melt, while salt transport may be critical for the stability of the exchanges. Hereby, ocean heat and salt transports play a disproportionally strong role in the climate system and realistic simulation is a requisite for reliable climate projections. The inconsistency between model results and observational data is here explained by the inability of coarse resolution models to simulate the overflow across the IFR (IF-overflow), which feeds back on the simulated IF-inflow.

——

http://onlinelibrary.wiley.com/doi/10.1002/joc.4519/full

Introduction: Global temperature evolution during the 20th century has been described and summarized in the IPCC-2013 AR5 Report (Stocker et al., 2013)from databases compiled in different institutions by Hansen et al. (2010), Lawrimore et al. (2011), Jones et al. (2012), and Rohde et al. (2013). The first warming phase was followed by a cooling period during 1940–1970, and then rapid warming occurred until the end of the century. During the most recent years, warming appears to have stopped or decreased in intensity, with this period being called a hiatus (Easterling and Wehner, 2009; Fyfe et al., 2013; Kosaka and Xie, 2013). The hiatus, as defined by the lack of a statistically significant warming trend line (Meehl, 2015), is receiving increasing attention because it was not correctly predicted in model outputs (Soon et al., 2004; Rahmstorf et al., 2007; Stockwell, 2009; Lüdecke et al., 2011; Cohen et al., 2013; Fyfe et al., 2013).

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064291/abstract

This article reports on the accuracy in aerosol- and cloud-free conditions of the radiation parameterizations used in climate models. Accuracy is assessed relative to observationally-validated reference models for fluxes under present-day conditions and forcing (flux changes) from quadrupled concentrations of carbon dioxide. Agreement among reference models is typically within 1 W/M2, while parameterized calculations are roughly half as accurate in the longwave and even less accurate, and more variable, in the shortwave. Absorption of shortwave radiation is underestimated by most parameterizations in the present day and has relatively large errors in forcing. Error in present-day conditions is essentially unrelated to error in forcing calculations. Recent revisions to parameterizations have reduced error in most cases. A dependence on atmospheric conditions, including integrated water vapor, means that global estimates of parameterization error relevant for the radiative forcing of climate change will require much more ambitious calculations.

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http://onlinelibrary.wiley.com/doi/10.1002/2014GL062596/abstract?campaign=wolacceptedarticle

Over the last 15 years, global mean surface temperatures exhibit only weak trends. Recent studies have attempted to attribute this so called temperature hiatus to several causes, amongst them incomplete sampling of the rapidly warming Arctic region. We here examine zonal mean temperature trends in satellite-based tropospheric data sets (based on data from (Advanced) Microwave Sounding Unit and Global Navigation Satellite System Radio Occultation instruments) and in global surface temperatures (HadCRUT4). Omission of successively larger polar regions from the global mean temperature calculations, in both tropospheric and surface data sets, shows that data gaps at high latitudes cannot explain the observed differences between the hiatus and the prehiatus period. Instead, the dominating causes of the global temperature hiatus are found at low latitudes. The combined use of several independent data sets, representing completely different measurement techniques and sampling characteristics, strengthens the conclusions.

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http://www.nature.com/nature/journal/v517/n7536/full/nature14117.html

Most present-generation climate models simulate an increase in global-mean surface temperature (GMST) since 1998, whereas observations suggest a warming hiatus. It is unclear to what extent this mismatch is caused by incorrect model forcing, by incorrect model response to forcing or by random factors.

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http://www.nature.com/news/indian-ocean-may-be-key-to-global-warming-hiatus-1.17505

For now, it seems that the hunt for the missing heat may continue. But scientists say it is important to get to the bottom of the story to fully explain the current hiatus and prepare for others that might occur in the future. “We need to understand the energy imbalance of the Earth,” Lee says.

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http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2531.html

Since the end of the twentieth century, global mean surface temperature has not risen as rapidly as predicted by global climate models (GCMs). This discrepancy has become known as the global warming ‘hiatus’ and a variety of mechanisms have been proposed to explain the observed slowdown in warming. Focusing on internally generated variability, we use pre-industrial control simulations from an observationally constrained ensemble of GCMs and a statistical approach to evaluate the expected frequency and characteristics of variability-driven hiatus periods and their likelihood of future continuation. Given an expected forced warming trend of ~0.2 K per decade, our constrained ensemble of GCMs implies that the probability of a variability-driven 10-year hiatus is ~10%, but less than 1% for a 20-year hiatus. 

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL063239/abstract

Annual incident solar radiation at the top of atmosphere (TOA) should be independent of longitudes. However, in many Coupled Model Intercomparison Project phase 5 (CMIP5) models, we find that the incident radiation exhibited zonal oscillations, with up to 30 W/m2 of spurious variations. This feature can affect the interpretation of regional climate and diurnal variation of CMIP5 results. This oscillation is also found in the Community Earth System Model (CESM). We show that this feature is caused by temporal sampling errors in the calculation of the solar zenith angle. The sampling error can cause zonal oscillations of surface clear-sky net shortwave radiation of about 3 W/m2 when an hourly radiation time step is used, and 24 W/m2 when a 3-hour radiation time step is used.

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http://www.nature.com/ngeo/journal/v8/n6/full/ngeo2438.html

Global mean surface warming has stalled since the end of the twentieth century, but the net radiation imbalance at the top of the atmosphere continues to suggest an increasingly warming planet. This apparent contradiction has been reconciled by an anomalous heat flux into the ocean, induced by a shift towards a La Niña-like state with cold sea surface temperatures in the eastern tropical Pacific over the past decade or so. A significant portion of the heat missing from the atmosphere is therefore expected to be stored in the Pacific Ocean. However, in situ hydrographic records indicate that Pacific Ocean heat content has been decreasing. Here, we analyse observations along with simulations from a global ocean–sea ice model to track the pathway of heat. We find that the enhanced heat uptake by the Pacific Ocean has been compensated by an increased heat transport from the Pacific Ocean to the Indian Ocean, carried by the Indonesian throughflow. As a result, Indian Ocean heat content has increased abruptly, which accounts for more than 70% of the global ocean heat gain in the upper 700 m during the past decade. We conclude that the Indian Ocean has become increasingly important in modulating global climate variability.

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http://www.nature.com/news/climatologists-to-physicists-your-planet-needs-you-1.17270?WT.mc_id=TWT_NatureNews

There is a misconception that the major challenges in physical climate science are settled. “That’s absolutely not true,” says Sandrine Bony, a climate researcher at the Laboratory of Dynamic Meteorology in Paris. “In fact, essential physical aspects of climate change are poorly understood.”…  [U]nderstanding how the warming climate might affect cloud cover, which influences the amount of sunlight reflected back into space and thus Earth’s energy cycle, is key to addressing these uncertainties. A major weakness of current climate models is their limited ability to simulate the convection by which humid air is lifted into the atmosphere and which drives cloud formation and rainfall. In some instances, the models cannot even agree on whether the future will bring more rain or less.

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2414.html

Equilibrium climate sensitivity to a doubling of CO2 falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models.

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http://onlinelibrary.wiley.com/doi/10.1002/qj.2530/abstract

The observed North Pacific high-pressure surface response during solar maximum is only simulated in some models, of which there are no distinguishing model characteristics. The lagged North Atlantic surface response is reproduced in both high- and low-top models, but is more prevalent in the former. In both cases, the magnitude of the [modeled] response is generally lower than in observations.

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http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-14-0124.1

The modeled spatial and temporal patterns of the leading EOFs [empirical orthogonal function]  ocean show large differences from observations, indicating that the physical mechanisms governing the diurnal cycle of oceanic ice clouds are more complicated and not well simulated by the current climate models.

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http://onlinelibrary.wiley.com/doi/10.1002/wcc.338/abstract

Global climate models experience great difficulties simulating eastern boundary regions, with one of the most notable shortcomings being warm sea-surface temperature biases that often exceed 5 K.

Glaciers, Ice Sheets, Sea Ice (23)

http://onlinelibrary.wiley.com/doi/10.1002/2015GL065750/full

The Amundsen Sea sector of the West Antarctic ice sheet has been losing mass in recent decades; however, long records of snow accumulation are needed to place the recent changes in context. Here we present 300 year records of snow accumulation from two ice cores drilled in Ellsworth Land, West Antarctica. The records show a dramatic increase in snow accumulation during the twentieth century, linked to a deepening of the Amundsen Sea Low (ASL), tropical sea surface temperatures, and large-scale atmospheric circulation. The observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the ASL is part of a longer trend.

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http://www.ingentaconnect.com/content/igsoc/jog/pre-prints/content-ings_jog_15j071 http://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses

Mass gains of the Antarctic ice sheet exceed losses [1992-2008]                                                                      Mass changes of the Antarctic ice sheet impact sea-level rise as climate changes, but recent rates have been uncertain. Ice, Cloud and land Elevation Satellite (ICESat) data (2003–08) show mass gains from snow accumulation exceeded discharge losses by 82 ± 25 Gt a–1, reducing global sea-level rise by 0.23 mm a–1. European Remote-sensing Satellite (ERS) data (1992–2001) give a similar gain of 112 ± 61 Gt a–1. Gains of 136 Gt a–1 in East Antarctica (EA) and 72 Gt a–1 in four drainage systems (WA2) in West Antarctic (WA) exceed losses of 97 Gt a–1 from three coastal drainage systems (WA1) and 29 Gt a–1 from the Antarctic Peninsula (AP).

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http://www.the-cryosphere-discuss.net/9/1555/2015/tcd-9-1555-2015.pdf                                                        Abstract: Six hundred and seven glaciers of the Shigar, Shashghan, Nubra and part of Shyok sub-basins of the Karakoram region were monitored using satellite data of years 1977, 1990, 2000, 2001, 2002, 2004, 2006, 2008, 2009, 2010, 2011 and 2013. …. Despite significant geographic and temporal variability betraying the 10 dynamic nature of many of the glaciers, in aggregate the population is roughly stable with less propensity toward retreat than most other glaciers in the nearby Himalaya and in the world. 341 glaciers exhibited no measured change throughout the 36 years of the study. Among other glaciers, no significant and sustained pattern of retreat or advance was observed.

Conclusion: The glaciers in our study area of the Karakoram include many advancing glaciers and many retreating ones, but most of the glaciers have remained nearly stable over several decades. A couple percent of the glaciers are surge types. There have been temporal changes in aggregate glacier behavior. Before 1990 the glaciers on average were either stable or retreating. In the last two decades Karakoram glaciers, on average, have experienced noticeable advances of their snouts and areas. The aggregate changes, 25 however, are small for every period considered.

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http://tsijournals.com/upload/ESAIJ_3873/Ereprint_ESAIJ_3873.pdf

In normal scientific practice models are built to account for all the known features of a physical phenomenon and are than validated or disproved by testing against observations or experiments. In the case of Antarctica, measurements of temperatures and sea ice extent show quite the reverse of the warming derived by modeling, assisted sometimes by the use of dubious data. Recently the big picture of cooling in Antarctica has been re-interpreted by focusing on just one place, Byrd station, where a poor quality record was used to produce “the most rapidly warming region on earth.” This result was achieved by ignoring all the other better quality stations in the area, which are in perfect agreement with the generally-agreed satellite temperatures and sea ice extent. Another example of highly-selective data is the conclusion of McMillan et al.(2014) of increased ice losses from Antarctica detected by the CryoSat- 2 mission which is based on only a 3- year old record of a satellite system estimating the ice thickness rather than the more precise ice surface area while neglecting measurement inaccuracies and consistency with other information. Rye et al. (2014) allege that along the margins of Antarctica the sea-level is rising at an increasing rate in response to increasing glacial discharge. This assertion is based on modeling and conflicts directly with the general understanding (shared even by the IPCC [www.ipcc.ch/ report/ar5/]) of lower temperatures and increasing ice cover. Here we contrast modeling with observational evidence using several recent papers and data as examples.

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http://sciencedomain.org/abstract/8837

A better understanding of the future climate pattern developments in the Arctic may only follow a better reconstruction of the past patterns of natural oscillations and the determination of the forcing and the resulting oscillations occurred in the climate parameters over different time scales. The proposed information for the past demonstrates the Walsh & Chapman reconstruction claiming a flat sea ice 1870 to 1950 is too simple. The Arctic sea ice experienced a drastic reduction that was phased with warming temperatures 1923 to 1940. This reduction was followed by a sharp cooling and sea ice recovery. This permits us to also conclude that very likely the Arctic sea ice extent also has a quasi-60 years’ oscillation. The recognition of a quasi-60 year’s oscillation in the sea ice extent of the Arctic similar to the oscillation of the temperatures and the other climate indices may permit us to separate the natural from the anthropogenic forcing of the Arctic sea ice. The heliosphere and the Earth’s magnetosphere may have much stronger influence on the climate patterns on Earth including the Arctic sea ices than has been thought.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL065704/full

Conclusion: There are no data with which we could easily compare our results to evaluate possible thickness changes and an easing of ice conditions for marine operations in the NWP [Northwest Passage]. For further evaluation, it is also important to consider that in Parry Channel, including VMS, i.e., in the waters of the northern NWP, in 2014 more ice survived the summer as MYI [multi-year ice] than in the nine most recent years but slightly less than during 1968–2015 on average. Between November 2014 and April 2015, winter air temperatures were between −0.5°C and −1.5°C colder than during 1980–2010 which could have led to slightly thicker level ice than average, notwithstanding snow effects.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064541/abstract

High-resolution measurements of ocean temperature and salinity in the Arctic Ocean’s Canada Basin reveal the importance of the release of solar-derived stored ocean heat on sea-ice growth. Locally-absorbed summer solar heat is stored in a Near Surface Temperature Maximum (NSTM) layer underlying the mixed layer. The heat content of the NSTM layer was anomalously large following summer 2007, which saw considerable sea-ice losses and intense solar absorption into the exposed surface ocean. Measurements provide evidence for the entrainment of NSTM-layer heat in fall/winter 2007–08 by shear-driven mixing, and convective mixing by the release of dense, salty plumes during sea-ice growth. While at least a portion of the NSTM-layer was eroded, deeper warm ocean layers remained unaffected. It is shown that the release of solar heat stored following summer 2007 was sufficient to have reduced sea-ice thickness at the end of the 2008 growth season by about 25%.

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2489.html

Changes in Arctic sea ice volume affect regional heat and freshwater budgets and patterns of atmospheric circulation at lower latitudes. Despite a well-documented decline in summer Arctic sea ice extent by about 40% since the late 1970s, it has been difficult to quantify trends in sea ice volume because detailed thickness observations have been lacking. Here we present an assessment of the changes in Northern Hemisphere sea ice thickness and volume using five years of CryoSat-2 measurements. Between autumn 2010 and 2012, there was a 14% reduction in Arctic sea ice volume, in keeping with the long-term decline in extent. However, we observe 33% and 25% more ice in autumn 2013 and 2014, respectively, relative to the 2010–2012 seasonal mean, which offset earlier losses. This increase was caused by the retention of thick sea ice northwest of Greenland during 2013 which, in turn, was associated with a 5% drop in the number of days on which melting occurred—conditions more typical of the late 1990s. In contrast, springtime Arctic sea ice volume has remained stable. The sharp increase in sea ice volume after just one cool summer suggests that Arctic sea ice may be more resilient than has been previously considered.

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http://www.earth-syst-dynam-discuss.net/6/2243/2015/esdd-6-2243-2015.html

The prospect of finding generic early warning signals of an approaching tipping point in a complex system has generated much recent interest. ….We apply these indicators to a simple conceptual system and satellite observations of Arctic sea ice area, the latter conjectured to have a bifurcation type tipping point. We find no detectable signal of the Arctic sea ice approaching a local bifurcation [tipping point].

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0076.1

The surface energy budget plays a critical role in determining the mass balance of the Greenland Ice Sheet, which in turn has significant implications for global sea levels. Nearly three years of data (January 2011–October 2013) are used to characterize the annual cycle of surface radiative fluxes and cloud radiative forcing (CRF) from the central Greenland Ice Sheet at Summit Station. The annual average CRF [cloud radiative forcing] is 33 W m−2, representing a substantial net cloud warming of the central Greenland surface. Unlike at other Arctic sites, clouds warm the surface during the summer. The surface albedo is high at Summit throughout the year, limiting the cooling effect of the shortwave CRF and thus the total CRF is dominated by cloud longwave warming effects in all months. All monthly mean CRF [cloud radiativer forcing] values are positive (warming), as are 98.5% of 3-hourly cases. The annual cycle of CRF is largely driven by the occurrence of liquid-bearing clouds, with a minimum in spring and maximum in late summer. Optically thick liquid-bearing clouds [liquid water path (LWP) > 30 g m−2] produce an average longwave CRF of 85 W m−2. Shortwave CRF is sensitive to solar zenith angle and LWP. When the sun is well above the horizon (solar zenith angle < 65°), a maximum cloud surface warming occurs in the presence of optically thin liquid-bearing clouds. Ice clouds occur frequently above Summit and have mean longwave CRF values ranging from 10 to 60 W m−2, dependent on cloud thickness.

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http://www.nature.com/ncomms/2015/151110/ncomms9798/full/ncomms9798.html

The stability of marine sectors of the Antarctic Ice Sheet (AIS) in a warming climate has been identified as the largest source of uncertainty in projections of future sea-level rise. Sea-level fall near the grounding line of a retreating marine ice sheet has a stabilizing influence on the ice sheets, and previous studies have established the importance of this feedback on ice age AIS evolution. Here we use a coupled ice sheet–sea-level model to investigate the impact of the feedback mechanism on future AIS retreat over centennial and millennial timescales for a range of emission scenarios. We show that the combination of bedrock uplift and sea-surface drop associated with ice-sheet retreat significantly reduces AIS [Antarctic Ice Sheet] mass loss relative to a simulation without these effects included. Sensitivity analyses show that the stabilization tends to be greatest for lower emission scenarios and Earth models characterized by a thin elastic lithosphere and low-viscosity upper mantle, as is the case for West Antarctica.

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http://www.the-cryosphere-discuss.net/9/1811/2015/tcd-9-1811-2015.pdf

Abstract: Recent mass balance measurements indicate a slight mass gain at Muztag Ata in the Eastern Pamir [China].  We extend these measurements both in space and time by using remote sensing data and present four decades of glacier variations in the en- 5 tire mountain massif.  … On average, the glaciers showed a small, insignificant shrinkage from 274.3 ± 10.6 km2 in 1973 to 272.7 ± 1.0 km2 in 2013 (−0.02 ± 0.1 % a−1 20 ). Average mass changes in the range of −0.03 ± 0.33 m w.e. a−1 (1973–2009) to −0.01 ± 0.30 m w.e. a−1 (1973–2013) reveal nearly balanced budgets for the last forty years. Indications of slightly positive trends after 1999 (+0.04 ± 0.27 m w.e. a−1 ) are confirmed by in-situ measurements.

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http://www.sciencedirect.com/science/article/pii/S0012821X15004100

Highlights: Ice mass loss (2003–2014) was approximately one order of magnitude [10 times] smaller than between 1995–2003.

Abstract: The northern Antarctic Peninsula is one of the fastest changing regions on Earth. The disintegration of the Larsen-A Ice Shelf in 1995 caused tributary glaciers to adjust by speeding up, surface lowering, and overall increased ice-mass discharge. … The contribution to sea level rise was estimated to be 18.8±1.8 Gt, corresponding to a 0.052±0.005 mm sea level equivalent [0.002 of an inch], for the period 1995–2014. 

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL065364/abstract

Predicted slow-down in the rate of Atlantic sea ice loss

Recent forecasts indicate that a spin-down of the thermohaline circulation that began near the turn of the century will continue, and this will result in near neutral decadal trends in Atlantic winter sea ice extent in coming years, with decadal growth in select regions.

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http://www.sciencedaily.com/releases/2015/12/151208134632.htm

This is the first time seismologists have been able to deploy instruments rugged enough to survive a winter in this part of the frozen continent, and so this is the first detailed look at Earth beneath this region. Not surprisingly, the maps show a giant blob of superheated rock about 60 miles beneath Mount Sidley [West Antartica], the last of a chain of volcanic mountains in Marie Byrd Land at one end of the transect. More surprisingly, they reveal hot rock beneath the Bentley Subglacial Trench, a deep basin at the other end of the transect.  The Bentley Subglacial Trench is part of the West Antarctic Rift System and hot rock beneath the region indicates that this part of the rift system was active quite recently. … While heat flow through Earth’s crust has been measured at at least 34,000 different spots around the globe, in Antarctica it has been measured in less than a dozen places. In July 2015, scientists reported the heat flow at one of these spots was four times higher than the global average.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL065750/full

Introduction: It is expected that the observed recent atmospheric warming in this region [Bellingshausen-Amundsen coast region between the Antarctic Peninsula and West Antarctica] will result in increased snow accumulation, although the stable water isotopes from Ellsworth Land ice cores have shown that the recent rise in temperature here is not unusual in the past 300 years [Thomas et al., 2013]. Therefore, it is unclear whether these recent glaciological changes are part of a longer term natural trend or associated with anthropogenic climate forcing.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00654.1?af=R

Record lows in Arctic sea ice extent are making frequent headlines in recent years. The change in albedo when sea ice is replaced by open water introduces a nonlinearity that has sparked an ongoing debate about the stability of the Arctic sea ice cover and the possibility of Arctic “tipping points”. Previous studies identified instabilities for a shrinking ice cover in two types of idealized climate models: (i) annual-mean latitudinally-varying diffusive energy balance models (EBMs) and (ii) seasonally-varying single-column models (SCMs). The instabilities in these low-order models stand in contrast with results from comprehensive global climate models (GCMs), which typically do not simulate any such instability. To help bridge the gap between low-order models and GCMs, we develop an idealized model that includes both latitudinal and seasonal variations. The model reduces to a standard EBM or SCM as limiting cases in the parameter space, thus reconciling the two previous lines of research. We find that the stability of the ice cover vastly increases with the inclusion of spatial communication via meridional heat transport or a seasonal cycle in solar forcing, being most stable when both are included. If the associated parameters are set to values that correspond to the current climate, the ice retreat is reversible and there is no instability when the climate is warmed. The two parameters have to be reduced by at least a factor of 3 for instability to occur. This implies that the sea ice cover may be substantially more stable than has been suggested in previous idealized modeling studies.

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http://advances.sciencemag.org/content/advances/1/6/e1500093.full.pdf

The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.

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http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-14-00018.1

The Amundsen Sea low (ASL) is a climatological low pressure center that exerts considerable influence on the climate of West Antarctica. Its potential to explain important recent changes in Antarctic climate, for example, in temperature and sea ice extent, means that it has become the focus of an increasing number of studies. Here, the authors summarize the current understanding of the ASL, using reanalysis datasets to analyze recent variability and trends, as well as ice-core chemistry and climate model projections, to examine past and future changes in the ASL, respectively. The ASL has deepened in recent decades, affecting the climate through its influence on the regional meridional wind field, which controls the advection of moisture and heat into the continent. Deepening of the ASL in spring is consistent with observed West Antarctic warming and greater sea ice extent in the Ross Sea. Climate model simulations for recent decades indicate that this deepening is mediated by tropical variability while climate model projections through the twenty-first century suggest that the ASL will deepen in some seasons in response to greenhouse gas concentration increases.

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http://www.igsoc.org/annals/56/69/a69a892.pdf

Observations of Southern Hemisphere sea ice from passive microwave satellite measurements show that a new record maximum extent of 19.58 million km2 was reached on 30 September, 2013, the extent is just over two standard deviations above the 1979-2012 mean and follows a similar record (19.48 million km2 ) in 2012. On the record day in 2013, sea-ice extent was greater than the 30-year average (1981-2010) in nearly all Southern Ocean regions. For the year as a whole, Southern Hemisphere sea-ice area and extent were well above average, and numerous monthly and daily records were broken.  Analysis of anomaly patterns and the atmospheric and oceanic events suggest that a sequence of regional wind and cold-freshened surface waters is likely responsible for the record maximum and the generally high 2013 extent.  In particular, the Ross Sea sector experience a combination of cold southerly winds associated with the position and depth of the Admundsen Sea low, and lower than normal sea surface temperatures (up to 2° C below normal). The resulting very high anomaly in ice extent in this region was a major component of the overall record maximum.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00733.1?af=R

In this study, observed temperature records of 12 stations from Antarctica Island, Coastline and Continental areas are analyzed by means of detrended fluctuation analysis (DFA). … [W]e find .. most of the Antarctic stations do not show any significant trends over the past several decades

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http://www.the-cryosphere.net/9/925/2015/tc-9-925-2015.pdf

Introduction: Only the wider Antarctic Peninsula region (including parts of West Antarctica) exhibits a large increase in air temperature (Bromwich et al., 2013), accompanied by disintegrating ice shelves and accelerated ice flow (Rignot et al., 2013; Rott et al., 2002). For East Antarctica, no general warming and increase in precipitation is found in surface observational data (Turner et al., 2005; Monaghan et al., 2006, 2008). This is important because an increase in precipitation, and hence increased surface mass balance (SMB), might mitigate sea level rise.

Discussion and conclusionWe conclude that, in the last 2 centuries, conditions in the interior DML [Dronning Maud Land, East Antarctica] have been fairly stable and only weakly influenced by changes in atmospheric dynamics. In the coastal areas, more complex processes are at work and the δ 18O and SMB [surface mass balance] derived from the firn cores cannot be fully explained yet.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0042.1

Wintertime Arctic sea ice extent has been declining since the late twentieth century, particularly over the Atlantic sector that encompasses the Barents–Kara Seas and Baffin Bay. This sea ice decline is attributable to various Arctic environmental changes, such as enhanced downward infrared (IR) radiation, preseason sea ice reduction, enhanced inflow of warm Atlantic water into the Arctic Ocean, and sea ice export. However, their relative contributions are uncertain. Utilizing ERA-Interim and satellite-based data, it is shown here that a positive trend of downward IR radiation [shortwave solar forcing] accounts for nearly half of the sea ice concentration (SIC) decline during the 1979–2011 winter over the Atlantic sector. Furthermore, the study shows that the Arctic downward IR radiation increase is driven by horizontal atmospheric water flux and warm air advection into the Arctic, not by evaporation from the Arctic Ocean. These findings suggest that most of the winter SIC trends can be attributed to changes in the large-scale atmospheric circulations.

Miscellaneous (6)

http://www.sciencedaily.com/releases/2015/02/150205142921.htm

http://onlinelibrary.wiley.com/doi/10.1002/2014GL063015/full

A new study shows that undersea volcanoes flare up on strikingly regular cycles, ranging from two weeks to 100,000 years — and, that they erupt almost exclusively during the first six months of each year. The pulses — apparently tied to short- and long-term changes in earth’s orbit, and to sea levels — may help trigger natural climate swings.

Seafloor eruption rates and mantle melting fueling eruptions may be influenced by sea level and crustal loading cycles at scales from fortnightly to 100 kyr. Recent mid-ocean ridge eruptions occur primarily during neap tides and the first 6 months of the year, suggesting sensitivity to minor changes in tidal forcing and orbital eccentricity. An ~100 kyr periodicity in fast-spreading seafloor bathymetry and relatively low present-day eruption rates at a time of high sea level and decreasing orbital eccentricity suggest a longer-term sensitivity to sea level and orbital variations associated with Milankovitch cycles. Seafloor spreading is considered a small but steady contributor of CO2 to climate cycles on the 100 kyr time scale; however, this assumes a consistent short-term eruption rate. Pulsing of seafloor volcanic activity may feed back into climate cycles, possibly contributing to glacial/interglacial cycles, the abrupt end of ice ages, and dominance of the 100 kyr cycle.

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http://onlinelibrary.wiley.com/doi/10.1111/1758-5899.12295/full

All climate policies by the US, China, the EU and the rest of the world, implemented from the early 2000s to 2030 and sustained through the century will likely reduce global temperature rise about 0.17°C in 2100. These impact estimates are robust to different calibrations of climate sensitivity, carbon cycling and different climate scenarios. Current climate policy promises will do little to stabilize the climate and their impact will be undetectable for many decades.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00656.1

Based on research showing that in the case of a strong aerosol forcing, this forcing establishes itself early in the historical record, a simple model is constructed to explore the implications of a strongly negative aerosol forcing on the early (pre 1950) part of the instrumental record. This model, which contains terms representing both aerosol-radiation and aerosol-cloud interactions well represents the known time history of aerosol radiative forcing, as well as the effect of the natural state on the strength of aerosol forcing. Model parameters, randomly drawn to represent uncertainty in understanding, demonstrates that a forcing more negative than −1.0 W m−2 is implausible, as it implies that none of the approximately 0.3 K temperature rise between 1850 and 1950 can be attributed to northern-hemispheric forcing. The individual terms of the model are interpreted in light of comprehensive modeling, constraints from observations, and physical understanding, to provide further support for the less negative ( −1.0 W m−2 ) lower bound. These findings suggest that aerosol radiative forcing is less negative and more certain than is commonly believed.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00550.1?af=R

Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations. The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least in part, of internal redistributions of heat, some of which must reflect water that has undergone long trajectories since last exposure to the atmosphere.

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http://www.sciencedirect.com/science/article/pii/S0013935114003661

Seasonal patterns in mortality have been recognised for decades, with a marked excess of deaths in winter, yet our understanding of the causes of this phenomenon is not yet complete. Research has shown that low and high temperatures are associated with increased mortality independently of season; however, the impact of unseasonal weather on mortality has been less studied. In this study, we aimed to determine if unseasonal patterns in weather were associated with unseasonal patterns in mortality. We obtained daily temperature, humidity and mortality data from 1988 to 2009 for five major Australian cities with a range of climates. We split the seasonal patterns in temperature, humidity and mortality into their stationary and non-stationary parts. A stationary seasonal pattern is consistent from year-to-year, and a non-stationary pattern varies from year-to-year. We used Poisson regression to investigate associations between unseasonal weather and an unusual number of deaths. We found that deaths rates in Australia were 20–30% higher in winter than summer. The seasonal pattern of mortality was non-stationary, with much larger peaks in some winters. Winters that were colder or drier than a typical winter had significantly increased death risks in most cities. Conversely summers that were warmer or more humid than average showed no increase in death risks. Better understanding the occurrence and cause of seasonal variations in mortality will help with disease prevention and save lives.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0572.1

Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer’s evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean…. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind-stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

Warming: Fewer Weather Extremes (4)

http://www.sciencemagazinedigital.org/sciencemagazine/30_january_2015?folio=540#pg98

http://www.sciencemag.org/content/347/6221/540.full

Our work illustrates a major constraint on the large-scale global atmospheric engine: As the climate warms, the system may be unable to increase its total entropy production enough to offset the moistening inefficiencies associated with phase transitions. This suggests that in a future climate, the global atmospheric circulation might comprise highly energetic storms due to explosive latent heat release, but in such a case, the constraint on work output identified here will result in fewer numbers of such [extreme weather] events. Earth’s atmospheric circulation thus suffers from the “water in gas problem” observed in simulations of tropical convection, where its ability to produce work is constrained by the need to convert liquid water into water vapor and back again to tap its fuel.

Incoming and outgoing solar radiation couple with heat exchange at Earth’s surface to drive weather patterns that redistribute heat and moisture around the globe, creating an atmospheric heat engine. … On a warming Earth, the increase in perceptible water has been identified as a reason for the tropical overturning to slow down,  and studies over a wide range of climates suggest that global atmospheric motions are reduced in extremely warm climates.   Models forced according to a climate change scenario [future global warming projections] also exhibit this behavior in their tropical circulation. … The evolution of W [work output] in response to anthropogenic forcing indicates a trend of -0.038 W/m-2 per 100 years per the 10-year running mean.

CONSTRAINED WORK OUTPUT OF THE MOIST ATMOSPHERIC HEAT ENGINE IN A WARMING CLIMATE

Editor’s Summary:  Global warming is expected to intensify the hydrological cycle, but it might also make the atmosphere less energetic. Laliberté et al. modeled the atmosphere as a classical heat engine in order to evaluate how much energy it contains and how much work it can do (see the Perspective by Pauluis). They then used a global climate model to project how that might change as climate warms. Although the hydrological cycle may increase in intensity, it does so at the expense of its ability to do work, such as powering large-scale atmospheric circulation or fueling more very intense storms.

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http://www.sciencedirect.com/science/article/pii/S0277379115301335

A comparison with North Atlantic and Western Mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods, suggesting a climatically-controlled mechanism for the occurrence of these storm periods. Besides, an in-phase storm activity pattern is found between the Western Mediterranean and Northern Europe. Spectral analyses performed on the Sr content revealed a new 270-year solar-driven pattern of storm cyclicity. For the last 3000 years, this 270-year cycle defines a succession of ten major storm periods (SP) with a mean duration of 96 ± 54 yr. Periods of higher storm activity are recorded from >680 to 560 cal yr BC (SP10, end of the Iron Age Cold Period), from 140 to 820 cal yr AD (SP7 to SP5) with a climax of storminess between 400 and 800 cal yr AD (Dark Ages Cold Period), and from 1230 to >1800 cal yr AD (SP3 to SP1, Little Ice Age). Periods of low storm activity occurred from 560 cal yr BC to 140 cal yr AD (SP9 and SP8, Roman Warm Period) and from 820 to 1230 cal yr AD (SP4, Medieval Warm Period).

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064127/abstract

Substantial changes in the hydrological cycle are projected for the 21st century, but these projections are subject to major uncertainties. In this context, the ‘dry gets drier, wet gets wetter’ (DDWW) paradigm is often used as a simplifying summary. However, recent studies cast doubt on the validity of the paradigm and also on applying the widely used P-E (precipitation-evapotranspiration) metric over global land surfaces. Here we show in a comprehensive CMIP5-based assessment that projected changes in mean annual P-E are generally not significant, except for high-latitude regions showing wetting conditions until the end of the 21st century. Significant increases in aridity do occur in many subtropical, but also adjacent humid regions. However, combining both metrics still shows that ca. 70% of all land area will not experience significant changes. Based on these findings we conclude that the DDWW paradigm is generally not confirmed for projected changes in most land areas.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0369.1?af=R

The response of precipitation minus evapotranspiration to climate warming: Why the “wet-get-wetter, dry-get-drier” scaling does not hold over land

Simulations with climate models show a land-ocean contrast in the response of P-E (precipitation minus evaporation or evapotranspiration) to global warming, with larger changes over ocean than over land. The changes over ocean broadly follow a simple thermodynamic scaling of the atmospheric moisture convergence: the so-called “wet-get-wetter, dry-get-drier” mechanism. Over land, however, the simple scaling fails to give any regions with decreases in P-E, and it overestimates increases in P-E compared to the simulations.

Climate of the Past (27)

http://www.clim-past-discuss.net/11/521/2015/cpd-11-521-2015.html

The June to August maximal temperature of the last millennium has been reconstructed using the statistical relation between Climatic Research Unit (CRU TS3.1) and δ18O data. The resulting millennial series is marked by the well-defined Medieval Warm Anomaly (AD 1000–1250), the Little Ice Age (AD 1450–1880) and the modern period (AD 1950–2010), and an overall average cooling trend of −0.6 °C/millennium. These climatic periods and climatic low frequency trends are in agreement with the only reconstruction available for northeastern Canada and others from nearby regions (Arctic, Baffin Bay) as well as some remote regions like the Canadian Rockies or Fennoscandia. Our temperature reconstruction clearly indicates that the Medieval Warm Anomaly has been warmer than the modern period, which is relatively cold in the context of the last 1000 years. However, the temperature increase during the last three decades is one of the fastest warming observed over the last millennium (+1.9 °C between 1970 and 2000). An additional key finding of this research is that the coldest episodes mainly coincide with low solar activities and the extremely cold period of the early 19th century has occurred when a solar minimum was in phase with successive intense volcanic eruptions. Our study provides a new perspective unraveling key mechanisms that controlled the past climate shifts in northeastern Canada.

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http://www.sciencedirect.com/science/article/pii/S0921818115000417#gr3

Most of the series of the Holocene temperatures from the Canadian Arctic and Greenland show a broad-scale similarity, as expressed in the loadings on the first component, with relatively cool temperatures in the early Holocene, maximum temperatures in the middle Holocene, although with some significant regional differences, and cooler temperatures in the late Holocene. The exceptions are in the west, which shows warmer temperatures until ~ 7-8 ka, average temperatures in the middle Holocene and cooler temperatures in the past 4 ka. Increased insolation (Milankovitch variations) along with southerly airflow to the west of the decaying ice sheet would have caused local heating in these areas in the early Holocene, whereas the Laurentide Ice Sheet and meltwater maintained cooler temperatures towards the east during this time (Renssen et al., 2009). The magnitude and timing of the warmer temperature in the reconstructions is roughly comparable to that predicted by orbital and ice sheet/meltwater forcing (Renssen et al., 2009).

[The below (bottom) graph from this paper shows that the Canadian Arctic and Greenland was as warm or warmer than present for most of the last 8,000 years.]

http://ars.els-cdn.com/content/image/1-s2.0-S0921818115000417-gr3.jpg

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http://www.jsg.utexas.edu/sloomis/files/Loomis_2015_Tana.pdf

Introduction: GDGT-based temperature records from equatorial East Africa have begun to illuminate the region’s thermal history and generally exhibit coherent trends and amplitudes of change on orbital timescales. For instance, these records suggest that, compared to pre-industrial period, temperatures were 3–5 °C cooler at the last glacial maximum (LGM; Powers et al., 2005; Tierney et al., 2008; Loomis et al., 2012) and between 1 and 3°C warmer during the mid-Holocene, ca. 7–5 ka (Powers et al., 2005; Tierney et al., 2008; Berke et al., 2012b; Loomis et al., 2012).

Sea surface temperature (SST) records from the Red Sea (Arz et al., 2003) and Eastern Mediterranean (Castañeda et al., 2010) show an abrupt ~5 °C warming between 15 ka and 14.5 ka as well [~1 °C per century]. This warming is consistent with the timing of the Bølling Oscillation recorded in Greenland ice cores (North Greenland Ice Core Project Members, 2004; Fig. 5a), which was driven by the resumption of Atlantic Meridional Overturning Circulation (AMOC) after H1 (McManus et al., 2004), suggesting that abrupt warming observed in much of the northern hemisphere (Shakun et al., 2012) was also felt in northern tropical Africa.  … Temperatures at Lake Tana gradually increase from 18.1 °C at [13,000 years ago] to 21.9 °C at [6,600 years ago], gradually cool to 19.5 °C at [2,000 years ago], and then cool more rapidly to 16.7 °C by the most recent sample at [400 years ago]. … Peak mid-Holocene temperatures in Africa are not the result of greenhouse gas radiative forcing, as CO2 reaches a relative minimum during the mid-Holocene.

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https://www.researchgate.net/profile/Hong_Yan15/publication/270338233_A_composite_sea_surface_temperature_record_of_the_northern_South_China_Sea_for_the_past_2500_years_A_unique_look_into_seasonality_and_seasonal_climate_changes_during_warm_and_cold_periods/links/54a7c8ad0cf257a6360af21d.pdf

The annual-mean SST anomalies for the 8 time windows are ranging from −2.2 °C (−8.6%) to 1.55 °C (5.6%) during the last 3000 years. The SSTs of warm period time-windows around AD 990 ± 40, AD 50 ± 40 and BC 535 ± 24 are 0.89 °C (3.2%), 1.55 °C (5.6%) and 0.1 °C (0.4%), higher than that during modern instrumental period of AD 1990–2000. The SSTs of cold period time-windows around AD 1464 ± 51, AD 495 ± 22, AD 487 ± 22 and BC 541 ± 24 are 1.08 °C (−3.9%), 2 °C (−7.8%) and 2.2 °C (−8.6%) and 0.4 °C (−1.6%), lower than that of the modern instrumental SST decade. It is worthwhile to note that the warmer SSTs in northern SCS around AD 990 ± 40 (3.2%) and AD 50 ± 40 (5.6%) occurred within the notable warm episodes of Medieval Warm Period (MWP, ≈AD 800–13001 ) and Roman Warm Period (RWP, ≈BC 400–AD 200), respectively. Conversely, the cooler SSTs around AD 1464 ± 51, AD 495 ± 22 and AD 487 ± 22 are consistent with the European cold periods of Little Ice Age (LIA, ≈AD 1400–1850) and Dark Age Cold Period (DACP, ≈AD 400–800).

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http://www.sciencedirect.com/science/article/pii/S0012821X15003027

Temperature estimates, based on Mg/Ca measurements of planktonic and benthic foraminifera (Neogloboquadrina dutertrei and Uvigerina spp  ., respectively) show higher [ocean] temperatures in the early Holocene, a cooling of2° by 8 kyr B.P. and after relatively stable temperatures to the present. The temperature signal is similar in direction and timing to a rather robust Holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the EEP.

—– http://www.sciencedirect.com/science/article/pii/S0277379115301165

Based on eustatic sea level variations, the Last Interglacial (hereafter LIG) covers approximately the time interval between 129 and 116 thousand of years ago (hereafter ka). The LIG appears exceptionally warm in the Antarctic EPICA Dome C (EDC) ice core in the context of the past 800 ka  and in many marine sediment records. It is characterised by atmospheric concentrations of greenhouse gases close to pre-industrial levels, particularly high boreal summer insolation [surface solar radiation] values, and a global mean sea level up to 5–10 m above present-day.

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http://repositorio.uchile.cl/bitstream/handle/2250/134713/Late-Holocene.pdf?sequence=1

[Graph on page 33 of this paper shows that modern sea surface temperatures near Chile are still lower than they were for most of the last millennium.]

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http://link.springer.com/article/10.1007/s41063-015-0019-3 [download pdf]

Pliocene [3-5 million years ago] Arctic Ocean summer SSTs were appreciably warmer than modern and seasonally sea-ice free conditions existed in some regions. Nonmarine proxy records from continental sections also point to a warm Pliocene climate in the high latitudes of the northern hemisphere. At Lake El’gygytgyn (Lake ‘‘E’’) in Siberia summer temperatures were 8 C warmer than modern and at Ellesmere Island, Canada, summer and MAT were 11.8 and 18.3 C higher than today.

The Cenozoic ecosystem changes in the Arctic described above are summarized in Figs. 5 and 6 within the context of climate changes over different timescales. Several conclusions can be made. First, a seasonally ice-free marginal and central Arctic Ocean was common … regionally during the early Holocene. During orbital climatic cycles of the last few hundred thousand years, interglacial periods were characterized by perennial and at times seasonal sea ice cover and inhabited by marine ecosystems similar to those of the pre-industrial Holocene. Some species thought to be dependent on summer sea ice (e.g., polar bears) survived through these periods. In contrast, during glacial periods the much smaller Arctic Ocean and much of the adjacent continents were covered with massive ice sheets, thick ice shelves, and sea ice making large regions virtually uninhabitable to most species that inhabit today’s Arctic. Despite the scale, frequency and rapidity of Quaternary climate changes, Arctic marine ecosystems associated with sea-ice habitats were extremely resilient, adapting through geographic range expansion into the Arctic during warm periods, and south into extra-Arctic regions during glacial periods. The stratigraphic record of the last 1.5 Ma indicates that no marine species’ extinction events occurred despite major climate oscillations.

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http://hol.sagepub.com/content/early/2015/07/02/0959683615591357

The reconstructed temperature record reveals an intensification of winter monsoon intensity near the year 100 CE [Roman Warm Period]. Prior to this transition, winter temperatures were >1.5°C warmer than today. Conditions similar to the present seem to have established after 450 CE, interrupted by a singular event near 950 CE with warmer temperatures and accordingly weak winter monsoon. Frequency analysis revealed significant 75-, 40-, and 37-year cycles, which are known from decadal- to centennial-scale resolution records of Indian summer monsoon variability and interpreted as solar irradiance forcing. Our first independent record of Indian winter monsoon activity confirms that winter and summer monsoons were modulated on the same frequency bands and thus indicates that both monsoon systems are likely controlled by the same driving force.

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https://www.blogs.uni-mainz.de/fb09climatology/files/2012/03/Esper_2015_Geochron.pdf

Results indicate that late 20th century warming has not been unique within the context of the past 750 years.

Our reconstruction contains greater amplitude than previous reconstructions derived from traditional tree-ring density data, and describes particularly cool conditions during the late 19th century. Some of these differences, including early warm periods in the 14th and 17th centuries, have been retained via δ13 C timeseries detrending — a novel approach in tree-ring stable isotope chronology development. The overall reduced variance in earlier studies points to an underestimation of pre-instrumental summer temperature variability derived from traditional tree-ring parameters.

[Fig. 2 c, page 55, indicates that the late 20th century warming has been similar to temperatures reached in the 1200s, 1400s, and 1700s.]

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http://hol.sagepub.com/content/25/2/323.short

The temperature maximum in our reconstruction [of Xinjiang, China] occurred around 700 cal. [years before present].

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http://www.clim-past.net/11/1153/2015/cp-11-1153-2015.pdfOur temperature reconstruction indicates that the Medieval Climate Anomaly was characterized by a temperature range similar to the one of the modern period in the study region. However, the temperature increase during the last 3 decades is one of the fastest  warming observed over the last millennium (+1.9 C between 1970–2000). An additional key finding of this research is that the coldest episodes mainly coincide with low solar activities and the extremely cold period of the early 19th century has occurred when a solar minimum was in phase with successive intense volcanic eruptions.

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http://www.sciencedirect.com/science/article/pii/S0012821X15003994

The early Eocene was the warmest interval of the Cenozoic, and included within it were several hyperthermal events, with the Paleocene–Eocene Thermal Maximum (PETM) the most pronounced of these. These globally warm climates extended into the Arctic and substantive paleobotanical evidence for high Arctic precipitation (MAP > 150 cm/yr) is indicative of an Arctic rainforest, which contradicts some climate models that show low Arctic precipitation.

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https://www.researchgate.net/profile/Jianfang_Hu/publication/279461052_Reconstruction_of_a_paleotemperature_record_from_03-37_ka_for_subtropical_South_China_using_lacustrine_branched_GDGTs_from_Huguangyan_Maar/links/5662950308ae4931cd5da329.pdf

The pattern consists of five cool and four warm periods, including two distinct phases within the Medieval Warm Period (900–1300 AD), the coldest temperature in the Little Ice Age (1550–1850 AD)

[Graph from the paper on page 174, Fig 5 e, shows temperatures in China were significantly warmer during the Medieval and Roman warm periods.]

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http://hol.sagepub.com/content/25/7/1124.abstract?rss=1

The most extensive forest cover occurred c. 7400–3800 cal. BP, corresponding to July temperatures of 0.5–1°C above the present [in the Scandinavian Mountains].

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http://hol.sagepub.com/content/25/8/1197.abstract?rss=1

Here, we present a first reconstruction of early Holocene seasonal water temperature cycle in an Arctic fjord based on stable oxygen isotope (δ18Oshell) profiles in shells of Arctica islandica (Bivalvia) from raised beach deposits in Dicksonfjorden, Svalbard, dated at 9954–9782 cal. yr BP. Reconstructed maximum and minimum bottom water temperatures for the assumed shell growth period between April and August of 15.2°C and 2.8°C imply a seasonality of about 12.4°C for the early Holocene. In comparison to modern temperatures, this indicates that average [Arctic] temperature declined by 6°C [since the early Holocene] and seasonality narrowed by 50%. This first palaeo-environmental description of a fjord setting during the Holocene Climate Optimum at Spitsbergen exceeds most previous global estimates (+1–3°C) [warmer than present during the early Holocene] but confirms studies indicating an amplified effect (+4–6°C) at high northern latitudes.

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http://hol.sagepub.com/content/25/8/1301.abstract?rss=1

Multi-proxy investigations of sediment lithology, geochemistry, benthic foraminifera, and δ18O and δ13C of Elphidium striatopunctatum were carried out on a sediment core SHUA3 (2.2 m long) spanning the last 3.6 ka [3,600 years] and recovered from Shuaiba Lagoon, eastern Red Sea coast. …  These proxies reached their highest and most prolonged levels during the AD 800–1550 interval, indicating warm conditions corresponding to the world ‘Medieval Warm Period’. 

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http://www.sciencedirect.com/science/article/pii/S0277379115000633

Here, we present a high-resolution relative glacier activity record covering the past ∼10,000 cal. a BP from the northern outlet of the Langfjordjøkelen ice cap in Arctic Norway…. The complete deglaciation of the valley of Sør-Tverrfjorddalen occurred ∼10,000 cal. a BP, followed by a reduced or absent glacier during the Holocene Thermal Optimum. 

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http://onlinelibrary.wiley.com/doi/10.1111/bor.12085/full

Shells of the blue mussel Mytilus edulis have been dated to occur between 9500 and 5400 cal. a BP in central East Greenland; this warmth-loving species does not live in the region anymore and indicates higher sea surface temperatures than at present and more extensive fjord water (Bennike & Wagner 2013). … According to studies of the Greenland NEEM ice-core, mean annual temperatures during the warmest part of the Eemian were as much as 8°C higher than during the last millennium, and from 127 000 to 118 300 years ago the mean annual temperature was 5°C higher (NEEM community members 2013). In central East Greenland, the mean summer temperature was 5°C higher than today (Bennike & Böcher 1994). … Pre-Holocene material in the sediment core may be interglacial, rather than interstadial. The flora and fauna include a number of species that do not live so far north today and the summer temperatures must have been several degrees higher than today when these species lived in the region.

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http://geology.gsapubs.org/content/early/2015/02/18/G36476.1.abstract

To determine the long-term sensitivity of the Greenland ice sheet to a warmer climate, we explored how it responded to the Holocene thermal maximum (8–5 cal. kyr B.P. [thousand years before present]; calibrated to calendar years before present, i.e., A.D. 1950), when lake records show that local atmospheric temperatures in Greenland were 2–4 °C warmer than the present.  Records from five new threshold lakes complemented with existing geological data from south of 70°N show that the ice margin was retracted behind its present-day extent in all sectors for a limited period between ca. 7 and 4 cal. kyr B.P. and in most sectors from ca. 1.5 to 1 cal. kyr B.P., in response to higher atmospheric and ocean temperatures.

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http://www.ingentaconnect.com/content/schweiz/njbgeol/2015/00000277/00000002/art00008

We present a multi-proxy record from Laguna Nassau (LN), a shallow lake which developed in a blowout depression in the semi-arid sandy lowlands of the Western Pampas of Argentina. This multi-proxy stacked record reveals the evolution of an incipient water body subjected to warm and dry conditions from ~900 to 770 cal yr BP, an interval that is coeval with the Medieval Climatic Anomaly (MCA) period. Vegetation was dominated locally by Typha, and regionally by the Espinal, represented by Celtis, along with psammophytic-halophytic communities in sand dunes and lowlands. After that, variable water-depths and unstable conditions occurred in the water body in relation to dry and humid climatic phases until ~200 cal yr BP, likely related to a transition from warm and dry conditions, corresponding to the MCA, to a colder and wet climatic setting during a period concurrent with the Little Ice Age (LIA).

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http://www.sciencedirect.com/science/article/pii/S0277379115000426

Here, we review geological records of Greenland Ice Sheet (GrIS) change, with emphasis on the warmer-than-present middle Holocene, and compare these records to published studies that numerically simulate GrIS behavior through the Holocene. Geological records are concentrated in West and Southwest Greenland, which are also the regions where the GrIS margin likely experienced the greatest distance of inland retreat during the middle Holocene. Several records spanning from Melville Bugt to Jakobshavn Isfjord in western Greenland indicate the GrIS achieved its minimum extent between 5 and 3 [thousand years ago], and farther south in the Kangerlussuaq region, new data presented here indicate the ice margin reached its minimum extent between ∼4.2 and 1.8 ka. In the Narsarsuaq region in southern Greenland, the GrIS likely achieved its minimum configuration between 7 and 4 [thousand years ago].

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http://www.sciencedirect.com/science/article/pii/S0277379114004776

By utilising proxy data it is possible to obtain palaeoclimatic records beyond the range of instrumental observations, which increase our understanding of long-term Arctic climate change. Here, a continuous record of past changes in Equilibrium-Line Altitude (ELA) has been reconstructed for the alpine glacier Karlbreen, located on the northwest coast of Spitsbergen [Arctic] (79° N), based on sediment analyses from a distal glacier-fed lake.  From about 9200 to 3500 cal. yr. BP [before present], the sedimentary record indicates that Karlbreen was very small or had completely melted away. Karlbreen was probably close to its maximum Holocene extent several times during the Neoglacial, first around 1700 cal. yr. BP, then later at ∼225 and ∼135 cal. yr. BP.

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http://www.sciencedirect.com/science/article/pii/S0277379114004120

We have surveyed and dated Last Interglacial fossil corals to ascertain peak sea level and hence infer maximum retreat of polar ice sheets during this time interval. We observe a pattern of gradually rising sea level in the Seychelles between ∼129 and 125 thousand years ago (ka), with peak eustatic sea level attained after 125 ka [thousand years ago] at 7.6 ± 1.7 m higher than present. After accounting for thermal expansion and loss of mountain glaciers, this sea-level budget would require 5–8 m of polar ice sheet contribution, relative to today’s volume, of which only 2 m came from the Greenland ice sheet. This result clearly identifies the Antarctic ice sheet as a significant source of melt water, most likely derived from one of the unstable, marine-based sectors in the West and/or East Antarctic ice sheet. Furthermore, the establishment of a +5.9 ± 1.7 m eustatic sea level position by 128.6 ± 0.8 ka would require that partial AIS [Antarctic Ice Sheet] collapse was coincident with the onset of the sea level highstand.

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http://www.the-cryosphere.net/9/179/2015/tc-9-179-2015.html                                                                                          In this paper, we propose a new sub-grid scale parameterization for the ice discharge into the ocean through outlet glaciers and inspect the role of different observational and palaeo constraints for the choice of an optimal set of model parameters. We show that the ice discharge parameterization enables us to simulate both the correct ice-sheet shape and mass balance partition at the same time without explicitly resolving the Greenland outlet glaciers. For model verification, we compare the simulated total and sectoral ice discharge with other estimates. For the model versions that are consistent with the range of observational and palaeo constraints, our simulated Greenland ice sheet contribution to Eemian [~125,000 years ago] sea-level rise relative to present-day amounts to 1.4 m [higher] on average (in the range of 0.6 and 2.5 m).

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http://www.pnas.org/content/112/3/702

In the middle-to-late Holocene [~4,000 years ago], Earth’s monsoonal regions experienced catastrophic precipitation decreases that produced green to desert state shifts. Resulting hydrologic regime change negatively impacted water availability and Neolithic cultures. Whereas mid-Holocene drying is commonly attributed to slow insolation reduction and subsequent nonlinear vegetation–atmosphere feedbacks that produce threshold conditions, evidence of trigger events initiating state switching has remained elusive. Here we document a threshold event ca. 4,200 years ago in the Hunshandake Sandy Lands of Inner Mongolia, northern China, associated with groundwater capture by the Xilamulun River. This process initiated a sudden and irreversible region-wide hydrologic event that exacerbated the desertification of the Hunshandake, resulting in post-Humid Period mass migration of northern China’s Neolithic cultures. The Hunshandake remains arid and is unlikely, even with massive rehabilitation efforts, to revert back to green conditions.

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http://www.nature.com/ncomms/2015/151110/ncomms9890/full/ncomms9890.html

Maximum rates of climate change are systematically underestimated in the geological record                       Our findings indicate that the true attainable pace of climate change on timescales of greatest societal relevance is underestimated in geological archives.

CO2 Greening the Earth, Crop Growth (3)

http://www.biogeosciences-discuss.net/12/11387/2015/bgd-12-11387-2015.html

We quantified the temporal trend and climatic sensitivity of vegetation phenology in dryland ecosystems in the US Great Basin during 1982–2011. Our results indicated that vegetation greenness in the Great Basin increased significantly during the study period … [C]limate warming played a strong role in extending GSL [growing season length] that in turn resulted in the upward trend in mean vegetation greenness during 1982–2011. Overall, our results suggested that changes in wintertime and springtime precipitation played a stronger role than temperature in affecting the interannual variability of vegetation greenness while climate warming was mainly responsible for the 30-year upward trend in the magnitudes of mean vegetation greenness in the dryland ecosystems during 1982–2011.

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http://onlinelibrary.wiley.com/doi/10.1002/joc.4505/abstract

In summary, climate change has prolonged FFP [frost free period], increased the heat resource, and slightly changed solar radiation resource during crop growing season, which is beneficial for agriculture in Northeast China.

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http://www.tandfonline.com/doi/abs/10.1080/02723646.2015.1120139

The Sahel region of Northern Africa is home to more than 50 million people for whom summer rainfall is a crucial water resource in terms of food security and societal stability. Using satellite-based Normalized Difference Vegetation Index (NDVI) and gridded observational precipitation records during 1982–2012, we detected a significant increase (p-value < 0.01) in both vegetation greenness and monsoon rainfall over the Sahel since the early 1980s.

 

Heat Change Happens First, Then CO2 Change (3)

 

http://www.clim-past.net/11/647/2015/cp-11-647-2015.pdf

Despite the substantial dispersion of CO2 estimations, a character and a chronology of CO2 concentration changes are much closer to temperature changes rather than to heat flux variations. It may mean no significant contribution of CO2 forcing to climatically caused heat flux and thus to the temperature increase during Pleistocene–Holocene warming. About 10 kyr BP the increase of carbon dioxide concentration was replaced by its fall which ended about 8 kyr BP. This local minimum [in CO2 concentration] is not consistent with either GST [ground surface temperature] or SHF [surface heat flux] histories. It is possible that the CO2 decrease was associated with a sharp increase of vegetation absorbing its excess. … The reconstructed surface heat flux reflects impact of all possible sources of radiative forcing. In addition to solar insolation, greenhouse gases (such as CO2) can be a source of additional forcing. On the other hand the increase of carbon dioxide may be a consequence of temperature increasing. Comparing the chronology of surface flux, temperature and carbon dioxide concentration changes, we can draw some conclusions about the causes of climate change. …  The increase of carbon dioxide concentrations occurred 2–3 thousands of years later than the heat flux increase and synchronously with temperature response. 

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http://www.sciencedirect.com/science/article/pii/S0012821X14008115

We find that oceanic carbon releases due to the AMOC resumption during stadial/interstadial transitions lead to an atmospheric CO2 increase. However, the atmospheric CO2 increases observed during the first parts of AIM12 (∼47.6 ka B.P.) and AIM8 (∼39.8 ka B.P.) occur during periods of weak AMOC (HS5 and HS4 respectively) and could instead be explained by enhanced Antarctic Bottom Water transport. Enhanced Antarctic Bottom Water formation is shown to effectively ventilate the deep Pacific carbon and lead to CO2 outgassing into the atmosphere. In addition, changes in the AMOC alone are not sufficient to explain the largest Antarctic Isotope Maxima (namely AIM12 and AIM8). Stronger formation of Antarctic Bottom Water during AIM12 and AIM8 would enhance the southern high latitude warming and lead to a better agreement with high southern latitude paleoproxy records. The robustness of this southern warming response is tested using an eddy-permitting coupled ocean sea–ice model. We show that stronger Antarctic Bottom Water formation contributes to Southern Ocean surface warming by increasing the Southern Ocean meridional heat transport.

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http://rsta.royalsocietypublishing.org/content/373/2054/20140421

Climate and carbon cycle are tightly coupled on many timescales, from interannual to multi-millennial timescales. Observations always evidence a positive feedback, warming leading to release of carbon to the atmosphere; however, the processes at play differ depending on the timescales. State-of-the-art Earth System Models now represent these climate-carbon cycle feedbacks, always simulating a positive feedback over the twentieth and twenty-first centuries, although with substantial uncertainty. Recent studies now help to reduce this uncertainty. First, on short timescales, El Niño years record larger than average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate-carbon cycle anomalies can be used as emerging constraint on the tropical land carbon response to future climate change. Second, centennial variability found in last millennium records can be used to constrain the overall global carbon cycle response to climatic excursions. These independent methods point to climate-carbon cycle feedback at the low-end of the Earth System Models range, indicating that these models overestimate the carbon cycle sensitivity to climate change. These new findings also help to attribute the historical land and ocean carbon sinks to increase in atmospheric CO2 and climate change.

 

 

Ocean Acidification (8)

 

http://onlinelibrary.wiley.com/doi/10.1002/2015GL064431/abstract

Here we reconstruct 222 years of biennial seawater pH variability in the Sargasso Sea from a brain coral, Diploria labyrinthiformis. Using hydrographic data from the Bermuda Atlantic Time-Series Study (BATS) and the coral derived pH record, we are able to differentiate pH changes due to surface temperature versus those from ocean circulation and biogeochemical changes. We find that ocean pH does not simply reflect atmospheric CO2 trends, but rather that circulation/biogeochemical changes account for >90% of pH variability in the Sargasso Sea and more variability in the last century than would be predicted from anthropogenic uptake of CO2alone.

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http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2541.html

Climate change is now the leading cause of coral-reef degradation and is altering the adaptive landscape of coral populations. Increasing sea temperatures and declining carbonate saturation states are inhibiting short-term rates of coral calcification, carbonate precipitation and submarine cementation. A critical challenge to coral-reef conservation is understanding the mechanisms by which environmental perturbations scale up to influence long-term rates of reef-framework construction and ecosystem function. Here we reconstruct climatic and oceanographic variability using corals sampled from a 6,750-year core from Pacific Panamá. Simultaneous reconstructions of coral palaeophysiology and reef accretion allowed us to identify the climatic and biotic thresholds associated with a 2,500-year hiatus in vertical accretion beginning ~4,100 years ago. Stronger upwelling, cooler sea temperatures and greater precipitation—indicators of La Niña-like conditions—were closely associated with abrupt reef shutdown. The physiological condition of the corals deteriorated at the onset of the hiatus, corroborating theoretical predictions that the tipping points of radical ecosystem transitions should be manifested sublethally in the biotic constituentsFuture climate change could cause similar threshold behaviours, leading to another shutdown in reef development in the tropical eastern Pacific.

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https://www.researchgate.net/profile/Gangjian_Wei/publication/283946141_Decadal_variability_in_seawater_pH_in_the_West_Pacific_Evidence_from_coral_d_11_B_records/links/5653244708aefe619b191e48.pdf

We here estimate the OA rates from the two long (>150 years) annually resolved pH records from the northern SCS (this study) and the northern GBR [Wei et al., 2009], and the results indicate annual rates of -0.00039 +/- 0.00025 yr and -0.00034 +/- 0.00022 yr for the northern SCS [South China Sea] and the northern GBR [Great Barrier Reef], respectively. It is worth noting that the errors of these estimates are fairly large with RSD of 65% for that these two time-series do not show significant decreasing trend for pH. Despite of such large errors, estimated from these rates, the seawater pH has decreased by about 0.07–0.08 U over the past 200 years in these regions.

[A graph from this paper (Fig. 2, page 5, red font) shows pH varying more in a span of a few years (0.1 to 0.4) than it has for the entirety of the last 200 years (0.07 to 0.08).]

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http://www.biogeosciences.net/12/4235/2015/bg-12-4235-2015.html

The effects of ocean acidification and increased temperature on physiology of six strains of the polar diatom Fragilariopsis cylindrusfrom Greenland were investigated. Experiments were performed under manipulated pH levels (8.0, 7.7, 7.4, and 7.1) and different temperatures (1, 5, and 8 °C) to simulate changes from present to plausible future levels. … By combining increased temperature and acidification, the two factors counterbalanced each other, and therefore no effect on the growth rates was found. … Based on these results, we anticipate that the polar diatom F. cylindrus will be unaffected by changes in temperature and pH within the range expected by the end of the century. In each simulated scenario, the variation in growth rates among the strains was larger than the variation observed due to the whole range of changes in either pH or temperature. Climate change may therefore not affect the species as such, but may lead to changes in the population structure of the species, with the strains exhibiting high phenotypic plasticity, in terms of temperature and pH tolerance towards future conditions, dominating the population.

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http://www.nature.com/nature/journal/v523/n7558/full/523008c.html

Heat tolerance in corals can be passed down the generations, suggesting that corals can adapt as the climate warms.

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http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2669930

Detrended correlation analysis of annual fossil fuel emissions and mean annual changes in ocean CO2 concentration in the sample period 1958-2014 shows no evidence that the two series are causally related. The finding is inconsistent with the claim that fossil fuel emissions have a measurable impact on the CO2 concentration of the oceans at a lag and time scale of one year. The results are presented with the disclaimer that the CO2 data time series is discontinuous.

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http://www.pnas.org/content/early/2015/10/01/1505586112.full.pdf?sid=26b9f3e1-4ff7-4247-821f-e806352a8708

The FOCE experiment was designed to simulate the effects of CO2-driven acidification predicted to occur by the end of this century (scenario RCP4.5) while simultaneously maintaining the exposure of corals to natural variations in their environment under in situ conditions. Analyses of skeletal growth (measured from extension rates and skeletal density) showed no systematic differences between low-pH FOCE treatments (Δ pH=0.05 to0.25 units below ambient) and present day controls (ΔpH=0) for calcification rates or the pH of the calcifying fluid (pH cf) … Furthermore, individual nubbins exhibited near constant δ11B compositions along their primary apical growth axes (±0.02 pHcf units) regardless of the season or treatment. Thus, under the highly dynamic conditions of the Heron Island reef flat, P. cylindrica up-regulated the pH of its calcifying fluid (pH cf ∼ 8.4 – 8.6), with each nubbin having near-constant pH cf values independent of the large natural seasonal fluctuations of the reef flat waters (pH∼ 7.7 to ∼ 8.3) or the superimposed FOCE treatments. This newly discovered phenomenon of pH homeostasis during calcification indicates that coral living in highly dynamic environments exert strong physiological controls on the carbonate chemistry of their calcifying fluid, implying a high degree of resilience to ocean acidification within the investigated ranges.

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http://www.biogeosciences.net/12/6869/2015/bg-12-6869-2015.html

Cold-water corals are important habitat formers in deep-water ecosystems and at high latitudes. Ocean acidification and the resulting change in aragonite saturation are expected to affect these habitats and impact coral growth. Counter to expectations, the deep water coral Lophelia pertusa has been found to be able to sustain growth even in undersaturated conditions. However, it is important to know whether such undersaturation modifies the skeleton and thus its ecosystem functioning. Here we used Synchrotron X-Ray Tomography and Raman spectroscopy to examine changes in skeleton morphology and fibre orientation. We combined the morphological assessment with boron isotope analysis to determine if changes in growth are related to changes in control of calcification pH. We compared the isotopic composition and structure formed in their natural environment to material grown in culture at lower pH conditions. Skeletal morphology is highly variable but shows no distinctive differences between natural and low pH conditions. … We suggest that as long as the energy is available to sustain the up-regulation, i.e. individuals are well fed, there is no detrimental effect to the skeletal morphology.

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https://www.newscientist.com/article/dn28468-growing-corals-bathe-themselves-in-acid-without-suffering-damage/?utm_source=NSNS&utm_medium=SOC&utm_campaign=hoot

More acidic water may be a sign of healthy corals, says a new study, muddying the waters still further on our understanding of how coral reefs might react to climate change.

Andreas Andersson of the Scripps Institution of Oceanography in San Diego, California, and his colleagues carefully monitored a coral reef in Bermuda for five years, and found that spikes in acidity were linked to increased reef growth.

“At first we were really puzzled by this,” says Andersson. “It’s completely the opposite to what we would expect in an ocean-acidification scenario.”

The researchers observed the chemistry of the water on the reef between 2007 and 2012. During that time, there were two sharp spikes in acidity – once in 2010 and again in 2011.

The team found that coral growth itself made the water more acidic as the corals sucked alkaline carbonate out of the water to build their skeletons. The corals also ate more food during these high-activity periods and pumped more CO2 into the water, increasing acidity further.

 

 

Urban Heat Island/Unreliable Temperature Record (6)

 

http://onlinelibrary.wiley.com/doi/10.1002/2014GL062803/abstract

Observations from the main mountain climate station network in the western United States (US) suggest that higher elevations are warming faster than lower elevations. This has led to the assumption that elevation-dependent warming is prevalent throughout the region with impacts to water resources and ecosystem services. Here, we critically evaluate this network’s temperature observations and show that extreme warming observed at higher elevations is the result of systematic artifacts and not climatic conditions. With artifacts removed, the network’s 1991–2012 minimum temperature trend decreases from +1.16 °C decade−1 to +0.106 °C decade−1 and is statistically indistinguishable from lower elevation trends. Moreover, longer-term widely used gridded climate products propagate the spurious temperature trend, thereby amplifying 1981–2012 western US elevation-dependent warming by +217 to +562%. In the context of a warming climate, this artificial amplification of mountain climate trends has likely compromised our ability to accurately attribute climate change impacts across the mountainous western US.

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http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-14-0295.1?af=R&utm_source=feedly&utm_medium=webfeeds

The trend of surface air temperature (SAT) is a critical indicator to climate change in varied spatial scales. Due to urbanization effects, however, the current SAT records of many urban stations can hardly meet the demands of the studies. Evaluation and adjustment of the urbanization effects on the SAT trends are needed, which requires an objective selection of reference (rural) stations. … The results showed a highly significant urbanization effect of 0.074°C/10yr and urbanization contribution of 24.9% for the national stations of mainland China for the time period 1961-2004

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http://www.sciencedaily.com/releases/2015/11/151118131726.htm

Temperatures in the urban core of Minneapolis, St. Paul and Bloomington average 2 °F higher in summer than in surrounding areas.  The differential spiked as much as 9 °F higher during a heat wave in July 2012.  Urban heat island effect is stronger at night in summer and during the day in winter. In urban areas during the winter when snow cover is less pervasive, temperatures are higher than rural areas in the daytime by an average of 2 °F.

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http://link.springer.com/article/10.1134%2FS000143381509011X#/page-1

This article presents the results of a study of the urban heat island (UHI) in the city of Apatity [Russian Arctic] during winter that were obtained according to the data of field meteorological measurements and satellite images. Calculations of the surface layer temperature have been made based on the surface temperature data obtained from satellite images. … As a result of the analysis of temperature fields, an intensive heat island (up to 3.2°C) has been identified that was estimated based on the underlying surface temperature, and its mean intensity over the observation period significantly exceeds the representative data for European cities in winter. It has also been established that the air temperature calculated according to the MODIS data is systematically higher under winter conditions than the air temperature from direct measurement data.

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http://www.sciencedirect.com/science/article/pii/S1364682615000577

HighlightsObserve an overestimation of temperature after including non-valid stations.

Abstract: Starting from a set of 6190 meteorological stations we are choosing 6130 of them and only for Northern Hemisphere we are computing average values for absolute annual MeanMinimumQ1, MedianQ3,Maximum temperature plus their standard deviations for years 1800–2013, while we use 4887 stations and 389 467 rows of complete yearly data. The data quality and the seasonal bias indices are defined and used in order to evaluate our dataset. After the year 1969 the data quality is monotonically decreasing while the seasonal bias is positive in most of the cases.

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http://www.sciencedirect.com/science/article/pii/S0169809515000988

Highlights

  • The seasonal and temporal variability and trends of UHI in Athens was studied. •UHI[the Urban Heat Island effect]accounts for almost half of Athens’ warming.

 

The study explores the interdecadal and seasonal variability of the urban heat island (UHI) intensity in the city of Athens. Daily air temperature data from a set of urban and surrounding non urban stations over the period 1970–2004 were used. Nighttime and daytime heat island revealed different characteristics as regards the mean amplitude, seasonal variability and temporal variation and trends. The difference of the annual mean air temperature between urban and rural stations exhibited a progressive statistically significant increase over the studied period, with rates equal to + 0.2 °C/decade. A gradual and constant increase of the daytime UHI intensity was detected, in contrast to the nighttime UHI intensity which increases only in summer, after the mid 1980s.

 

 

Drought (9)

 

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00616.1?af=R

Portions of western North America have experienced prolonged drought over the last decade. This drought has occurred at the same time as the global warming hiatus – a decadal period with little increase in global mean surface temperature. We use climate models and observational analyses to clarify the dual role of recent tropical Pacific changes in driving both the global warming hiatus and North American drought. When we insert observed tropical Pacific wind stress anomalies into coupled models, the simulations produce persistent negative sea surface temperature anomalies in the eastern tropical Pacific, a hiatus in global warming, and drought over North America driven by SST-induced atmospheric circulation anomalies. In our simulations the tropical wind anomalies account for 92% of the simulated North American drought during the recent decade, with 8% from anthropogenic radiative forcing changes. This suggests that anthropogenic radiative forcing is not the dominant driver of the current drought, unless the wind changes themselves are driven by anthropogenic radiative forcing.

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http://advances.sciencemag.org/content/1/10/e1500561

Megadroughts reconstructed over north-central Europe in the 11th and mid-15th centuries reinforce other evidencefrom North America and Asia that droughts were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century, with an inadequate understanding of their causes.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0260.1

The current California drought has cast a heavy burden on statewide agriculture and water resources, further exacerbated by concurrent extreme high temperatures. Furthermore, industrial-era global radiative forcing brings into question the role of long-term climate change on CA drought. How has human-induced climate change affected California drought risk? The model simulations show that increases in radiative forcing since the late 19th Century induces both increased annual precipitation and increased surface temperature over California, consistent with prior model studies and with observed long-term change. As a result, there is no material difference in the frequency of droughts defined using bivariate indicators of precipitation and near-surface (10-cm) soil moisture, because shallow soil moisture responds most sensitively to increased evaporation driven by warming, which compensates the increase in the precipitation. However, when using soil moisture within a deep root zone layer (1-m) as co-variate, droughts become less frequent because deep soil moisture responds most sensitively to increased precipitation. The results illustrate the different land surface responses to anthropogenic forcing that are relevant for near-surface moisture exchange and for root zone moisture availability. The latter is especially relevant for agricultural impacts as the deep layer dictates moisture availability for plants, trees, and many crops. The results thus indicate the net effect of climate change has made agricultural drought less likely, and that the current severe impacts of drought on California’s agriculture has not been substantially caused by long-term climate changes.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00774.1?af=R&

An analysis of the October 2013–September 2014 precipitation in the western United States and in particular over the California–Nevada region suggests this anomalously dry season, while extreme, is not unprecedented in comparison with the approximately 120-yr-long instrumental record of water year (WY; October–September) totals and in comparison with a 407-yr WY precipitation reconstruction dating back to 1571. Over this longer period, nine other years are known or estimated to have been nearly as dry or drier than WY 2014. The 3-yr deficit for WYs 2012–14, which in California exceeded the annual mean precipitation, is more extreme but also not unprecedented, occurring three other times over the past approximate 440 years in the reconstruction.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00689.1

SST forcing does not significantly affect drought intensity or frequency of occurrence, even for very persistent “megadroughts” of 15 yr or more in length. In both the CESM1.0.3 and NADA, with the exception of the Southeast United States, droughts in all regions have intensities, persistence lengths, and occurrence frequencies statistically consistent with a red noise null hypothesis. This implies that SST forcing is not the dominant factor in generating drought and therefore that many decadal megadroughts are caused by a combination of internal atmospheric variability and coupling with the land surface, with SST anomalies playing only a secondary role.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00860.1?af=R

The causes of the California drought during November to April winters of 2011/12 to 2013/14 are analyzed using observations and ensemble simulations with seven atmosphere models forced by observed SSTs. … [T]he precipitation deficit during the drought was dominated by natural variability, a conclusion framed by discussion of differences between observed and modeled tropical SST trends.

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http://onlinelibrary.wiley.com/doi/10.1002/2015EA000100/abstract?campaign=woletoc

[F]or the past century %drought has not changed, even though global PET [potential evapotranspiration] and temperature (T) have increased.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL063456/abstract

California has experienced severe drought in 2012–2014 (which appears to be continuing into 2015), with especially low winter precipitation and mountain snowpack in winter 2013–2014. However, the extent to which climate change is implicated in the drought, if at all, is not clear. By applying modeling and statistical approaches, we construct a historical record of California snowpack, runoff, and other hydrological variables of almost 100 years in length, and use the reconstructed records to analyze climate trends in the Sierra Nevada and their impact on extreme drought events in the historic record. We confirm a general warming trend and associated decreasing trends in spring snowpack and runoff. We find that the warming may have slightly exacerbated some extreme events (including the 2013–2014 drought and the 1976–1977 drought of record), but the effect is modest; instead, these drought events are mainly the result of variability in precipitation.

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http://www.cpc.ncep.noaa.gov/products/outreach/CDPW40/LYON_CDPW_2015.pdf

  • Recent drying during the long rains primarily due to decadal variability of Tropical Pacific SSTs. NOTE: This represents about 10% of variance.
  • It’s possible ACC [anthropogenic climate change] may have acted to enhance the severity of recent droughts, but it cannot account for the abrupt nature of the recent decline or past decadal periods of drought, such as 1914-1925.
  • CMIP5 models exhibit major errors in simulating the obs. [observed] East African climate and large scale SST patterns. These errors are amplified in projections —> Little confidence in current projections of EA climate projections

 

Floods (2)

 

http://www.clim-past-discuss.net/11/4833/2015/cpd-11-4833-2015.pdf

Flood frequency in the discharge record is significantly correlated to changes in solar activity during solar cycles 16–23 (r = −0.47, p < 0.0001, n = 73) [1920s-2000s]. Flood frequency is higher when solar activity is reduced. These correlations between flood frequency and solar activity might provide empirical support for the solar top-down mechanism expected to modify the mid-latitude storm tracks over Europe by model studies. A lag of flood frequency responses in the Ammer discharge record to changes in solar activity of about one to three years could be explained by a modelled ocean–atmosphere feedback delaying the atmospheric reaction to solar activity variations up to a few years.

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http://www.hydrol-earth-syst-sci.net/19/3517/2015/hess-19-3517-2015.html

A compilation of 46 case studies across Europe with reconstructed discharges demonstrates that (1) in most cases present flood magnitudes are not unusual within the context of the last millennium, although recent floods may exceed past floods in some temperate European rivers (e.g. the Vltava and Po rivers); (2) the frequency of extreme floods has decreased since the 1950s, although some rivers (e.g. the Gardon and Ouse rivers) show a reactivation of rare events over the last two decades.

 

 

Hurricanes (6)

 

http://linkis.com/wiley.com/lXQQS

Our record of tropical cyclone activity reveals no significant trends in the total number of tropical cyclones (tropical storms and hurricanes) in the best sampled regions for the past 318 years. However, the total number of hurricanes in the 20th century is 20% lower than in previous centuries. Likewise, even in the incompletely sampled region north of the Lesser Antilles there is no trend in numbers but there is also a reduction in hurricane frequency in the 20th century. Likewise, 10–20°N tropical cyclone totals in 1807–1816, the highest 10-year value in 318 years, occurred when tropical Atlantic nighttime marine air temperature from 10–20°N 18–43°W was 0.64°C (±0.40°C) lower than in 1951–1980 [Chenoweth, 2001], even lower than in 1905–1925. Long-term variations in the number of tropical cyclones do not show any evidence of increasing storm frequency and have declined a nonstatistically significant amount.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL063652/abstract

As of the end of the 2014 hurricane season, the US has experienced no major hurricane landfall since Hurricane Wilma in 2005, a drought that currently stands at nine years. Here, we use a stochastic tropical-cyclone model to calculate the mean waiting time for multi-year landfall droughts. We estimate that the mean time to wait for a nine-year drought is 177 years. We also find that the average probability of ending the drought with a major landfall in the next year is 0.39, and is independent of the drought duration, as one would expect for a Bernoulli process.

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http://onlinelibrary.wiley.com/doi/10.1002/2015GL064929/abstract

More tropical cyclones in a cooler climate?

Recent review papers reported that many high-resolution global climate models consistently projected a reduction of global tropical cyclone (TC) frequency in a future warmer climate, although the mechanism of the reduction is not yet fully understood. Here we present a result of 4K-cooler climate experiment. The global TC frequency significantly increases in the 4K-cooler climate compared to the present climate. This is consistent with a significant decrease in TC frequency in the 4K-warmer climate. For the mechanism of TC frequency reduction in a warmer climate, upward mass flux hypothesis and saturation deficit hypothesis have been proposed. The result of the 4K-cooler climate experiment is consistent with these two hypotheses. One very interesting point is that the experiment has clearly shown that TC genesis is possible at sea surface temperature (SST) well below 26°C which has been considered as the lowest SST limit for TC genesis.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00769.1?af=R

This study investigates the decadal change in tropical cyclone (TC) activity over the South China Sea (SCS) in the boreal summer (June-August) since the early 1990s and explores possible causes behind it. Results show that the SCS TC [South China Sea tropical cyclone] activity experienced an abrupt decadal decrease at around 2002/2003. Compared to the TC activities from the early 1990s to 2002, the number of TCs formed in the SCS markedly decreased from 2003 through the early 2010s. Moreover, most of the TCs were primarily confined within the SCS basin during this period. The TCs that formed during the epoch 2003-2011 usually moved west-northwestward and rapidly weakened after making landfall.

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http://www.sciencedirect.com/science/article/pii/S1364682615300262?np=y

Three tropical cyclogenesis precursors, (absolute vorticity, relative humidity, vertical shear) and the combined Genesis Potential Index are investigated in order to analyse their behaviour during three different phases (descending, minimum and ascending) of the solar cycle. The correlation between these tropical cyclogenesis precursors and the Dst geomagnetic index is also assessed, with the main finding being that the correlations between both the Genesis Potential Index and the vertical shear with the Dst index are statistically significant. This result suggests that the relationship between geomagnetic [solar] activity and tropical cyclones might be modulated by the influence of geomagnetic activity on the vertical wind shear.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0188.1

Ten years ago, Webster et al. documented a large and significant increase in both the number as well as the percentage of category 4 and 5 hurricanes for all global basins from 1970 to 2004, and this manuscript examines whether those trends have continued when including 10 additional years of data. In contrast to that study, as shown here, the global frequency of category 4 and 5 hurricanes has shown a small, insignificant downward trend while the percentage of category 4 and 5 hurricanes has shown a small, insignificant upward trend between 1990 and 2014. Accumulated cyclone energy globally has experienced a large and significant downward trend during the same period. The primary reason for the increase in category 4 and 5 hurricanes noted in observational datasets from 1970 to 2004 by Webster et al. is concluded to be due to observational improvements at the various global tropical cyclone warning centers, primarily in the first two decades of that study.

 

Low Climate Sensitivity (4)

 

http://multi-science.atypon.com/doi/pdf/10.1260/0958-305X.26.6-7.1055

The central dogma is critically evaluated in the anthropogenic global warming (AGW) theory of the IPCC, claiming the Planck response is 1.2K when CO2 is doubled. The first basis of it is one dimensional model studies with the fixed lapse rate assumption of 6.5K/km. It is failed from the lack of the parameter sensitivity analysis of the lapse rate for CO2 doubling. The second basis is the Planck response calculation by Cess in 1976 having a mathematical error. Therefore, the AGW theory is collapsed along with the canonical climate sensitivity of 3K utilizing the radiative forcing of 3.7W/m2 for CO2 doubling. The surface climate sensitivity is 0.14-0.17K in this study with the surface radiative forcing of 1.1W/m2

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http://link.springer.com/article/10.1007%2Fs00382-014-2342-y

Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived using the comprehensive 1750–2011 time series and the uncertainty ranges for forcing components provided in the Intergovernmental Panel on Climate Change Fifth Assessment Working Group I Report, along with its estimates of heat accumulation in the climate system. The resulting estimates are less dependent on global climate models and allow more realistically for forcing uncertainties than similar estimates based on forcings diagnosed from simulations by such models. Base and final periods are selected that have well matched volcanic activity and influence from internal variability. Using 1859–1882 for the base period and 1995–2011 for the final period, thus avoiding major volcanic activity, median estimates are derived for ECS of 1.64 K and for TCR of 1.33 K.

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http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2573.html

A key uncertainty in projecting future climate change is the magnitude of equilibrium climate sensitivity (ECS), that is, the eventual increase in global annual average surface temperature in response to a doubling of atmospheric CO2 concentration. The lower bound of the likely range for ECS given in the IPCC Fifth Assessment Report was revised downwards to 1.5 °C, from 2 °C in its previous report, mainly as an effect of considering observations over the warming hiatus—the period of slowdown of global average temperature increase since the early 2000s. Here we analyse how estimates of ECS change as observations accumulate over time and estimate the contribution of potential causes to the hiatus. We find that including observations over the hiatus reduces the most likely value for ECS from 2.8 °C to 2.5 °C, but that the lower bound of the 90% range remains stable around 2 °C. We also find that the hiatus is primarily attributable to El Niño/Southern Oscillation-related variability and reduced solar forcing.

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http://link.springer.com/article/10.1007/s11434-014-0699-2

An irreducibly simple climate-sensitivity model is designed to empower even non-specialists to research the question how much global warming we may cause. In 1990, the First Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) expressed “substantial confidence” that near-term global warming would occur twice as fast as subsequent observation. Given rising CO2 concentration, few models predicted no warming since 2001. Between the pre-final and published drafts of the Fifth Assessment Report, IPCC cut its near-term warming projection substantially, substituting “expert assessment” for models’ near-term predictions. Yet its long-range predictions remain unaltered. The model indicates that IPCC’s reduction of the feedback sum from 1.9 to 1.5 W m−2 K−1 mandates a reduction from 3.2 to 2.2 K in its central climate-sensitivity estimate; that, since feedbacks are likely to be net-negative, a better estimate is 1.0 K; that there is no unrealized global warming in the pipeline; that global warming this century will be <1 K; and that combustion of all recoverable fossil fuels will cause <2.2 K global warming to equilibrium. Resolving the discrepancies between the methodology adopted by IPCC in its Fourth and Fifth Assessment Reports that are highlighted in the present paper is vital. Once those discrepancies are taken into account, the impact of anthropogenic global warming over the next century, and even as far as equilibrium many millennia hence, may be no more than one-third to one-half of IPCC’s current projections.

 

8 responses to “Skeptic Papers 2015”

  1. ADESSO E' IMPOSSIBILE IGNORARLI ... SOLO NEL 2015 SONO STATI PUBBLICATI OLTRE 250 PEER-REVIEWED SCIENTIFICI CHE METTONO IN SERIO DUBBIO LA SCIENZA "RISOLTA" DEL CLIMA! : Attività Solare ( Solar Activity )

    […] P. Gosselin 16 febbraio 2016Il lettore Kenneth Richard ha compilato e presentato una lunga lista di circa 250 pubblicazioni scientifiche sul clima peer-reviewed a partire dal 2015 che come premessa sostiene che il clima terrestre è guidato in gran parte […]

  2. R. Shearer
  3. bit chilly

    but, but, but, scientific consensus ,but !

  4. Impossible To Ignore – In 2015 Alone Massive 250 Peer Reviewed Scientific Papers Cast Doubt On Climate Science | NOT A LOT OF PEOPLE KNOW THAT

    […] Kenneth Richard has compiled and submitted a comprehensive list of some 250 peer-reviewed scientific papers from 2015 on climate, all supporting the premise that the Earth’s climate is driven in large part by […]

  5. 2015: Et år med ekstremt mye realistisk klimaforskning | Klimarealistene

    […] basert på observasjoner i naturen er til nå identifisert for fjoråret, den komplette listen er her. Det er en rapport på hver eneste hverdag og litt til. Dette er i tillegg til en tilsvarende […]

  6. Nordgrönlands klimat de senaste tusen åren - Stockholmsinitiativet - Klimatupplysningen

    […] NoTrickZon publicerades för en tid sedan en lista med sammandrag av 250 olika artiklar som publicerats under 2015 som ger mer eller mindre stöd för […]

  7. 250 Peer-Reviewed Papers Doubt AGW in 2015 – ClimateTheTruth.com

    […] Richard presents a list of 250 peer-reviewed papers published in 2015 supporting the skeptical position that natural factors are in fact a dominant […]

  8. Recent Energy And Environmental News – March 7th 2016 | PA Pundits - International

    […] 250 peer-reviewed AGW skeptical papers, just in 2015 […]

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