Part 1. Natural Mechanisms Of Weather, Climate Change
Solar Influence On Climate (84)
Yan et al., 2017 Morpho- and hydrodynamic variations seem to coincide with northern hemispheric solar forcing. The Medieval Warm Period (MWP) until about 1270 CE displays generally moist and warm climate conditions with minor fluctuations [stability], likely in response to variations in summer monsoon intensity. The three-partite period of the Little Ice Age (LIA), shows hydrologically unstable conditions between 1350 and 1530 CE with remarkably colder periods, assigned to a prolonged seasonal ice cover. … Seasonal freezing periods in excess of the average time of frozen water bodies also occurred in periods of the well-known grand solar minima and indicate stronger seasonality, possibly independent from variations in summer monsoon strength but with links to global northern hemispheric climate.
Li et al., 2017 We suggest that solar activity may play a key role in driving the climatic fluctuations in NC [North China] during the last 22 centuries, with its quasi ∼100, 50, 23, or 22-year periodicity clearly identified in our climatic reconstructions. … It has been widely suggested from both climate modeling and observation data that solar activity plays a key role in driving late Holocene climatic fluctuations by triggering global temperature variability and atmospheric dynamical circulation … In short, the mechanism of the climatic variations in NC can be likely summarized as follows. The strengthened solar activity could be significantly amplified by the variations in ultraviolet radiation as well as clouds (e.g., Haigh, 1996; Tinsley, 2000), resulting in the marked variability in global surface temperature. … Additionally, increased El Nino-Southern Oscillation (ENSO) strength (possibly El Niño-like phases) during drying periods, increased volcanic eruptions and the resulting aerosol load during cooling periods, as well as high volumes of greenhouse gases such as CO2 and CH4 during the recent warming periods, may also play a role in partly affecting the climatic variability in NC, superimposing on the overall solar-dominated long-term control (e.g., Wanner et al., 2008; Tan et al., 2011; Kobashi et al., 2013; Chen et al., 2015a,b).
Yndestad and Solheim, 2017 Deterministic models based on the stationary periods confirm the results through a close relation to known long solar minima since 1000 A.D. and suggest a modern maximum period from 1940 to 2015. The model computes a new Dalton-type sunspot minimum from approximately 2025 to 2050 and a new Dalton-type period TSI minimum from approximately 2040 to 2065. … Periods with few sunspots are associated with low solar activity and cold climate periods. Periods with many sunspots are associated with high solar activity and warm climate periods. … Studies that employ cosmogenic isotope data and sunspot data indicate that we are currently leaving a grand activity maximum, which began in approximately 1940 and is now declining (Usoskin et al., 2003; Solanki et al., 2004; Abreu et al., 2008). Because grand maxima and minima occur on centennial or millennial timescales, they can only be investigated using proxy data, i.e., solar activity reconstructed from 10Be and 14C time-calibrated data. The conclusion is that the activity level of the Modern Maximum (1940–2000) is a relatively rare event, with the previous similarly high levels of solar activity observed 4 and 8 millennia ago (Usoskin et al., 2003). Nineteen grand maxima have been identified by Usoskin et al. (2007) in an 11,000-yr series. … Twenty-seven grand minima are identified with a total duration of 1900 years, or approximately 17% of the time during the past 11,500 years (Usoskin et al., 2007). An adjustment-free reconstruction of the solar activity over the last three millennia confirms four grand minima since the year 1000: Maunder (1640–1720), Spörer (1390–1550), Wolf (1270–1340) and Oort (1010–1070) (Usoskin et al., 2007). … A cold period was also observed during the time of the Dalton minimum. The Maunder and the Dalton minima are associated with less solar activity and colder climate periods. In this investigation, minimum solar activity periods may serve as a reference for the identified minimum irradiations in the TSI oscillations.
Nan et al., 2017 The SST variation shows a millennial period of ~ 1500-yr and centennial periods of 131-yr and 113-yr. The ~ 1.5 kyr cycle dominated the period of 8.9–5.5 cal. kyr BP, suggesting a tele-connection between the Yellow Sea SST and global climate changes, might through the Kuroshio current. Centennial periods dominated almost all of cold periods recorded in core BY14, implying the signature of solar irradiance cycles by means of the strengthened East Asia Winter Monsoon (EAWM).
Deng et al., 2017 The results indicate that the climate of the Medieval Climate Anomaly (MCA, AD 900–1300) was similar to that of the Current Warm Period (CWP, AD 1850–present), which contradicts previous studies. … As for the Little Ice Age (LIA, AD 1550–1850), the results from this study, together with previous data from the Makassar Strait, indicate a cold and wet period compared with the CWP and the MCA in the western Pacific. The cold LIA period agrees with the timing of the Maunder sunspot minimum and is therefore associated with low solar activity.
Koutsodendris et al., 2017 The record represents the southernmost annually laminated (i.e., varved) archive from the Balkan Peninsula spanning the Little Ice Age, allowing insights into critical time intervals of climate instability such as during the Maunder and Dalton solar minima. … [W]et conditions in winter prevailed during 1740–1790 AD, whereas dry winters marked the periods 1790–1830 AD (Dalton Minimum) and 1830–1930 AD, the latter being sporadically interrupted by wet winters. This variability in precipitation can be explained by shifts in the large-scale atmospheric circulation patterns over the European continent that affected the Balkan Peninsula (e.g., North Atlantic Oscillation). … Representing one of the strongest global climate instabilities during the Holocene, the Little Ice Age (LIA) is marked by a multicentennial-long cooling (14the19th centuries AD) that preceded the recent ‘global warming’ of the 20th century. The cooling has been predominantly attributed to reduced solar activity and was particularly pronounced during the 1645-1715 AD and 1790-1830 AD solar minima, which are known as Maunder and Dalton Minima, respectively.
Tejedor et al., 2017 Reconstructed long-term temperature variations match reasonably well with solar irradiance changes since warm and cold phases correspond with high and low solar activity, respectively. … The main driver of the large-scale character of the warm and cold episodes may be changes in the solar activity. The beginning of the reconstruction starts with the end of the Spörer minimum. The Maunder minimum, from 1645 to 1715 (Luterbacher et al., 2001) seems to be consistent with a cold period from 1645 to 1706. In addition, the Dalton minimum from 1796 to 1830 is detected for the period 1810 to 1838. However, a considerably cold period from 1778 to 1798 is not in agreement with a decrease in the solar activity. Four warm periods – 1626–1637, 1800–1809, 1845– 1859, and 1986–2012 – have been identified to correspond to increased solar activity.
Zawiska et al., 2017 The chironomid-based temperature reconstruction from Lake Atnsjøen in Eastern Norway with mean resolution of 30 years provided evidence that large-scale processes, such as the NAO fluctuations and solar activity modified local climate, and subsequently affected lakes functioning. The three minor cooling periods were reconstructed in the first half of the Millennium: 1050–1150, 1270–1370, 1440–1470 CE, that coincide with solar activity minima: Oort, Wulf, and Spörer respectively. Furthermore, a two peaked cooling period in the second half of the Millennium was identified that coincided with the LIA. These changes co-occurred with the prevailing negative NAO index. … The beginning of the 1270–1370 CE cooling coincide with Wulf solar activity minimum suggesting that the climate was responding to Sun activity. The climate cooling synchronous to this solar minimum had almost global range and it has been recorded from Europe, Arctic, North America and Antarctica (Osborn and Briffa, 2006; PAGES 2k Consortium, 2013) but again not in Greenland (Osborn and Briffa, 2006). … The beginning of the 1440–1470 CE cold period is synchronous to the pronounce negative NAO phase (Trouet et al., 2009). … Maunder solar minimum caused a very deep negative NAO index phase (Shindell et al., 2001), which consecutively lead to significant drop in the reconstructed temperature. … The temperature reconstruction from Lake Atnsjøen indicates that recent and ongoing climate warming began already in 1800 CE following the LIA. Temperatures increased very fast, from 8.5 to 12.8 °C during the first 75 years [1800-1875], but in the 20th century the increase became less pronounced. … The warming at the beginning of 19th century in the region of Lake Atnsjøen coincides with a reconstruction from Southern Finland (Luoto, 2013), and a record from Northern Sweden (Osborn and Briffa, 2006). Its onset correlates with the positive NAO index and increased solar activity.
Rydval et al., 2017 [T]he recent summer-time warming in Scotland is likely not unique when compared to multi-decadal warm periods observed in the 1300s, 1500s, and 1730s … All six [Northern Hemisphere] records show a warmer interval in the period leading up to the 1950s, although it is less distinct in the CEU reconstruction. [E]xtreme cold (and warm) years observed in NCAIRN appear more related to internal forcing of the summer North Atlantic Oscillation. … There is reasonable agreement in general between the records regarding protracted cold periods which occur during the LIA and specifically around the Maunder solar minimum centred on the second half of the seventeenth century and to some extent also around the latter part of the fifteenth century coinciding with part of the Spörer minimum (Usoskin et al. 2007).
Abrantes et al., 2017 Reconstructed cold conditions in Iberia, with an average 0.5 ºC colder SST in the northern sites and 1.2ºC in the southern sites, characterize most of the 15th to 18th centuries. The transition from warm to colder climatic conditions occurs around 1300 CE associated with the Wolf solar minimum. The coldest SSTs are detected between 1350 and 1850 CE, on Iberia during the well-known Little Ice Age (LIA) (Bradley and Jones, 1993), with the most intense cooling episodes related with other solar minima events, and major volcanic forcing and separated by intervals of relative warmth (e.g. (Crowley and Unterman, 2013; Solanki et al., 2004; Steinhilber et al., 2012; Turner et al., 2016; Usoskin et al., 2011). During the 20th century, the southern records show unusually large decadal scale SST oscillations in the context of the last 2 millennia, in particular after the mid 1970’s, within the Great Solar Maximum (1940 – 2000 (Usoskin et al., 2011)) and the “greater salinity anomaly” event in the northern Atlantic (Dickson et al., 1988), or yet the higher global temperatures of the last 1.4 ky detected by (Ahmed et al., 2013).
Cui e thal, 2017 According to Chinese history, the Ming dynasty (1368-1644) was subjected to intensive environmental and economic crises that accompanied the unfavorable climate of the Little Ice Age (LIA). This situation likely led to the collapse of the Ming dynasty. … During this period, central China experienced frequent periods of increased desertification and decreased biological productivity, which limited the expansion of the Ming domain northward and the dynasty’s control over western China. [G]enerally weak monsoons [occurred] from the 14th to the 19th centuries punctuated by four severe droughts during 1476-1502, 1509-1537, 1577-1590 and 1604-1653. These drought events are evident in all three time series, indicating that the climatic trends were regional rather than local. These dry periods are correlated with reduced summer insolation [solar minima] in the Northern Hemisphere, a southward displacement of the Intertropical Convergence Zone (ITCZ) and a weak EASM [East Asian Summer Monsoon].
Williams et al., 2017 Reconstructed SSTs significantly warmed 1.1 ± 0.30°C … from 1660s to 1800 (rate of change: 0.008 ± 0.002°C/year), followed by a significant cooling of 0.8 ± 0.04°C … until 1840 (rate of change: 0.02 ± 0.001°C/year), then a significant warming of 0.8 ± 0.16°C from 1860 until the end of reconstruction in 2007 (rate of change: 0.005 ± 0.001°C/year).” [Sea surface temperatures warmed faster from 1660s-1800 than they did from 1860-2007.] … In fact, the SST reconstruction significantly co-varied with a reconstruction of solar irradiance [Lean, 2000] on the 11-year periodicity only from ~1745 to 1825. In addition, the reconstructed SSTs were cool during the period of lower than usual solar irradiance called the Maunder minimum (1645–1715) but then warmed and cooled during the Dalton minimum (1795–1830), a second period of reduced solar irradiance. … The Dalton solar minimum and increased volcanic activity in the early 1800s could explain the decreasing SSTs from 1800 to 1850 … [T]hese data suggest a complex combination of solar irradiance, volcanic activity, internal ocean dynamics and external anthropogenic forcing explain the variability in Aleutian SSTs for the past 342 years.
Didkovsky et al., 2017 Radiative forcing of the Earth’s atmosphere plays a significant role in its thermal and chemical balance (Haigh, 1994; Haigh et al., 2010). Effects of heating and cooling are influenced by long-term solar-cycle changes. One example of such change compiled from sources that show sensitivity to the changes of solar activity (Hoyt and Schatten, 1998) is the Maunder Minimum of 1645 to about 1715 (Maunder, 1890). These observations demonstrate the effects of solar-activity changes during the Maunder Minimum for which low to near-zero sunspot numbers persisted for about six solar cycles (SC) with a SC-averaged period (for SC 1 to 22) of 11 years (Hathaway, 2010).
Nan et al., 2017 Furthermore, our temperature records, within age uncertainty, coincides with the changes of the solar irradiance changes, suggesting a possible link between solar forcing and climate variability. … The relationship between the solar irradiance and climate change has been demonstrated by lots of studies (He et al., 2013; Kroonenberg et al., 2007; Sagawa et al., 2014; Soon et al., 2014). It was suggested that the solar activity was a primary driving force of climatic variations in the Holocene (Bond et al., 2001; Wang et al., 2005). Small solar perturbations can be magnified by different feedback mechanisms and may ultimately lead to climatic oscillations on several time scales, such as annual to decadal and/or centennial scales, as well as millennial scales (Haigh, 1996; Bond et al., 2001).
Pandey and Dubey, 2017 The Maunder minimum (1645-1715) refers to a period when very few sunspots were observed. During this period, the Earth climate was cooler than normal. This period mimics the solar cycle climate change connections. The particles and electromagnetic radiations flowing from solar activity outbursts are important for long-term climate variations. There is an abrupt and drastic cooling in the climate can be possible in near future due to large scale melting of global ice by global warming, and prolonged sunspot minima. There is a close correlation between variations in the 11-year sunspot cycle and Earth’s climate. Solar activity varies on shorter-time scales, including the 11- year sunspot cycle and longer-term as Milankovitch cycle.
Park, 2017 Late Holocene climate change in coastal East Asia was likely driven by ENSO variation. Our tree pollen index of warmness (TPIW) shows important late Holocene cold events associated with low sunspot periods such as Oort, Wolf, Spörer, and Maunder Minimum. Comparisons among standard Z-scores of filtered TPIW, ΔTSI, and other paleoclimate records from central and northeastern China, off the coast of northern Japan, southern Philippines, and Peru all demonstrate significant relationships [between solar activity and climate]. This suggests that solar activity drove Holocene variations in both East Asian Monsoon (EAM) and El Niño Southern Oscillation (ENSO). In particular, the latter seems to have predominantly controlled the coastal climate of East Asia to the extent that the influence of precession was nearly muted during the late Holocene.
Chapanov et al., 2017 DECADAL CYCLES OF EARTH ROTATION, MEAN SEA LEVEL AND CLIMATE, EXCITED BY SOLAR ACTIVITY … But recently, another mechanism of climate variations, due to cosmic rays was proposed (Kilifarska and Haight, 2005; Kilifarska, 2008, 2011; Velinov et al., 2005). According to the new models, the cosmic rays produce a ionization of the atmosphere, changes of atmosphere conductivity, lightning, and an increase of ozone concentration. The ozone plays significant role in climate variations, so the new models of cosmic ray influences on Earth atmosphere may explain the observed correlation between cosmic rays and climate variations. … The shape of solar cycles is rather different from sinusoidal form, so they affect geosystems by many short-term harmonics. A possible solar origin of decadal variations of Earth rotation, mean sea level and climate indices is investigated by the harmonics of Jose, de Vries and Suess cycles with centennial periods of 178.7, 208 and 231 years. The common decadal cycles of solar-terrestrial influences are investigated by long time series of Length of Day (LOD), Mean Sea Level (MSL) variations at Stockholm, ElNiño/Southern Oscillation (ENSO), temperature and precipitation over Eastern Europe, Total Solar Irradiance (TSI), Wolf’s Numbers Wn and North-South solar asymmetry. A good agreement exists between the decadal cycles of LOD [length of day], MSL [mean sea level], climate and solar indices whose periods are between 12-13, 14-16, 16-18 and 28-33 years. … The Total Solar Irradiance (TSI), Wolf’s Numbers (Wn) and North-South (N-S) solar asymmetry expose different spectral peaks, amplitude modulation and phases from these bands. These solar time series represent thermal heating over the Earth, solar wind (space weather) and solar magnetic field variations. The decadal cycles of N-S [North-South] solar asymmetry strongly affect corresponding cycles of El Nino/Southern Oscillation (ENSO).
Helama et al., 2017 (full) Solar proxy data (Steinhilber et al., 2009) consistently illustrate low activity between AD 400 and 700, with a notable seventh-century solar minimum, the millennial-scale solar changes culminating over these centuries and thus during the DACP [Dark Ages Cold Period] (Scafetta, 2012). Interestingly, there is multiple proxy evidence showing that reduced solar activity may modulate the North Atlantic Oscillation (NAO) towards its negative phase (Gray et al., 2010). Since the NAO is a leading pattern of climate variability in the global atmosphere, and the negative NAO phase is generally associated with cooler temperatures particularly over western Europe and eastern North-America for both the winter (Wanner et al., 2001; Hurrell and Deser, 2010) and summer seasons (Folland et al., 2009), a prolonged negative NAO phase could thus result in cold temperatures at least over some parts of the Northern Hemisphere continents.
Yukimoto et al., 2017 A delayed response of the winter North Atlantic oscillation (NAO) to the 11-year solar cycle has been observed and modeled in recent studies. The result of this study supports a previous hypothesis that suggests that the 11-year solar cycle signals on the Earth’s surface are produced through a downward penetration of the changes in the stratospheric circulation. … The importance of the North Atlantic oscillation (NAO) for the European weather and climate conditions has been known for a long time (Walker and Bliss 1932; van Loon and Rogers 1978; Hurrell et al. 2003). NAO is the dominant intrinsic mode of atmospheric variability over the Atlantic sector (Hurrell and Deser 2009). … The present result confirms the previous hypothesis reported by Kodera et al. (2016), which stated that the major solar influence on the Earth’s surface can be produced through changes in stratospheric circulation, and the spatial structure of the solar signal at the Earth’s surface is largely conditioned by atmosphere’s interaction with the ocean.
Wang et al., 2017 The identification of causal effects is a fundamental problem in climate change research. Here, a new perspective on climate change causality is presented using the central England temperature (CET) dataset, the longest instrumental temperature record, and a combination of slow feature analysis and wavelet analysis. The driving forces of climate change were investigated and the results showed two independent degrees of freedom —a 3.36-year cycle and a 22.6-year cycle, which seem to be connected to the El Niño–Southern Oscillation cycle and the Hale sunspot cycle, respectively.
Gray et al., 2017 “There are several proposed mechanisms through which the 11-year solar cycle (SC) could influence the Earth’s climate, as summarised by Figure 1. These include: (a) the direct impact of solar irradiance variability on temperatures at the Earth’s surface, characterised by variation in the total incoming solar irradiance (TSI); (b) the indirect impact of variations through the absorption of Ultra-Violet (UV) radiation in the upper stratosphere associated with the presence of ozone, with accompanying dynamical responses that extend the impact to the Earth’s surface; (c) the indirect impact of variations in energetic particle fluxes into the thermosphere, mesosphere and upper stratosphere at high geomagnetic latitudes; and (d) the impact of variations in the generation of ions by galactic cosmic ray (GCR) penetration into the troposphere. Although different in their nature, these four pathways may not work in isolation but their influence could be synergetic.”
Zharkova et al., 2017 “Using a summary curve of two eigen vectors of solar magnetic field oscillations derived with Principal Components Analysis (PCA) from synoptic maps for solar cycles 21-24 as a proxy of solar activity, we extrapolate this curve backwards three millennia revealing 9 grand cycles lasting 350-400 years each. The summary curve shows a remarkable resemblance to the past sunspot and terrestrial activity: grand minima – Maunder Minimum (1645-1715 AD), Wolf minimum (1280-1350 AD), Oort minimum (1010-1050 AD) and Homer minimum (800 900 BC); grand maxima – modern warm period (1990-2015), medieval warm period (900-1200 AD), Roman warm period (400-10 BC) and others. We verify the extrapolated activity curve by the pre-telescope observations of large sunspots with naked eye, by comparing the observed and simulated butterfly diagrams for Maunder Minimum (MM), by a maximum of the terrestrial temperature and extremely intense terrestrial auroras seen in the past grand cycle occurred in 14-16 centuries.”
“We confirm the occurrence of upcoming Modern grand minimum in 2020-2053, which will have a shorter duration (3 cycles) and, thus, higher solar activity compared to MM [Maunder Minimum]. … One of the examples of fitting incorrectly the oscillating function with a linear regression approach is shown by Akasofu (2010) (see her Fig. 9), when explaining the modern era recovery of the Earth from the little ice period and the incorrect use of a linear part of the temperature variations for the extremely incorrect prediction of the terrestrial temperature growth in the next century.”
Harde, 2017 “[A] naturally generated [CO2 emission] contributes more than 95% to the overall emission, and its generation rate and the respective absorption rate sensitively respond on global temperature variations. … [The] well known delayed response of CO2 and methane (CH4) to sea and air temperature changes (see, e.g., Petit et al. ; Monnin et al. ; Caillon et al. ; Torn and Harte ; Humlum et al. ; Salby ) are not considered in AR5. … As long as any natural variations in the CO2 concentrations are not accurately known, the ECS [equilibrium climate sensitivity to CO2 doubling] cannot be used as a reliable indicator only for an anthropogenic global warming.”
“The IPCC denies any noticeable solar influence on the actual climate, although strong evidence of an increasing solar activity over the last century exists (see, e.g., Hoyt & Schatten ; Willson & Mordvinov ; Shapiro et al. ; Ziskin & Shaviv ; Scafetta & Willson ; Usoskin et al. ; Zhao & Feng ; Soon et al. ). … From these studies we conclude that the measured temperature increase of 0.74∘ C over the time 1880–2000 and the observed cloud changes of −4% over the period 1983– 2000 can best be explained by a cloud feedback mechanism, which is dominated by the solar influence. Therefore, it seems quite reasonable to use a model mean of [climate sensitivity to doubled CO2] = 0.7°C, yielding a CO2 initiated warming of 0.3°C [1880-2000] and a solar contribution of 0.44°C [1880-2000].”
Pande et al., 2017 “Ozone is a highly reactive, naturally occurring ingredient of the stratosphere that is produced from oxygen by sunlight. It is one of the most important chemicals in both the stratosphere and troposphere. Apart from absorbing the harmful ultaviolet radiation from the sun, it [ozone] also plays an important role in determining earth’s climate. Solar variability affects ozone through radiative heating in atmosphere. Solar UV radiation is absorbed by atmospheric ozone. It is responsible for both the creation and destruction of ozone. … The total ozone was found to be enhanced during magnetically disturbed conditions which are associated with peak solar activity periods. Angell and Korshover (1976) concluded that there is nearly in-phase relationship between sunspot number and total ozone.”
Le Mouël et al., 2017 [S]olar activity contains an important component that has undergone clear oscillations of ≈90 years over the past three centuries, with some small but systematic longer-term evolution of “instantaneous” period and amplitude. Half of the variance of solar activity on these time scales can be satisfactorily reproduced as the sum of a monotonous multi-secular increase, a ≈90 -year Gleissberg cycle, and a double-peaked (≈10.0 and 11.0 years) Schwabe cycle (the sum amounts to 46% of the total variance of the signal). The Gleissberg-cycle component definitely needs to be addressed when attempting to build dynamo models of solar activity. The first SSA component offers evidence of an increasing long-term trend in sunspot numbers, which is compatible with the existence of the modern grand maximum.
Wen et al., 2017 “A warmer and wetter climate prevailed since ∼4800 a BP and was interrupted by a sharp cold reversal at approximately 3300 a BP that was likely caused by solar irradiance forcing, which resulted in a global cold climatic change and glacier advance.”
Munz et al., 2017 “Decadal resolution record of Oman upwelling indicates solar forcing of the Indian summer monsoon (9–6 ka) … We use geochemical parameters, transfer functions of planktic foraminiferal assemblages and Mg / Ca palaeothermometry, and find evidence corroborating previous studies showing that upwelling intensity varies significantly in coherence with solar sunspot cycles. The dominant ∼ 80–90-year Gleissberg cycle apparently also affected bottom-water oxygen conditions.”
Allan et al., 2017 “Speleothem is now regarded as valuable archive of climatic conditions on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores. … [T]race elements in speleothems have the potential to provide high resolution insights into palaeoclimatic variability during the Holocene. A deeper analysis reveals several periods of significant rapid climate change during the Holocene (at 10.7-9.2 ka, 8.2-7.9 ka, 7.2-6.2 ka, 4.8-4.5 ka, and 3-2.4 ka BP), which are similar to the cold events detected from different natural paleoclimate archivers. A comparison between the geochemical analysis of Père Noël speleothem and solar activity (sunspot number) reveals a significant correlation. Spectral analysis methods reveal common solar periodicities (Gleissberg cycle, de Vries cycle, unnamed 500 year, Eddy cycles, and Hallstatt cycle). The geochemical analyses have the potential to prove that PN speleothem is sensitive to changes in solar activity on centennial and millennial timescales during the Holocene.”
Woodson et al., 2017 “The last ca. 1000 years recorded the warmest SST averaging 28.5°C. We record, for the first time in this region, a cool interval, ca. 1000 years in duration, centered on 5000 cal years BP concomitant with a wet period recorded in Borneo. The record also reflects a warm interval from ca. 1000 to 500 cal years BP that may represent the Medieval Climate Anomaly. Variations in the East Asian Monsoon (EAM) and solar activity are considered as potential drivers of SST trends. However, hydrology changes related to the El Nino-Southern Oscillation (ENSO) variability, ~ shifts of the Western Pacific Warm Pool and migration of the Intertropical Convergence Zone are more likely to have impacted our SST temporal trend. … The SA [solar activity] trends (Steinhilber et al., 2012) are in general agreement with the regional cooling of SST (Linsley et al., 2010) and the SA [solar activity] oscillations are roughly coincident with the major excursions in our SST data.”
Li et al., 2017 “The main driving forces behind the Holocene climatic changes in the LYR [Lower Yangtze Region, East China] area are likely summer solar insolation associated with tropical or subtropical macro-scale climatic circulations such as the Intertropical Convergence Zone (ITCZ), Western Pacific Subtropical High (WPSH), and El Niño/Southern Oscillation (ENSO).”
Chen et al., 2017 The 11-year cycle suggests the influence of sunspot activity (Hale, 1924) on streamflow variations in the Tien Shan. The impact of variations in solar activity on streamflow series and other climate phenomena have been reported from North America and Europe, based on instrumental records (Zanchettin et al., 2008; Perry, 2006 ; Prokoph et al., 2012). A strong positive correlation was also found between solar activity and streamflow in South American rivers (Mauas et al., 2011). … To further investigate the links between the solar activity and streamflow of the Tien Shan, we examined the relationship between PC1 and the number of sunspots, using correlation and wavelet coherency analyses. A significant linkage was found at the quasi-11-year scale from the 1700–2000s.
Kuroda, 2017 The Polar-night Jet Oscillation (PJO) is the dominant mode of stratospheric variability in the Southern Hemisphere (SH), and persists from mid-winter to spring. The influence of the 11-year solar cycle on modulation of the PJO from late winter to spring is examined using observations and three 42-year simulations from a chemistry-climate model. … We suggest that UV modulation of the interactions between planetary waves and zonal-mean flow in the stratosphere, rather than direct diabatic processes as suggested in a previous study, is the source of solar cycle modulation of the PJO.
Shi et al., 2017 Meanwhile, the stronger (weaker) EASM/ASM during the MCA (LIA) was associated with expansion (retreat) of the local Intertropical Convergence Zone and an enhanced (reduced) zonal temperature gradient over the equatorial Pacific. Our results imply that the synchronous change in the Asian–Australian monsoon may be caused by inherent solar variations, further strengthening previous findings.
Xiao et al., 2017 Spectral analysis of Tsuga and evergreen oak pollen percentages shows statistically significant periodicities of ~1500 and ~200 years at the ≥95% confidence level, which suggests that insolation and feedback interactions on millennial to centennial scales are the primary forcing mechanisms of the southwest monsoon and past climatic change during the Holocene in northwestern Yunnan Province, southwestern China.
Chang et al., 2017 “The chironomid-based record from Heihai Lake shows a summer temperature fluctuation within 2.4°C in the last c. 5000 years from the south-east margin of the QTP [Qinghai–Tibetan Plateau]. … The summer temperature changes in this region respond primarily to the variation in the Asian Summer Monsoon. The variability of solar activity is likely an important driver of summer temperatures, either directly or by modifying the strength and intensity of the Indian Ocean Summer Monsoon. … We observed a relatively long-lasting summer cooling episode (c. 0.8°C lower than the 5000-year average) between c. 270 cal. BP and AD c. 1956. … The record shows cooling episodes occurred at c. 3100, 2600, 2100 and 1600 cal. BP. This is likely related to the period defined as the Northern Hemisphere Little Ice Age (LIA; c. AD 1350–1850, equivalent to 600–100 cal. BP). These possibly relate to the 500-year quasi-periodic solar cycle. Cooling stages between c. 270 and 100 cal. BP were also recorded and these are possibly linked to the LIA suggesting a hemisphere-wide forcing mechanism for this event.”
Lei et al., 2017 “The precipitation variability on decadal to multi-centurial generally always reflects changes in solar activity and large-scale circulation, e.g., the ENSO and the EASM [East Asian Summer Monsoon] (Chen et al., 2011; Vleeschouwer et al., 2012; Feng et al., 2014). [D]uring the MWP [Medieval Warm Period], the wetter climate in this region was consistent with more frequent ENSO events, stronger EASM and higher solar activity, whereas the opposite was found for the LIA. In particular, d13Cac fluctuations on multi-decadal to centennial scales is consistent with the changes in solar activity, with fewer dry intervals corresponding to periods of minimum solar activity within dating errors, which are referred to as the Oort Minimum (AD 1010-1050), Wolf Minimum (AD 1280-1340), Sporer Minimum (AD 1420-1530), Maunder Minimum (AD 1645-1715) and Dalton Minimum (AD 1795-1820). These results suggest that climate change in southeastern China is sensitive to ENSO and the EASM, which may be driven by solar activity.”
Zhang et al., 2017 “The record suggests the summer temperature varies by ~2.5 °C across the entire period. A generally warmer period occurred between c.8500 and c.6000 cal yr BP and a cooling trend was initiated from c.5500 cal yr BP. The overall pattern broadly matches the summer insolation at 30N and the Asian Summer Monsoon records from the surrounding regions suggesting that summer temperatures from the southeast margin of the QTP respond to insolation forcing and monsoon driven variability on a multi-millennial time scale. Modifications of this overall trend are observed on the finer temporal resolution and we suggest that solar activity could be an important mechanism driving the centennial-scale variability. It may have a strengthened effect in the late Holocene when the monsoon influence weakened.”
Luoto and Nevalainen, 2017 “Here,http://notrickszone.com/wp-content/uploads/2017/05/Holocene-Cooling-Greenland-Ice-Sheet-Zhang-2017.jpg we use completely synchronized paleolimnological proxy-based records of air temperature and effective precipitation from two Scandinavian lakes with ∼2000-year sediment profiles. We show that the relationship between air temperature and precipitation (T/P ratio) is synchronous in both study sites throughout the records suggesting warm and dry conditions at ∼300–1100 CE and cold and wet conditions at ∼1200–1900 CE. Owing to the significantly increased air temperatures, the most recent T/P ratio has again turned positive. During the first millennium of the Common Era, the T/P mimics patterns in Southern Oscillation index, whereas the second millennium shows response to the NAO index but is also concurrent with solar irradiance shifts. [T]he causes for the LIA [Little Ice Age [1200-1900 CE], are not well defined owing to its highly variable nature (Wanner et al. 2011; Luoto and Nevalainen 2016; Zawiska et al. 2017). Yet, in addition to a persistent strongly negative NAO index phase during the LIA, it was most likely forced by decreased solar irradiance (including Spörer, Maunder and Dalton solar minima), increased volcanic activity (aerosols), and changes in Atlantic Ocean circulation patterns (Grove 2001; Goosse et al. 2005; Wanner et al. 2011).”
Li et al., 2017 “Correlations between paleotemperature records from the North Atlantic and solar activity suggest that changes in solar output may cause significant shifts in the climate of the North Atlantic region. To test the role of solar activity on summer SST at our study site in West Greenland, we conducted a cross-correlation analysis between our reconstructed summer SST record and a total solar irradiance (TSI) series. The results indicate that the maximum correlation coefficient (0.284) of summer SST [sea surface temperatures] and TSI [total solar irradiance] records is obtained at nearly zero time-lag (-6 time-lag), which means that variations in solar activity affected the summer SST variability in the study area. … A significant positive relationship between summer SSTs on the North Icelandic shelf and solar irradiance reconstructed from 10Be and 14C records during the Holocene was also demonstrated by Jiang et al. This finding is also supported by recent climate model simulations using the Community Climate System Model version 4 (CCSM4). The model results show a strong positive correlation between SST and solar irradiance in the pathway of the IC, indicating that a reduced frequency of Atlantic blocking events during periods of high solar irradiance promotes warmer and saltier conditions in the pathway of the IC due to stronger circulation of the subpolar gyre. … Spectral analyses indicate that significant centennial-scale variations are superimposed on the long-term orbital trend. The dominant periodicities are 529, 410, and 191 years, which may be linked to the well-known 512- and 206-year solar cycles. Cross-correlation analyses between the summer SSTs and total solar irradiance through the last 5000 years indicate that the records are in phase, providing evidence that variations in solar activity impacted regional summer SST variability. Overall, the strong linkage between solar variability and summer SSTs is not only of regional significance, but is also consistent over the entire North Atlantic region.”
Orme et al., 2017 “The north-south index shows that storm tracks moved from a southern position to higher latitudes over the past 4000 yr, likely driven by a change from meridional to zonal atmospheric circulation, associated with a negative to positive North Atlantic Oscillation shift. We suggest that gradual polar cooling (caused by decreasing solar insolation in summer and amplified by sea-ice feedbacks) and mid-latitude warming (caused by increasing winter insolation) drove a steepening of the winter latitudinal temperature gradient through the late Holocene, resulting in the observed change to a more northern winter storm track.”
Serykh and Sonechkin, 2017 “The global climate is a quasi-periodically forced dynamic system [1, 2]. In addition to the annual cycle of the heat transport from the Sun and the diurnal cycle of the Earth’s rotation, other external periodical forces exist, which are potentially able to cause climate fluctuations. The lunar and solar tides are such causes on the time scales of the order of one day. On the decadal scale, these causes are 11-year variations in the Sun spots (the Wolf cycle) and its double period manifested in the changes in the heliospheric field polarity (the Hale cycle). The existence of secular solar cycles is also possible (Gleissberg and Suess cycles found in a number of Sun spots). Calculations indicate that an approximately 180-year cycle exists in the rotation of the Sun around the center of mass of the Solar system. The authors of  suggest that it is related to the sequence of significant decreases in the solar activity in the last millennium known as the Oort, Wolf, Spörer, Maunder, and Dalton periods. Paleoclimatic evidence of climate cooling during these periods exists. We can conclude on this basis that the ONI [ENSO index] dynamics [are] governed predominantly by two periodical external forces (the annual heat transport to the climatic system from the Sun and the Chandler wobble of the Earth’s poles) and that the system is not chaotic. This fact indicates that a principal possibility exists for long-term (many years in advance) ENSO forecasts.”
Kitaba et al., 2017 “The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. … Greater terrestrial cooling indicates that a reduction of insolation [solar radiation reaching the surface] is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect.”
Perșoiu et al., 2017 “Throughout the Holocene, the subterranean ice block in Scărișoara Ice Cave responded sensitively to changes in both winter temperature and moisture source. During this time period, winter temperature in ECE [East Central Europe] was mainly controlled by insolation [solar radiation] changes. The interplay between insolation variability, SST changes in the North Atlantic, and the influence of the lingering Laurentide Ice Sheet modulated the dynamics of large-scale atmospheric circulation.”
Luthardt and Rößler “The 11 yr solar cycle, also known as Schwabe cycle, represents the smallest-scaled solar cyclicity and is traced back to sunspot activity (Douglass, 1928; Lean, 2000), which has a measurable effect on the Earth’s climate, as indicated by the Maunder minimum (Usoskin et al., 2015). Global climate feedback reactions to solar irradiance variations caused by sunspots are complex and hypothesized to be triggered by (1) variation in total energy input (Cubasch and Voss, 2000), (2) the influence of ultraviolet light intensity variation on composition of the stratosphere (Lean and Rind, 2001), (3) the effect of cosmic rays on cloud formation (Marsh and Svensmark, 2000; Sun and Bradley, 2002), and/or (4) the effect of high-energy particles on the strato- and mesosphere (Jackman et al., 2005). … [L]ike today, sunspot activity caused fluctuations of cosmic radiation input to the atmosphere, affecting cloud formation and annual rates of precipitation“
Cosentino et al., 2017 A review of the literature indicates that the climate was significantly less stable than previously supposed during the Holocene, since its warming trend was characterized by relevant short-term cooling events occurring at decennial and centennial scale (Dansgaard et al., 1993; Bond et al., 1999; Mayewski et al., 2004). The most recent cold phase was the Little Ice Age (LIA), which caused the expansion of glaciers in the alpine regions at lower latitudes. Several authors have linked this cooler climatic condition to a period of reduced solar activity (Mauquoy et al., 2002), which caused a decrease in summer insolation (Wanner et al., 2011). … [T]he cooling event known as Little Ice Age (LIA)… persisted more or less from the 13th to the 19th century (Perry and Hsu, 2000). … Furthermore, the fluctuations occurring in the frequency curve of H. balthica could be related to several brief cooling events which characterize the LIA, namely Wolf, Sporer, Maunder and Dalton [solar minimum periods] (Lamb, 1984; Mauquoy et al., 2002).
Huo and Xiao, 2017 In this paper, the authors investigate a particular feature, the ocean heat content (OHC) anomaly, in different phases of the total solar irradiance (TSI) cycle. The results show that almost opposite spatial patterns appear in the tropical Pacific during the ascending and declining phases of the TSI cycle. Further analysis reveals the presence of the quasi-decadal (~11-year) solar signal in the SST [sea surface temperature], OHC [ocean heat content] and surface zonal wind anomaly field over the tropical Pacific with a high level of statistical confidence (>95%). … In Misios and Schmidt (2012), the ensemble simulations from an AOGCM showed that the tropical SST oscillates almost in-phase with the 11-year solar cycle. White and Liu (2008) also found the fluctuation of the upper ocean warming to be in-phase with TSI on the decadal scale during the twentieth century, governed by a resonant excitation of the tropical delay action oscillator and solar forcing, and the warming stage lagged the solar peak year by one to three years. … [P]atterns of OHC and potential temperature anomalies in the tropical Pacific are quite spatially symmetric in the ascending and declining phases, which seems phase-locked with the phases of the TSI cycle. The most significant regions of the OHC anomaly are locate just in the high correlation areas (beyond the 95% confidence level), which are ‘solar-sensitive’ regions with a clear quasi-11-year period.
Stein et al., 2017 The causes that are controlling the decrease in sea ice are still under discussion. In several studies changes in extent, thickness and drift of Arctic sea ice are related to changes in the overall atmospheric circulation patterns as reflected in the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The NAO and AO are influencing changes of the relative position and strength of the two major surface-current systems of the Arctic Ocean. … The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon, coinciding with major glacier advances on Franz Josef Land, Spitsbergen and Scandinavia. The increase in sea ice may have resulted from the continuing cooling trend due to decreased solar insolation and reduced heat flow from the Pacific. … The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon as PIP25-based sea ice records from the Fram Strait, Laptev Sea, East Siberian Sea and Chukchi Sea display a generally quite similar evolution, all coinciding with the decrease in solar radiation … The main factors controlling the millennial variability in sea ice and surface-water productivity are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long-term decrease in summer insolation, whereas short-term centennial variability observed in the high-resolution middle Holocene record was possibly triggered by solar forcing.
Schmutz, 2017 For the first time, model calculations show a plausible way that fluctuations in solar activity could have a tangible impact on the climate. Studies funded by the Swiss National Science Foundation expect human-induced global warming to tail off slightly over the next few decades. A weaker sun could reduce temperatures by half a degree.
Sha et al., 2017 The reconstruction indicates warm conditions with reduced sea-ice cover, associated with the Holocene Thermal Maximum, from ca. 6700 to 5000 cal. yr BP. … A distinct increase in sea-ice cover began at 1750 cal. yr BP, with absolute maximum values during the last millennium. … In order to assess the contribution of different potential forcing factors to sea-ice conditions off West Greenland, we evaluated the relationship between our sea-ice reconstruction and solar activity, as well as with the strength of ocean circulation. The observed agreement between the sea-ice record and solar activity suggests that solar forcing may have been an important trigger for sea-ice variability off West Greenland during the last 5000 yr.
Huang et al., 2017 (full paper) Various scientific studies have investigated the causal link between solar activity (SS) and the earth’s temperature (GT). [T]he corresponding CCM [Convergent Cross Mapping] results indicate increasing significance of causal effect from SS [solar activity] to GT [global temperature] since 1880 to recent years, which provide solid evidences that may contribute on explaining the escalating global tendency of warming up recent decades. … The connection between solar activity and global warming has been well established in the scientific literature. For example, see references [1–10]. … Among which, the SSA [Singular Spectrum Analysis] trend extraction is identified as the most reliable method for data preprocessing, while CCM [Convergent Cross Mapping] shows outstanding performance among all causality tests adopted. The emerging causal effects from SS [solar activity] to GT [global temperatures], especially for recent decades, are overwhelmingly proved, which reflects the better understanding of the tendency of global warming.
Matveev et al., 2017 An increase in atmospheric moisture for the warm period of the year (May–September) since 1890s, and mean annual temperatures since the 1950s was identified. During the same time period, there was a marked increase in amplitude of the annual variations for temperature and precipitation. … These fluctuations are consistent with 10–12-years Schwabe–Wolf, 22-years Hale, and the 32–36-years Bruckner Solar Cycles. There was an additional relationship found between high-frequency (short-period) climate fluctuations, lasting for about three years, and 70–90-years fluctuations of the moisture regime in the study region corresponding to longer cycles.
Schwander et al., 2017 Influence of solar variability on the occurrence of Central European weather types from 1763 to 2009 … Weather types and reanalysis data show that the 11-year solar cycle influences the late winter atmospheric circulation over Central Europe with colder (warmer) conditions under low (high) solar activity. Model simulations used for a comparison do not reproduce the imprint of the 11-year solar cycle found in the reanalyses data. … Atmospheric circulation over Europe is strongly correlated to the NAO and hence solar activity is thought to have an influence on weather conditions in Europe in winter. Studies show a preference of cold winters in Europe to be associated with minima in the 11-year solar cycle (e.g., Lockwood et al., 2010; Sirocko et al., 2012). … The 247-year long analysis [1763-2009] of the 11-year solar cycle impact on late winter European weather patterns suggest a reduction in the occurrence of westerly flow types linked to a reduced mean zonal flow under low solar activity. Following these observation, we estimate the probability to have cold conditions in winter over Europe to be higher under low solar activity than under high activity. Also similar [cold] conditions can occur during periods of prolonged reduced total solar irradiance. … Solar activity can have effects on the atmospheric circulation through three different mechanisms. These effects may arise from direct changes in total solar irradiance (TSI), from changes in stratospheric ozone induced by changes in solar UV, or from changes in stratospheric ozone induced by energetic particles, whose flux is modulated by solar activity. The ~1 Wm-2 variation in TSI over an 11-yr sunspot cycle corresponds to a change in the radiation forcing of about ~0.17 Wm-2.
Fu et al., 2017 The influences of solar activity and large-scale climate modes (e.g. the El Niño/Southern Oscillation — ‘ENSO’) have been identified in many geophysical processes. The combined influences of solar activity and ENSO on the first leaf and bloom dates of lilacs were identified for most of the stations with records spanning ≥ 33 years. In the 11-year band, both increasing solar activity (SSN) and El Niño caused delays in the first leaf and bloom events of the cloned lilac during the 1980s in the northeastern United States.
Zielhofer et al., 2017 Western Mediterranean Holocene record of abrupt hydro-climatic changes … Imprints of North Atlantic meltwater discharges, NAO and solar forcing …Early Holocene winter rain minima are in phase with cooling events and millennial-scale meltwater discharges in the sub-polar North Atlantic. … [A] significant hydro-climatic shift at the end of the African Humid Period (∼5 ka) indicates a change in climate forcing mechanisms. The Late Holocene climate variability in the Middle Atlas features a multi-centennial-scale NAO-type pattern, with Atlantic cooling and Western Mediterranean winter rain maxima generally associated with solar minima.
Sun et al., 2017 [A]t least six centennial droughts occurred at about 7300, 6300, 5500, 3400, 2500 and 500 cal yr BP. Our findings are generally consistent with other records from the ISM [Indian Summer Monsoon] region, and suggest that the monsoon intensity is primarily controlled by solar irradiance on a centennial time scale. This external forcing may have been amplified by cooling events in the North Atlantic and by ENSO activity in the eastern tropical Pacific, which shifted the ITCZ further southwards. The inconsistency between local rainfall amount in the southeastern margin of the QTP and ISM intensity may also have been the result of the effect of solar activity on the local hydrological cycle on the periphery of the plateau.
Zhai, 2017 ENSO is negatively/positively correlated with SSN [sunspot number] when SSN is large/small. … [S]olar activity may take effect on the ENSO, and such an impact should undergo an accumulation procedure (phase delay). XWT also indicates the existence of the impact. It is found that the index is negatively correlated with SSN when SSN is large during a certain long-term interval, and positively when SSN is small. Strong El Niño is inferred to be taken place in decade(s) to come.
Fischel et al., 2017 On a Holocene timescale, we conclude that the northeastern Caribbean SST [sea surface temperatures] and circulation regime have been mainly dependent on the position of the ITCZ [inter-tropical convergence zone], which, in turn, is controlled by changes in hemispheric solar insolation. Caribbean climate is directly controlled by the position of the inter-tropical convergence zone (ITCZ), where converging NE and SE trade winds creates a lowpressure convection zone with high precipitation rates (Philader et al., 1996; Schmidt et al., 2006). In addition to the seasonal variations in the position of the ITCZ, the long-term N–S migration of the ITCZ is largely determined by decadal to millennial changes in solar forcing (Haug et al., 2001; Schneider et al., 2014).
Zhu et al., 2017 Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Niño−Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere−oceanic circulation driven by solar activity.
Du et al., 2017 Although the global warming has been successfully attributed to the elevated atmospheric greenhouses gases, the reasons for spatiotemporal patterns the warming rates are still under debate. In this paper, we report surface and air warming based on observations collected at 1,977 stations in China from 1960 to 2003. Our results show that the warming of daily maximum surface (Ts-max) and air (Ta-max) temperatures showed a significant spatial pattern, stronger in the northwest China and weaker in South China and the North China Plain. These warming spatial patterns are attributed to surface shortwave solar radiation (SSR) and precipitation, the key parameters of surface energy budget.
Zhai, 2017 The time series of sunspot number and the precipitation in the north-central China (108° ∼ 115° E, 33° ∼ 41° N) over the past 500 years (1470–2002) are investigated, through periodicity analysis, cross wavelet transform and ensemble empirical mode decomposition analysis. The results are as follows: the solar activity periods are determined in the precipitation time series of weak statistical significance, but are found in decomposed components of the series with statistically significance; the Quasi Biennial Oscillation (QBO) is determined to significantly exist in the time series, and its action on precipitation is opposite to the solar activity; the sun is inferred to act on precipitation in two ways, with one lagging the other by half of the solar activity period.
Malik et al., 2017 [W]e investigate the impact of internal climate variability and external climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that AMO, PDO, and Total Solar Irradiance (TSI) play a considerable role in controlling the wet and dry decades of ISMR [Indian summer monsoon rainfall]. Resembling observational findings most of the dry decades of ISMR occur during a negative phase of AMO and a simultaneous positive phase of PDO.
Xiao et al., 2017 Solar wind and electric-microphysical process is the key mechanism that affects climate … We investigated the influencing mechanism of high-energetic particle precipitation modulated by solar wind on the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). On a day-to-day time scale, Zhou, Tinsley, and Huang (2014) and Huang et al. (2013) found that the minima in AO and NAO indices only lagged 0~2 days of the solar wind speed (SWS) minima during years of high stratospheric aerosol loading, which suggests a much faster mechanism of solar influence on the atmospheric system compared to the ozone destruction process. From the perspective of year-to-year variation, Xiao and Li (2016) and Zhou et al. (2016) showed a robust relationship between SWS [solar wind speed] and NAO in boreal winter. These aforementioned studies indicate that the wintertime Iceland Low in the North Atlantic was very sensitive to solar wind variations and played an important role in the process of solar wind and electric-microphysical effects on climate. Moreover, under the condition of a weak electric field, we have demonstrated the marked impact of cloud droplet electricity on the collision efficiency of cloud condensation nuclei. This, in turn, suggests that the collision in a cloud microphysics process constitutes the core link between atmospheric electricity and climate (Tinsley and Leddon 2013; Tinsley and Zhou 2013, 2014). Furthermore, Tinsley and Zhou (2015) improved the collision and parameterization scheme that varied with electric quantity in a cloud microphysics process and quantitatively evaluated the effects of high-energetic particle flux on cloud charge. This achievement not only supports the marked association of solar activity with weather and climate change on various time scales, but also but also avails the quantitative accession of solar impacts on climate. It is worth noting that the successful establishment development of a theoretical model regarding of the influencing process of solar energetic particles on the atmosphere improves the development of global climate models.
Vyklyuk et al., 2017 Hurricane genesis modelling based on the relationship between solar activity and hurricanes … There are a number of works concerning the Sun–Earth connections and their influence on atmospheric motions. There are a number of observations which show that within a few days after energetic solar eruptions (flares, coronal mass ejections and eruptive prominences), there are diverse meteorological responses of considerable strength (Gomes et al. 2012). … Conclusion: [T]here are several indications which are in favor that the beginning of violent cyclonic motions in Earth’s atmosphere may be caused by charged particles from the solar wind.
Katsuki et al., 2017 Typhoon frequency in East Asia is synchronous with the solar irradiance. … Several studies documented typhoon pattern changes in response to the El Niño/Southern Oscillation (ENSO). … The fluctuation of the solar activity plays a key role in regulating the westerly jet movement. The multi-centennial scale of the typhoon frequency in mid-latitude East Asia is therefore caused by changes in the solar activity and ENSO conditions.
Moreno et al., 2017 Understanding the Sun-Earth’s climate coupling system is both an essential and an urgent issue, with great progress achieved over the last decades (e.g., Haigh, 2007; Soon et al., 2014 for a review). Recently, Brugnara et al. (2013) referred that the Euro–Atlantic sector, in which Portugal is located, seems to be a region with a particularly strong solar influence on the troposphere, finding a significant change in the mean late winter circulation over Europe, which culminates in detectable impacts on the near-surface climate. Jiang et al. (2015) suggested that (i) climate in the northern North Atlantic regions follows SA [solar activity] fluctuations on multidecadal to centennial time scales, and (ii) it is more susceptible to the influence of those fluctuations throughout cool periods with, for instance, less vigorous ocean circulation. Similar results were found by Gómez-Navarro et al. (2012) in the context of climate simulations for the second millennium over the Iberian Peninsula, recognizing that temperature and precipitation variability is significantly affected at centennial time scales by variations in the SA [solar activity]. … Grand Minima and Dalton-type Minimum scenarios are broadly characterized by (i) lower TSI (i.e., lower available PAR) (Lean, 1991, and references therein), (ii) development of cloudiness (e.g., Usoskin and Kovaltsov, 2008), and (iii) decreased global/regional air surface temperatures (e.g., Neukom et al., 2014) in tandem with greater regional precipitation variability. … The connections between solar phenomena and the lower atmosphere processes can be explained by two kind of mechanisms: (i) “top-to-down”, influencing the pole-to-equator temperature gradient and exerting an impact on the modulation of the atmospheric circulation cells, weakening or strengthening the zonal winds, and (ii) “bottom-to up” that directly impact on the radiation fluxes, energy balance and temperatures on the ground. Both finally impact the atmospheric circulation modes responsible for the global/regional precipitation and temperature patterns (e.g., Gray et al., 2010; Martin-Puertas et al., 2012; Thiéblemont et al., 2015).
Douglass et al., 2017 Using a newly reported Pacific sea surface temperature data set, we extend a prior study that assigned El Niño episodes to distinct sequences. Within these sequences the episodes are phase-locked to subharmonics of the annual solar irradiance cycle having two- or three-year periodicity. There are 40 El Niño episodes occurring since 1872, each found within one of eighteen such sequences. Our list includes all previously reported events. Three El Niño episodes have already been observed in boreal winters of 2009, 2012 and 2015, illustrating a sequence of 3-year intervals that began in 2008. If the climate system remains in this state, the next El Niño is likely to occur in boreal winter of 2018.
Zhang et al., 2017 The frequencies represent the influence of the Pacific Decadal Oscillation (PDO) and solar activity on the precipitation from the southwestern United States. In addition, solar activity has exerted a greater effect than PDO on the precipitation in the southwestern United States over the past 120 years. By comparing the trend of droughts with the two fundamental frequencies, we find that both the droughts in the 1900s and in the 21st century were affected by the PDO and solar activity, whereas the droughts from the 1950s to the 1970s were mainly affected by solar activity.
Hood, 2017 QBO/Solar Modulation of the Boreal Winter Madden-Julian Oscillation: A Prediction for the Coming Solar Minimum … The Madden-Julian Oscillation (MJO), also known as the 30-60 day oscillation, is the strongest of the intraseasonal climate oscillations in the tropics and has significant derivative effects on extratropical circulation and intraseasonal climate. … Here, evidence is presented that tropical upwelling changes related to the 11-year solar cycle also modulate the boreal winter MJO. Based on 37.3 years of MJO amplitude data, the largest amplitudes and occurrence rates, and the weakest static stabilities in the tropical lower stratosphere, occur during the QBOE phase under solar minimum (SMIN) conditions while the smallest amplitudes and strongest static stabilities occur during the QBOW phase under solar maximum (SMAX) conditions.
Orme et al., 2017 Past changes in the North Atlantic storm track driven by insolation and sea-ice forcing … We suggest that gradual polar cooling (caused by decreasing solar insolation in summer and amplified by sea-ice feedbacks) and mid-latitude warming (caused by increasing winter insolation) drove a steepening of the winter latitudinal temperature gradient through the late Holocene, resulting in the observed change to a more northern winter storm track.
Page, 2017 Data related to the solar climate driver are discussed and the solar cycle 22 low in the neutron count (high solar activity) in 1991 is identified as a solar activity millennial peak and correlated with the millennial peak – inversion point – in the RSS temperature trend in about 2004. The cyclic trends are projected forward and predict a probable general temperature decline in the coming decades and centuries. Estimates of the timing and amplitude of the coming cooling are made. If the real climate outcomes follow a trend which approaches the near term forecasts of this working hypothesis, the divergence between the IPCC forecasts and those projected by this paper will be so large by 2021 as to make the current, supposedly actionable, level of confidence in the IPCC forecasts untenable. … Unless the range and causes of natural variation, as seen in the natural temperature quasi-periodicities, are known within reasonably narrow limits, it is simply not possible to even begin to estimate the effect of anthropogenic CO2 on climate. Given the lack of any empirical CO2-climate connection reviewed earlier and the inverse relationship between CO2 and temperature [during the Holocene, when CO2 rose as temperatures declined] seen in Figure 2, and for the years 2003.6–2015.2 in Figure 4, during which CO2 rose 20 ppm, the simplest and most rational working hypothesis is that the solar ‘activity’ increase is the chief driver of the global temperature increase since the LIA.
Huhtamaa and Helama, 2017 Throughout the written history of Finland, delayed onset of summer and night frost have been named as the main reasons for crop failure and famine. … Our reconstruction suggests that in the 8th–10th centuries AD, when continuous crop cultivation was established in Finland, the risk of temperature-driven crop failure was notably lower and the crops were generally higher than during the historical period (c. 13th century ad onwards). The continuous period of high crop yields coincides with an episode of multi-centennial summer season warmth, associated with the MCA [Medieval Climate Anomaly] in the region and around north-west Europe (Goosse et al., 2012; Luoto and Helama, 2010; Ogilvie et al., 2000; Sundqvist et al., 2010). … The rapid mid-15th century cooling, which followed a major atmospheric circulation change over the North Atlantic (Dawson et al., 2007; Meeker and Mayewski, 2002) and coincided with the culmination of the Spörer solar minimum (Miyahara et al., 2006), has been evidenced in various summer and winter season reconstructions of the region (Haltia-Hovi et al., 2007; Helama et al., 2009b; Klimenko and Solomina, 2010; Luoto and Helama, 2010; Zhang et al., 2015). … The culmination of the ‘LIA’ [Little Ice Age] in Finland has been commonly dated to the late 17th and early 18th centuries ad (Luoto, 2013; Luoto and Helama, 2010; Tiljander et al., 2003), which is synchronous with the onset of the phase of the lowest yield ratios in our reconstruction. The Maunder solar minima (c. 1645–1715) and several volcanic eruptions preceded the culmination (Shindell et al., 2003).
Gray et al., 2017 There is growing evidence that variability associated with the 11-year solar cycle has an impact at the Earth’s surface and influences its weather and climate. Although the direct response to the Sun’s variability is extremely small, a number of different mechanisms have been suggested that could amplify the signal, resulting in regional signals that are much larger than expected. In this paper the observed solar cycle signal at the Earth’s surface is described, together with proposed mechanisms that involve modulation via the total incoming solar irradiance and via modulation of the ultra-violet part of the solarspectrum that influences ozone production in the stratosphere.
Hood, 2017 QBO/Solar Modulation of the Boreal Winter Madden-Julian Oscillation … The Madden-Julian Oscillation (MJO), also known as the 30-60 day oscillation, is the strongest of the intraseasonal climate oscillations in the tropics and has significant derivative effects on extratropical circulation and intraseasonal climate. … Here, evidence is presented that tropical upwelling changes related to the 11-year solar cycle also modulate the boreal winter MJO. Based on 37.3 years of MJO amplitude data, the largest amplitudes and occurrence rates, and the weakest static stabilities in the tropical lower stratosphere, occur during the QBOE phase under solar minimum (SMIN) conditions while the smallest amplitudes and strongest static stabilities occur during the QBOW phase under solar maximum (SMAX) conditions. Conversely, when the QBO and solar forcings are opposed (QBOW/SMIN and QBOE/SMAX), the difference in occurrence rates becomes statistically insignificant.
Gan et al., 2017 Temperature responses to the 11-year solar cycle in the mesosphere from the 31-year (1979-2010) … Atmospheric response to the solar cycle (SC) here refers to atmospheric variability induced by the 11-year solar activity cycle. The SC [solar cycle] response originates mainly from large (4-8%) solar UV spectral irradiance change (in the range of 200-250 nm) from solar minimum to maximum condition, while the total solar flux stays nearly constant (0.1%) [Donnelly, 1991; Lean et al., 1997; Woods and Rottman, 1997; Beig et al., 2008; Gary et al., 2010]. The variability of the solar UV spectral irradiance affects the thermal structure of the atmosphere by directly changing the total energy deposited and indirectly modifying the photochemistry and dynamics of the atmosphere. In addition to the equatorial Quasi-Biennial Oscillation (QBO) [Baldwin et al., 2011] and the El Niño-Southern Oscillation (ENSO) [Li et al., 2013], the 11-year SC is also a significant source to the inter-annual variability in the mesosphere and lower (MLT) region.
Lihua, 2017 The modulation action from solar activity plays an important role in the temperature change, and there is a possible association existing in the global land-ocean temperature and solar activity on decade time scales. … About 11-year period, a remarkable oscillation of solar activity, continually exists in wavelet transform of solar variation. According to the cross wavelet transform, solar activity influences global land-ocean temperature change on ~11-year time scales during 1935-1995 with above the 5 % significance level.
Utomo, 2017 A similar result was also found for the relationship between solar activity and cosmic ray flux with a negative correlation, i.e. 0.69/year. When solar activities decrease, the clouds cover rate increase due-0.61/month and – to secondary ions produced by cosmic rays. The increase in the cloud cover rate causes the decrease in solar constant value and solar radiation on the earth’s surface [cooling]. … The increase in the formation rate of cloud would affect the decrease in the intensity of solar radiation reaching the Earth’s surface. The relationship between cosmic rays and solar constant is an “opposite” relationship because of the negative correlation type (r < 0). The phenomenon of “opposite” is in a good agreement with the result by Svensmark (1997) who found a correlation between temperature and global cloud coverage with the cosmic rays. … [T]he climate also depends on variations in the flux of solar energy received by the earth’s surface. Variation in the solar energy flux is caused by variations in solar activity cycle. Thus the climate is a manifestation of how solar radiation is absorbed, redistributed by the atmosphere, land and oceans, and ultimately radiated back into space. Every variation of solar energy received at the earth’s surface and reradiated by the earth into space will have a direct impact on climate change on Earth.
Biktash, 2017 The effects of total solar irradiance (TSI) and volcanic activity on long-term global temperature variations during solar cycles 19–23 [1954-2008] were studied. It was shown that a large proportion of climate variations can be explained by the mechanism of action of TSI [total solar irradiance] and cosmic rays (CRs) on the state of the lower atmosphere and other meteorological parameters. … Recent studies by Pudovkin and Raspopov, Tinsley, and Swensmark have shown that the Earth’s cloud coverage is strongly influenced by cosmic ray intensity. Conditions in interplanetary space, which can influence GCRs and climate change, have been studied in numerous works. As has been demonstrated by Biktash, the long-term CR count rate and global temperature variations in 20–23 solar cycles are modulated by solar activity and by the IMF (interplanetary magnetic field). A possible geophysical factor which is able to affect the influence of solar activity on the Earth’s climate is volcanism. The effects of volcanism can lead to serious consequences in the atmosphere and the climate.
Warming Trend Since 1980s Explained By Surface Solar Radiation (Cloud Cover Reduction)
Sanchez-Lorenzo et al., 2017 Trends of all-sky downward surface solar radiation (SSR) from satellite-derived data over Europe (1983–2010) are first presented. The results show a widespread (i.e., non-local dimension) increase in the major part of Europe, especially since the mid-1990s in the central and northern areas and in springtime. There is a mean increase of SSR of at least 2 W m− 2 per decade from 1983 to 2010 over the whole Europe, which, taking into account that the satellite-derived product lacks of aerosol variations, can be mostly related to a decrease in the cloud radiative effects over Europe. … Downward surface solar radiation (SSR) is a critical part of the Global Energy Balance and the climate system … A widespread decrease of SSR from the 1950s to the 1980s [when global cooling occurred] has been observed (Liepert, 2002; Stanhill and Cohen, 2001; Wild, 2009), followed by an increase of SSR since the mid-1980s [when global warming occurred]… Pinker et al. (2005) used a different product (2.5° resolution) and found that the derived global mean SSR [surface solar radiation] series underwent a significant increase of 1.6 W m−2 per decade from 1983 to 2001. … On the other hand, Hatzianastassiou et al. (2005) derived a SSR product from 1984 to 2000 (2.5° resolution) and reported a significant increase of +2.4 W m−2 per decade in the global mean series, which is considerably higher than the results from Pinker et al. (2005) and Hinkelman et al. (2009).
Urban et al., 2017 From the 1950s to the 1980s, a decline in the intensity of solar radiation was observed (Stanhill and Cohen 2001; Liepert 2002). This phenomenon was dubbed “global dimming”. Later research demonstrated that from the mid-1980s onwards, an increase in solar radiation followed, which was referred to as “global brightening” (Wild et al. 2005; Pinker et al. 2005). Reasons for shifts in radiation trends have not been fully determined; these may result from changes in atmospheric transparency caused by variations in cloud cover or concentrations of anthropogenic aerosols (Wild 2009). … An important work that covered as many as 237 stations grouped into the five climatic regions and concerned, inter alia, sunshine duration trends from 1961 to 2004 in six South American countries, was published by Raichijk (2012). The results of that study confirm downward trends in sunshine duration from the 1950s until the 1980s and upward ones since the beginning of the 1990s, which were also observed in other regions of the world. Satellite short-wave radiation data spanning the period from 1984 to 2005 confirm the results obtained at ground sunshine duration measurement stations in all five climatic regions of South America. Upward sunshine duration trends are associated with an increase in the intensity of solar radiation and a decrease in cloud cover (Raichijk 2012). It should be stressed that both insolation and cloud cover are primarily related to atmospheric circulation and are influenced by heat balance and local conditions (Dubicka and Limanówka 1994).
Boers et al., 2017 A 50-year [1966-2015] hourly dataset of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to trends in all-sky radiation. The trend in all-sky radiation was expressed as a linear combination of trends in fractional cloudiness, clear-sky radiation and cloud-base radiation (radiation emanating from the bottom of clouds). All three trends were derived from the data records. The results indicate that trends in all three components contribute significantly to the observed trend in all-sky radiation. Trends (per decade) in fractional cloudiness, all-sky, clear-sky and cloud-base radiation were respectively 0.0097 ± 0.0062, 1.81 ± 1.07 W m−2, 2.78 ± 0.50 W m−2, and 3.43 ± 1.17 W m−2.
Antón et al., 2017 This study focuses on the analysis of the daily global solar radiation (GSR) reconstructed from sunshine duration measurements at Madrid (Spain) from 1887 to 1950. Additionally, cloud cover information recorded simultaneously by human observations for the study period was also analyzed and used to select cloud-free days. First, the day-to-day variability of reconstructed GSR data was evaluated, finding a strong relationship between GSR and cloudiness. The second step was to analyze the long-term evolution of the GSR data which exhibited two clear trends with opposite sign: a marked negative trend of − 36 kJ/m2 per year for 1887–1915 period and a moderate positive trend of + 13 kJ/m2 per year for 1916–1950 period, both statistically significant at the 95% confidence level. Therefore, there is evidence of “early dimming” and “early brightening” periods in the reconstructed GSR [global solar radiation] data for all-sky conditions in Madrid from the late 19th to the mid-20th centuries.
Sanchez-Lorenzo et al., 2017 Clouds play a major role in the climate system, but large uncertainties remain about their decadal variations. Here we report a widespread decrease in cloud cover since the 1970 s over the Mediterranean region, in particular during the 1970 s–1980 s, especially in the central and eastern areas and during springtime. Confidence in these findings is high due to the good agreement between the interannual variations of cloud cover provided by surface observations and several satellite-derived and reanalysis products, although some discrepancies exist in their trends.
Alexandri et al., 2017 In this work, the spatiotemporal variability of surface solar radiation (SSR) is examined over the Eastern Mediterranean region for a 31-year period (1983–2013). … The satellite-based data from CERES (Cloud and the Earth’s Radiant Energy System), GEWEX (Global Energy and Water Cycle Experiment) and ISCCP (International Satellite Cloud Climatology Project) underestimate SSR while the reanalysis data from the ERA-Interim overestimate SSR compared to CM SAF SARAH. Using a radiative transfer model and a set of ancillary data, these biases are attributed to the atmospheric parameters that drive the transmission of solar radiation in the atmosphere, namely, clouds, aerosols and water vapor [CO2 not mentioned].. … The CM SAF SARAH SSR trend was found to be positive (brightening) and statistically significant at the 95% confidence level (0.2 ± 0.05 W/m2/year [2 W m-2 per decade].
Natural Oscillation (ENSO, NAO, AMO, PDO) Climate Influence (31)
Park et al., 2017 According to our results, the central Mexican climate has been predominantly controlled by the combined influence of the 20-year Pacific Decadal Oscillation (PDO) and the 70-year Atlantic Multidecadal Oscillation (AMO). However, the AMO probably lost much of its influence in central Mexico in the early 20th century and the PDO has mostly driven climate change since.
Zhu et al., 2017 This study analyzes the effects of fifteen major teleconnections on terrestrial ecosystem carbon fluxes during 1951-2012 using an ensemble of nine Dynamic Global Vegetation Models. We map the global pattern of the dominant teleconnections and find that these teleconnections significantly affect GPP variations over more than 82.1% of the global vegetated area, through mediating the global temperature, and regional precipitation and cloud cover. The El-Niño/Southern Oscillation, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation are strongly correlated with global, hemispherical, and continental carbon fluxes and climatic variables, while the Northern Hemisphere teleconnections have only regional influences.
Muñoz et al., 2017 Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5°C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT [mean annual temperature] varied from ca. 2.5°C below to 3.5°C above present-day temperature. Warm periods (11,410, 10,700, 9700, 6900, 4000, 2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact [on the pollen proxy record]. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. … The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO [El Niño-Southern Oscillation] and ITCZ [Intertropical Convergence Zone] as the main climate change-driving mechanisms in Frontino. … From ca. 8000 cal yr BP, climate in both areas was under the dual influence of ENSO and ITCZ, thereby showing existing teleconnections between the tropical Pacific and Atlantic oceans.
Clarke et al., 2017 Corresponding ~4-8 year periodicities identified from Wavelet analysis of particle size data from Pescadero Marsh in Central Coast California and rainfall data from San Francisco reflect established ENSO periodicity, as further evidenced in the Multivariate ENSO Index (MEI), and thus confirms an important ENSO control on both precipitation and barrier regime variability.
Douglass et al., 2017 Using a newly reported Pacific sea surface temperature data set, we extend a prior study that assigned El Niño episodes to distinct sequences. Within these sequences the episodes are phase-locked to subharmonics of the annual solar irradiance cycle having two- or three-year periodicity. There are 40 El Niño episodes occurring since 1872, each found within one of eighteen such sequences.
Macdonald and Sangster, 2017 Statistically significant relationships between the British flood index, the Atlantic Meridional Oscillation and the North Atlantic Oscillation Index are identified. The use of historical records identifies that the largest floods often transcend single catchments affecting regions and that the current flood-rich period is not unprecedented. … Solar forcing can manifest itself in a variety of different ways on flood patterns through modification of the climate (Benito et al., 2004). Several series indicated increased flood frequency during the late eighteenth century corresponding to the Dalton Minimum (AD 1790–1830), with notable flooding across catchments in the 8-year period AD 1769 1779, which was a climatic period considered to include the sharpest phases of temperature variability during the “Little Ice Age” (Lamb, 1995; Wanner et al., 2008).
de Inglés and Jesús, 2017 The temperature in Azores depends on the position of the Gulf Stream (GS). A positive (negative) NAO phase enhances (reduces) the Gulf Stream (GS) velocity that increases (reduce) the amount of Eddies around Bermuda driving towards north (east) the GS and heating up high (medium) latitudes. Therefore, a negative phase of NAO favors the GS [Gulf Stream] heat to reach Azores. Since the temperature in Azores is modulated by the oceanic circulation, the AMO also plays an important role. The AMO is reflected in Ponta Delgada by the amplitude between maximum and minimum mean annual temperatures, which means an increase on seasonality. The AMO positive phase is reflected as an increase on temperatures in Lake Azul reconstruction. Otherwise, the AMO negative phase is masked by other climatic patterns. The precipitation in Azores is mainly triggered by the NAO phase
Muller et al., 2017 Over the past two decades, the number of paleotempestology records has increased substantially for sites along the Northwest Atlantic Ocean, Gulf of Mexico and Caribbean Sea, the South Pacific Ocean, and the Northwest Pacific and Indian Ocean regions. The most obvious characteristic of these records is that they reveal extended alternating periods of either greater or lesser tropical cyclone activity over centennial and millennial timescales. In these studies, researchers have shown that large-scale climatic features such as ENSO, sea surface temperatures (SSTs), the latitudinal position of the intertropical convergence zone (ITCZ), and the North Atlantic Oscillation (NAO) are likely driving the alternating long-term behavior of tropical cyclones in global oceanic basins.
Lapointe et al., 2017 This paper investigates an annually-laminated (varved) record from the western Canadian Arctic and finds that the varves are negatively correlated with both the instrumental Pacific Decadal Oscillation (PDO) during the past century and also with reconstructed PDO over the past 700 years, suggesting drier Arctic conditions during high-PDO phases, and vice versa. These results are in agreement with known regional teleconnections, whereby the PDO is negatively and positively correlated with summer precipitation and mean sea level pressure respectively. This pattern is also evident during the positive phase of the North Pacific Index (NPI) in autumn. Reduced sea-ice cover during summer–autumn is observed in the region during PDO− (NPI+) and is associated with low-level southerly winds that originate from the northernmost Pacific across the Bering Strait and can reach as far as the western Canadian Arctic. These climate anomalies are associated with the PDO− (NPI+) phase and are key factors in enhancing evaporation and subsequent precipitation in this region of the Arctic.
Levine et al., 2017 The Atlantic Multidecadal Oscillation (AMO) is the dominant mode of multi-decadal SST variability in the Atlantic Ocean. Changes in AMO-related tropical Atlantic SSTs are known to force changes in the Walker Circulation in the tropical Pacific Ocean. We show that these changes to the Walker Circulation modify ENSO stability on both annual and multi-decadal timescales leading to a distinctive pattern of multi-decadal ENSO variability that we find in observations, ocean reanalyses and conceptual and coupled model experiments.
Valdés-Pineda et al., 2017 This study analyzes these low-frequency patterns of precipitation in Chile (>30 years), and their relationship to global Sea Surface Temperatures (SSTs), with special focus on associations with the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO) indices. … We conclude that a significant multi-decadal precipitation cycle between 40 and 60 years is evident at the rain gauges located in the subtropical and extratropical regions of Chile. This low-frequency variability seems to be largely linked to PDO and AMO modulation.
Liu et al., 2017 Land and sea surface temperatures, precipitation, and storm tracks in North America and the North Pacific are controlled to a large degree by atmospheric variability associated with the Pacific North American (PNA) pattern. … Our reconstruction shows that PNA has been strongly and consistently correlated with sea surface temperature variation, solar irradiance, and volcanic forcing over the period of record, and played a significant role in translating these forcings into decadal-to-multidecadal hydroclimate variability over North America.
Manatsa et al., 2017 ENSO has been known to influence the trends of summer warming over Southern Africa. In this work, we used observational and reanalysis data to analyze the relationship between ENSO and maximum surface air temperature (SATmax) trends during the three epochs created by the ENSO phase shifts around 1977 and 1997 for the period 1960 to 2014. We observed that while ENSO and cloud cover remains the dominant factor controlling SATmax [maximum surface air temperature] variability, the first two epochs had the predominant La Niña (El Niño)-like events connected to robust positive (negative) trends in cloud fraction.
Kozachek et al., 2017 No unusual recent change is detected in the isotopic composition or in the accumulation rate record, in contrast with the observed warming trend from regional meteorological data. The accumulation rate appears significantly related to the NAO index, in agreement with the earlier results for the Djankuat glacier (Shahgedanova et al., 2005). As a result, the isotopic composition of the ice cores appears mostly related to characteristics of large–scale atmosphere circulation such as the NAO index…. Tielidze (2016) reports a recent increase in the annual mean temperatures at different elevations in the Georgian Caucasus. The region experienced glacier area loss over the 20th century at an average annual rate of 0.4 %, with a higher rate in eastern Caucasus than in the central and western sections. The analysis of the temperature and radiation regime of glaciers at the ablation period has been performed in the vicinity of El’brus recently (Toropov et al., 2016). The authors prove that the observed waning of glaciers cannot be explained by an increase in temperature during the ablation period because of an increase in precipitation during the accumulation period. They concluded that the main driver of glacier retreat is the increase in the solar radiation balance by 4 % for the 2001–2010 period, which corresponds to the increase in ablation by 140 mm per ablation season (Toropov et al., 2016).
Lim et al., 2017 Our study demonstrated that flood frequency and climate changes at centennial-to-millennial time scales in South Korea have been coupled mainly with ENSO activity, suggesting that the hydrologic changes, including flooding and drought, in East Asia are coupled to the centennial-to-millennial-scale atmospheric-oceanic circulation changes represented by the ENSO pattern.
Valdés-Pineda et al., 2017 This study analyzes these low-frequency patterns of precipitation in Chile (>30 years), and their relationship to global Sea Surface Temperatures (SSTs), with special focus on associations with the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO) indices. … We conclude that a significant multi-decadal precipitation cycle between 40 and 60 years is evident at the rain gauges located in the subtropical and extratropical regions of Chile. This low-frequency variability seems to be largely linked to PDO and AMO modulation.
Reynolds et al., 2017 Evidence derived from instrumental observations suggest that Atlantic variability, associated with changes in SSTs and fluctuations in the strength of the Atlantic Meridional Overturning Circulation (AMOC), is directly linked with broader scale climate variability, including Brazilian and Sahel precipitation (Folland et al., 1986 and Folland et al., 2001), Atlantic hurricanes and storm tracks (Goldenberg et al., 2001 and Emanuel, 2005), and North American and European temperatures (Sutton and Hodson, 2005, Knight et al., 2006 and Mann et al., 2009). Furthermore, evidence derived from palaeoceanographic records suggests that a reduction in the meridional heat transport through the surface components of the AMOC was in part responsible for the reductions in temperatures associated with the Medieval Climate Anomaly (MCA; 1000–1450) to Little Ice Age (LIA; 1450–1850) transition (Lund et al., 2006, Trouet et al., 2009, Trouet et al., 2012, Wanamaker et al., 2012 and Moffa-Sánchez et al., 2014).
Fan and Yang, 2017 The wintertime Arctic temperature decreased from 1979 to 1997 and increased rapidly from 1998 to 2012, in contrast to the global mean surface air temperature [which] increased between 1979 and 1997, followed by a hiatus… A recent study suggests a possible role of the Pacific Ocean decadal oscillation in regulating wintertime climate in the Arctic (Screen and Francis 2016). … The ‘‘greenhouse effect’’ of water vapor and clouds [CO2 not mentioned as contributing to the GHE] may amplify the effect of winds on Arctic winter climate. … The objectives of this study are to assess how much natural–internal variability has contributed to climate changes in these [Arctic] regions from 1979 to 2012 … In summary, the correlation analyses presented in this paper shows a natural mode of Arctic winter variability resulting from the Nordic–Siberian seesaw of meridional winds […] is associated with two-thirds of the interannual variance [cooling-warming] of winter-mean Arctic temperature between 1979 and 2012, and possibly contributed a substantial fraction of the observed Arctic amplification [1998-2012 warming] in this period.
Myoung et al., 2017 This study examines the relationship between the North Atlantic Oscillation (NAO) and snowmelt in spring in the upper southwestern states of the US (UP_SW) including California, Nevada, Utah, and Colorado, using SNOTEL datasets for 34 years, 1980-2014. We find statistically significant negative correlations between NAO averages in the snowmelt period and timings of snowmelt, i.e., positive NAO phases in spring enhance snowmelt, and vice versa. … The underlying mechanism for this link is that a positioning of upper-tropospheric anticyclonic (cyclonic) circulations over the western US that are associated with development of the positive (negative) NAO phases tend to bring warmer-and-drier (colder-and-wetter) spring weather conditions to the region. The temperature variations related with the NAO phases also strongly modulate the snowfall-rainfall partitioning. The relationship between NAO and spring snowmelt can serve as key information for the warm season water resources management in the UP_SW.
Gao et al., 2017 We find that negative correlations between the atmospheric temperature in the tropics and ENSO are observed at 17–30 km in the lower stratosphere at a lag of 1 to 4 months and at a lead of 1 month. Out-of-phase temperature variation is observed in the troposphere over the mid-latitude band and in-phase behaviour is observed in the lower stratosphere. Interestingly, we also find that there is a significant negative correlation at a lag of 1–3 months from 32 km to 40 km in the mid-latitude region of the Northern Hemisphere. The atmospheric temperature variations over mid-latitude regions in both hemispheres are closely related to the QBO [quasi-biennial oscillation].
Hao and He, 2017 Using long-term observational data and numerical model experiments, this study found that the Atlantic Multidecadal Oscillation (AMO) affects the influence of ENSO-like sea surface temperature anomalies (SSTAs, which contain variability of both El Niño-Southern Oscillation and Pacific Decadal Oscillation) on the interannual change in the East Asian winter monsoon (EAWM). In the observations, the out-of-phase relationship between the ENSO-like and EAWM was significantly intensified when the AMO and ENSO-like were in-phase. Warmer-than-normal winters occurred across East Asia when the ENSO-like and AMO were positively in-phase, with a significantly weakened Siberian High and anomalous anticyclones over the western North Pacific. The opposite patterns occurred under negatively in-phase conditions.
Zaitchik, 2017 The Madden-Julian Oscillation (MJO) is the dominant mode of sub-seasonal climate variability in the global tropics. As such it represents an opportunity for intra-seasonal rainfall prediction and, perhaps, for explaining dynamics that underlie longer term variability and trends. … A number of studies have identified statistical links between MJO and sub-seasonal rainfall variability in West, East, and Southern Africa. … On longer time scales, there is evidence that MJO activity both modulates and is modulated by the El Niño Southern Oscillation and the Indian Ocean Dipole. The implications of these interactions for MJO connections to Africa require further research, as does the potential for trends in MJO behavior and impacts on Africa under global climate change.
Reischelmann et al., 2017 We document that long-term patterns in temperature and precipitation are recorded in dripwater patterns of Bunker Cave and that these are linked to the North Atlantic Oscillation (NAO).
Lopez et al., 2017 This study reconstructs a century-long South Atlantic Meridional Overturning Circulation (SAMOC) index. The reconstruction is possible due to its covariability with sea surface temperature (SST). A singular value decomposition (SVD) method is applied to the correlation matrix of SST and SAMOC. The SVD is performed on the trained period (1993-present) for which Expendable Bathythermographs (XBT) and satellite altimetry observations are available. The joint modes obtained are used in the reconstruction of a monthly SAMOC timeseries from 1870 to present. The reconstructed index is highly correlated to the observational-based SAMOC timeseries during the trained period and provides a long historical estimate. It is shown that the Interdecadal Pacific Oscillation (IPO) is the leading mode of SAMOC-SST covariability, explaining ~85% with the Atlantic Niño accounting for less than 10%. The reconstruction shows that SAMOC has recently shifted to an anomalous positive period, consistent with a recent positive shift of the IPO.
Wu et al., 2017 The enhanced warming observed in the Eastern China Coastal Waters (ECCW) during the last half-century has received considerable attentions. However, the reason for this warming is still a subject of debate. Based on four different Sea Surface Temperature datasets, we found that the most significant warming occurred in boreal winter during 1982–1998, although the warming trends derived from these datasets differ in magnitude. We suggest that the rapid warming during winter is a result of the asymmetry in the El Niño–Southern Oscillation teleconnection, through which El Niño events induce significant warming over the ECCW at its peak, whereas La Niña events fail to do the opposite that would completely reverse the trends; in addition, there were more El Niño than La Niña events during the recent decades. All these contribute to the winter warming during 1982–1998.
Schwartz and Garfinkel, 2017 European and eastern United States (U.S.) wintertime weather is strongly influenced by large-scale modes of variability in the Northern Hemisphere such as the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). The negative phase of the NAO has been linked to both the Madden Julian Oscillation (MJO) phase with convection in the West Pacific (phase 6 and 7) and to stratospheric sudden warmings (SSW), but the relative role of each phenomena is not clear, and the two phenomena are themselves linked, as more than half of SSW events were preceded by blackphases 6 and 7 of the MJO.
He et al., 2017 As pointed out by Cohen et al. (2014) that continental winter SAT [surface temperature] trends since 1990 exhibit cooling over the midlatitudes. The negative trends extend from Europe eastward to East Asia, with a center of maximum magnitude to the west of the Baikal. As reviewed above, the AO/NAO [Arctic Oscillation/North Atlantic Oscillation] shows an in-phase relationship with the SAT [surface temperatures] over Eurasia. … [T]he negative trend in the AO/NAO might explain the recent Eurasian winter cooling. … Additionally, the relationship between the winter AO and surface-climate anomalies in the following spring might be modulated by the 11-year solar cycle (Chen and Zhou, 2012). The spring temperature anomalies in northern China related to the previous winter AO were larger and more robust after high solar cycle winters. However, spring temperature anomalies became very small and insignificant after the low solar cycle winters. … Numerous atmospheric scientists have documented that the AO could impact significantly the climate over Europe and Far East. … It is evident that a positive winter AO causes warmer winters over East Asia through enhancing Polar westerly jet which prevents cold Arctic air from invading low latitudes.
Bianchette et al., 2017 Seven periods of increased water level, varying in duration, occurred during the backbarrier period, with El Niño-Southern Oscillation (ENSO) likely the main climatic mechanism causing these periodic shifts in the paleo-precipitation levels. We suggest that the deepest water levels detected over the last ~3200 years correlate with periods of increased ENSO activity.
Lachniet et al., 2017 [M]onsoon dynamics appear to be linked to low-frequency variability in the ENSO and NAO, suggesting that ocean-atmosphere processes in the tropical oceans drive rainfall in Mesoamerica. … Climate model output suggests decreasing rainfall as a consequence of anthropogenic greenhouse gas radiative forcing (Rauscher et al., 2008; Saenz-Romero et al., 2010). Our data show, however, that the response of the monsoon will be strongly modulated by the changes in ENSO and the NAO mean states … Our data also show that the magnitude of Mesoamerican monsoon variability over the modern era when the anthropogenic radiative forcing has dominated over solar and volcanic forcings (Schmidt et al., 2012) is within the natural bounds of rainfall variations over the past 2250 years. This observation suggests that if anthropogenic forcing has impacted the Mesoamerican monsoon, the signal has yet to be detected above the level of natural climate variability, and the monsoon response to direct radiative forcing and indirect ocean-atmosphere forcings may yet to be fully realized.
Rossby Waves, Ozone Climate Modulation
Gong et al., 2017 During the past three decades, the most rapid warming at the surface has occurred during the Arctic winter. By analyzing daily ERA-Interim data, we found that the majority of the winter warming trend north of 70°N can be explained by the trend in the downward infrared radiation (IR). This downward IR trend can be attributed to an enhanced poleward flux of moisture and sensible heat into the Arctic by poleward propagating Rossby waves, which increases the total column water and temperature within this region. This enhanced moisture flux is mostly due to changes in the planetary-scale atmospheric circulation rather than an increase in moisture in lower latitudes. The results of this study lead to the question of whether Arctic amplification has mostly arisen through changes in the Rossby wave response to greenhouse gas forcing and its impact on moisture transport into the Arctic.
Xie et al., 2017 Antarctic stratospheric ozone depletion is thought to influence the Southern Hemisphere tropospheric climate. Recently, Arctic stratospheric ozone (ASO) variations have been found to affect the middle-high latitude tropospheric climate in the Northern Hemisphere. This paper demonstrates that the impact of ASO can extend to the tropics, with the ASO variations leading El Niño-Southern Oscillation (ENSO) events by about 20 months.
Modern Climate In Phase With Natural Variability (10)
Seviour, 2017 Weakening and shift of the Arctic stratospheric polar vortex: Internal variability or forced response? … By comparing large ensembles of historical simulations with pre-industrial control simulations for two coupled climate models, the ensemble mean response of the vortex is found to be small relative to internal variability. There is also no relationship between sea-ice decline and trends in either vortex location or strength. Despite this, individual ensemble members are found to have vortex trends similar to those observed, indicating that these trends may be primarily a result of natural internally-generated climate variability.
Xie and Zhang, 2017 The North America continent experienced an extremely anomalous dipole climate in the 2014/2015 winter with record-breaking cold temperature anomalies in the east and warm anomalies in the west. … [W]e conclude that the 2014/2015 winter extreme dipole climate is a low-probability event that is primarily caused by internal atmospheric variability based on the single model CAM4.
Shi et al., 2017 Five of the six coupled ocean-atmosphere climate models of the Paleoclimate Modeling Intercomparison Project Phase III (PMIP3), can reproduce the south-north dipole mode of precipitation in eastern China, and its likely link with ENSO. However, there is mismatch in terms of their time development. This is consistent with an important role of the internal variability in the precipitation field changes over the past 500 years.
Conroy et al., 2017 20th century precipitation variability in southern Tibet falls within the range of natural variability in the last 4100 yr, and does not show a clear trend of increasing precipitation as projected by models. Instead, it appears that poorly understood multidecadal to centennial internal modes of monsoon variability remained influential throughout the last 4100 yr. … Until we have a predictive understanding of multidecade to multi-century variability in the Asian monsoon system, it would be wise to consider the risk of prolonged periods of anomalously dry and wet monsoon conditions to be substantial (Ault et al., 2014). Such variability may also explain why the predicted anthropogenic increase in Asian monsoon precipitation is not widely observed.
Macdonald and Sangster, 2017 The findings identify that whilst recent floods are notable, several comparable periods of increased flooding are identifiable historically, with periods of greater frequency (flood-rich periods). Statistically significant relationships between the British flood index, the Atlantic Meridional Oscillation and the North Atlantic Oscillation Index are identified. The use of historical records identifies that the largest floods often transcend single catchments affecting regions and that the current flood-rich period is not unprecedented.
Hu et al., 2017 [I]t was a challenge to predict the evolution of this warm event, especially for its growth. That is consistent with the fact that the SSTAs [sea surface temperature anomalies] in extratropical oceans are largely a consequence of unpredictable atmospheric variability. [T]he marked differences in both the spatial distribution and amplitude between Figs. 4 and 3 suggest that maybe only a fraction of the observed variability in NEPO was forced by the SSTA while a large amount of the observed variability may have been a consequence of the atmospheric internal variability (noise). That is consistent with the conclusion from some recent works in examining the climate variability in mid- and high latitudes of the Northern Hemisphere, such as Baxter and Nigam (2015), Hartmann (2015), Lee et al. (2015), Seager et al. (2015), Watson et al. (2016), and Jha et al. (2016). … The remarkable amplitude differences between the observations (Fig. 3) and the simulations (Fig. 4) plus the large fluctuation of the pattern correlation (Figs. 5a, 6a), are indicative of the importance of the atmospheric internal variability (noise) in driving the observed anomalies in NEPO [northeastern Pacific Ocean]. [I]t was a challenge to predict the persistent SST anomalies in the northeastern Pacific because the SST anomaly in NEPO [northeastern Pacific Ocean] is largely controlled by unpredictable stochastic [random] atmosphere variability. [CO2 and/or anthropogenic forcing is not mentioned once in the paper.]
Goldsmith et al., 2017 The EAM [East Asian Monsoon] intensity and northern extent alternated rapidly between wet and dry periods on time scales of centuries. Lake levels were 60 m higher than present during the early and middle Holocene, requiring a twofold increase in annual rainfall [relative to today], which, based on modern rainfall distribution, requires a ∼400 km northward expansion/migration of the EAM.
Stegall and Kunkel, 2017 These results indicate that there is potential skill in use of GCMs [climate models] to provide projections of hot and cold extremes on the 30-yr timescale. However, it is important to note that natural variability is comparable to the forced signal on this timescale and thus introduces uncertainty.
Bordbar et al,, 2017 The observed trends in the tropical Pacific surface climate are still within the range of the long-term internal variability spanned by the models but represent an extreme realization of this variability. Thus, the recent observed decadal trends in the tropical Pacific, though highly unusual, could be of natural origin. We note that the long-term trends in the selected PWC indices exhibit a large observational uncertainty, even hindering definitive statements about the sign of the trends.
Bhaskar et al., 2017 Quantitative assessment of drivers of recent [1984-2005] global temperature variability … Measurements of greenhouse gases: CO2, CH4 and N2O; volcanic aerosols; solar activity: UV radiation, total solar irradiance (TSI) and cosmic ray flux (CR); El Niño Southern Oscillation (ENSO) and Global Mean Temperature Anomaly (GMTA) made during 1984–2005 are utilized to distinguish driving and responding signals of global temperature variability. Estimates of their relative contributions reveal that CO2 ( ∼24%), CH4 ( ∼19%) and volcanic aerosols ( ∼23%) are the primary contributors to the observed variations in GMTA [Global Mean Temperature Anomaly]. While UV ( ∼9%) and ENSO ( ∼12%) act as secondary drivers of variations in the GMTA, the remaining play a marginal role in the observed recent global temperature variability. Interestingly, ENSO and GMTA mutually drive each other at varied time lags. … [A]ll the constituents of natural forcings together seem to make contributions equal to the greenhouse gases in the context of recent global temperature variability. [76% of changes global temperatures are not driven by CO2. Water vapor and clouds, the dominant contributors to the greenhouse effect, are oddly excluded from consideration in this study.]
Cloud/Aerosol Climate Influence (5)
Stozhkov et al., 2017 One of the most important problems facing humanity is finding the physical mechanism responsible for global climate change, particularly global warming on the Earth. … Summation of these periodicities for the future (after 2015) allows us to forecast the next few decades. The solid heavy line in Fig. 1 shows that cooling (a drop in ΔT values) is expected in the next few decades. … Figure 2 shows the dependence between the annual average changes ΔT in the global temperature in the near-surface air layer and charged particle flux N in the interval of altitudes from 0.3 to 2.2 km. We can see there is a connection between values ΔТ [temperature] and N [charged particle flux]: with an increase in cosmic ray flux N, the values of changes of global temperature decrease. This link is expressed by the relation ΔT = –0.0838N + 4.307 (see the dashed line in Fig. 2), where the ΔT values are given in °C, and the N values (in particle/min units) are related to the charged particle flux measured at an altitude of 1.3 km. The correlation coefficient of the line with the experimental data is r = –0.62 ± 0.08. … Our results could be connected with the mechanism of charged particle fluxes influencing the Earth’s climate; it includes, first of all, the effect charged particles have on the accelerated formation of centers of water vapor condensation, and thus on the increase in global cloud cover. The total cloud cover is directly connected with the global temperature of the near surface air layer.
Tang et al., 2017 The results show that aerosol direct effect cannot fully explain the decadal variations in the global radiation over China between 1980 and 2010, though it has a considerable effect on global radiation climatology. There are significant differences between the trends of clear-sky global radiation impacted by aerosols and those of all-sky global radiation impacted by aerosols and clouds, and the correlation coefficient for the comparison is very low. Therefore, the variations in all-sky global radiation over China are likely to be due to changes in cloud properties and to interactions between clouds and aerosols.
Glotfelty and Zhang, 2017 Enhancements in cloud formation in the Arctic and Southern Ocean and increases of aerosol optical depth (AOD) in central Africa and South Asia dominate the change in surface radiation in both scenarios [during 2050 – 2100], leading to global average dimming of 1.1 W m−2 and 2.0 W m−2 in the RCP4.5 and RCP8.5 scenarios, respectively. Declines in AOD [aerosol optical depth], cloud formation, and cloud optical thickness from reductions of emissions of primary aerosols and aerosol precursors under RCP4.5 result in near surface warming of 0.2 °C from a global average increase of 0.7 W m−2 in surface downwelling solar radiation. This warming leads to a weakening of the Walker Circulation in the tropics, leading to significant changes in cloud and precipitation that mirror a shift in climate towards the negative phase of the El Nino Southern Oscillation. [Cloud and aerosols dominate the change in surface solar radiation, overwhelming the effects of anthropogenic CO2 emissions.]
Solomon et al., 2017 A number of feedbacks are found that damp the warming effect of the clouds. Thin mixed-phase clouds increase the downward longwave fluxes by 100 W m−2, but upward daytime surface longwave fluxes increase by 20 W m−2 (60 W m−2 at night) and net shortwave fluxes decrease by 40 W m−2 (partially due to a 0.05 increase in surface albedo), leaving only 40 W m−2 available for melt. This 40 W m−2 is distributed between the turbulent and conductive ground fluxes, so it is only at times of weak turbulent fluxes (i.e., at night or during melt) that this energy goes into the conductive ground flux, providing energy for melt. From these results it is concluded that it is the integrated impact of the clouds over the diurnal cycle (the preconditioning of the snowpack by the clouds at night) that made melt possible during this 3-day period. These findings are extended to understand the pattern of melt observed over the GIS. … Mixed-phase clouds are common at Summit (Shupe et al. 2013) and play a critical role in the Arctic surface energy balance (Shupe and Intrieri 2004), radiatively warming the highly reflective surface at Summit year-round (Miller et al. 2015).
Nicolas et al., 2017 During the short Antarctic summer, strong onshore winds may by themselves raise the ice sheet’s surface temperature (Ts) up to the melting point (through exchange of sensible heat), especially at low elevations. However, Ts [surface temperature] is ultimately controlled by the full surface energy budget (SEB), being the net of radiative (short- and longwave) and turbulent (sensible and latent) heat fluxes. Clouds exert an important influence on the SEB by modulating the radiative fluxes, primarily by enhancing downwelling longwave radiation and attenuating incoming solar radiation. In particular, low-level liquid-bearing clouds can have a determinant role in either causing or prolonging melting conditions over ice sheets. … Positive (anticyclonic) geopotential height anomalies in the South Pacific, such as those observed in January 2016, are a typical signature of El Niño teleconnections, as seen both in observations and climate model simulations. This type of atmospheric pattern promotes warm air advection to the Ross sector, which explains why surface melt in this area tends to be associated with El Niño-like conditions. [CO2 not mentioned as a factor in West Antarctica ice melt]
Volcanic/Tectonic Climate Influence (2)
Kelley, 2017 Volcanology: Vulcan rule beneath the sea … Over 70% of the volcanism on Earth occurs beneath an ocean veil. … Satellite data reveal more than 100,000 extinct and active seamounts that mark sites of past and present volcanic activity. [O]bservations imply that submarine volcanoes may play an important role in cycling carbon and sulfur through the Earth, oceans and atmosphere. … [T]he flux of volatiles from these systems remains poorly quantified and the significance of these volcanoes as part of the deep carbon and sulfur cycles on a global scale is unknown.
Viterito, 2017 The Correlation of Seismic Activity and Recent Global Warming (CSARGW) demonstrated that increasing seismic activity in the globe’s high geothermal flux areas (HGFA) is strongly correlated with global temperatures (r=0.785) from 1979-2015. The mechanism driving this correlation is amply documented and well understood by oceanographers and seismologists. Namely, increased seismic activity in the HGFA (i.e., the mid-ocean’s spreading zones) serves as a proxy indicator of higher geothermal flux in these regions. The HGFA include the Mid-Atlantic Ridge, the East Pacific Rise, the West Chile Rise, the Ridges of the Indian Ocean, and the Ridges of the Antarctic/Southern Ocean. This additional mid-ocean heating causes an acceleration of oceanic overturning and thermobaric convection, resulting in higher ocean temperatures and greater heat transport into the Arctic. This manifests itself as an anomaly known as the “Arctic Amplification,” where the Arctic warms to a much greater degree than the rest of the globe. Applying the same methodology employed in CSARGW, an updated analysis through 2016 adds new knowledge of this important relationship while strengthening support for that study’s conclusions. The correlation between HGFA seismic frequency and global temperatures moved higher with the addition of the 2016 data: the revised correlation now reads 0.814, up from 0.785 for the analysis through 2015. This yields a coefficient of determination of .662, indicating that HGFA [high geothermal flux area] seismicity accounts for roughly two-thirds of the variation in global temperatures since 1979.
Challenging The Theoretical Greenhouse Effect As Temperature Driver (4)
Hertzberg et al., 2017 This study examines the concept of ‘greenhouse gases’ and various definitions of the phenomenon known as the ‘Atmospheric Radiative Greenhouse Effect’. The six most quoted descriptions are as follows: (a) radiation trapped between the Earth’s surface and its atmosphere; (b) the insulating blanket of the atmosphere that keeps the Earth warm; (c) back radiation from the atmosphere to the Earth’s surface; (d) Infra Red absorbing gases that hinder radiative cooling and keep the surface warmer than it would otherwise be – known as ‘otherwise radiation’; (e) differences between actual surface temperatures of the Earth (as also observed on Venus) and those based on calculations; (f) any gas that absorbs infrared radiation emitted from the Earth’s surface towards free space. It is shown that none of the above descriptions can withstand the rigours of scientific scrutiny when the fundamental laws of physics and thermodynamics are applied to them.
Blaauw, 2017 This paper demonstrates that global warming can be explained without recourse to the greenhouse theory. This explanation is based on a simple model of the Earth’s climate system consisting of three layers: the surface, a lower and an upper atmospheric layer. The distinction between the atmospheric layers rests on the assumption that the latent heat from the surface is set free in the lower atmospheric layer only. The varying solar irradiation constitutes the sole input driving the changes in the system’s energy transfers. All variations in the energy exchanges can be expressed in terms of the temperature variations of the layers by means of an energy transfer matrix. It turns out that the latent heat transfer as a function of the temperatures of the surface and the lower layer makes this matrix next to singular. The near singularity reveals a considerable negative feedback in the model which can be identified as the ‘Klimaversta¨rker’ presumed by Vahrenholt and Lu¨ning. By a suitable, yet realistic choice of the parameters appearing in the energy transfer matrix and of the effective heat capacities of the layers, the model reproduces the global warming: the calculated trend in the surface temperature agrees well with the observational data from AD 1750 up to AD 2000.
Nikolov and Zeller, 2017 Our analysis revealed that GMATs [global mean annual temperatures] of rocky planets with tangible atmospheres and a negligible geothermal surface heating can accurately be predicted over a broad range of conditions using only two forcing variables: top-of-the-atmosphere solar irradiance and total surface atmospheric pressure. The hereto discovered interplanetary pressure-temperature relationship is shown to be statistically robust while describing a smooth physical continuum without climatic tipping points. This continuum fully explains the recently discovered 90 K thermal effect of Earth’s atmosphere. The new model displays characteristics of an emergent macro-level thermodynamic relationship heretofore unbeknown to science that has important theoretical implications. A key entailment from the model is that the atmospheric ‘greenhouse effect’ currently viewed as a radiative phenomenon is in fact an adiabatic (pressure-induced) thermal enhancement analogous to compression heating and independent of atmospheric composition. Consequently, the global down-welling long-wave flux presently assumed to drive Earth’s surface warming appears to be a product of the air temperature set by solar heating and atmospheric pressure. In other words, the so-called ‘greenhouse back radiation’ is globally a result of the atmospheric thermal effect rather than a cause for it. … The down-welling LW radiation is not a global driver of surface warming as hypothesized for over 100 years but a product of the near-surface air temperature controlled by solar heating and atmospheric pressure … The hypothesis that a freely convective atmosphere could retain (trap) radiant heat due its opacity has remained undisputed since its introduction in the early 1800s even though it was based on a theoretical conjecture that has never been proven experimentally.
Allmendinger, 2017 The cardinal error in the usual greenhouse theory consists in the assumption that photometric or spectroscopic IR-measurements allow conclusions about the thermal behaviour of gases, i.e., of the atmosphere. They trace back to John Tyndall who developed such a photometric method already in the 19th century. However, direct thermal measurement methods have never been applied so far. Apart from this, at least twenty crucial errors are revealed which suggest abandoning the theory as a whole. In spite of its obvious deficiencies, this theory has so far been an obstacle to take promising precautions for mitigating the climate change. They would consist in a general brightening of the Earth surface, and in additional measures being related to this. However, the novel effects which were found by the author, particularly the absorption of incident solar-light by the atmosphere as well as its absorption capability of thermal radiation, cannot be influenced by human acts.
Part 2. Unsettled Science, Ineffective Climate Modeling
Climate Model Unreliability/Biases/Errors and the Pause (19)
Hedemann et al., 2017 (full paper) During the first decade of the twenty-first century, the Earth’s surface warmed more slowly than climate models simulated. This surface-warming hiatus is attributed by some studies to model errors in external forcing, while others point to heat rearrangements in the ocean caused by internal variability, the timing of which cannot be predicted by the models. However, observational analyses disagree about which ocean region is responsible. Here we show that the hiatus could also have been caused by internal variability in the top-of-atmosphere energy imbalance. Energy budgeting for the ocean surface layer over a 100-member historical ensemble reveals that hiatuses are caused by energy-flux deviations as small as 0.08 W m−2, which can originate at the top of the atmosphere, in the ocean, or both. Budgeting with existing observations cannot constrain the origin of the recent hiatus, because the uncertainty in observations dwarfs the small flux deviations that could cause a hiatus. The sensitivity of these flux deviations to the observational dataset and to energy budget choices helps explain why previous studies conflict, and suggests that the origin of the recent hiatus may never be identified. … The observed trend deviated by as much as −0.17 ◦C per decade from the CMIP5 (Coupled Model Intercomparison Project Phase 5) ensemble-mean projection—a gap two to four times the observed trend. The hiatus therefore continues to challenge climate science.
Xie et al., 2017 As the recent global warming hiatus has attracted worldwide attention, we examined the robustness of the warming hiatus in China and the related dynamical mechanisms in this study. Based on the results confirmed by the multiple data and trend analysis methods, we found that the annual mean temperature in China had a cooling trend during the recent global warming hiatus period, which suggested a robust warming hiatus in China. The warming hiatus in China was dominated by the cooling trend in the cold season, which was mainly induced by the more frequent and enhanced extreme-cold events.
Xian and Fu, 2017 Despite continually increasing concentrations of greenhouse gas, there has been a hiatus in rising global temperatures during the 21st century.
Liu and Zhou, 2017 Here, we divided recent decades into the recent hiatus period [1998-2013] and the preceding warming period (1983–1998) to investigate the atmospheric footprint. We use a process-resolving analysis method to quantify the contributions of different processes to the total temperature changes. We show that the increasing rate of global mean tropospheric temperature was also reduced during the hiatus period. The decomposed trends due to physical processes, including surface albedo, water vapour, cloud, surface turbulent fluxes and atmospheric dynamics, reversed the patterns between the two periods. … [C]limate models designed to represent the physics and dynamics of the climate system project that GMST [global mean surface temperature] continued to rise in the early 2000s. Dominant mechanisms proposed to understand the hiatus included the internal climate variability and ocean heat uptake and transport; however, the differences in the atmospheric footprint of recent warming slowdown remains unclear in terms of the dynamical and physical processes.
Rosenblum and Eisenman, 2017 Observations indicate that the Arctic sea ice cover is rapidly retreating while the Antarctic sea ice cover is steadily expanding. State-of-the-art climate models, by contrast, typically simulate a moderate decrease in both the Arctic and Antarctic sea ice covers. … [W]e find that simulated Arctic sea ice retreat as fast as observed would occur less than 1% of the time. This implies that the models are not consistent with the observations. In the Antarctic, we find that simulated sea ice expansion as fast as observed typically corresponds with too little global warming, although these results are more equivocal. We show that because of this, the simulations do not capture the observed asymmetry between Arctic and Antarctic sea ice trends. This suggests that the models may be getting the right sea ice trends for the wrong reasons in both polar regions.
Zanchettin, 2017 Multiple lines of evidence from climate observations, reconstructions, and simulations point to the potential of volcanic eruptions, tropospheric aerosols, and solar activity to substantially impact on decadal climatic variability. However, uncertainties and gaps of knowledge in the characterization of forced decadal climate responses remain large, and only a few studies have systematically tackled the implication of these forcing agents for decadal predictability and prediction. For all forcing agents, major limitations in understanding arise from incompleteness and shortness of the instrumental observations concerning the forcing as well as the climate response. Further issues concern the deficient representation of key processes in climate models and limitations inherent to reconstructed evidence.
Zuidema et al., 2017 Most contemporary coupled atmosphere–ocean general circulation models (CGCMs) produce a climate that is significantly more symmetric about the equator than in observations (Mechoso et al. 1995; Davey et al. 2002; Biasutti et al. 2006; de Szoeke and Xie 2008; Richter et al. 2016; Richter 2015; Siongco et al. 2015). Outstanding features include positive sea surface temperature (SST) errors south-southeast of the equator (Fig. 1a), collocated in part with an intertropical convergence zone (ITCZ) precipitation band (Fig. 1b) much stronger than that observed in nature. The “double ITCZ” error is further implicated in the simulated Hadley circulation, seasonal cycle and winds on the equator, and equatorial modes of variability, such as El Niño–Southern Oscillation (ENSO) in the Pacific, casting doubt on the ability to model and predict both regional and global climate. … OAFlux allows for more ocean warming than is observed, an error that implies the CMIP5 model net flux biases are even larger, by at least 10 W m−2 … Mean CMIP5 net CRE biases are very large, up to 40 W m−2, relative to CERES values. … The CMIP5 models generally continue to underestimate subtropical stratocumulus cloud cover relative to observations, similar to CMIP3 (Klein et al. 2013) … The history in understanding the wind contribution to SST error growth is closely tied to that of model resolution. …The wind bias is linked to incorrect model-dependent distributions of tropical precipitation (Biasutti et al. 2006; Richter and Xie 2008; Richter et al. 2012; Siongco et al. 2015).
Ahlström et al., 2017 Our results suggest that climate biases could be responsible for a considerable fraction of the large uncertainties in ESM [Earth system models] simulations of land carbon fluxes and pools, amounting to about 40% of the range reported for ESMs. We conclude that climate bias-induced uncertainties must be decreased to make accurate coupled atmosphere-carbon cycle projections.
Zhang et al., 2017 [R]obust projections for extreme short-duration rainfall is challenging … because of our poor understanding of its past and future behaviour. The characterization of past changes is severely limited by the availability of observational data. Climate models, including typical regional climate models, do not directly simulate all extreme rainfall producing processes, such as convection. … [T]he observed precipitation–temperature scaling relationships have been established almost exclusively by linking precipitation extremes with day-to-day temperature variations. These scaling relationships do not appear to provide a reliable basis for projecting future precipitation extremes.
Zhou et al., 2017 The evaluation results show that 5 out of 30 climate models can well capture the observed APO [Asian-Pacific Oscillation]-related features in a comprehensive way, including the strengthened South Asian high (SAH), deepened North Pacific trough (NPT) and northward East Asian jet (EAJ) in the upper troposphere. [83% of climate models cannot capture the APO features comprehensively.]
Stouffer et al., 2017 There are a number of systematic model biases that appear in all phases of CMIP that remain a major climate modeling challenge. These biases need increased attention to better understand their origins and consequences through targeted experiments. Improving understanding of the mechanisms’ underlying internal climate variability for more skillful decadal climate predictions and long-term projections remains another challenge for CMIP6.
Oka and Watanabe, 2017 The warming rate of global-mean surface temperature slowed down during 1998-2012. Previous studies pointed out role of increasing ocean heat uptake during this global warming slowdown, but its mechanism remains under discussion.
Zhou and Penner, 2017 Observation-based studies have shown that the aerosol cloud lifetime effect or the increase of cloud liquid water path (LWP) with increased aerosol loading may have been overestimated in climate models.
Barcikowska et al., 2017 How global temperature will evolve over the next decade or so remains unclear (Knutson et al. 2016), although the most recent warming hiatus, observed in surface temperature records over the period 1998–2014, has challenged the scientific community in terms of consistency of models versus observations and in the attribution of the phenomena (Kosaka and Xie 2013; England et al. 2014; McGregor et al. 2014; Fyfe et al. 2012). Further, it has triggered discussions of the impacts of related unforced (Chen and Tung 2014) and additional unmodeled forced contributions (Schmidt et al. 2014) on observed climate changes. Recent studies (Kosaka and Xie 2013; England et al. 2014; Meehl et al. 2011, 2013) have attributed the slowdown to a negative interdecadal Pacific oscillation (IPO) phase, which has caused anomalous surface cooling over the equatorial eastern Pacific. On the other hand, the model hindcast experiments of Chikamoto et al. (2012, 2015) suggest an important role of the Atlantic multidecadal oscillation (AMO) in predicting the recently observed cooling and associated La Niña SST pattern over the equatorial eastern Pacific. … The relative roles of internal climate variability and radiative forcing in causing the multidecadal variations in the North Atlantic and Northern Hemisphere since the late 1800s remain under debate (Booth et al. 2012; Zhang et al. 2013) … [N]ot only cooling over the North Atlantic but also preceding cooling over the tropical Pacific appears to be related to the three reconstructed global SST stagnation periods (1880–1900s, 1940s–60s, and 2000s–10s). The results suggest that the observed decadal SST stagnation periods (including the recent pause) stem from more than one climate component (internal variability and/or radiatively forced). Moreover, these components may also have a mutual influence upon each other (e.g., AMO could modulate the IPO and/or PDO by setting the initial stage for their evolution). These findings are in agreement with previous studies (McGregor et al. 2014; Li et al. 2016) highlighting the role of Atlantic warming in enhancing the Walker circulation cell and cooling the eastern tropical Pacific since the early 1990s.
Cionco and Soon, 2017 Our detailed analysis of the periods present in STOF [short-term orbital forcing], as perturbed by Solar System bodies, yields a very rich dynamical modulation on annual-to-decadal timescales when compared to previous results. In addition, we addressed, for the first time, the error committed considering daily insolation as a continuous function of orbital longitudes with respect to the nominal values, i.e., calculating the corresponding daily insolation with orbital longitudes tabulated at noon. We found important relative differences up to ± 5%, which correspond to errors of 2.5 W m −2 in the daily mean insolation, for exactly the same calendar day and set of astro-climatic parameters. This previously unrecognized error could have a significant impact in both the initial and boundary conditions for any climate modeling experiment. … A close inspection from the United Nations Fifth Assessment Report tells us that STOF [short-term orbital forcing] is indirectly assumed to be unimportant and play no climatic role. The primary argument and assumption in neglecting changes in orbital forcing for climatic changes over the last few thousand years, last century or even last decade seemed to be from the claim that globally-averaged radiative forcing is small or negligible. … We … wish to call for a more direct accounting for STOF, as a true boundary condition, in all climatic simulations in that the effects from local and regional perspective are clearly not negligible nor unimportant in terms of seasonal dynamical evolution of the coupled air-sea-land system.
Hope et al., 2017 We evaluate GMST using two approaches: analysis of archived output from atmospheric, oceanic general circulation models (GCMs) and calculations conducted using a computational framework developed by our group, termed the Empirical Model of Global Climate (EM-GC). Comparison of the observed rise in GMST over the past 32 years with GCM output reveals these models tend to warm too quickly, on average by about a factor of two. Most GCMs likely represent climate feedback in a manner that amplifies the radiative forcing of climate due to greenhouse gases (GHGs) too strongly.
Smith et al., 2017 Here, we used coupled atmosphere-biosphere simulations using the Community Earth System Model (CESM) to assess how acclimation-induced changes in photosynthesis influence global climate under present-day and future (RCP 8.5) conditions. … In the present-day simulations, the photosynthetic response was not as strong and cooling in highly vegetated regions was less than warming elsewhere, leading to a net global increase in temperatures of 0.04°C. Precipitation responses were variable and rates did not change globally in either time period. These results, combined with carbon-cycle effects, suggest that models without acclimation may be overestimating positive feedbacks between climate and the land surface in the future.
Molteni et al., 2017 It is widely accepted that natural decadal variability played a major role in the slowdown in global warming observed in the 21st century, with sea-surface cooling in the tropical Pacific recognized as a major contributor. However, the warming pause was most pronounced during boreal winter, with northern-hemisphere flow anomalies also playing a role. Here we quantify the contribution of extra-tropical heat exchanges by comparing geopotential and temperature anomalies simulated by ensembles of seasonal forecasts with similar ocean temperature but different heat fluxes north of 40 N, as a result of planetary-wave variability. We show that an important part of heat flux anomalies is associated with decadal variations in the phase of a specific planetary-wave pattern. In model simulations covering the last three decades, this variability pattern accounts for a decrease of 0.35 °C/decade in the post-1998 wintertime temperature trend over northern continents.
Kravtsov, 2017 Global and regional warming trends over the course of the twentieth century have been nonuniform, with decadal and longer periods of faster or slower warming, or even cooling. Here we show that state-of-the-art global models used to predict climate fail to adequately reproduce such multidecadal climate variations. In particular, the models underestimate the magnitude of the observed variability and misrepresent its spatial pattern. Therefore, our ability to interpret the observed climate change using these models is limited.
Failing Renewable Energy, Climate Policies (8)
Janković and Shultz, 2017 [A] preindustrial climate may remain a policy goal, but it is unachievable in reality. … In 2011, the nonprofit science and outreach organization Climate Communication—whose staff and science advisors include, among others, Richard Sommerville, Jerry Melillo, Ken Kaldeira, Kerry Emanuel, Michael Mann, and Michael Oppenheimer—issued the following statement:
“As the climate has warmed, some types of extreme weather have become more frequent and severe in recent decades, with increases in extreme heat, intense precipitation, and drought. … All weather events are now influenced by climate change because all weather now develops in a different environment than before.”
Yet, this statement, as well as numerous others in the popular literature and media stories, contradicts the scientific evidence. [R]educing the complexity of climate change (as if a single outcome were known) into the soundbite of “climate change means more extreme weather” is a massive oversimplification—if not misstatement—of the true state of the science. … With such events seemingly outside the expected natural range of possibilities, the media increasingly turned to blaming climate change for the severe weather (e.g., Janković 2006; Hulme 2014). “The good cause—one that most of us support—can all too readily corrupt the conduct of science, especially science informing public policy, because we prefer answers that support our political preferences, and find science that challenges them less comfortable” (Kellow 2008). … [A]ttribution claims allow policy-makers to put forward a case for morally robust policies based on mitigation of greenhouse emissions. Weather extremes are proxies of climate crisis, dismantling the climate complexity into the simpler and more visible conventional idiom of atmospheric hazard. … [I]t remains to be determined whether such [CO2 emission reduction] plans ought to be legitimized by a presumed rise in future weather extremes and whether a successful implementation of such plans would result in a demonstrable reduction of socioeconomic damages caused by supercharged weather. If neither of these results is justified, a policy based on attribution claims (and [fear]) runs the risk of being ill advised, ineffective, and disingenuous. … Reducing carbon emissions, regardless of how effective, cannot of itself reduce weather impacts (e.g., Schultz and Janković 2014). … Climate change is not a discrete problem independent of development imperatives, nor is it manageable by a policy based on a mere scientific consensus (Prins et al. 2010). [E]ven if anthropogenic climate change were effectively stopped, extreme weather would continue. Members of the public and governmental representatives who had been sold on the idea that “stopping climate change will reduce extreme weather events” would understandably question their bill of goods, reducing scientific credibility.
Harris, 2017 China’s Paris pledge on climate change: inadequate and irresponsible … China’s pledge is little more than business as usual. Significant ethical obligations arise from China’s role as the largest national source of greenhouse gas pollution and home to hundreds of millions of affluent consumers. The Paris Agreement disregards such obligations. The inadequacy and irresponsibility of China’s Paris pledge exposes some fundamental flaws in the international climate change negotiations and agreements, demonstrating that science and environmental studies cannot be disconnected from ethics and justice.
Clack et al., 2017 The scenarios of [Jacobson et al., 2015, “Low-cost solution to the grid reliability problem with 100% penetration of intermittent wind, water, and solar for all purposes”] can, at best, be described as a poorly executed exploration of an interesting hypothesis. The study’s numerous shortcomings and errors render it unreliable as a guide about the likely cost, technical reliability, or feasibility of a 100% wind, solar, and hydroelectric power system. It is one thing to explore the potential use of technologies in a clearly caveated hypothetical analysis; it is quite another to claim that a model using these technologies at an unprecedented scale conclusively shows the feasibility and reliability of the modeled energy system implemented by midcentury. From the information given by [Jacobson et al., 2015], it is clear that both hydroelectric power and flexible load have been modeled in erroneous ways and that these errors alone invalidate the study and its results.
Heard et al., 2017 While many modelled scenarios have been published claiming to show that a 100% renewable electricity system is achievable, there is no empirical or historical evidence that demonstrates that such systems are in fact feasible. Of the studies published to date, 24 have forecast regional, national or global energy requirements at sufficient detail to be considered potentially credible. We critically review these studies using four novel feasibility criteria for reliable electricity systems needed to meet electricity demand this century. [N]one of the 24 studies provides convincing evidence that these basic feasibility criteria can be met. Of a maximum possible unweighted feasibility score of seven, the highest score for any one study was four. … On the basis of this review, efforts to date seem to have substantially underestimated the challenge and delayed the identification and implementation of effective and comprehensive decarbonization pathways. … To date, efforts to assess the viability of 100% renewable systems, taking into account aspects such as financial cost, social acceptance, pace of roll-out, land use, and materials consumption, have substantially underestimated the challenge of excising fossil fuels from our energy supplies. This desire to push the 100%-renewable ideal without critical evaluation has ironically delayed the identification and implementation of effective and comprehensive decarbonization pathways. We argue that the early exclusion of other forms of technology from plans to decarbonize the global electricity supply is unsupportable, and arguably reckless. … The realization of 100% renewable electricity (and energy more broadly) appears diametrically opposed to other critical sustainability issues such as eradication of poverty, land conservation and reduced ecological footprints, reduction in air pollution, preservation of biodiversity, and social justice for indigenous people.
Vass, 2017 Renewable energies cannot compete with forest carbon sequestration to cost-efficiently meet the EU carbon target for 2050 … [T]he average cost per unit emissions reduction is more than twice as high for renewables as for forest carbon sequestration. Hence, the results indicate that renewables are unable to compete with forest carbon sequestration unless they receive continued government support.
Emery et al., 2017 Although climate change mitigation and energy security policies are generally expected to be compatible with air pollution and health cost reductions (McCollum et al., 2013), there is evidence that first-generation alternative fuels such as corn ethanol lead to higher health costs due to air pollution than conventional fuels [gasoline] (Hill et al., 2009). … We find that life-cycle non-GHG air pollutant emissions, particularly NOX [nitrous oxides] and PM [particulates], are higher for corn ethanol and other biofuel blends than conventional petroleum fuels. Emissions of volatile organic compounds (VOCs) and carbon monoxide (CO) increase by 9–50% per 100 km traveled for high-ethanol blends from corn grain and combined grain and stover feedstocks. NOX, PM [particulates], and SOX [sulfur dioxides] increase by 71–124% from corn grain and 56–110% from combined grain and stover, relative to conventional gasoline. Biodiesel blends show an increase of 1–11% (B20) and 4–55% (B100) in air pollution, with the largest increases in VOC [volatile organic compounds] and SOX [sulfur dioxides] emissions. … The total social costs of ethanol blends are higher than that of gasoline, due in part to higher life-cycle emissions of non-GHG pollutants and higher health and mortality costs per unit.
Mahapatra and Ratha, 2017 The Paris deal is founded on a voluntary basis without any legally binding caps. The Paris Agreement is a relatively toothless one, which does not bind countries to actual emission limits, and has no mechanisms to impose actions. No sanctions will fall on any country that fails to come up to these intentions. The poor nations want clear promises to increase the aid for them, while the USA and other rich nations favour vaguer wording. Professor James Hansen—credited as being the father of climate change awareness— said that ‘the deal is worthless words’ (Wente, 2015). The final text contains only bland platitudes. There is no necessary connection between the legally binding nature of an international agreement and its effectiveness in producing outcomes (Lake, 2015). The agreement delineates an aim for reducing temperatures to a 2°C above pre-industrial levels, but does not commit.
Richardson and Kumar, 2017 A growing human population creates a larger demand for food products and makes conservation of resources and increased efficiency of agricultural production more vital. … These results conclude that feed production systems are more energy efficient and less environmentally costly than corn-based ethanol. … [A]ccording to the findings of this study, biofuels, derived for the purpose of producing energy with little environmental impacts, actually use more energy at a higher environmental cost than the alternative crop use. As technology stands now, in terms of energy and environmental sustainability, the benefits of switching land uses to the production of corn-based transportation biofuels are not as favorable as continuing to produce corn for feed/food consumption.
Wind Power Harming The Environment, Biosphere (4)
Gortsas et al., 2017 Infrasound, low frequency noise and soil vibrations produced by large wind turbines might disturb the comfort of nearby structures and residents. In addition repowering close to urban areas produces some fears to the nearby residents that the level of disturbance may increase. Due to wind loading, the foundation of a wind turbine interacts with the soil and creates micro-seismic surface waves that propagate for long distances and they are able to influence adversely sensitive measurements conducted by laboratories located far from the excitation point.
Frick et al., 2017 Large numbers of migratory bats are killed every year at wind energy facilities. However, population-level impacts are unknown as we lack basic demographic information about these species. We investigated whether fatalities at wind turbines could impact population viability of migratory bats, focusing on the hoary bat (Lasiurus cinereus), the species most frequently killed by turbines in North America. Using expert elicitation and population projection models, we show that mortality from wind turbines may drastically reduce population size and increase the risk of extinction. For example, the hoary bat population could decline by as much as 90% in the next 50 years if the initial population size is near 2.5 million bats and annual population growth rate is similar to rates estimated for other bat species (λ = 1.01). Our results suggest that wind energy development may pose a substantial threat to migratory bats in North America. If viable populations are to be sustained, conservation measures to reduce mortality from turbine collisions likely need to be initiated soon. Our findings inform policy decisions regarding preventing or mitigating impacts of energy infrastructure development on wildlife.
Liu and Barlow, 2017 Wind energy has developed rapidly over the last two decades to become one of the most promising and economically viable sources of renewable energy. Although wind energy is claimed to provide clean renewable energy without any emissions during operation, but it is only one side of the coin. The blades, one of the most important components in the wind turbines, made with composite, are currently regarded as unrecyclable. With the first wave of early commercial wind turbine installations now approaching their end of life, the problem of blade disposal is just beginning to emerge as a significant factor for the future. … The research indicates that there will be 43 million tonnes of blade waste worldwide by 2050 with China possessing 40% of the waste, Europe 25%, the United States 16% and the rest of the world 19%.
Ramirez-Tejeda et al., 2017 Globally, more than seventy thousand wind turbine blades were deployed in 2012 and there were 433 gigawatts (GW) of wind installed capacity worldwide at the end of 2015. Moreover, the United States’ installed wind power capacity will need to increase from 74 GW to 300 GW3 to achieve its 20% wind production goal by 2030. … The wind turbine blades are designed to have a lifespan of about twenty years, after which they would have to be dismantled due to physical degradation or damage beyond repair. … Estimations have suggested that between 330,000 tons/year by 2028 and 418,000 tons/year by 2040 of composite material from blades will need to be disposed worldwide. That would be equivalent to the amount of plastics waste generated by four million people in the United States in 2013. This anticipated increase in blade manufacturing and disposal will likely lead to adverse environmental consequences. … Despite its negative consequences, landfilling has so far been the most commonly utilized wind turbine blade disposal method. … Landfilling is especially problematic because its high resistance to heat, sunlight, and moisture means that it will take hundreds of years to degrade in a landfill environment. The wood and other organic material present in the blades would also end up in landfills, potentially releasing methane, a potent greenhouse gas, and other volatile organic compounds to the environment.
Elevated CO2 Greens Planet, Produces Higher Crop Yields (4)
Bastos et al., 2017 The sustained increasing vegetation activity trend (greening) in the Northern Hemisphere (NH) has been a prominent feature in satellite observations since the 1980s and is consistently simulated by models. The trend in vegetation greenness has been linked to increasing growing season length at high latitudes and enhancemed terrestrial CO2 uptake in northern ecosystems. The greening pace has been associated with asymmetric effects of climate trends in vegetation activity or variations in the climate forcing. It has also been shown that regional greening trends are further attributed to land use change, land management, CO2 fertilization, and nitrogen deposition
Li et al., 2017 [M]aternal CO2 environment modulated the response of wheat plants to drought stress in terms of biomass production, [such that] plants reared from seeds harvested from the e[levated CO2] maternal growth environment eliminated the negative impact of drought stress on DM [dry biomass]. … [T]ransgenerational exposure to e[CO2] also attenuated the negative impact of drought on evapotranspiration in wheat plants. … [T]ransgenerational exposure of wheat plants to e[CO2] could attenuate the negative impact of drought stress in terms of DM and WUE [water use efficiency].
Brandt et al., 2017 Here we used a passive microwave Earth observation data set to document two different trends in land area with woody cover for 1992–2011: 36% of the land area (6,870,000 km2) had an increase in woody cover largely in drylands, and 11% had a decrease (2,150,000 km2), mostly in humid zones. Increases in woody cover were associated with low population growth, and were driven by increases in CO2 in the humid zones and by increases in precipitation in drylands, whereas decreases in woody cover were associated with high population growth.
[press release] Africa has become greener in the last 20 years … [M]ore CO2 in the atmosphere together with a wetter, warmer planet, provides conditions that help trees and bushes to grow.
Bastin et al., 2017 We show that in 2015, 1327 million hectares of drylands had more than 10% tree-cover, and 1079 million hectares comprised forest. Our estimate is 40 to 47% higher than previous estimates, corresponding to 467 million hectares of forest that have never been reported before. This increases current estimates of global forest cover by at least 9%.
Warming Beneficial, Does Not Harm Humans, Wildlife (3)
Fan et al., 2017 Summer insolation [surface solar radiation] in the Northern Hemisphere began to increase 12,000 yr ago and reached a maximum (7% greater than the present value) from 10,000 to 9000 yr ago (Laskar et al., 2004). … We suggest that hydrological and ecological changes in the EASM margin during the Holocene were closely related to the combined effects of regional precipitation and temperature which were ultimately controlled by the Northern Hemisphere summer insolation [solar radiation], the boundary conditions and the physical environment of ocean current. Our data suggest that future global warming scenarios would potentially be beneficial for the hydrological and ecological conditions of the EASM margin, while small decreases in the precipitation and temperature superimposed on the long-term deteriorated climate may cause large declines in the hydrology and ecology in the semi-arid regions of northern China.
Crockford, 2017 Data collected between 2007 and 2015 reveal that polar bear numbers have not declined as predicted and no subpopulation has been extirpated. Several subpopulations expected to be at high risk of decline have remained stable and at least one showed a marked increase in population size over the entire period. Another at-risk subpopulation was not counted but showed marked improvement in reproductive parameters and body condition with less summer ice. As a consequence, the hypothesis that repeated summer sea ice levels of below 5 mkm2 will cause significant population declines in polar bears is rejected. This result indicates that the ESA and IUCN judgments to list polar bears as threatened based on future risks of habitat loss were hasty generalizations that were scientifically unfounded, which suggests that similar predictions for Arctic seals and walrus may be likewise flawed, while the lack of a demonstrable ‘sea ice decline = population decline’ relationship for polar bears invalidates updated survival model outputs that predict catastrophic population declines should the Arctic become ice-free in summer.
Baresel et al., 2017 The Earth has known several mass extinctions over the course of its history. One of the most important happened at the Permian-Triassic boundary 250 million years ago. Over 95% of marine species disappeared and, up until now, scientists have linked this extinction to a significant rise in Earth temperatures. But researchers have now discovered that this extinction took place during a short ice age which preceded the global climate warming. It’s the first time that the various stages of a mass extinction have been accurately understood and that scientists have been able to assess the major role played by volcanic explosions in these climate processes.
Warming, Acidification Not Harming Oceanic Biosphere (3)
Toyofuku et al., 2017 Ongoing ocean acidification is widely reported to reduce the ability of calcifying marine organisms to produce their shells and skeletons. Whereas increased dissolution due to acidification is a largely inorganic process, strong organismal control over biomineralization influences calcification and hence complicates predicting the response of marine calcifyers. Here we show that calcification is driven by rapid transformation of bicarbonate into carbonate inside the cytoplasm, achieved by active outward proton pumping. Moreover, this proton flux is maintained over a wide range of pCO2 levels. We furthermore show that a V-type H+ ATPase is responsible for the proton flux and thereby calcification. External transformation of bicarbonate into CO2 due to the proton pumping implies that biomineralization does not rely on availability of carbonate ions, but total dissolved CO2 may not reduce calcification, thereby potentially maintaining the current global marine carbonate production.
(press release) [A] group of scientists discovered to their own surprise that some tiny unicellular shellfish (foraminifera) make better shells in an acidic environment. This is a completely new insight.
Schaum et al., 2017 Here, we use a decade-long experiment in outdoor mesocosms to investigate mechanisms of adaptation to warming (+4 °C above ambient temperature) in the green alga Chlamydomonas reinhardtii, in naturally assembled communities. Isolates from warmed mesocosms had higher optimal growth temperatures than their counterparts from ambient treatments. Consequently, warm-adapted isolates were stronger competitors at elevated temperature and experienced a decline in competitive fitness in ambient conditions, indicating adaptation to local thermal regimes. Higher competitive fitness in the warmed isolates was linked to greater photosynthetic capacity and reduced susceptibility to photoinhibition. These findings suggest that adaptive responses to warming in phytoplankton could help to mitigate projected declines in aquatic net primary production by increasing rates of cellular net photosynthesis.
Kienzle et al., 2017 Rising temperatures increased recruitment of brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia)
Decreases In Extreme, Unstable Weather With Warming (3)
Zhang et al., 2017 Based on continuous and coherent severe weather reports from over 500 manned stations, for the first time, this study shows a significant decreasing trend in severe weather occurrence across China during the past five decades. The total number of severe weather days that have either thunderstorm, hail and/or damaging wind decrease about 50% from 1961 to 2010. It is further shown that the reduction in severe weather occurrences correlates strongly with the weakening of East Asian summer monsoon which is the primary source of moisture and dynamic forcing conducive for warm-season severe weather over China.
Kawamura et al., 2017 Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instability with bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets. [Cooling elicits more climate instability.]
Heller, 2017 The hurricane analysis conducted by Burn and Palmer (2015) determined that hurricane activity was subdued during the [warm] Medieval Climate Anomaly (MCA) (~900-1350 CE) and became more produced during the [cold] Little Ice Age (LIA) (~1450-1850 CE), followed by a period of variability occurred between ~1850 and ~1900 before entering another subdued state during the industrial period (~1950-2000 CE). In general, the results of this study corroborate these findings … [W]hile hurricane activity was greater during the LIA, it also had more frequent periods of drought compared to the MCA (Burn and Palmer 2014), suggesting that climate fluctuations were more pronounced in the LIA compared to the MCA. The changes in the diatom distribution and fluctuations in chl-a recorded in this study starting around 1350 also indicate that variations in climate have become more distinct during the LIA and from ~1850-1900. … [C]limate variability has increased following the onset of the Little Ice Age (~1450-1850 CE), however it is difficult to distinguish the impacts of recent anthropogenic climate warming on hurricane activity from those of natural Atlantic climate regimes, such as ENSO.
No Increasing Trends In Intense Hurricanes (3)
Choi et al., 2017 This study analysed the time series of tropical cyclone (TC) frequency during October–December (OND) for 32 years (1980–2011). There was a strong decreasing trend of TCs until recently, and the TC sharply decreased from 1996 after the statistical change-point analysis was applied to this time series.
Chen et al., 2017 Results indicate that the midlatitude summer cyclone activity over East Asia exhibits decadal changes in the period of 1979–2013 and is significantly weakened after early 1990s. … Moreover, there is a close linkage between the weakening of cyclonic activity after the early 1990s and the nonuniform surface warming of the Eurasian continent. Significant warming to the west of Mongolia tends to weaken the north–south temperature gradient and the atmospheric baroclinicity to its south and eventually can lead to weakening of the midlatitude cyclone activity over East Asia.
Wellford et al., 2017 Since the late 1800s, in contrast to much of the Southeastern USA, the Georgia coast has experienced infrequent hurricane landfalls, particularly in recent decades. As a result, coastal storm preparedness complacency appears to be rampant along the Georgia coastline. Both local and state governments were unprepared for shadow evacuation during Hurricane Floyd in 1999. The study described here includes an examination of temporal and spatial trends in hurricane landfall along the Georgia coast from 1750 to 2012. Since 1750, 18 of the 24 recorded hurricanes that made landfall along the Georgia coast occurred between 1801 and 1900, yet the hurricane intensities have declined since 1851.
No Increasing Trends In Drought/Flood Frequency, Severity (2)
McAneney et al., 2017 [A] 122-year record of major flooding depths at the Rarawai Sugar Mill on the Ba River in the northwest of the Fijian Island of Viti Levu is analysed. … It exhibits no statistically significant trends in either frequency or flood heights, once the latter have been adjusted for average relative sea-level rise. This is despite persistent warming of air temperatures as characterized in other studies. There is a strong dependence of frequency (but not magnitude) upon El Niño-Southern Oscillation (ENSO) phase, with many more floods in La Niña phases. The analysis of this long-term data series illustrates the difficulty of detecting a global climate change signal from hazard data, even given a consistent measurement methodology (cf HURDAT2 record of North Atlantic hurricanes) and warns of the strong dependence of any statistical significance upon choices of start and end dates of the analysis.
McCabe et al., 2017 In this study, a monthly water-balance model is used to simulate monthly runoff for 2109 hydrologic units (HUs) in the conterminous United States (CONUS) for water-years 1901 through 2014. … Results indicated that … the variability of precipitation appears to have been the principal climatic factor determining drought, and for most of the CONUS, drought frequency appears to have decreased during the 1901 through 2014 period.
Natural CO2, Methane Sources Out-Emit Human Source (4)
Harde, 2017 The anthropogenic contribution to the actual CO2 concentration is found to be 4.3%, its fraction to the CO2 increase over the Industrial Era is 15% and the average residence time 4 years. … Under present conditions the natural emissions contribute 373 ppm and anthropogenic emissions 17 ppm to the total concentration of 390 ppm (2012). For the average residence time we only find 4 years. … The stronger increase of the concentration over the Industrial Era up to present times can be explained by introducing a temperature dependent natural emission rate as well as a temperature affected residence time. With this approach not only the exponential increase with the onset of the Industrial Era but also the concentrations at glacial and cooler interglacial times can well be reproduced in full agreement with all observations. So, different to the IPCC’s interpretation the steep increase of the concentration since 1850 finds its natural explanation in the self accelerating processes on the one hand by stronger degassing of the oceans as well as a faster plant growth and decomposition, on the other hand by an increasing residence time at reduced solubility of CO2 in oceans. … Together this results in a dominating temperature controlled natural gain, which contributes about 85 % to the 110 ppm CO2 increase over the Industrial Era, whereas the actual anthropogenic emissions of 4.3 % only donate 15 %. These results indicate that almost all of the observed change of CO2 during the Industrial Era followed, not from anthropogenic emission, but from changes of natural emission.
Carey et al., 2017 While scientists and policy experts debate the impacts of global warming, Earth’s soil is releasing roughly nine times more carbon dioxide to the atmosphere than all human activities combined.
Ruppel and Kessler, 2017 On the contemporary Earth, gas hydrate is dissociating in specific terrains in response to post-LGM [last glacial maximum] climate change and probably also due to warming since the onset of the Industrial Age. Nevertheless, there is no conclusive proof that the released methane is entering the atmosphere at a level that is detectable against the background of ~555 Tg yr−1 CH4 emissions. The IPCC estimates are not based on direct measurements of methane fluxes from dissociating gas hydrates, and many numerical models adopt simplifications that do not fully account for sinks, the actual distribution of gas hydrates, or other factors, resulting in probable overestimation of emissions to the ocean-atmosphere system.
Turner et al., 2017 We conclude that the current surface observing system does not allow unambiguous attribution of the decadal trends in methane without robust constraints on OH variability, which currently rely purely on methyl chloroform data and its uncertain emissions estimates.
[press release] [M]ethane emissions might not have increased dramatically in 2007 after all. Instead, the most likely explanation has less to do with methane emissions and more to do with changes in the availability of the hydroxyl (OH) radical, which breaks down methane in the atmosphere. As such, the amount of hydroxyl in the atmosphere governs the amount of methane. If global levels of hydroxyl decrease, global methane concentrations will increase — even if methane emissions remain constant, the researchers say. … When atmospheric concentrations of methane increase, it may not be correct to chalk it up solely to an increase in methane emissions
Stenhouse et al., 2017 American Meteorological Society [m]embers who said the global warming of the last 150 years was mostly caused by human activity (53% of full sample) … Members who are convinced of largely human-caused climate change expressed that debate over global warming sends an unclear message to the public. Conversely, members who are unconvinced of human-caused climate change often felt that their peers were closed-minded and suppressing unpopular views. These two groups converged, however, on one point: politics was seen as an overwhelmingly negative influence on the debate.
Jones and Ricketts, 2017 [S]ince the mid-20th century, most observed warming has taken place in four events: in 1979/80 and 1997/98 at the global scale, 1988/89 in the Northern Hemisphere and 1968–70 in the Southern Hemisphere. Temperature is more step-like than trend-like on a regional basis. Satellite temperature is more step-like than surface temperature. … [S]tep-like changes are also present in tide gauge observations, rainfall, ocean heat content and related variables. [A]cross a selection of tests, a simple stepladder model better represents the internal structures of warming than a simple trend, providing strong evidence that the climate system is exhibiting complex system behaviour on decadal timescales. This model indicates that in situ warming of the atmosphere does not occur; instead, a store-and-release mechanism from the ocean to the atmosphere is proposed. It is physically plausible and theoretically sound. The presence of step-like – rather than gradual – warming is important information for characterising and managing future climate risk. [Climate models predicated on CO2 forcing indicate a gradual, not step-like warming.]
Coleman and Schwartz, 2017 Data revealed 713 blizzards over the 55 years, with a mean of 13 events per season. Seasonal blizzard frequency ranged from one blizzard in 1980/81 to 32 blizzards in 2007/08. Federal disaster declarations resulting from blizzards totaled 57, with more than one-half of them occurring in the twenty-first century. Storm Data attributed 711 fatalities during the 55-yr study period, with an average of one individual per event; 2044 injuries were reported, with a mean of nearly three per blizzard. Property damage totaled approximately $9.11 billion in unadjusted dollars, with an approximate mean of $12.6 million per storm. Seasonal blizzard frequencies displayed a distinct upward trend, with a more substantial rise over the past two decades. … The modeled increase in blizzard activity showed a nearly fourfold upsurge between the start and end of the study period at 5.9 and 21.6 blizzards, respectively. On the basis of current model trends, the expected blizzard total for a season is 32 blizzards by 2050; uncertainty exists on whether the linear trend will continue or stabilize in the near future.
Ivy et al., 2017 Recent research has demonstrated that the concentrations of anthropogenic halocarbons have decreased in response to the worldwide phaseout of ozone depleting substances. Yet, in 2015 the Antarctic ozone hole reached a historical record daily average size in October. Model simulations with specified dynamics and temperatures based on a reanalysis suggested that the record size was likely due to the eruption of Calbuco, but did not allow for fully-coupled dynamical or thermal feedbacks. We present simulations of the impact of the 2015 Calbuco eruption on the stratosphere using the Whole Atmosphere Community Climate Model with interactive dynamics and temperatures. Comparisons of the interactive and specified dynamics simulations indicate that chemical ozone depletion due to volcanic aerosols played a key role in establishing the record-sized ozone hole of October 2015. The analysis of an ensemble of interactive simulations with and without volcanic aerosols suggests that the forced response to the eruption of Calbuco was an increase in the size of the ozone hole by 4.5 million km2.
Alcock et al., 2017 The rise in greenhouse gas emissions from air travel could be reduced by individuals voluntarily abstaining from, or reducing, flights for leisure and recreational purposes. In theory, we might expect that people with pro-environmental value orientations and concerns about the risks of climate change, and those who engage in more pro-environmental household behaviours, would also be more likely to abstain from such voluntary air travel, or at least to fly less far. … [W]e found that, after accounting for potential confounders, there was no association between individuals’ environmental attitudes, concern over climate change, or their routine pro-environmental household behaviours, and either their propensity to take non-work related flights, or the distances flown by those who do so.
Maibach et al., 2017 Nearly half of weathercasters (49%) are convinced that the climate change over the past 50 years has been mostly or entirely due to human activity
McKinley et al., 2017 That the growth of the partial pressure of CO2 gas in the atmosphere ( pCO2 atm) drives a growing oceanic sink is consistent with our basic understanding that, as the globally averaged atmosphere-to-ocean pCO2 gradient increases, carbon accumulation in the ocean will occur at an increasing rate (Section 3). This behavior has been illustrated clearly with models [not observations] forced with only historically observed increases in pCO2 atm and no climate variability or change (Graven et al. 2012, Ciais et al. 2013). Nonetheless, critical mysteries remain and weigh heavily on our ability to quantify relationships between the perturbed global carbon cycle and climate change. … The current inability to accurately quantify the mean CO2 sink regionally or locally also suggests that present-day observational constraints are inadequate to support a detailed, quantitative, and mechanistic understanding of how the ocean carbon sink works and how it is responding to intensifying climate change. This lack of mechanistic understanding implies that our ability to model (Roy et al. 2011, Ciais et al. 2013, Frolicher et al. 2015, Randerson et al. ¨ 2015), and thus to project the future ocean carbon sink, including feedbacks caused by warming and other climate change, is seriously limited. … The sum of the available evidence indicates that variability in the ocean carbon sink is significant and is driven primarily by physical processes of upwelling, convection, and advection. Despite evidence for a growing sink when globally integrated (Khatiwala et al. 2009, 2013; Ciais et al. 2013; DeVries 2014), this variability, combined with sparse sampling, means that it is not yet possible to directly confirm from surface observations that long-term growth in the oceanic sink is occurring. … [T]his CESM-LE analysis further illustrates that variability in CO2 flux is large and sufficient to prevent detection of anthropogenic trends in ocean carbon uptake on decadal timescales.
Remy et al., 2017 We compared palaeofire and simulated climatic data over the last 7000 years to assess causes of large wildfire events in three coniferous boreal forest regions in north-eastern Canada. These regions span an east-west cline, from a hilly region influenced by the Atlantic Ocean currently dominated by Picea mariana and Abies balsamea to a flatter continental region dominated by Picea mariana and Pinus banksiana. The largest wildfires occurred across the entire study zone between 3000 and 1000 cal. BP. In western and central continental regions these events were triggered by increases in both the fire-season length and summer/spring temperatures, while in the eastern region close to the ocean they were likely responses to hydrological (precipitation/evapotranspiration) variability.