Part 2. Natural Mechanisms Of Weather, Climate Change
Solar Influence On Climate
Rajesh and Tiwari, 2018 The major harmonics centred at ~ 63 ± 5, 22 ± 2, and 10 ± 1 years are similar to solar periodicities and hence may represent solar forcing, while the components peaking at around 7.6, 6.3, 5.2, 4.7, and 4.2 years apparently falls in the frequency bands of El-Nino-Southern Oscillations linked to the oceanic internal processes. Our analyses also suggest evidence for the amplitude modulation of ~ 9–11 and ~ 21–22 year solar cycles, respectively, by 104 and 163 years in northern and southern hemispheric SST data [during 1850 to 2014]. The absence of the above periodic oscillations in CO2 fails to suggest its role on observed inter-hemispheric SST difference. The cross-plot analysis also revealed strong influence of solar activity on linear trend of NH- and SH-SST [Northern/Southern Hemisphere Sea Surface Temperature] in addition to small contribution from CO2. Our study concludes that (1) the long-term trends in northern and southern hemispheric SST variability show considerable synchronicity with cyclic warming and cooling phases and (2) the difference in cyclic forcing and non-linear modulations stemming from solar variability as a possible source of hemispheric SST differences. … The trend components of NH-SST and SH-SST show strong relationship with TSI [Total Solar Irradiance] trend variations and poor in relation with global CO2 trend.
Lubin et al., 2018 Over the past decade there has been increasing realization and concern that the steady and high solar luminosity of the past century may transition to greater variability later this century (Abreu et al. 2008; Feulner & Rahmstorf 2010; Lockwood 2010). Specifically, the Sun may descend into a period of low magnetic activity analogous to the historical Maunder minimum (MM; circa 1640–1715; Eddy 1976). A resulting decrease in total solar irradiance (TSI) impacting the terrestrial lower atmosphere energy budget is linked to changes in high-latitude circulation patterns that strongly influence the climate of Europe and the Atlantic sector of the Arctic and subArctic (Song et al. 2010; Meehl et al. 2013), and may also influence Antarctic climate (Orsi et al. 2012). Studies have also shown the importance of stratospheric response to a grand minimum (e.g., Gray et al. 2010; Bolduc et al. 2015; Maycock et al. 2015). Over a solar cycle and certainly in response to a future grand minimum, irradiance variability at middle ultraviolet (UV) wavelengths that drive oxygen photolysis and ozone chemistry is much larger that that of the TSI. Resulting changes to stratospheric ozone abundance alter the stratosphere–troposphere temperature gradient and feed back to tropospheric planetary wave refraction, further altering climatically relevant circulation patterns (Maycock et al. 2015). With this realization that both direct radiative and indirect stratospheric influences affect terrestrial climate under a solar grand minimum, it is important to understand how UV irradiance would respond to such a large and prolonged change in solar magnetic activity.
Zherebtsov et al., 2018 Based on a complex analysis of hydrometeorological data, it has been shown that changes in the temperature of the troposphere and the World Ocean reflect a response both to individual helio-geophysical perturbations and to long-term changes (1854–2015) of solar and geomagnetic activity. It is established that the climatic response to the influence of solar and geomagnetic activity is characterized by considerable spatio-temporal heterogeneity, is of a regional nature, and depends on the general circulation of the atmosphere. The largest contribution of solar activity to the global climate changes was observed in the period 1910–1943. … For the last 1000 years, the world climate experienced changes that quite closely corresponded to variations in SA [solar activity]: in the 11th–13th centuries, when SA was high, there was a warm period (the “medieval climatic optimum”), and two distinct temperature drops in the small ice age (16th–17th centuries) correspond to the Maunder and Spörer minima. A general rise in the level of SA [solar activity] occurred after the completion of the Maunder minimum [1700s], and the world climate became warmer during most of this period. … It is shown that solar activity contributed significantly to the global climate change, mainly during the first warming in the 20th century (1910–1943). This period is characterized by a significant positive trend in the level of geomagnetic activity that was maximal over the entire considered time interval (1868–2015) and coincided with enhanced meridional heat transfer in the North Atlantic.
Song et al., 2018 [A] general warm to cold climate trend from the mid-Holocene to the present, which can be divided into two different stages: a warmer stage between 6842 and 1297 cal yr BP and a colder stage from 1297 cal yr BP to the present. … The general cooling trend may represent a response to decreasing solar insolation; however, the relative dryness or wetness of the climate may have been co-determined by westerlies and the East Asian summer monsoon (EASM). The climate had a teleconnection with the North Atlantic region, resulting from changes in solar activity.
Cionco et al., 2018 Here we argue that both the in situ mean-daily insolation and the LIG [latitudinal insolation gradients] metrics are important for a fuller and more comprehensive study of how the changes of the external insolation forcing may trigger, sustain and modulate the local, regional and hemispheric scales of climate on decadal, multidecadal to centennial timescales. LIG [latitudinal insolation gradients] which, in turn, can be closely associated with the modulation of LTG or the so-called equator-to-pole temperature gradient (Lindzen 1994; Soon and Legates 2013) that in turn represents a clear negative feedback on the broad, hemispheric scale. Local in situ mean-daily insolation clearly emulates the role imagined by Milankovic´ but has been recently re-proposed and shown, for example, by Soon (2009) to play a key role for the Arctic-mediated modulation of the multidecadal to centennial scale climate variations observed using both available instrumental thermometer, rain-gauges and paleoclimatic proxies records.
Shi et al., 2018 The results show that during periods of strong solar activity, the solar shortwave heating anomaly from the climatology in the tropical upper stratosphere triggers a local warm anomaly and strong westerly winds in mid-latitudes, which strengthens the upward propagation of planetary wave 1 but prevents that of wave 2. … The Sun is the most important source of energy in the Earth’s climate system and variations in the intensity of solar radiation influence both the weather and climate (Chen et al., 2015; Rind, 2002, 2008; Shang et al., 2013; Wang et al., 2015; Zhao et al., 2012). Gray et al. (2010) showed that there are two main mechanisms, bottom-up mechanism and top-down mechanism, by which solar activity affects the Earth’s climate. The top-down mechanism is connected to solar ultraviolet radiation. Solar ultraviolet radiation is mainly absorbed by ozone in the tropical stratosphere, which changes the meridional temperature gradient and wind field in the atmosphere. This further affects the propagation of stratospheric planetary waves in the winter hemisphere (Balachandran and Rind, 1995). Therefore, the solar radiation change can affect the interaction between the stratospheric circulation and the planetary waves (Haigh, 1996, 1999; Kodera and Kuroda, 2002; Shindell et al., 1999, 2006).
Moreno, 2018 A number of revealed common key changes in the main assemblages’ composition has been attributed to larger scale climatic shifts, particularly as regards the transitions firstly from the Medieval Climatic Anomaly (MCA) to the Little Ice Age (LIA), and next from the LIA to the Current Warm Period (CWP) in the Iberian Peninsula, as well as to major temperature–precipitation excursions throughout the LIA and directly correlated with sustained negative phases of the NAO index in periods of lowest SA [solar activity], known as Grand Solar Minima. It is also found, throughout the application of spectral and cross wavelet methods, that in the time span analyzed (from the 1300s to present), the signals of solar forcing in both foraminiferal and x paleoclimatic records were intermittent, with the regional climate modulated by the solar secular Gleissberg cycle, especially after AD 1700–1750, following the Maunder Minimum (1645–1715).
Booth, 2018 The TCR [transient climate response] to doubled CO2 is less than 2K (1.93 ± 0.26K). Only 1.1K of HadCRUT4 warming is expected between 2000 and 2100AD. ∼35% of the warming during 1980–2001 was from solar variability, by 2 different analyses. Temperature is nearly 3 times as sensitive to solar radiation as to CO2 radiation. A model for ocean warming estimates equilibrium sensitivity as 15% greater than TCR.
Oliva et al., 2018 Cold period during 1645–1706 (Maunder solar minimum). Cold period during 1810–1838 (Dalton solar minimum). Warm period during the mid-20th and 21st centuries (modern solar maximum). LIA [Little Ice Age] was characterized by a cold phase having lower annual and summer temperatures relative to the long-term mean, consistent with the solar minima. … The record shows rapid cooling since the start of the Spörer Minimum, which intensified during the Maunder Minimum (with the lowest estimated temperature being 2 °C lower than the recent average). A later increase in the temperature and another slight cooling probably coincided with the Dalton Minimum. Particularly cold winters occurred during the MCA (from 1090 to 1179), during the LIA onset (1350) and from the late 15th to early 16th centuries. Winter temperatures would have been approximately 0.5 °C lower during the LIA (1500–1900) than during the 20th century. … [T]he Maunder Minimum coincided with a cold period from 1645 to 1706, and the Dalton Minimum (1796–1830) is correlated with a cold stage spanning the years from 1810 to 1838. Four warm periods (1626–1637, 1800–1809, 1845–1859, and 1986–2012) coincided with periods of increased solar activity. … The gradual increase in temperature during the second half of the 19th century resulted in significant glacier retreat, with rates of receding [in the second half of the 19th century] similar to those recorded during the last decades of the 20th century and in the early 21st century (Chueca et al., 2008). … The colder climate of the LIA was accompanied by severe droughts, floods, and cold/heat waves that showed significant spatio-temporal variation across the Iberian mountains. … The 20th century did not show unprecedented warmth over the last 800 years.
Maley et al., 2018 Chase et al. (2010) showed that solar forcing modulated by variations in the Earth’s geomagnetic shield is “a potentially important factor driving climate at suborbital timescales in both the northern and southern tropics.” In Africa particularly, “the minimum of the geomagnetic dipole moment was linked to a relatively humid phase (at 8000–7000 cal yr BP); the sharp increase in dipole strength at ca. 3800 cal yr BP is concurrent with the beginning of a drought phase, and the maximum dipole moment with a relatively arid phase (at 2500–2000 cal yr BP)” (Chase et al., 2010, p.42, fig. 3 and 6). … Moreover, in the framework of the climatic teleconnections occurring between the Atlantic and the Pacific Oceans, Emile-Geay et al. (2007) and Gray et al. (2010) estimated that solar influences could have impacted the climatic circulation above the Pacific Ocean, as ENSO and ITCZ activity, and hence could have played a role in these climatic teleconnections, as described during the late Holocene. As the effect of these Sun-Earth interactions on global climates remains a matter of debate, it appears that the recent increase in lightning activity in Central Africa, mainly in the Congo Basin, could result from some kind of solar influence, as was also the case for forest fragmentation between ca. 2500 and 2000 cal yr BP.
Lockwood et al., 2018 During the Dalton minimum [1797-1825] these reconstructions predict an average Ap that is roughly half of that during the modern maximum [1938-2000] but the number of storm-like days (with <Ap>=1dy > Apo) falls radically by an order of magnitude. … For the Maunder minimum, the mean Ap is lower than for the modern grand maximum by a factor of about 5 and the reconstructions predict no storm-like days would have been detected. Given the strong correlation between annual means of AE and Ap (r = 0.98), it is not surprising that the reconstructed AE index behaves in a somewhat similar way to Ap, with average values relative to the modern maximum that are roughly halved for the Dalton minimum and a fifth for the Maunder minimum. … The number of strong substorm-like hours p.a. in the Dalton minimum [1797-1825] is predicted to have been 140 compared to 512 in the modern grand maximum [1938-2000]. … In the Maunder minimum this to falls 28 per annum (i.e. this predicts a total of 1,680 substorm-like hours during the 60 years of the Maunder minimum compared to 30,720 for the 60 years of the modern grand maximum). … Looking to the future, the weakening of Earth’s magnetic moment means that the terrestrial disturbance levels during a future repeats of the solar Dalton and Maunder minima will be weaker and we here quantify this effect for the first time.
Ukhvatkina et al., 2018 It is well known that cold and warm periods of the climate are correlated with intensive solar activity (e.g., the Medieval Warm Period), while decreases in temperature occur during periods of low solar activity (e.g., the Little Ice Age; Lean and Rind, 1999; Bond et al., 2001). … . Long cold periods from 1643 to 1667 and from 1675 to 1690 that were revealed for another territory (Lyu et al., 2016; Wilson et al., 2016) coincided with the Maunder Minimum (1645–1715), an interval of decreased solar irradiance (Bard et al., 2000). The coldest year in this study (1662) was revealed in this period too. The Dalton minimum period centered in 1810 is also notable. … We suppose that a 9-year cycle may be related to solar activity, as, first of all, many authors showed influence of solar activity on the climate variability (Bond et al., 2001; Lean and Rind, 1999; Lean, 2000; Mann et al., 2009; Zhu et al., 2016). Secondly, the significant correlation between of the August–December minimum temperature reconstruction and TSI [total solar irradiance] can be regarded as additional evidence of this assumption. Finally, there is a coincidence of the reconstructed cold periods with the Maunder Minimum (1645–1715) and the Dalton minimum period centered in 1810. The solar activity influence in the region is traditionally associated with an indirect effect on the circulation of the atmosphere (Erlykin et al., 2009; Fedorov et al., 2015). In the second half of the 20th century the solar radiation intensity changes contributed to more intensive warming of the equatorial part of the Pacific Ocean and more active inflow of warm air masses to the north (Fedorov et al., 2015). … Close periodicity is revealed in long-term climate reconstructions and is linked to the quasi-200-year solar activity cycle in other studies (Raspopov et al., 2008, 2009). Raspopov et al. (2008) showed that in tree-ring-based reconstructions the cycle varies from 180 to 230 years. Moreover, the high correlation between the minimum temperature reconstructions and TSI, and also the revealed link between the reconstructed temperatures and solar activity minima, lead us to suppose that the solar activity may be the driver of the 200-year cycle. Such climate cycling, linked not only to temperature but also to precipitation, is revealed for the territories of Asia, North America, Australia, the Arctic, and the Antarctic (Raspopov et al., 2008).
Knizova et al., 2018 Weng (2005) has shown that the intensity of the seasonal forcing, modulated by the 11-year solar activity, is likely an important factor causing different dominant timescales in regional sea-surface temperatures. Even a small change in the solar constant may result in a regime change in the response with various dominant time scales. The large-term climatological study of Scafetta (2014) reveals solar signatures within surface temperature records taking into account the non-linearity of the systems since these systems are related through complex and non-linear processes. Various atmospheric parameters are in some periods positively and in others negatively correlated with solar activity. The study shows that using only one solar index does not capture all the complexity of the solar influences on the atmosphere.
Ma et al., 2018 Solar activity has the profound influence to geodynamics processes, and the Sun directly or indirectly affects some terrestrial phenomena on the Earth. Some studies showed variation of solar activity closely relates to global and regional climate change (Rasmus, 2006; Miyahara et al., 2008; Mendoza & Velasco, 2009; Ogurtsov et al., 2013; Dergachev et al., 2016). After analyzing the solar variation, global and regional sea-surface temperature, Weng (2005) concluded that inter-annual and centennial climate change signals were not purely internal, but also external because of the existence of the solar activity cycle. Kilcik et al. (2008) made use of surface air temperature, pressure and tropospheric absorbing aerosol data as climate parameters and solar flare index data as solar activity indicator, to study effect of solar activity on the surface air temperature of Turkey. With Indian temperature series of more than one-hundred years, Aslam (2014) investigated the influence of solar activity on regional climate. Results indicated that the solar variation may still be contributing to ongoing climate change.
Qin et al., 2018 Three quasi-oscillations with cycles of 31–22, 22–18, and 12–8 years may reflect the joint influence of PDO, southern oscillation, and solar activity on climate variation in the Qinling Mountains. … he third cycle of 12–8 years exhibited 18 distinct cold-hot events, which were approximately equivalent to the changes of solar activity and sunspot activity and corresponded to the 11-year cycle of drought in northwestern China (Cai and Liu. 2007). Nevertheless, tree growth may also be affected by solar activity through the influence on temperature variations, since solar activity has been inferred from tree-ring data in many regions worldwide (Murphy 1990; Damon et al. 1998; Rigozo et al. 2007; Wang and Zhang 2011; Duan and Zhang 2014). These three cycles indicate the June July temperature of the Mt. Taibai timberline in the Qinling Mountains is most likely affected by large-scale atmosphere-ocean interactions and solar activity, as suggested in other tree-ring records in northern China (Liu et al. 2005b, 2011; Bao et al. 2012; Liu et al. 2013).
Bhushan et al., 2018 The study observed that the periods of drift-ice events inferred based on the increase in the Hematite Stain Grains (HSG) correlates reasonable well with the low concentration of detritial proxies implying reduced precipitation induced runoff in the lake catchment (weak ISM). The present study thus indicates that the short-term ISM [Indian Summer Monsoon] variability in the central Himalaya were coupled with the northern latitude climatic events and solar forcing played a major role in modulating the Holocene millennial to centennial scale climatic fluctuations.
Zhang et al., 2018 The climate proxies and quasi-period of Lugu Lake indicate the ASWM [Asian Southwest Monsoon] intensified with an increase by LSI [low-latitude solar insolation] and solar activity during the early Holocene. … During the late Holocene, LSI [low-latitude solar insolation] and ASWM [Asian Southwest Monsoon] gradually decreased, and the climatic quasi-period signals recorded the progressive southward of ITCZ precipitation and solar activity. It exhibited an apparent synchrony with a large amount of climatic records from ASWM region. Moreover, the signals of human activities are not significant in driving periodic regularity, but only in the records of climate proxies. These suggest that LSI [low-latitude solar insolation] and solar activity dominated the climate change of ASWM region over the Holocene.
Zaffar et al., 2018 Various methods have been used to secure the certainty of significant relations among the sunspot cycles and some of the terrestrial climate parameters such as temperature, rainfall, and ENSO. This study investigates the behavior of ENSO cycles and mean monthly sunspot cycles. Sunspot cycles range from 1755 to 2016 whereas, ENSO cycles range from 1866 to 2012. … The results of this study confirm that during the period 1980–2000, ENSO cycles were very active. Simultaneously, ENSO was active for the periods 1982–1983, 1986–1987, 1991–1993, 1994–1995, and 1997–1998; these periods include two strongest periods of the century viz., 1982–1983 and 1997–1998. Sunspot cycles and ENSO cycles both were found to be persistent. Self-similar fractal dimensions exhibited a better persistency and a better correlation as compared to self-affine fractal dimension. This research is a part of a larger research project investigating the correlation of sunspot cycles and ENSO cycles, and the influence of ENSO cycles on variations of the local climatic parameters which in turn depends on solar activity changes. … The influence of the earth climatic condition of oscillations of solar activity is measurable only in the long-run duration. The solar cycles (solar activity) and ENSO episode are correlated with each other. Theory describes the relationship between sunspots and ENSO phenomena is premature, but now is established by a collection of evidence that the solar cycle moderates wind field in the stratosphere and troposphere.
White et al., 2018 Our data, together with published work, indicate both a long-term trend in ENSO strength due to June insolation [solar] forcing and high-amplitude decadalcentennial fluctuations; both behaviors are shown in models. The best-supported mechanism for insolation-driven dampening of ENSO is weakening of the upwelling feedback by insolation-forced warming/deepening of thermocline source waters. … Another potential source of decadal-centennial forcing is total solar irradiance, which varied more in the early Holocene than the mid- to late Holocene (Marchitto et al., 2010). Changing solar irradiance is theoretically capable of affecting ENSO via ocean dynamical cooling (Emile-Geay et al., 2007), and is correlated with centennial-scale variations in early Holocene ENSO (Marchitto et al., 2010). Overall, the apparent increase in decadal-centennial variability in early Holocene ENSO strength shown in coral/mollusk records [Cobb et al., 2013; Emile-Geay et al., 2016] is likely an accurate representation of ENSO’s behavior in response to a range of forcings. However, these short-term fluctuations cannot be taken as evidence for the lack of a long-term insolation-forced trend. … Overall, model results are consistent with Holocene proxy data in showing a long-term trend in ENSO strength due to insolation forcing, superimposed on short-term fluctuations in ENSO strength.
Surface Solar Radiation Influence On Climate
Pfeifroth et al., 2018 The incoming solar radiation is the essential climate variable that determines the Earth’s energy cycle and climate. In this study, these new climate data records are compared to surface measurements in Europe during the period 1983–2015. The results show an overall brightening period since the 1980s onward (comprised between 1.9 and 2.4 W/m2/decade), with substantial decadal and spatial variability. The strongest brightening is found in eastern Europe in spring. … We conclude that the major part of the observed trends in surface solar radiation in Europe is caused by changes in clouds and that remaining differences between the satellite- and the station-based data might be connected to changes in the direct aerosol effect and in snow cover.
Feng and Wang, 2018 Surface Incident solar radiation (Rs), which is also often referred to as the downward solar irradiance, is a key parameter in many climate and ecological processes, such as evapotranspiration, canopy photosynthesis, net primary production, crop growth management, and so on. Long-term Rs datasets with global coverage and reasonable accuracy have a great value these days. Globally-distributed ground observations of Rs began in 1958, and provide solid evidence for global dimming and brightening.
ENSO, NAO, AMO, PDO Climate Influence
Paolo et al., 2018 Satellite observations over the past two decades have revealed increasing loss of grounded ice in West Antarctica, associated with floating ice shelves that have been thinning. Thinning reduces an ice shelf’s ability to restrain grounded-ice discharge, yet our understanding of the climate processes that drive mass changes is limited. Here, we use ice-shelf height data from four satellite altimeter missions (1994–2017) to show a direct link between ice-shelf height variability in the Antarctic Pacific sector and changes in regional atmospheric circulation driven by the El Niño/Southern Oscillation. This link is strongest from the Dotson to Ross ice shelves and weaker elsewhere. During intense El Niño years, height increase by accumulation exceeds the height decrease by basal melting, but net ice-shelf mass declines as basal ice loss exceeds ice gain by lower-density snow.
Di Rita et al., 2018 When the timing of these patterns is compared with the climate proxy data available from the same core (planktonic foraminifera assemblages and oxygen stable isotope record) and with the NAO (North Atlantic Oscillation) index, it clearly appears that the main driver for the forest fluctuations is climate, which may even overshadow the effects of human activity. We have found a clear correspondence between phases with negative NAO index and forest declines. In particular, around 4200 cal BP, a drop in AP (Arboreal Pollen) confirms the clearance recorded in many sites in Italy south of 43N. Around 2800 cal BP, a vegetation change towards open conditions is found at a time when the NAO index clearly shows negative values. Between 800 and 1000 AD, a remarkable forest decline, coeval with a decrease in the frequencies of both Castanea and Olea, matches a shift in the oxygen isotope record towards positive values, indicating cooler temperatures, and a negative NAO. Between 1400-1850 AD, in the time period chronologically corresponding to the LIA (Little Ice Age), the Gaeta record shows a clear decline of the forest cover, particularly evident after 1550 AD, once again in correspondence with negative NAO index. … A previous study on this core (Margaritelli et al., 2016) provided a detailed reconstruction of the main climate oscillations over the last 4.5 ka, identifying nine time intervals associated with archaeological/cultural periods (top of Eneolithic ca. 2410 BC, Early Bronze Age ca. 2410 BC ca. 1900 BC, Middle Bronze Age Iron Age ca.1900-500 BC, Roman Period ca. 500 BC – 550 AD, Dark Age ca. 550-860 AD, Medieval Climate Anomaly ca. 860-1250 AD, Little Ice Age ca. 1250-1850 AD, Industrial Period ca. 1850-1950 AD, Modern Warm Period ca. 1950 AD – present day). The good correspondence between climate oscillations and archaeological intervals underlines the role exerted by climate change in determining rises and declines of civilizations. Within these time intervals, planktonic foraminifera and oxygen stable isotope data have allowed us to detect a series of past climate changes on decadal to millennial time scale, linked to dynamics of ocean-atmospheric coupling or to solar activity, such as the 4.2 ka event, four Roman solar minima, the Medieval Cold Period and the Maunder event.
Mallory et al., 2018 The AO [Arctic Oscillation] has positive and negative phases that infuence broad weather patterns across the northern hemisphere (Thompson et al. 2000). For example, during the positive phase of the AO, atmospheric pressure over the Arctic is lower than average, which tends to result in warmer and wetter winters in northern regions as warmer air is able to move further north (Thompson et al. 2000; Aanes et al. 2002). … From 1988 to 1996, the summer intensity of the AO was largely in the positive phase, with a mean value of 0.207 (± 0.135 SE), and this was a period of population stability or growth for each of the three herds that we examined here. In contrast, from 1997 to 2016 the summer AO has remained largely in the negative phase [cooling], with a mean value of − 0.154 (± 0.077 SE), and over this period the Bathurst, Beverly, and Qamanirjuaq herds declined in abundance. … Our results suggest that during periods of positive AO intensity, warmer temperatures on the summer range result in improved growing conditions for vascular plants that benefts foraging caribou. Conversely, negative summer AO intensity is associated with cooler temperatures with associated shorter growing seasons and increased precipitation on the Beverly summer range. … We found that positive intensities of the Arctic Oscillation (AO) in the summer were associated with warmer temperatures, improved growing conditions for vegetation, and better body condition of caribou. Over this same period, the body condition of female caribou was positively related to fecundity. We further identified that population trajectories of caribou herds followed the direction of the AO: herds increased under positive AO intensity, and decreased under negative AO intensity.
Perner et al., 2018 [W]e find evidence of distinct late Holocene millennial-scale phases of enhanced El Niño/La Niña development, which appear synchronous with northern hemispheric climatic variability. Phases of dominant El Niño-like states occur parallel to North Atlantic cold phases: the ‘2800 years BP cooling event’, the ‘Dark Ages’ and the ‘Little Ice Age’, whereas the ‘Roman Warm Period’ and the ‘Medieval Climate Anomaly’ parallel periods of a predominant La Niña-like state. Our findings provide further evidence of coherent interhemispheric climatic and oceanic conditions during the mid to late Holocene, suggesting ENSO as a potential mediator.
Mohammadi and Goudarzi , 2018 Sensitivity of solar radiation (H), wind speed (V) and precipitation (P) to ENSO events in California is studied. There are high relationships of El Niño and La Niña events with variations of H [solar radiation], P [wind speed] and V [precipitation] in California.
Valdés-Pineda et al., 2018 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.
Ahn et al., 2018 These findings suggest that the variability at this site is remotely driven by processes such as those causing the Pacific Decadal Oscillation, rather than locally driven by processes such as increased or decreased vertical mixing of nutrients. … [I]t was shown that similar-sampling-frequency analyses of modern observations at this location reveal SST variability that is dominated by the PDO.
Stolpe et al., 2018 Multidecadal internal climate variability centered in the North Atlantic is evident in sea surface temperatures and is assumed to be related to variations in the strength of the Atlantic Meridional Overturning Circulation (AMOC). In this study, the extent to which variations in the AMOC may also alter hemispheric and global air temperature trends and ocean heat content during the past century is examined. … AMOC strength influences the air-sea heat flux into the high-latitude ocean, where a strengthening of the AMOC leads to decreased storage of heat in the Atlantic and a larger fraction of the heat taken up by the global ocean accumulates in the top 300 m compared to the case of a weakening AMOC. The spread in the amount of heat stored in the global ocean below 300 m is similar across the CESM members as in a set of CMIP5 models, confirming the AMOC as a “control knob” on deep-ocean heat storage. By influencing the ocean heat uptake efficiency and by shifting the pattern of heat uptake, global air temperatures are significantly altered on a multidecadal time scale by AMOC variability.
Bollasina and Messori, 2018 It is shown that the NAO generates a significant climate response over East Asia during both the dry and wet seasons, whose spatial pattern is highly dependent on the phase of the NAO’s life cycle. Temperature and precipitation anomalies develop concurrently with the NAO mature phase, and reach maximum amplitude 5–10 days later. These are shown to be systematically related to mid and high-latitude teleconnections across the Eurasian continent via eastward-propagating quasi-stationary Rossby waves instigated over the Atlantic and terminating in the northeastern Pacific. These findings underscore the importance of rapidly evolving dynamical processes in governing the NAO’s downstream impacts and teleconnections with East Asia.
Qin et al., 2018 Central China result from anomaly patterns in the large-scale atmospheric circulation in the mid-latitude Northern Hemisphere associated with the PDO [Pacific Decadal Oscillation]. Specifically, during the negative phase of the PDO (1945–1976 and 2003–2014) […] produces southerly advection of warm and moist air into North Central China, leading to increased precipitation there. These results reinforce the notion that PDO has a large impact on SON [September–November] rainfall over North Central China on decadal timescales.
Huang et al., 2018 A period of weak chemical weathering, related to cold and dry climatic conditions, occurred during the Little Ice Age (LIA), whereas more intense chemical weathering, reflecting warm and humid climatic conditions, was recorded during the Medieval Warm Period (MWP). Besides, an intensification of chemical weathering in Poyang Lake during the late Holocene agrees well with strong ENSO activity, suggesting that moisture variations in central China may be predominantly driven by ENSO variability. … Rao et al. (2016b) demonstrated that a humid late-Holocene in central China and an arid late-Holocene in southern and northern China were significantly related to strong ENSO activity. Thus, it seems that ENSO forcing may be likely dominant factor controlling moisture variations in central China.
Modern Climate In Phase With Natural Variability
Ault et al., 2018 The western United States was affected by several megadroughts during the last 1200 years, most prominently during the Medieval Climate Anomaly (MCA; 800 to 1300 CE). A null hypothesis is developed to test the possibility that, given a sufficiently long period of time, these events are inevitable and occur purely as a consequence of internal climate variability. The null distribution of this hypothesis is populated by a linear inverse model (LIM) constructed from global sea surface temperature anomalies and self-calibrated Palmer drought severity index data for North America. Despite being trained only on seasonal data from the late twentieth century, the LIM produces megadroughts that are comparable in their duration, spatial scale, and magnitude to the most severe events of the last 12 centuries. The null hypothesis therefore cannot be rejected with much confidence when considering these features of megadrought, meaning that similar events are possible today, even without any changes to boundary conditions. In contrast, the observed clustering of megadroughts in the MCA, as well as the change in mean hydroclimate between the MCA and the 1500–2000 period, are more likely to have been caused by either external forcing or by internal climate variability not well sampled during the latter half of the twentieth century.
Brickman et al., 2018 In 2012, 2014, and 2015 anomalous warm events were observed in the subsurface waters in the Scotian Shelf region of eastern Canada. Monthly output from a high resolution numerical ocean model simulation of the North Atlantic ocean for the period 1990-2015 is used to investigate this phenomenon. … The observed warming trend can be attributed to an increase in the frequency of creation of warm anomalies during the last decade. Strong anomalous events are commonly observed in the data and model, and thus should be considered as part of the natural variability of the coupled atmosphere-ocean system.
Kendon et al., 2018 Natural variability appears to dominate current observed trends (including an increase in the intensity of heavy summer rainfall over the last 30 years) … [T]he attribution of rainfall trends to human influence on local and regional scales is not yet possible (Sarojini et al., 2016).
The CO2 Greenhouse Effect – Climate Driver?
Davis et al., 2018 [T]he contemporary global warming increase of ~0.8 °C recorded since 1850 has been attributed widely to anthropogenic emissions of carbon dioxide (CO2) into the atmosphere. Recent research has shown, however, that the concentration of CO2 in the atmosphere has been decoupled from global temperature for the last 425 million years [Davis, 2017] owing to well-established diminishing returns in marginal radiative forcing (ΔRF) as atmospheric CO2 concentration increases. Marginal forcing of temperature from increasing CO2 emissions declined by half from 1850 to 1980, and by nearly two-thirds from 1850 to 1999 [Davis, 2017]. Changes in atmospheric CO2 therefore affect global temperature weakly at most. The anthropogenic global warming (AGW) hypothesis has been embraced partly because “…there is no convincing alternative explanation…” [USGCRP, 2017] (p. 12). … The ACO [Antarctic Centennial Oscillation] provides a possible [natural] alternative explanation in the form of a natural climate cycle that arises in Antarctica, propagates northward to influence global temperature, and peaks on a predictable centennial timetable. … The period and amplitude of ACOs oscillate in phase with glacial cycles and related surface insolation associated with planetary orbital forces. We conclude that the ACO: encompasses at least the EAP; is the proximate source of D-O oscillations in the Northern Hemisphere; therefore affects global temperature; propagates with increased velocity as temperature increases; doubled in intensity over geologic time; is modulated by global temperature variations associated with planetary orbital cycles; and is the probable paleoclimate precursor of the contemporary Antarctic Oscillation (AAO). Properties of the ACO/AAO are capable of explaining the current global warming signal.
Gray, 2018 [T]he globe’s annual surface solar absorption of 171 Wm-2 is balanced by about half going to evaporation (85 Wm-2) and the other half (86 Wm-2) going to surface to atmosphere upward IR (59 Wm-2) flux and surface to air upward flux by sensible heat transfer (27 Wm-2). Assuming that the imposed extra CO2 doubling IR blockage of 3.7 Wm-2 is taken up and balanced by the earth’s surface as the solar absorption is taken up and balanced, we should expect a direct warming of only ~ 0.5°C for a doubling of the CO2. The 1°C expected warming that is commonly accepted incorrectly assumes that all the absorbed IR goes to balancing outward radiation (through E = σT4- e.g., the Stefan-Boltzmann law) with no energy going to evaporation. … This analysis shows that the influence of doubling atmospheric CO2 by itself (without invoking any assumed water vapor positive feedback) leads to only small amounts of global warming which are much less than predicted by GCMs.
Part 3. Unsettled Science, Failed Climate Modeling
Climate Model Unreliability/Biases/Errors and the Pause
Collins et al., 2018 Here there is a dynamical gap in our understanding. While we have conceptual models of how weather systems form and can predict their evolution over days to weeks, we do not have theories that can adequately explain the reasons for an extreme cold or warm, or wet or dry, winter at continental scales. More importantly, we do not have the ability to credibly predict such states. Likewise, we can build and run complex models of the Earth system, but we do not have adequate enough understanding of the processes and mechanisms to be able to quantitatively evaluate the predictions and projections they produce, or to understand why different models give different answers. … The global warming ‘hiatus’ provides an example of a climate event potentially related to inter-basin teleconnections. While decadal climate variations are expected, the magnitude of the recent event was unforeseen. A decadal period of intensified trade winds in the Pacific and cooler sea surface temperatures (SSTs) has been identified as a leading candidate mechanism for the global slowdown in warming.
Shen et al., 2018 The results showed that both future climate change (precipitation and temperature) and hydrological response predicted by the twenty GCMs [climate models] were highly uncertain, and the uncertainty increased significantly over time. For example, the change of mean annual precipitation increased from 1.4% in 2021–2050 to 6.5% in 2071–2100 for RCP4.5 in terms of the median value of multi-models, but the projected uncertainty reached 21.7% in 2021–2050 and 25.1% in 2071–2100 for RCP4.5.
Hunziker et al., 2018 About 40 % of the observations are inappropriate for the calculation of monthly temperature means and precipitation sums due to data quality issues. These quality problems undetected with the standard quality control approach strongly affect climatological analyses, since they reduce the correlation coefficients of station pairs, deteriorate the performance of data homogenization methods, increase the spread of individual station trends, and significantly bias regional temperature trends. Our findings indicate that undetected data quality issues are included in important and frequently used observational datasets and hence may affect a high number of climatological studies. It is of utmost importance to apply comprehensive and adequate data quality control approaches on manned weather station records in order to avoid biased results and large uncertainties.
Roach et al., 2018 Consistent biases in Antarctic sea ice concentration simulated by climate models … The simulation of Antarctic sea ice in global climate models often does not agree with observations. [M]odels simulate too much loose, low-concentration sea ice cover throughout the year, and too little compact, high-concentration cover in the summer. [C]urrent sea ice thermodynamics contribute to the inadequate simulation of the low-concentration regime in many models.
Scanlon et al., 2018 The models underestimate the large decadal (2002–2014) trends in water storage relative to GRACE satellites, both decreasing trends related to human intervention and climate and increasing trends related primarily to climate variations. The poor agreement between models and GRACE underscores the challenges remaining for global models to capture human or climate impacts on global water storage trends. … Increasing TWSA [total water storage anomalies] trends are found primarily in nonirrigated basins, mostly in humid regions, and may be related to climate variations. Models also underestimate median GRACE increasing trends (1.6–2.1 km3/y) by up to a factor of ∼8 in GHWRMs [global hydrological and water resource models] (0.3–0.6 km3/y). Underestimation of GRACE-derived TWSA increasing trends is much greater for LSMs [global land surface models], with four of the five LSMs [global land surface models] yielding opposite trends (i.e., median negative rather than positive trends) … Increasing GRACE trends are also found in surrounding basins, with most models yielding negative trends. Models greatly underestimate the increasing trends in Africa, particularly in southern Africa. .. TWSA trends from GRACE in northeast Asia are generally increasing, but many models show decreasing trends, particularly in the Yenisei.
Subtracting the modeled human intervention contribution from the total land water storage contribution from GRACE results in an estimated climate-driven contribution of −0.44 to −0.38 mm/y. Therefore, the magnitude of the estimated climate contribution to GMSL [global mean sea level] is twice that of the human contribution and opposite in sign. While many previous studies emphasize the large contribution of human intervention to GMSL [global mean sea level], it has been more than counteracted by climate-driven storage increase on land over the past decade. … GRACE-positive TWSA trends (71 km3/y) contribute negatively (−0.2 mm/y) to GMSL, slowing the rate of rise of GMSL, whereas models contribute positively to GMSL, increasing the rate of rise of GMSL.
van Oldenborgh et al., 2018 [I]t was widely assumed that the probability and severity of heat waves in India are increasing due to global warming, as they do in other parts of the world. However, we do not find positive trends in the highest maximum temperature of the year in most of India since the 1970s (except spurious trends due to missing data). Decadal variability cannot explain this, but both increased air pollution with aerosols blocking sunlight and increased irrigation leading to evaporative cooling have counteracted the effect of greenhouse gases up to now. Current climate models do not represent these processes well and hence cannot be used to attribute heat waves in this area.
Failing Renewable Energy, Climate Policies
Schäfer et al., 2018 Multiple types of fluctuations impact the collective dynamics of power grids and thus challenge their robust operation.
(press release) More renewables mean less stable grids, researchers find … [I]ntegrating growing numbers of renewable power installations and microgrids onto the grid can result in larger-than-expected fluctuations in grid frequency.
Jewell et al., 2018 Hopes are high that removing fossil fuel subsidies could help to mitigate climate change by discouraging inefficient energy consumption and levelling the playing field for renewable energy. Here we show that removing fossil fuel subsidies would have an unexpectedly small impact on global energy demand and carbon dioxide emissions and would not increase renewable energy use by 2030. Removing subsidies in most regions would deliver smaller emission reductions than the Paris Agreement (2015) climate pledges and in some regions global subsidy removal may actually lead to an increase in emissions, owing to either coal replacing subsidized oil and natural gas or natural-gas use shifting from subsidizing, energy-exporting regions to non-subsidizing, importing regions.
Elevated CO2: Greens Planet, Higher Crop Yields
Pau et al., 2018 Long-term increases in tropical flowering activity across growth forms in response to rising CO2 and climate change … Here, we analyze a 28-year record of tropical flower phenology in response to anthropogenic climate and atmospheric change. We show that a multidecadal increase in flower activity is most strongly associated with rising atmospheric CO2 concentrations using yearly aggregated data. Compared to significant climatic factors, CO2 had on average an approximately three-, four-, or fivefold stronger effect than rainfall, solar radiation, and the Multivariate ENSO Index, respectively.
Zeng et al., 2018 Leaf area index (LAI) is increasing throughout the globe, implying the Earth greening. Global modelling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, we used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement by 8% between the early 1980s and the early 2010s is modelled to have caused increases of 12.0 ±2.4 mm yr-1 in evapotranspiration and 12.1 ±2.7 mm yr-1 in precipitation — about 55 ±25% and 28 ±6% of the observed increases in land evapotranspiration and precipitation, respectively.
Warming Beneficial, Does Not Harm Humans, Wildlife
Feng et al., 2018 [E]nvironmental conditions in years with less ice cover were more favorable for C. glacialis development than those with more ice cover. The highest success rate (85.3%) occurred in 2012, coincident with the year of the lowest sea ice extent among the 35-year study period. Transition-zone annual mean temperature was negatively correlated with September-mean sea ice extent (r = −.92, p < .01), as was food availability (r = −.96, p < .01). Annual mean temperature and food for the transition-zone individuals also showed significant upward trends although temperature appeared to have much higher variability than food. In the Chukchi Sea, significant increases in the biomass and abundance of zooplankton (particularly C. glacialis) were found in recent warm years as compared to the earlier cold years (Ershova et al., 2015). The strong positive correlation between mean developmental stage of C. glacialis and sea surface temperature from that study agreed with our modeling results, both suggesting that warmer temperatures sped up C. glacialis cohort developmental process.
Yang et al., 2018 Adélie penguin populations as inferred from […] southern Cape Bird declined slightly from ∼1450 to ∼1600 AD, began to rise afterward and reached their highest level in ∼1700 AD, then declined with fluctuations to the lowest levels through ∼1900 AD. For the past 100 yr, Adélie penguin populations experienced a sharp rise and drop. Monitoring data have shown that Adélie penguins at Cape Bird had an increasing trend in the 1970s, likely linked with changes in sea-ice extent and polynya size, but also with variation in competition with minke whales (Ainley et al., 2005; Wilson et al., 2001). Our study suggests that the penguin populations increased in the 1960s as well, consistent with their research. … Over the past 500 yr at Cape Bird, Adélie penguin populations increased during the cold period (∼1600–1825 AD), which is inconsistent with the general pattern in other studies, for example, penguin populations increased when climate became warmer, and vice versa (Emslie et al., 2007; Huang et al., 2009; Sun et al., 2000).
No Increasing Trends In Intense Hurricanes
Truchelut and Staeling, 2018 The extremely active 2017 Atlantic hurricane season concluded an extended period of quiescent continental United States tropical cyclone landfall activity that began in 2006, commonly referred to as the landfall drought. We introduce an extended climatology of U.S. tropical cyclone activity based on accumulated cyclone energy (ACE) and use this data set to investigate variability and trends in landfall activity. The [hurricane landfall] drought years between 2006 and 2016 recorded an average value of total annual ACE [accumulated cyclone energy] over the U.S. that was less than 60% of the 1900–2017 average. Scaling this landfall activity metric by basin-wide activity reveals a statistically significant downward trend since 1950, with the percentage of total Atlantic ACE expended over the continental U.S. at a series minimum during the recent drought period.
Klotzbach et al., 2018 Continental United States (CONUS) hurricane-related inflation-adjusted damage has increased significantly since 1900. However, since 1900 neither observed CONUS [Continental United States] landfalling hurricane frequency nor intensity show significant trends, including the devastating 2017 season.
No Increasing Trend In Drought/Flood Frequency, Severity
Guo et al., 2018 In drought-prone regions like Central Asia, drought monitoring studies are paramount to provide valuable information for drought risk mitigation. In this paper, the spatiotemporal drought characteristics in Central Asia are analyzed from 1966 to 2015 using the Climatic Research Unit (CRU) dataset. Central Asia showed an overall wetting trend with a switch to drying trend since 2003.
Temperature Change Leads CO2 Change, Processes Governing CO2 Changes ‘Poorly Understood’
Koutavas et al., 2018 The EEP [eastern equatorial Pacific] stack shows persistent covariation with Antarctic temperature on orbital and millennial timescales indicating tight coupling between the two regions. This coupling however cannot be explained solely by CO2 forcing because in at least one important case, the Marine Isotope Stage (MIS) 5e–5d glacial inception, both regions cooled ∼5–6.5 thousand years before CO2 decreased. More likely, their covariation was due to advection of Antarctic climate signals to the EEP by the ocean. … . The discovery that atmospheric CO2 covaries with Antarctic temperature and global ice volume (Lorius et al., 1990; Lüthi et al., 2008; Petit et al., 1999) has propelled CO2 to the forefront as climatic “globalizer”. However, the processes governing CO2 variability are themselves poorly understood, and likely require an oceanic/climatic trigger in the first place (Adkins, 2013; Ferrari et al., 2014; Sigman et al., 2010). Antarctic ice core records are furthermore ambiguous with regard to the causal relationship between CO2 and temperature. Phase relationships show CO2 lagging behind temperature in the obliquity band (Jouzel et al., 2007) and across some major transitions (Caillon et al., 2003; Fischer et al., 1999; Kawamura et al., 2007; WAIS Divide Project Members, 2013), most prominently during the Marine Isotope Stage (MIS) 5e–5d boundary, i.e. the last glacial inception. Antarctic cooling at this time was associated with a major Milankovitch signal, and appears to have transpired almost entirely before the change in CO2 concentration. It remains unclear whether the temperature lead was restricted to Antarctica or was broader.
Ozone ‘Hole’ Still Widening Since 1998 (Despite CFC Ban)
Ball et al, 2018 Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60° S and 60° N has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60° S and 60° N. We find that total column ozone between 60° S and 60° N appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.
Arctic Methane Emissions Natural, Not Anthropogenic
Wallmann et al., 2018 Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming … Methane seepage from the upper continental slopes of Western Svalbard has previously been attributed to gas hydrate dissociation induced by anthropogenic warming of ambient bottom waters. Here we show that sediment cores drilled off Prins Karls Foreland contain freshwater from dissociating hydrates. However, our modeling indicates that the observed pore water freshening began around 8 ka BP when the rate of isostatic uplift outpaced eustatic sea-level rise. The resultant local shallowing and lowering of hydrostatic pressure forced gas hydrate dissociation and dissolved chloride depletions consistent with our geochemical analysis. Hence, we propose that hydrate dissociation was triggered by postglacial isostatic rebound rather than anthropogenic warming.
Mortality From Storm Surges/Flooding Decreasing
Bouwer and Jonkman, 2018 Global mortality from storm surges is decreasing … Changes in society’s vulnerability to natural hazards are important to understand, as they determine current and future risks, and the need to improve protection. Very large impacts including high numbers of fatalities occur due to single storm surge flood events. Here, we report on impacts of global coastal storm surge events since the year 1900, based on a compilation of events and data on loss of life. We find that over the past, more than eight thousand people are killed and 1.5 million people are affected annually by storm surges. The occurrence of very substantial loss of life (>10 000 persons) from single events has however decreased over time. Moreover, there is a consistent decrease in event mortality, measured by the fraction of exposed people that are killed, for all global regions, except South East Asia.
No Centennial-Scale Changes In Relative Humidity Since 1820s
Shi et al., 2018 Here, we average four tree-ring width chronologies from the southeastern Tibetan Plateau (TP) over their common intervals and reconstruct the variability in regional relative humidity (RH) from the previous May to the current March over 1751–2005. In contrast to the summer drying associated with centennial-scale warming and the weakening of the Asian summer monsoon, our RH [relative humidity] reconstruction shows no significant centennial trend from the 1820s through the 2000s.