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The out‐of‐phase mode of winter surface air temperature anomalies (SATAs) over northern Central Asia (NCA; 45°–65°N, 40°–100°E) between January and February is investigated in this study. This mode corresponds to warm (cold) SATAs in January (February) over NCA and is mainly modulated by the enhanced tropical convection anomalies over the Maritime Continent in previous late December, associated with MJO phase 4. These tropical convection anomalies can induce anomalous tropospheric Rossby‐wave sources over the North Pacific in late December. The eastward‐propagating Rossby‐wave train, triggered by these anomalous Rossby‐wave sources, can cause negative and positive tropospheric geopotential height anomalies over the Greenland–Scandinavia region and NCA in the following early–mid‐January, subsequently leading to warm SATAs over NCA in January. The negative geopotential height anomalies over the Greenland–Scandinavia region in early–mid‐January can trigger upward‐propagating wave activity fluxes (WAFs) into the stratosphere, resulting in negative stratospheric geopotential height anomalies in late January–early February. These stratospheric anomalies, by triggering downward‐propagating WAFs, can in turn lead to positive tropospheric geopotential height anomalies over the Greenland–Scandinavia region in early February. These anomalies over the Greenland–Scandinavia region can maintain themselves in the following mid‐ and late February by feedback of anomalous storm tracks, and cause negative geopotential height anomalies and subsequently cold SATAs over NCA in February by triggered southeastward‐propagating Rossby‐wave train. [ABSTRACT FROM AUTHOR]

Central Asia (CA) has experienced a faster temperature rise than the global land over the past decades. However, the role of regional/global drivers and their associated underlying biophysical mechanisms is poorly explored. Here, we combined observations and model simulations to show that the rapid warming in CA was overwhelmingly contributed by rapid spring warming (i.e., 49.23%). The decrease of cloud cover (CLD) was the main driver of spring warming in CA, leading to the surface receiving more solar radiation, consequently heating the surface air temperature, and contributing almost 40.79% to the spring warming. Besides, the strengthening of sea level pressure states results in continuous subsidence of vertical motion over CA, which was unfavorable for cloud formation. Our study will deepen our understanding of the climate evolution in the arid CA. Plain Language Summary: Central Asia (CA) has experienced a faster temperature rise than the global land over the past decades, which has brought unprecedented challenges to the survival and flourishing of life. The role of drivers and their associated underlying biophysical mechanisms is explored here. We conclude that the temperature increase in CA is overwhelmingly contributed by rapid warming in spring (i.e., 49.23%), and the rapidly increasing trend will continue till the end of this century. The decrease of cloud cover (CLD) was the main driver of spring warming in CA, leading to the surface receiving more solar radiation, and consequently heating the surface air temperature, contributing almost 40.79% to the spring warming. Besides, the strengthening of sea level pressure states results in subsidence of vertical motion over CA, which was unfavorable for cloud formation. Key Points: The rapid spring warming contributed most to the annual temperature increase in Central Asia (CA) among other seasonsThe rapid spring average temperature rise in arid CA was mainly driven by the decreased cloud coverThe increase in sea level pressure led to the subsidence of vertical motion over CA and consequently the decreased cloud cover [ABSTRACT FROM AUTHOR]

The recent summer surface air temperature (SAT) changes over densely populated Eurasia exhibit a non‐uniform pattern with amplified warming over Europe and East Asia (EA) but weak warming over Central Asia (CA), forming a wave train‐like structure. However, the key factors that determine this non‐uniform warming pattern remain unclear. By analyzing observations and model simulations, here, we show that more than half of the SAT multidecadal variations from 1950 to 2014 over Europe‐west Asia and EA may have resulted from external forcing, rather than from internal variability in the Atlantic as previously thought. In contrast, the recent SAT over CA is influenced mainly by internal variations in the Atlantic and Pacific oceans. Large ensemble model simulations suggest that the forced SAT multidecadal variations over Eurasia are mainly caused by changes in greenhouse gases and aerosols. Our findings provide strong evidence for major impacts of external forcing on multidecadal climate variations over Eurasia. Plain Language Summary: Previous studies have documented non‐uniform decadal warming rates in summer since the mid‐1990s over densely populated Eurasia, with amplified warming over Europe and East Asia (EA) but weak warming over Central Asia. This unique tripole warming pattern and its cause have attracted considerable attention. It may arise from internal variability (IV; e.g., Atlantic Multidecadal Oscillation [AMO]) and/or external forcing. Furthermore, it was found that the recent AMO resulted from both IV and decadal changes in aerosols. Thus, the relative contributions of IV and external forcing to the recent Eurasian warming pattern remain unclear. Here we show that the surface air temperature multidecadal variations since 1950 over Eurasia are caused by both IV and external forcing, with more than half of the variations over Europe‐west Asia and EA resulted from external forcing (i.e., greenhouse gases [GHGs] and aerosols), in contrast to the previous notion that the non‐uniform warming is mainly originated from the Atlantic Ocean. Looking ahead into the upcoming decades, aerosols will continue to decrease, whereas the AMO will likely be in its positive phase. These changes, together with continued increases in GHGs, will accelerate warming trends over Eurasia and further exacerbate summer heat waves. Key Points: More than half of the multidecadal surface air temperature (SAT) variations from 1950 to 2014 over Europe‐west Asia and East Asia resulted from external forcingThe forced SAT multidecadal variations over Eurasia are mainly caused by changes in greenhouse gases and aerosolsOur study helps reconcile human and natural drivers of the tripole pattern of multidecadal summer temperature variations over Eurasia [ABSTRACT FROM AUTHOR]

This study finds a significantly decreasing (increasing) trend (1979–2018) of sea level pressure (SLP) over coastal East Asia (far North Pacific) during May and June, which resembles the negative (positive) Pacific Decadal Oscillation (PDO) (North Pacific Oscillation, NPO)‐like pattern. Thus, we examine May composite differences between early and late Indian summer monsoon (ISM) onset years. Sea surface temperature (SST) differences show that early (late) ISM onset is accompanied by a negative (positive) PDO‐like state. Whereas, in SLP, an intense low pressure over northwestern India, the Arabian Sea to Southeast Asia (far North Pacific, East Asia) is associated with the early (late) onset. During the early onset, warm surface air temperature (SAT) anomalies over southeast Russia propagate towards Central Asia to the Middle East and the northwest Indian subcontinent, strengthening the land‐sea thermal contrast, which subsequently strengthens the monsoon low. We thus show how the positive NPO, negative PDO, and high spring Bering Sea ice link with the SAT anomalies. In the early onset, more wave packets generated in response to these North Pacific anomalies propagate towards the Atlantic and European region, reaching and converging over the northwest Indian subcontinent. The warm surface anomalies possibly draw eastward‐propagating waves towards northwest India, thus intensifying the monsoon low there. Meanwhile, in the CAM5 PDO simulation, we observe a similar pattern of atmospheric responses, where warm SAT anomalies associated with stationary Rossby wave trains propagate from the North Pacific towards the North Atlantic to Central Asia and the northwest Indian subcontinent, strengthening the monsoon low. Terefore, our study highlights the crucial role of the North Pacific anomalies in modulating the ISM onset processes via atmospheric pathways. [ABSTRACT FROM AUTHOR]

The precipitation variability is subject to impacts of both ocean and land surface condition changes. The present study investigates the role of land surface condition in the interannual variation of the early rainy season (May–June) precipitation over the Indochina Peninsula. A precursory signal is identified in surface air temperature (SAT) during March–April over central Asia after the late 1970s. The air temperature anomalies extend to middle troposphere and persist to early summer (May–June) and modulate the land‐sea thermal contrast and lower‐level and upper‐level winds over the North Indian Ocean and thus affect the early rainy season precipitation over the Indochina Peninsula. The maintenance of SAT anomalies over central Asia is related to that of surface heat flux anomalies that in turn is attributed to the persisting atmospheric wind anomalies. The precursory signal is weak before the late 1970s due to the lack of persisting atmospheric wind anomalies. The interdecadal change in the persistence of central Asian SAT anomalies is associated with a difference in the distribution of the North Atlantic sea surface temperature (SST) anomalies. After the late 1970s, the North Atlantic SST anomalies with a southwest‐northeast distribution excite a wave train that extends from the North Atlantic to central Asia during May–June. Before the late 1970s, the wave train associated the North Atlantic SST anomalies with a south–north distribution is confined to the North Atlantic region. [ABSTRACT FROM AUTHOR]

In this study, the climate changes over Arid Central Asia (ACA) during the mid‐Holocene (approximately 6,000 calendar years ago, MH) and the Last Glacial Maximum (approximately 21,000 calendar years ago, LGM) were investigated using multimodel simulations derived from the Paleoclimate Modelling Intercomparison Project Phase 3 (PMIP3). During the MH, the multimodel median (MMM) shows that in the core region of ACA, the regionally averaged annual surface air temperature (SAT) decreases by 0.13°C and annual precipitation decreases by 3.45%, compared with the preindustrial (PI) climate. The MMM of the SAT increases by 1.67/0.13°C in summer/autumn, whereas it decreases by 1.23/1.11°C in spring/winter. The amplitude of the seasonal cycles of the SAT increases over ACA due to different MH orbital parameters. For precipitation, the regionally averaged MMM decreases by 5.77%/5.69%/0.39%/5.24% in spring/summer/autumn/winter, respectively. Based on the analysis of the aridity index (AI), compared with the PI, a drier climate appears in southern Central Asia and western Xinjiang due to decreasing precipitation. During the LGM, the MMM shows that the regionally averaged SAT decreases by 5.04/4.36/4.70/5.12/5.88°C and precipitation decreases by 27.78%/28.16%/31.56%/27.74%/23.29% annually and in the spring, summer, autumn, and winter, respectively. Robust drying occurs throughout almost the whole core area. Decreasing precipitation plays a dominant role in shaping the drier conditions, whereas strong cooling plays a secondary but opposite role. In response to the LGM external forcings, over Central Asia and Xinjiang, the seasonal cycle of precipitation has a smaller amplitude compared with that under the PI climate. In the model‐data comparison, the simulated MH moisture changes over ACA are to some extent consistent with the reconstructions, further confirming that drier conditions occurred during that period than during the PI. [ABSTRACT FROM AUTHOR]

Central Asia witnessed progressive aridification during the Miocene, commonly related to mountain uplift, the Paratethys retreat and global climate cooling. However, the formation of Miocene lakes in Central Asia seems to oppose drier conditions, suggesting that the precise timing, extent and forcing of the aridification is still not well constrained. This study presents a facies model for the alluvial–lacustrine part of the Middle to Late Miocene of the Ili Basin, obtained from two successions. The model enables the semi‐quantitative assessment of regional water level and salinity, and characterizes the control of water level on evaporite formation and diagenesis. Both the proximal Kendyrlisai and the distal Aktau successions show an overall increase in water availability from dry mudflat deposits to lacustrine sedimentation with a transitional playa phase. Increasing evaporation rates outpaced the water supply and caused groundwater salinization. Subsequent lake expansion coincided with a basin‐wide desalinization and required a shift to a positive water budget. A climatic control of the hydrological evolution is inferred due to abrupt salinization and a minor tectonic influence. The long‐term water accumulation is probably related to the hydrological closure of the basin in the early Middle Miocene (15·3 Ma). Starting at 14·3 Ma, the step‐wise salinization occurred simultaneously with the global cooling of the Miocene Climate Transition. The Miocene Climate Transition led to extreme aridity in the Ili Basin, highlighted by the early diagenetic formation of displacive anhydrite in the basin centre. The expansion of the freshwater lake (12·7 to 11·5 Ma) was possibly promoted by lower evaporation rates due to decreasing air temperatures in the Ili Basin after the Miocene Climate Transition. The extreme aridity in the Ili Basin is interpreted as a continental counterpart to the Badenian Salinity Crisis in the Central Paratethys. This emphasizes the role of atmospheric forcing on evaporite sedimentation across Eurasia during the Middle Miocene. [ABSTRACT FROM AUTHOR]

ABSTRACT: Central Asia, a typical arid and semi‐arid area, is very sensitive to climate change and is projected to undergo vigorous warming trend in future. However, it is still unclear how extreme temperatures have changed. Therefore, using the daily maximum and minimum temperatures collected from 108 stations in the study area from 1981 to 2015, the spatial–temporal variations in extreme temperature in Central Asia were analysed on both annual and seasonal scales based on 11 indices from The Expert Team on Climate Change Detection and Indices. Results show that: (1) from 1981 to 2015, all extreme temperature values exhibited increasing trends on an annual scale, but maximum temperature (TMAX) increased faster than the minimum temperature (TMIN), leading to an overall increase in the diurnal temperature range (DTR). Most of the stations in Central Asia, except for those in Xinjiang (China), exhibited an increasing trend in DTR, while most of the stations in Xinjiang (China) exhibited reversely significant decreasing trends. (2) TMAX, TMIN and DTR increased significantly, mainly during spring and summer. The trends of most warm extreme indices (warm days, warm nights and warmest days) indicate that the warming mainly occurred in spring, while most cold extreme indices (cool days, cool nights and coldest nights) exhibited significant warming trends in autumn. Dominant warming during spring and autumn can lead to longer summers, which may further accelerate the frequencies and magnitudes of temperature extremes. (3) Additionally, TMAX, TMIN and the percentile‐based warm indices all exhibited significant increasing trends from southwestern Central Asia (Turkmenistan) to eastern Central Asia (Xinjiang (China)) via the Tianshan Mountains. Although the percentile‐based cold indices showed decreasing trends in this region, they were too minor to offset the overall warming trend. With longer summers, stronger and more prolonged melting seasons were detected in the mountains of Central Asia. [ABSTRACT FROM AUTHOR]