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This study classifies the spatial distribution of heavy precipitation in summer (June–August) from 1979 to 2021 in the three provinces of Northeast China (TPNC) into two patterns by using the self‐organizing maps (SOM) neural network, and then quantitatively analyzes their moisture transport channels and sources using the Lagrangian model. The results show that the summer heavy precipitation in TPNC can be divided into the northern and southern patterns according to the distribution of the heavy precipitation. Both patterns of heavy precipitation are affected by the low‐level vortex west of TPNC, but the strength and shape of the low vortex are different. The northern pattern is mainly influenced by the westerly flow in the vortex in the mid‐high latitudes, which transports moisture from the upstream westerly region into TPNC. The southern pattern is mainly affected by the southerly jet stream southeast of TPNC, which conveys a large amount of moisture from the East Asian summer monsoon region into TPNC. In terms of the summer climatological mean, the northern pattern has a higher precipitation recycling rate, while the southern pattern has a lower recycling rate. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) projection has attracted much attention, whereas there are few investigations on the future changes of the EASM northern boundary. The boundary migration would influence the distribution of precipitation and the related vegetation, and its projection is important for policy development of climate change adaptation. In this study, based on the median of 22 selected Coupled Model Intercomparison Project Phase 6 (CMIP6) models, the linear trends of meridional movement of the EASM northern boundary are found to be 0.45−1.39° of latitude during 2015–2099 based on the three precipitation‐based metrics under three shared socioeconomic pathway scenarios. Spatially, the multimetric climatological EASM northern boundary displays a 70–170 km northwestward advance during 2080–2099 compared to 1981–2010. Such an advance also holds true for most individual models, but the migration magnitudes vary with metrics, scenarios and models. The strengthened EASM in association with the intensified land–sea thermal contrast and the enhanced atmospheric water vapour content in response to global warming account for the northwestward advance of the EASM northern boundary, which is related to the increased possibility of the negative phase of the Pacific decadal oscillation in the future. Additionally, the thermodynamic component due to the increased moisture content contributes more than the dynamic term arising from the reinforced EASM circulations to the intensified precipitation and northwestward migration of the EASM northern boundary. The future advance of the EASM northern boundary favours a "northern flood and southern drought" precipitation pattern over eastern China, which would partly mitigate drought conditions in northern arid regions. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) and associated summer precipitation patterns over eastern China have exhibited interannual and interdecadal variations in recent decades, but whether the precipitation modes vary with climate conditions remains unclear. In this study, we investigate the changes in summer precipitation modes over eastern China and associated mechanisms in simulated past and future warm periods, namely, the last interglacial (LIG), mid-Holocene, and the twenty-first century under the Shared Socioeconomic Pathway (SSP) based on representative concentration pathway 8.5 (SSP5–8.5) scenario, using Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The model evaluation indicates that only one out of nine CMIP6 models, specifically the Community Earth System Model, version 2 (CESM2), can well reproduce the observed summer precipitation modes at the present. The empirical orthogonal function (EOF) analyses of the CESM2 simulations reveal that during the warm periods induced by either orbital parameters or greenhouse gas concentrations, the first leading mode of summer precipitation switches from its present meridional tripolar structure to a dipole pattern, and the second leading mode is generally a meridional tripolar mode that differs from the present dipole pattern. This summer precipitation regime interchange in the warm intervals is associated with the formation of the dipole and tripolar circulation patterns. The large-scale circulation changes responsible for the altered precipitation modes are attributed to the enhanced EASM and relevant southerly winds due to intensified land–sea thermal contrast, although the external forcings and the magnitude of EASM enhancement are different in the interglacial and future periods. [ABSTRACT FROM AUTHOR]

Stratospheric aerosol injection (SAI) has been proposed as a potential measure to alleviate global warming; however, uncertainties exist in its regional climate impacts. This study investigates the influence of the SAI on the East Asian winter monsoon (EAWM) by analyzing the G6sulfur simulation from the Geoengineering Model Intercomparison Project. Our results show that the SAI intensifies the Siberian high and Aleutian low, enhances the low‐level northerly winds along the coast of East Asia and deepens the East Asian trough during 2080–2099, reversing the weakening of EAWM in high‐emission Shared Socioeconomic Pathway scenario (SSP5‐8.5). Comparison between the G6sulfur and SSP5‐8.5 simulations indicates that, the SAI‐induced strong cooling in the central equatorial Pacific excites a poleward‐propagating Rossby wave train and strengthen the EAWM. Meanwhile, the negative vorticity advection in the middle troposphere and the radiative cooling over the Siberian high region caused by SAI also intensify the EAWM. Plain Language Summary: Atmospheric greenhouse gas concentrations have increased since the industrial revolution, and they have profoundly affected the climate system and human society. According to a proposed solar radiation modification method, stratospheric aerosol injection (SAI) can partly offset greenhouse gas‐induced warming by scattering solar radiation, but its regional climate impacts are not well understood. In this study, we focus on how the East Asian winter monsoon, one of the most active climate systems in boreal winter, responds to the SAI using simulations from six state‐of‐the‐art climate models. We find that the SAI significantly enhances the East Asian winter monsoon in the late 21st century. The propagation of atmospheric wave caused by SAI‐induced sea surface temperature change is the primary reason. Key Points: Stratospheric aerosol injection in G6sulfur offsets half of winter warming and 80% of precipitation increase in SSP5‐8.5 over East AsiaThe poleward Rossby wave train induced by stratospheric aerosol injection strengthens the East Asian winter monsoonBoth the 500‐hPa negative vorticity advection and tropospheric radiative cooling over the Siberian high region enhance the Siberian high [ABSTRACT FROM AUTHOR]

The teleconnection between the Atlantic Multidecadal Oscillation (AMO) and eastern China summer precipitation (ECSP) for the modern period has been emphasized in the past few decades. We test its stability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) based on the composite results of the median of six models under the Paleoclimate Modeling Intercomparison Project Phase3 (PMIP3) framework. During the MCA, ECSP generally increases in positive AMO phases relative to negative phases, similar to the modern teleconnection, while during the LIA, the precipitation tends to reduce over eastern China, especially in the Yangtze River basin. Decomposing the precipitation change on the basis of a diagnostic moisture budget manifests that the different AMO-related precipitation changes stem from distinct effects of circulation-induced moisture convergence during the two periods. Compared with negative AMO phases, positive AMO phases during the MCA show an anomalous lower-level cyclone and upper-level anticyclone over eastern China that facilitate the upward motion anomaly and precipitation excess. During the LIA, a barotropic anticyclone centers in Northeast China and weakens the high-level westerlies over eastern China; this favors descending and upper-level divergence anomalies and leads to precipitation decreases. The distinct convergence changes are determined by differing propagation paths of the AMO-induced teleconnection wave train during the two periods. [ABSTRACT FROM AUTHOR]

We investigate the interannual variability of surface air temperature in the twenty-first century using the Coupled Model Intercomparison Project Phase 6 (CMIP6) model data under three shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5). Relative to 1961−2014, the interannual variability of annual temperature is projected to increase by 6%, 6%, and 12% globally in the 2051–2100 period under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, respectively, with an average increase of 10–22% in low latitudes and decrease of 3–28% in high-latitude oceans. The spatial pattern of wintertime variability changes is mainly determined by variations in the meridional temperature gradient. Sea ice losses and variations in snow extent in the mid to high latitudes are both related with large variability decreases according to analysis of the underlying surface. In South America and South Africa, the variability enhancement is related to the adjustment of the wet–dry status, while that in South Asia and central Africa depends more on the positive longwave radiative effect due to the increase in clouds. In tropical oceans, the increases in sea surface temperature variabilities and air–sea interactions dominate the enhanced surface air temperature variability. [ABSTRACT FROM AUTHOR]

Based on historical simulations and projections under two scenarios of the Shared Socioeconomic Pathways (SSP2‐4.5 and SSP5‐8.5) provided by 32 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we investigate the future precipitation seasonality changes over China by two indices, the dimensionless seasonality index (DSI) and the relative seasonality index (SI), and the associated physical mechanisms by moisture budget diagnosis. The results show that relative to the baseline period 1995–2014, the DSI is enhanced across almost all of China at the end of the 21st century, with stronger magnitudes in southeastern China and the southern Tibetan Plateau and weaker magnitudes in northwestern China, and national‐mean enhancements are 15% (7%–21%) and 23% (15%–29%) for the multimodel median (25th–75th percentile range across models) under the SSP2‐4.5 and SSP5‐8.5 scenarios, respectively. Projected SI changes show large regional differences, with decreases in northern China and increase in southern China, leading to little change for the national mean. The DSI and SI changes are associated with uneven distributions of changes in absolute amounts and relative proportions of precipitation among seasons, respectively. Further analysis reveals that the contributions of different moisture budget terms to precipitation changes vary across seasons, resulting in changes in the seasonal distribution of precipitation and thus the DSI and SI changes. Specifically, the thermodynamic component of vertical moisture advection primarily determines the greater magnitude of increased precipitation in summer than in winter in most of China, resulting in the DSI change. The reduction in residual term dominates the diminished winter precipitation in southern China, leading to more precipitation concentrated in summer for given annual precipitation and thus the intensification in SI, while the opposite holds true in northern China. [ABSTRACT FROM AUTHOR]

ABSTRACT: Using daily output from 29 climate models provided by the Coupled Model Intercomparison Project Phase 5, we project signals in 12 extreme temperature indices and 12 extreme precipitation indices relative to 1986–2005 over China associated with a 2 °C global warming above pre‐industrial levels under representative concentration pathways 4.5 (RCP4.5) and 8.5 (RCP8.5). The model output reflects the following projected changes: (1) It is robust and statistically significant that warm extremes are more frequent, more persistent, and more intense than those during the baseline period of 1986–2005, and local signals emerge from natural internal variability over most of China. In particular, southern China faces severe heat stress in summer based on warm extreme indices. (2) It is robust and statistically significant that there are fewer cold extremes in China. Most models show no significant changes in the longest duration and intensity of most cold extremes in southern China and northwest China. (3) The multi‐model median shows that more frequent and more intense wet extremes that deliver greater amounts of extreme precipitation occur in China, with a regional mean increase of 16.7–42.8 mm (8–42%) in total amount of annual wet extremes, but these changes are not significant and do not exceed natural internal variability over most of the country. Spatially, the Tibetan Plateau and northeast China have robust and significant changes in part of precipitation extremes, and some changes begin to emerge from natural internal variability at local scale. There are benefits to limiting global warming for China, including less frequent and less persistent warm extremes when comparing 1.5 °C with 2 °C of global warming and a later occurrence of significant changes in climate extremes when compared an intermediate mitigation scenario RCP4.5 with a high emission scenario RCP8.5. [ABSTRACT FROM AUTHOR]

Using the multimodel simulations from phase 6 of the Coupled Model Intercomparison Project (CMIP6), we investigate the aridity changes in China and the associated mechanisms during the three geological periods of the Last Interglacial (LIG), Last Glacial Maximum (LGM), and mid-Holocene (MH), as well as the three future scenarios of the shared socioeconomic pathways of SSP1-2.6, SSP2-4.5, and SSP5-8.5. The aridity index is used to measure terrestrial moisture, which combines the effects of both precipitation and potential evapotranspiration (PET), with the latter representing the amount of water consumed by the atmosphere. The results show that relative to the preindustrial period, the total dryland area in China varies by −15%, 6%, and −13% during the LIG, LGM, and MH, respectively, and slightly varies in the three future scenarios. Over China, LGM dryland expansion and future dryland contraction are mainly attributed to precipitation changes, MH dryland contraction is mainly caused by PET changes, and LIG dryland contraction is comparably caused by PET and precipitation changes. For the LGM and three future scenarios, temperature is the leading factor of PET changes, while during the MH and LIG, the change in relative humidity is the main factor. In comparison, the simulated aridity changes in China are generally consistent with the reconstructed moisture changes for the three past periods, although uncertainties exist in reconstructions during the LGM and MH. [ABSTRACT FROM AUTHOR]

The signal of climate change is emerging against a background of natural internal variability. The time of emergence ( ToE) is an indicator of the magnitude of the climate change signal relative to this background variability and may be useful for climate impact assessments. In this work, we examined the ToE of surface air temperature and precipitation over China under a medium mitigation scenario Representative Concentration Pathway 4.5 based on 30 satisfactory global climate models that are chosen from the Coupled Model Intercomparison Project Phase 5. Major conclusions are: the earliest ToE of annual and seasonal temperature occurs in the eastern Qinghai-Tibetan Plateau between 2006 and 2012 for S/ N > 1.0 and between 2020 and 2030 for S/ N > 2.0, which is 10-20 years sooner than in Northeast China where the latest ToE appears in the country. Consistent with previous studies at the global scale, the median ToE for most of China occurs sooner in summer (2008-2020 for S/ N > 1.0 and 2020-2045 for S/ N > 2.0), while for Northeast and North China the median ToE occurs sooner in autumn (2015-2025 for S/ N > 1.0 and 2040-2050 for S/ N > 2.0). For the ToE of temperature, the inter-model uncertainty is at least 24 years in all five regions of concern and more than 85 years in some seasons, and the inter-model uncertainty in one season for which the earliest median ToE occurs is the smallest among the seasons. For precipitation, the early ToE occurs in the northeastern Qinghai-Tibetan Plateau for the annual mean, and seasonally it occurs first in winter in northern Northeast China and southwestern Northwest China and in winter and spring in the northeastern Qinghai-Tibetan Plateau. For southern China, the median ToE will not occur until 2090. [ABSTRACT FROM AUTHOR]

Based on a 153-year (1948-2100) transient simulation of East Asian climate performed by a high resolution regional climate model (RegCM3) under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario, the potential future changes in mean and extreme climates over China in association with a global warming of 2°C with respect to pre-industrial times are assessed in this study. Results show that annual temperature rises over the whole of China, with a greater magnitude of around 0.6°C compared to the global mean increase, at the time of a 2°C global warming. Large-scale surface warming gets stronger towards the high latitudes and on the Qinghai-Tibetan Plateau, while it is similar in magnitude but somewhat different in spatial pattern between seasons. Annual precipitation increases by 5.2%, and seasonal precipitation increases by 4.2%-8.5% with respect to the 1986-2005 climatology. At the large scale, apart from in boreal winter when precipitation increases in northern China but decreases in southern China, annual and seasonal precipitation increases in western and southeastern China but decreases over the rest of the country. Nationwide extreme warm (cold) temperature events increase (decrease). With respect to the 1986-2005 climatology, the country-averaged annual extreme precipitation events R5d, SDII, R95T, and R10 increase by 5.1 mm, 0.28 mm d, 6.6%, and 0.4 d respectively, and CDD decreases by 0.5 d. There is a large spatial variability in R10 and CDD changes. [ABSTRACT FROM AUTHOR]

Abstract: The East Asian summer (June–July–August) monsoon (EASM) is typically thought to have been stronger during interglacial periods based on spatially sparse proxy data. On a large scale, however, whether this view is true and if so, its underlying dynamic mechanisms remain unclear. Using all pertinent experiments within the Paleoclimate Modeling Intercomparison Project (PMIP), here we present an analysis of the EASM during the mid-Holocene, 6000years ago. Supporting the paleodata, the mid-Holocene EASM, as measured by regionally averaged meridional wind at 850hPa, became stronger than the baseline period in 27 out of 28 PMIP models with a demonstrable ability to simulate the modern EASM climatology. On average, the EASM strengthened by 32% across all the models and by a larger magnitude in 23 coupled models (35%) than in five atmospheric models (20%). It is proposed that an enhanced land–sea thermal contrast, and hence sea level pressure gradient, between the East Asian continent and adjacent oceans as a result of orbital forcing was responsible for the EASM strengthening during the mid-Holocene. [Copyright &y& Elsevier]

We evaluate the performance of climate models from the Coupled Model Intercomparison Project phases 5 (CMIP5) and 6 (CMIP6) in simulating the weather regimes over East Asia during the period from 1961 to 2005. The circulation patterns, frequencies and transition probabilities of the weather regimes are obtained by categorizing the daily 500‐hPa geopotential height (Z500) anomalies using the k‐means clustering algorithm. We identify four winter (WWR1‐4) and three summer weather regimes (SWR1‐3) in both reanalysis datasets and CMIP5/6 models. Significant increasing (declining) frequency trends in WWR3 (WWR4) and SWR2 (SWR1) are found in the ERA5 and NCEP/NCAR reanalysis datasets. On the whole, both generations of models demonstrate reasonable abilities to reproduce the circulation patterns of weather regimes based on the Z500 anomaly fields but overall underestimate the intensities of weather regime patterns, underestimate the occurrence frequencies of WWR3, SWR2, and SWR3, and overestimate the frequencies of WWR1, WWR2, WWR4, and SWR1. In terms of both the ensemble‐mean and pairwise comparisons, the CMIP6 models generally perform better than their CMIP5 counterparts in reproducing the circulation pattern intensities, occurrence frequencies during the whole period and the linear frequency trends and transition probabilities of the weather regimes both in winter and summer. Further analysis shows a highly positive correlation between the total frequency and transition performances but a lower correlation between the biases in the total frequency and intensity of weather regime patterns. The improved skill of CMIP6 over the CMIP5 models in reproducing the weather regimes over East Asia may be partly related to the increased vertical atmospheric resolution in the model. [ABSTRACT FROM AUTHOR]

Using the experiments undertaken by 36 climate models participating in the Paleoclimate Modeling Intercomparison Project (PMIP), this study examines annual and seasonal surface temperatures over China during the mid-Holocene. Compared to the present or preindustrial climate, 35 out of the 36 PMIP models reproduced colder-than-baseline annual temperature, with an average cooling of 0.4 K, during that period. Seasonal temperature change followed closely the change in incoming solar radiation at the top of the atmosphere over China during the mid-Holocene. Temperature was reduced (elevated) in boreal winter and spring (summer) in all of the PMIP models, with an average of 1.4 K (1.0 K) at the national scale. Colder (warmer)-than-baseline temperatures were derived from 14 of the 16 atmosphere-only (18 of the 20 coupled) models during the mid-Holocene boreal autumn. Interactive ocean was found to lead to a warming effect on annual (0.3 K), boreal winter (0.5 K), and boreal autumn (0.7 K) temperatures, with reference to the atmosphere-only models. Interactive vegetation had little impact in terms of six pairs of coupled models with and without vegetation effects. The above results are in stark contrast to warmer-than-present annual and winter climate conditions as derived from multiproxy data for the mid-Holocene. Coupled models generally perform better than atmosphere-only models. [ABSTRACT FROM AUTHOR]

The purpose of this study was to design and test a statistical-dynamical scheme for the extraseasonal (one season in advance) prediction of summer rainfall at 160 observation stations across China. The scheme combined both valuable information from the preceding observations and dynamical information from synchronous numerical predictions of atmospheric circulation factors produced by an atmospheric general circulation model. First, the key preceding climatic signals and synchronous atmospheric circulation factors that were not only closely related to summer rainfall but also numerically predictable were identified as the potential predictors. Second, the extraseasonal prediction models of summer rainfall were constructed using a multivariate linear regression analysis for 15 subregions and then 160 stations across China. Cross-validation analyses performed for the period 1983-2008 revealed that the performance of the prediction models was not only high in terms of interannual variation, trend, and sign but also was stable during the whole period. Furthermore, the performance of the scheme was confirmed by the accuracy of the real-time prediction of summer rainfall during 2009 and 2010. [ABSTRACT FROM AUTHOR]

Abstract: Using the results of 25 climate models under the framework of the Paleoclimate Modelling Intercomparison Project (PMIP) and available proxy data, this study examines the regional climate of China during the Last Glacial Maximum (LGM: 21,000years ago). Compared to the baseline climate, results show that annual surface temperature decreased by 2.00°–7.00°C in China during that period, with an average of 4.46°C, for the ensemble mean of all models. Annual precipitation and evaporation during the LGM were 5–40% less than the baseline values, with an average reduction of 20% (0.60mm/day) and a reduction of 21% (0.41mm/day) at the national scale, based on results from 15 out of the 25 models. These models were selected for their ability to simulate the modern precipitation climatology and for the availability of suitable evaporation data. Both the geographical distribution and magnitude of changes in surface temperature, precipitation, and evaporation during the LGM varied with the seasons and with the models, particularly at the sub-regional scale. Model-data comparisons revealed that the 25 models successfully reproduced the surface cooling trend during the LGM, but they failed to reproduce its magnitude in all four regions of comparison, particularly in the Hexi Corridor and in North and Northeast China. The simulations with computed sea surface temperatures (SSTs) were in better agreement with proxy estimates of surface temperature than those with prescribed SSTs. On the other hand, large-scale LGM-minus-baseline anomalies in annual precipitation minus evaporation agreed well, in a qualitative manner, with lake status-based reconstructions of changes in annual water budgets in East China and the region of 35°–42°N, 74°–97°E. On the eastern Qinghai–Tibetan Plateau, drier climates from the 15 models agreed with pollen-based reconstructions. For most parts of West China excluding the Qinghai–Tibetan Plateau, the simulations with computed (prescribed) SSTs are consistent (inconsistent) with reconstructed moister conditions. [Copyright &y& Elsevier]

Based on the observation and reanalysis data through 1948-2004, the vertical shear of zonal wind, outgoing longwave radiation, and divergence fields in the lower and upper troposphere during summer are revealed to correlate significantly with the concurrent western North Pacific (WNP) typhoon frequency, and they therefore can be regarded as predictors for the WNP typhoon activity anomaly. After that, the 34-year (1970-2003) ensemble hindcast experiments are performed by the nine-level atmospheric general circulation model developed at the Institute of Atmospheric Physics Under the Chinese Academy of Sciences (IAP9L-AGCM), aiming to investigate the numerical predictability of the summer vertical shear of zonal wind and divergence field in the lower troposphere. It is found that the temporal correlation coefficients between the hindcast and observation are 0.70 and 0.62 for the vertical shear of zonal wind and divergence field, respectively. This suggests that the model possesses a large potential skill for predicting the large-scale climate background closely related to the WNP typhoon activity, and the model is therefore capable of performing the real-time numerical prediction of the WNP typhoon activity anomaly to some extent. [ABSTRACT FROM AUTHOR]

Reports on the extraseasonal ensemble numerical predictions of winter climate over China. Use of the Atmospheric General Circulation Model developed at the Institute of Atmospheric Physics under the Chinese Academy of Sciences; Evaluation of the winter climate predictability over China; Prediction skill of air temperature and geopotential height.

Identifying potential external forcings on dryland aridity at various timescales and clarifying underlying mechanisms can advance our knowledge of dryland climate behaviors. To address this issue, we examine the past 21 ka using a set of transient simulations driven by realistic climatic forcings, as well as multiple types of proxies. The simulations suggest the evolution of dryland aridity and dominant forcings vary over time and region. On average, global drylands feature two-phase aridification at the orbital scale: the first phase occurs before the Holocene and is dominated by ice sheet melting and rising greenhouse gas (GHG) concentrations, followed by the second phase driven by the summer insolation decrease over northern high latitudes after the early Holocene; different from the wetness during the orbital-scale glacial period, millennium-scale cold events forced by meltwater discharges correspond to desiccation, punctuating the long-term trend during the last deglaciation. In addition, the average aridity changes for drylands are larger than those for global landmasses under all forcings except GHG concentrations. Spatially, the dominant external forcings and aridity responses to the same forcing vary regionally, mainly related to the latitude and hemisphere. Further diagnosis indicates the manners to affect aridity, namely through altering precipitation or evaporative capacity, vary by forcing. The aforementioned evolution of the simulated aridity matches well with the proxies in most dryland zones. This study provides a scenario of time-varying responses of dryland aridity to external forcings over the last 21 ka and may shed light on the future changes. • Dryland aridity over the past 21 ka is examined using simulations and proxies. • It is consistent across simulated aridity index, runoff, and soil moisture. • Dominant external forcings on dryland aridity have varied with time and region. • Aridity changes over dryland are larger than those over the global land. • Simulations match well with proxies. [ABSTRACT FROM AUTHOR]

In terms of five categories of East Asian summer monsoon (EASM) indices and one classic meridional wind index, we project the EASM intensity change over the 21st century using 27 global climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) under the mid‐range combined scenarios of Shared Socioeconomic Pathways and Representative Concentration Pathways (SSP2‐4.5). Results show that future changes in the EASM intensity are index‐ and model‐dependent. Relative to the reference period 1985–2014, the EASM intensity strengthens slightly based on the east–west thermal contrast indices but varies little as a whole based on the southwest monsoon indices over the 21st century, with large discrepancies among the models. However, it tends to weaken over time based on the other three categories of indices, including the north–south thermal contrast indices, the shear vorticity indices, and the South China Sea monsoon indices. In terms of the meridional wind index that directly measures the EASM circulation in the lower troposphere and holds valid under future global warming, the EASM intensity strengthens significantly over the 21st century as a consequence of increases in zonal and meridional land–sea thermal contrasts between the East Asian continent and the adjacent oceans of western North Pacific and South China Sea. There are certain relationships between the trends of the meridional wind index and other EASM indices. The projections are overall consistent between the ensemble means of all available 27 models and the 14 good models as selected according to their abilities to simulate the present EASM climatology, but with different magnitudes. [ABSTRACT FROM AUTHOR]

During January 21–24, 2016, most land areas in the Northern Hemisphere experienced extreme low temperatures. In North America, a historic snowstorm hit the northern and eastern United States. In East Asia, an unprecedented cold wave occurred and led to record‐breaking low temperatures in many regions. In this study, observational analyses revealed that both extreme events were triggered by a remarkable change in atmospheric circulation in the Arctic region in early January 2016, which switched from a concentric ring pattern to a dipole pattern. The dipole pattern resulted in two inverted Ω‐shaped circulation patterns that dominated the North America and East Asia. The inverted Ω‐shaped circulation patterns induced remarkable tropopause folding, which conveyed high‐potential‐vorticity cold air downwards from the lower stratosphere of Arctic to the middle and lower troposphere of North America, which increased cyclonic vorticity and negative height perturbations, and converged with moist air from the western North Atlantic and Gulf Stream, resulting in a severe snowstorm in the northern and eastern United States from 22 to 24 January. In East Asia, the tropopause folding transported high‐potential‐vorticity cold air downwards to the middle and lower troposphere of East Asia, resulting in the outbreak of a severe cold wave in East Asia from 21 to 24 January. [ABSTRACT FROM AUTHOR]

In the boreal summer and autumn of 2023, the globe experienced an extremely hot period across both oceans and continents. The consecutive record-breaking mean surface temperature has caused many to speculate upon how the global temperature will evolve in the coming 2023/24 boreal winter. In this report, as shown in the multi-model ensemble mean (MME) prediction released by the Institute of Atmospheric Physics at the Chinese Academy of Sciences, a medium-to-strong eastern Pacific El Niño event will reach its mature phase in the following 2–3 months, which tends to excite an anomalous anticyclone over the western North Pacific and the Pacific-North American teleconnection, thus serving to modulate the winter climate in East Asia and North America. Despite some uncertainty due to unpredictable internal atmospheric variability, the global mean surface temperature (GMST) in the 2023/24 winter will likely be the warmest in recorded history as a consequence of both the El Niño event and the long-term global warming trend. Specifically, the middle and low latitudes of Eurasia are expected to experience an anomalously warm winter, and the surface air temperature anomaly in China will likely exceed 2.4 standard deviations above climatology and subsequently be recorded as the warmest winter since 1991. Moreover, the necessary early warnings are still reliable in the timely updated medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction. [ABSTRACT FROM AUTHOR]

Using the Lagrangian model FLEXPART and the quantitative method WaterSip, moisture sources of summer (June–July–August) precipitation over eastern China are investigated for the period 1979–2009 in this study. It is found that the Indochinese Peninsula plus southern China, the South China Sea, the northwestern Pacific Ocean, the Asian continent, and the Bay of Bengal are the major moisture sources in our results, and the moisture from eastern China, the Arabian Sea, and the Indian subcontinent also has minor contributions. Note that the contribution of the oceanic sources substantially surpasses that of the continental sources, and the contributions of sources exhibit interannual variations during 1979–2009, especially in the Indochinese Peninsula plus southern China, the South China Sea, the northwestern Pacific Ocean, the Asian continent, and the Bay of Bengal. Moreover, moisture sources have evident monthly variations and seasonal cycle features, which are responsible for supplying moisture to precipitating over eastern China in the different monsoonal periods. In addition, the major moisture sources for different intensities of precipitation over eastern China vary considerably; for light and moderate precipitation, a great amount of moisture originates from the local and northwestern continental regions and eastern oceanic regions adjacent to eastern China, while more moisture comes from southwestern oceanic sources and the surrounding continental regions of them for heavy precipitation. [ABSTRACT FROM AUTHOR]

Using the Lagrangian model FLEXPART and the quantitative method WaterSip, moisture sources of summer (June–July–August) precipitation over eastern China are investigated for the period 1979–2009 in this study. It is found that the Indochinese Peninsula plus southern China, the South China Sea, the northwestern Pacific Ocean, the Asian continent, and the Bay of Bengal are the major moisture sources in our results, and the moisture from eastern China, the Arabian Sea, and the Indian subcontinent also has minor contributions. Note that the contribution of the oceanic sources substantially surpasses that of the continental sources, and the contributions of sources exhibit interannual variations during 1979–2009, especially in the Indochinese Peninsula plus southern China, the South China Sea, the northwestern Pacific Ocean, the Asian continent, and the Bay of Bengal. Moreover, moisture sources have evident monthly variations and seasonal cycle features, which are responsible for supplying moisture to precipitating over eastern China in the different monsoonal periods. In addition, the major moisture sources for different intensities of precipitation over eastern China vary considerably; for light and moderate precipitation, a great amount of moisture originates from the local and northwestern continental regions and eastern oceanic regions adjacent to eastern China, while more moisture comes from southwestern oceanic sources and the surrounding continental regions of them for heavy precipitation. [ABSTRACT FROM AUTHOR]

In this study, we project the global terrestrial changes in Aridity Index (AI), as defined by the ratio of annual precipitation to potential evapotranspiration (PET), at 2 and 4°C levels of global warming above the preindustrial conditions based on the outputs from 21 Coupled Model Intercomparison Project Phase 5 models under the Representative Concentration Pathways 8.5 (RCP8.5) scenario. Compared to the preindustrial period, the global terrestrial annual precipitation will increase by an average of 0.02% (3%), the annual PET will increase by 6% (15%) and AI will decrease by 0.1 (0.2) at the 2°C (4°C) warming level. More remarkable decreases in the annual AI are seen in the northern high latitudes, where will also experience greater increases in PET and precipitation. In general, the seasonal changes in AI display a similar spatial pattern to the annual changes and are characterized by the greatest decrease in December–January–February and the smallest in June–July–August. The largest expansion of drylands occurs in semi‐arid regions, followed by the expansion of arid regions, with area changes of 4% (7%) and 3% (4%) under the 2°C (4°C) scenario, respectively. Further analyses indicate that the AI changes are determined by PET in the northern high latitudes, and the contribution of PET to AI increases from the 2 to 4°C warming levels. Furthermore, changes in thermodynamic factors contribute most to the PET, and at a higher level of global warming, the contribution of thermodynamic factors increases and that of dynamic factors decreases. [ABSTRACT FROM AUTHOR]

The assumption of a stationary global signal linked to El Niño–Southern Oscillation (ENSO) events is often used in paleo-ENSO proxy data interpretation. This paper attempts to investigate whether the assumption is valid during the last glacial maximum (LGM) over the region 60°S–90°N, 60°E−60°W. Using four models within phase 3 of the Paleoclimate Modeling Intercomparison Project framework that well reproduce ENSO-induced variabilities, differences from the preindustrial period to LGM in the ENSO-related sea surface temperature pattern and its impacts are investigated. Compared to the preindustrial period, the ENSO impacts are revealed to weaken and shift eastward during the LGM. According to multimodel medians, ENSO impacts on precipitation and near-surface air temperature are attenuated over most regions of concern, with percentage changes in both parameters averaging −21% for the whole region; the ENSO-induced Pacific–North America (PNA) teleconnection pattern is weakened, manifested by the 41% diminished center over the North Pacific and the almost vanished activity centers over the continent. Spatially, there is a zonal contraction of 13° for the sea surface warming of ENSO, as well as eastward migration over 10° for the ENSO-induced positive precipitation anomaly center over the tropical Pacific and the PNA teleconnection pattern outside the tropics. The aforementioned changes are linked to the altered climatic background during the LGM, which features a 16° eastward shift for the Pacific Walker circulation rising branch and a weakened waveguide in the midlatitudes. The results suggest that the hypothesis of stationary ENSO impacts should be applied cautiously to the past. [ABSTRACT FROM AUTHOR]

The eastern China summer precipitation is related to the Pacific Decadal Oscillation (PDO) on interdecadal time scales in modern times, but it remains unclear whether such a relationship holds prior to the instrumental period. We examine this relationship during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). According to a composite analysis using simulations of the HadCM3 model, which is selected from nine available climate models, the PDO–eastern China summer precipitation relationship varies with climatic background. The modern relationship features deficient precipitation over North and South China and excessive precipitation in the Yangtze–Huai River Valley in positive PDO phases compared with negative phases. In contrast, there is more precipitation over South and North China but less in the Yangtze–Huai River Valley during the MCA and widespread below-normal summer precipitation over eastern China during the LIA. Such different PDO-related precipitation patterns between the MCA and LIA are closely linked to distinct changes in local atmospheric circulation. Compared with negative PDO phases, positive phases during the MCA show an anomalous Pacific–Japan/East Asia–Pacific pattern over East Asia and strengthened high-level westerlies centering on 120°E and 25–30°N, which lead to the triple pattern in the precipitation anomaly. During the LIA, a cyclonic anomaly occurs over the South China Sea–Philippine Sea in the lower and middle troposphere, and two upper-level low trough anomalies occur over East Asia, causing the anomalous precipitation deficit. The different PDO-related local circulations are found to be relevant to the thermodynamic effect of low-latitude sea surface temperature and summer precipitation over India, as well as the propagation of upstream wave trains. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) intensified during the early to mid-Holocene relative to the present primarily due to orbital forcing. However, on the regional scale, changes in the monsoonal precipitation exhibit considerable spatial disparity, and the underlying mechanisms remain unresolved. In this study, the dynamic processes responsible for the difference of the EASM precipitation between the mid-Holocene and preindustrial period are systematically examined using the CMIP5 multimodel simulations. The moisture budget diagnostic identifies vertical motion as the key factor determining the cross-like precipitation pattern in East Asia. Relative to the preindustrial period, the mid-Holocene anomalous ascending motion corresponds well with the excessive precipitation over northern and southern China, and vice versa for west-central China, the Korean peninsula, Japan, and its marginal seas. In the framework of the moist static energy budget, the increased insolation and the attendant intensification of land–sea thermal contrast give rise to anomalous ascending motions, while descending motions are fundamentally forced by the decreased latitudinal insolation gradient. In particular, thermodynamic changes, namely, the reduced pole–equator temperature and humidity gradients, account for the downward motions over the northwestern Pacific. Dynamic changes, namely, the weakened westerlies, play a leading role in suppressing updrafts in west-central China. This study highlights that the orbital-scale monsoonal precipitation changes are not solely determined by local radiative forcing as repeatedly emphasized before. The latitudinal uneven distribution of insolation is crucial to explain the spatial inhomogeneity in the EASM precipitation changes during the Holocene. [ABSTRACT FROM AUTHOR]

This study examines changes in aridity levels during the mid-Holocene (approximately 6000 cal. yr ago) using multi-model simulations from the Paleoclimate Modelling Intercomparison Project Phase III. Overall, there is little difference in the total area of drylands from the preindustrial period; global drylands are 8% wetter than during the preindustrial period as measured by an aridity index; and 16% of preindustrial drylands convert to a wetter climate subtype, double the sum of zones that are replaced by a drier category. Considerable variations are present among regions with major contractions of each dryland subtype from northern Africa to South Asia and the main expansions of arid, semiarid, and dry subhumid climates in southern hemisphere continents. The difference in precipitation is the leading factor of the aforementioned changes. The second factor is the altered potential evapotranspiration as mainly induced by relative humidity, which contributes to additional aridity changes in a same direction as precipitation does. The collective effects of precipitation and relative humidity account for more than 80% of the dryland variations. In comparison, the simulated aridity change is in reasonable agreement with reconstructions, while there are model–data discrepancies for Australia and uncertainties across proxies for southern Africa. [ABSTRACT FROM AUTHOR]

Based on numerical experiments undertaken with nine climate models, the glacier equilibrium line altitudes (ELAs) in western China during the last glacial maximum (LGM) are investigated to deepen our understanding of the surface environment on the Tibetan Plateau. Relative to the preindustrial period, the summer surface air temperatures decrease by 4–8°C while the annual precipitation decreases by an average of 25% across the Tibetan Plateau during the LGM. Under the joint effects of reductions in summer temperature and annual precipitation, the LGM ELAs in western China are lowered by magnitudes that vary with regions. The ELAs in the southern margin and northwestern Tibetan Plateau decline by approximately 1100 m; the central hinterland, by 650–800 m; and the eastern part, by 550–800 m, with a downward trend from southwest to northeast. The reduction in ELAs is no more than 650 m in the Tian Shan Mountains within China and approximately 500–600 m in the Qilian Mountains and Altai Mountains. The high-resolution models to reproduce the low values of no more than 500 m in ELA reductions in the central Tibetan Plateau, which are consistent with the proxy records from glacier remains. The accumulation zones of the Tibetan Plateau glaciers are mainly located in the marginal mountains during the LGM and have areas 2–5 times larger than those of the modern glaciers but still do not reach the central part. [ABSTRACT FROM AUTHOR]

Using the numerical experiments undertaken by nine climate models within the framework of the Paleoclimate Modeling Intercomparison Project Phase 3 (PMIP3), the ensemble simulations with the Community Earth System Model for the last millennium (CESM-LME), and proxy data, we investigate the climate over China during the 'Little Ice Age' (LIA; from 1450 to 1850 CE) against the background of the last millennium (from 850 to 1850 CE). The surface air temperature averaged over China generally decreased over time during the last millennium, with several multi-decadal to centennial variations superimposed on the long-term cooling. Relative to the climatology of the last millennium, the annual surface temperature during the LIA decreased over the country, with an average cooling of −0.07°C for the median of the PMIP3 models. Different magnitudes of cooling occurred in all seasons except spring. The cooling over China during the LIA was largely attributed to changes in volcanic eruptions and land use, while the change in orbital parameters played a role on a seasonal scale. The precipitation over China during the LIA decreased for the annual mean and summer and autumn but slightly increased in winter and spring. Model–data comparisons indicate that the models reproduced the colder and drier climate of the LIA reasonably, although there are some differences in certain aspects. [ABSTRACT FROM AUTHOR]

In 2012, the World Bank released a report and stated that a 4 °C increase in global temperature relative to the pre‐industrial levels would be devastating. However, there is a lack of scientific literature on the changes in climate associated with a 4 °C temperature increase. Based on the daily temperature and precipitation data from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we project the global terrestrial changes in the extreme values of temperature and precipitation in association with a warming of 4 °C above the pre‐industrial levels using the Representative Concentration Pathways 8.5 (RCP8.5) scenario. The results indicated that cold extremes will decrease and warm extremes will increase. More remarkable signals in temperature extremes based on daily minimum temperature are expected, and local changes in temperature extremes generally extend beyond the natural internal variability. Significant signals in the frequency of temperature extremes appear in low latitudes, while the temperature changes of the coldest and hottest days are great in northern high latitudes. Large signal‐to‐noise ratios for warm extremes mainly occur in low latitudes, while those of cold extremes are not uniformly distributed. More intense and frequent heavy precipitation is also projected. Signals in high‐precipitation extremes are prominent in high latitudes and usually exceed the local natural internal variability. Changes in extreme dry events are high in the extratropics and generally lie within the background noise. Relative to the 1.5 °C global warming scenario, there would be more violent temperature and precipitation extremes with the 4 °C warming level, and these extremes would pose more threats to natural and human systems. Additionally, small inter‐model uncertainty occurs in the regions with remarkable signals for high precipitation‐related extremes and cold days and nights, while the opposite trend is seen for extreme dry events and other temperature extremes. There are more warm and fewer cold extremes at 4 °C global warming above the pre‐industrial levels, and changes in temperature extremes generally exceed the natural internal variability. More intense and frequent heavy precipitation is projected, and increases in heavy extremes usually exceed the natural internal variability in high latitudes. The inter‐model uncertainty of heavy precipitation extremes and cold days and nights is generally small in the regions with great signals, while the opposite holds for the other temperature extremes and the extreme dry events. In the figure, signal (shading) and signal‐to‐noise ratio (S/N, hatched/dotted areas) associated with the 4 °C level of global warming relative to the pre‐industrial levels for annual coldest night (TNn, units: °C and °C/°C) over land as derived from the median of the 19 climate models under RCP8.5. The orange lines in the right panels indicate the zonal mean changes in the signal and S/N, with the vertical dashed lines representing the global terrestrial averaged value for each variable. [ABSTRACT FROM AUTHOR]

Motivated by studies of tropical expansion under modern global warming, the behavior of the tropical belt during the Last Glacial Maximum (LGM) relative to the preindustrial period has been investigated in this study, using simulations from phase 3 of the Paleoclimate Modelling Intercomparison Project (PMIP3) under the framework of phase 5 of the Coupled Model Intercomparison Project (CMIP5). The tropical belt width changes determined by multiple metrics present two opposite tendencies. One refers to the poleward migration of the tropical edge as measured by the steep tropopause gradient and the subtropical jet, and the other suggests that the LGM tropics become narrower as measured by the Hadley cell extent, the eddy-driven jet, and the latitude where precipitation minus evaporation equals zero. The magnitude of such changes widely differs across models and metrics. In absolute terms, the multimodel mean total width changes range from 0.6° to 1.7° among metrics, with contributions predominantly from the Northern Hemisphere. Furthermore, the two metrics that indicate tropical widening are located in the upper troposphere. Such widening is closely related to the vertical and meridional temperature gradient changes in the subtropical regions. The other metrics are located in the middle and lower troposphere, and their variations are directly or indirectly related to changes in the low-level baroclinicity. The diverse responses of metrics to the LGM boundary conditions suggest that the tropical belt width changes and their climatic impacts are distinguished by the different measurements. The selection of metrics should correspond to the specific tropical properties of concern. [ABSTRACT FROM AUTHOR]

This study investigates terrestrial moisture changes and associated mechanisms during the last glacial maximum (LGM; approximately 21,000 calendar years ago) using multi-model simulations from the Paleoclimate Modelling Intercomparison Project phase 3 (PMIP3). Considering that terrestrial moisture is not determined solely by precipitation, an aridity index (AI) is employed for measuring the terrestrial moisture by combining the effects of both precipitation and potential evapotranspiration (PET), where the latter represents atmospheric water demand and is greatly decreased mainly by the intense cooling during the LGM. Compared to the preindustrial period, the magnitude of global mean terrestrial moisture change is small, as the wetness brought by decreased PET counteracts the dryness induced by decreased precipitation. Regionally, the moisture changes depend on the different combinations of changes in precipitation and PET: (i) drying occurs where precipitation deceases and PET hardly changes, such as the northern tropical Americas and Southeast Asia; (ii) wetting is found in regions with precipitation increases and PET decreases (e.g., northwestern Africa and the central Andes), and their contributions are comparable; (iii) in particular, wetting can also occur in regions of decreased precipitation if a sufficient decrease in PET also occurs (i.e., southeastern North America and the northern and southern parts of eastern Asia), with the latter wetting effect reversing the former drying effect. The multi-model median field is consistent with available paleo-records in southern North America, the northern tropical Americas, the Andes, northwestern Africa, the southern Iberian Peninsula, southwestern Africa, the central part of eastern Asia, and Java but disagrees with proxies in Australia, central Brazil, southeastern Africa, the northern Iberian Peninsula, and the southern part of eastern Asia. [ABSTRACT FROM AUTHOR]

Using a set of numerical experiments from 39 CMIP5 climate models, we project the emergence time for 4◦C global warming with respect to pre-industrial levels and associated climate changes under the RCP8.5 greenhouse gas concentration scenario. Results show that, according to the 39 models, the median year in which 4◦C global warming will occur is 2084. Based on the median results of models that project a 4◦C global warming by 2100, land areas will generally exhibit stronger warming than the oceans annually and seasonally, and the strongest enhancement occurs in the Arctic, with the exception of the summer season. Change signals for temperature go outside its natural internal variabilities globally, and the signal-tonoise ratio averages 9.6 for the annual mean and ranges from 6.3 to 7.2 for the seasonal mean over the globe, with the greatest values appearing at low latitudes because of low noise. Decreased precipitation generally occurs in the subtropics, whilst increased precipitation mainly appears at high latitudes. The precipitation changes in most of the high latitudes are greater than the background variability, and the global mean signal-to-noise ratio is 0.5 and ranges from 0.2 to 0.4 for the annual and seasonal means, respectively. Attention should be paid to limiting global warming to 1.5◦C, in which case temperature and precipitation will experience a far more moderate change than the natural internal variability. Large inter-model disagreement appears at high latitudes for temperature changes and at mid and low latitudes for precipitation changes. Overall, the intermodel consistency is better for temperature than for precipitation. [ABSTRACT FROM AUTHOR]

ABSTRACT: In this study, moisture sources for different intensities of summer (June–July–August) rainfall over the Chinese Loess Plateau (CLP) were investigated by performing a transient simulation for the period 1979–2009 using the Lagrangian particle dispersion model FLEXPART. The results showed that continental areas surrounding the CLP, namely northwestern China–eastern central Asia and central eastern China, were major moisture source regions for summer rainfall over the CLP and that oceanic moisture originated from the East China Sea, the South China Sea, the Bay of Bengal, and the Arabian Sea played a secondary role. The moisture contribution of northwestern China–eastern central Asia to the CLP significantly decreased with increasing intensity of rainfall, whereas the contribution of central eastern China to the CLP slightly increased. Moreover, the moisture contribution of oceanic source regions to the CLP increased with the increased rainfall intensity. The East China Sea and the Bay of Bengal were the two most substantial oceanic moisture source regions for the 0–5th percentile (0–P5th) to 50th–75th percentile (P50th–P75th) rainfall classes, whereas the South China Sea and the Bay of Bengal were the two most substantial oceanic moisture source regions for the 75th–95th percentile (P75th–P95th) and the 95th–100th percentile (P95th–P100th) rainfall classes. [ABSTRACT FROM AUTHOR]

Based upon simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), the vertical and regional characteristics of the northernwesterlies during the LastGlacialMaximum(LGM) are investigated in this study. At the Northern Hemispheric scale, all nine available models simulate a poleward shift of the 200-hPa jet, and eight models simulate an equatorward shift of the 850-hPa jet compared to the preindustrial period; these shifts are of approximately 28-38 latitude for the arithmetic multimodel mean. The uppertropospheric cooling in the tropics, possibly due to reduced latent heat release, is expected to account for the poleward shift of the 200-hPa jet through the thermal wind relationship. Changes in the midlatitude baroclinic instability in response to the amplified polar cooling are associated with the jet stream in the lower troposphere through anomalous eddy activity. In particular, the types of predominant baroclinic eddies are regionally dependent. The behavior of the 850-hPa jet over the North Pacific is steered by transient eddies and characterized by a southward displacement during the LGM. By contrast, the remarkable enhancement of the NorthAtlantic jet stream throughout the troposphere is associated with the notably increased stationary eddy momentum convergence, presumably due to the presence of the Laurentide ice sheet over North America. In comparison with the proxy records, although there is no observational evidence explicitly indicating changes of the upperlevel northern westerlies, the simulated LGM 850-hPa westerly wind field is indirectly concordant with the reconstructed moisture conditions over the Mediterranean region and southwestern North America. [ABSTRACT FROM AUTHOR]

Abstract Based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) daily dataset, we investigate changes of the terrestrial extreme climates given that the global mean temperature increases persistently under the Representative Concentration Pathways 8.5 (RCP8.5) scenario. Compared to preindustrial conditions, more statistically significant extreme temperatures, precipitations, and dry spells are expected in the 21st century. Cold extremes decrease and warm extremes increase in a warmer world, and cold extremes tend to be more sensitive to global warming than the warm ones. When the global mean temperature increases, cold nights, cold days, and warm nights all display nonlinear relationships with it, such as the weakening of the link projected after 3 °C global warming, while the other indices generally exhibit differently, with linear relationships. Additionally, the relative changes in the indices related to extreme precipitation show significantly consistent linear changes with the global warming magnitude. Compared with the precipitation extremes, changes in temperature extremes are more strongly related to the global mean temperature changes. For the projection of the extreme precipitation changes, models show higher uncertainty than that in extreme temperature changes, and the uncertainty for the precipitation extremes becomes more remarkable when the global warming exceeds 5 °C. [ABSTRACT FROM AUTHOR]

This study investigated the impacts of Tibetan Plateau vertical heating (TPVH) on the Asian summer monsoon (ASM) on the interdecadal scale since the beginning of the 20th century. The ASM, corresponding to TPVH, generally enhances on the interdecadal scale. In the upper troposphere, the upper‐level westerly and easterly jet streams shift northwards in Asia, with two meridional "southern low and northern high" wave‐like patterns dominating in East Asia and India, respectively. In the lower troposphere, the summer monsoonal airflow and convergence zone migrate northwards in Asia, and two meridional "southern high and northern low" patterns appear in East Asia and India, respectively. Thus, TPVH can strengthen the baroclinicity over northern East Asia and northern India, but weaken it over southern East Asia and southern India. Moreover, two anomalous meridional circulation cells are identified in East Asia and India, with ascending branches in their northern parts and descending branches in their southern parts. Eventually, the ASM strengthens, leading to a southern dry and northern wet pattern in East Asia and India. [ABSTRACT FROM AUTHOR]

Observational analysis shows that the Atlantic multidecadal variability (AMV) is associated with climate variability in the Northern Hemisphere through a zonal atmospheric teleconnection extending from the North Atlantic Ocean and propagating eastward around the Northern Hemisphere. We studied the fidelity of model simulations in reproducing the observed summer AMV and the associated impacts on the mid-latitude climate by analysing simulations using the National Centre for Atmospheric Research Community Earth System Model Version 1 (CESM1), including CESM1 North Atlantic idealized and pacemaker simulations, CESM1 large ensemble twentieth century uninitialized simulations and large ensemble initialized CESM1 decadal predictions. To further compare the fidelity of CESM1, we also analysed large ensemble simulations from three other models. Our results suggest that the uninitialized large ensemble simulations from all models can produce an AMV time evolution and its regional climate impacts similar to the observations to certain degree. By initializing the observed oceanic condition in decadal prediction simulations, the simulated AMV and its regional impacts are closer to the observed ones than those in uninitialized ensemble simulations. In addition, the pacemaker simulations that nudged the time-evolving observed North Atlantic sea surface temperature anomalies produce spatiotemporal characteristics of the AMV and AMV climate impacts closer to the observed ones than the uninitialized simulations. We conclude that although coupled models can produce AMV and its regional impacts similar to observed, proper initialization and bias correction of the sea surface temperature spatial and temporal structure can improve this capability. [ABSTRACT FROM AUTHOR]

ABSTRACT Towards a better insight into the timing and climate change associated with a 2 °C global warming above pre-industrial levels in the 21st century, here we perform an analysis of all pertinent experiments within the framework of the Coupled Model Intercomparison Project Phase 5 ( CMIP5). Considering equally all available CMIP5 models, the probability of crossing the 2 °C target before the year 2100 is 26, 86, and 100% for the Representative Concentration Pathways 2.6 ( RCP2.6), 4.5 ( RCP4.5), and 8.5 ( RCP8.5) scenarios, respectively, with the median years of 2054 for RCP4.5 and 2042 for RCP8.5. A 2 °C global warming would not be felt equally round the globe: stronger warming occurs over land than over the ocean, and the strongest warming occurs in the Arctic. Almost all temperature changes are larger than natural internal variability. Global average signal-to-noise ratios ( S/N) of annual and seasonal temperature changes are in the range 3.2-5.0, and the largest values occur at low latitudes due to the lower background variability. Precipitation tends to increase at high latitudes but decrease in the subtropics, while all changes are smaller than natural internal variability except in parts of the high northern latitudes. The S/N of annual (seasonal) precipitation changes averages only 0.2 (no more than 0.1) for the globe. [ABSTRACT FROM AUTHOR]

The surface air temperature seasonal cycle in China has clearly changed in response to global warming, but its future projection has yet to be studied. Here, we investigate the performance and projection of the temperature seasonal cycle in China in 32 global climate models participating in the Coupled Model Intercomparison Project 6 (CMIP6). The characteristics of the temperature seasonal cycle, as represented by the amplitude and phase, are measured by the Fourier transform. The results show that the CMIP6 models can reasonably capture the observed typical temperature seasonal cycle feature with clear north–south gradients both for amplitude and phase in China. In the twenty‐first century, the models robustly project a delay in the phase across the whole country and a reduction in the amplitude in most of China relative to the reference period. Those changes are similar in the two shared socioeconomic pathway (SSP) scenarios, with overall larger magnitudes in the SSP5‐8.5 scenario than in the SSP2‐4.5 scenario. Projected amplitude changes are mainly linked to surface energy flux changes, especially latent heat flux changes. In response to future global warming, larger increases in the latent heat flux and thus stronger surface evaporative cooling lead to weaker surface warming in summer than in winter, contributing to a decrease in the amplitude of the temperature seasonal cycle in most regions of China. [ABSTRACT FROM AUTHOR]

Using all relevant climate experiments archived in phases 3 and 4 of the Paleoclimate Modeling Intercomparison Project (PMIP3/4), we examine the interannual variability change in global-scale surface air temperature and associated physical mechanisms during the Last Glacial Maximum (LGM). The results show that relative to the preindustrial period, the LGM interannual temperature variability increased by 20% globally, which was mainly attributed to the large-scale increase in the meridional temperature gradient, especially at midlatitudes. Larger magnitudes of change occurred in areas where the underlying surface properties, such as the surface altitude, land–sea distribution, and ice sheet extent, differed from those in the preindustrial period. In addition, the relationship between changes in the meridional temperature gradient and the interannual temperature variability became closer in the winter hemisphere. In the tropical land regions, changes in interannual temperature variability are mainly related to the adjustment of latent and sensible heat fluxes during the LGM. [ABSTRACT FROM AUTHOR]

ABSTRACT Based on observation and reanalysis data, 77 coupled global climate models ( GCMs) participating in the Intergovernmental Panel on Climate Change ( IPCC) Third ( TAR), Fourth ( AR4), and Fifth ( AR5) Assessment Reports are evaluated in terms of their ability to simulate the mean state and year-to-year variability of surface air temperature at 2 m and precipitation over China and the climatological East Asian monsoon for the late decades of the 20th century. Results show that GCMs reliably reproduce the geographical distribution of the variables considered. Compared with observations, however, most GCMs have topography-related cold biases (although these are smaller than those found in previous studies), excessive precipitation, an underestimated southeast-northwest precipitation gradient, an overestimated magnitude and spatial variability of the interannual variability of temperature and precipitation, and an inadequate strength of the East Asian monsoon circulation. Pairwise comparison reveals that GCMs continue to improve from the TAR via the AR4 to the AR5 for temperature, but have little change for precipitation and the East Asian monsoon. The ability of GCMs varies with season and is affected to certain degree by their horizontal resolutions. Both the arithmetic mean and the median of multiple GCMs are little affected by filtering GCMs in terms of their ability, and the multi-model mean outperforms most of individual GCMs in every respect. [ABSTRACT FROM AUTHOR]

The last glacial maximum (LGM, ca. 21,000 years ago) has been extensively investigated for better understanding of past glacial climates. Global-scale monsoon changes, however, have not yet been determined. In this study, we examine global monsoon area (GMA) and precipitation (GMP) as well as GMP intensity (GMPI) at the LGM using the experiments of 17 climate models chosen from the Paleoclimate Modelling Intercomparison Project (PMIP) according to their ability to reproduce the present global monsoon climate. Compared to the reference period (referring to the present day, ca. 1985, for three atmospheric plus two atm–slab ocean models and the pre-industrial period, ca. 1750, for 12 fully coupled atmosphere–ocean or atmosphere–ocean–vegetation models), the LGM monsoon area increased over land and decreased over the oceans. The boreal land monsoon areas generally shifted southward, while the northern boundary of land monsoon areas retreated southward over southern Africa and South America. Both the LGM GMP and GMPI decreased in most of the models. The GMP decrease mainly resulted from the reduced monsoon precipitation over the oceans, while the GMPI decrease was derived from the weakened intensity of monsoon precipitation over land and the boreal ocean. Quantitatively, the LGM GMP deficit was due to, first, the GMA reduction and, second, the GMPI weakening. In response to the LGM large ice sheets and lower greenhouse gas concentrations in the atmosphere, the global surface and tropospheric temperatures cooled, the boreal summer meridional temperature gradient increased, and the summer land–sea thermal contrast at 40°S – 70°N decreased. These are the underlying dynamic mechanisms for the LGM monsoon changes. Qualitatively, simulations agree with reconstructions in all land monsoon areas except in the western part of northern Australia where disagreements occur and in South America and the southern part of southern Africa where there is uncertainty in reconstructions. Simulations do not support an inter-hemispheric anti-phasing of monsoon intensity change as suggested by proxy data. [ABSTRACT FROM AUTHOR]

We retrospectively investigate the skill of climate models within the IPCC TAR, AR4, and AR5 for the near-surface (2 m) air temperature changes in China. Those models are found to be skillful in projecting the subsequent climatology and trend of the temperature changes in China during 2002–2018 from several to ten years ahead, with higher scores for the climatology than for the trend. Among various emission scenarios for all the three assessment reports, although the long-term projections at the end of the 21st century are remarkably diverse, the near-term temperature projections differ slightly. [Display omitted] Climate change has attracted significant attention due to its increasing impacts on various aspects of the world, and future climate projections are of vital importance for associated adaptation and mitigation, particularly at the regional scale. However, the skill level of the model projections over China in the past more than ten years remains unknown. In this study, we retrospectively investigate the skill of climate models within the Third (TAR), Fourth (AR4), and Fifth (AR5) Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC) for the near-term projections of near-surface (2 m) air temperature changes in China. Those models are revealed to be skillful in projecting the subsequent climatology and trend of the temperature changes in China during 2002–2018 from several to ten years ahead, with higher scores for the climatology than for the trend. The model projections display cold biases against observations in most of China, while the nationally averaged trend is overestimated by TAR models during 2002–2018 but underestimated by AR4 models during 2008–2018. For all emission scenarios, there is no obvious difference between the equal- and unequal-weighted averages based on the arithmetic averaging and reliability ensemble averaging method respectively, however the uncertainty range of projection is narrowed after weighting. The near-term temperature projections differ slightly among various emission scenarios for the climatology but are largely different for the trend. [ABSTRACT FROM AUTHOR]

Towards a better insight into orbital-scale changes in global monsoon, here we examine global monsoon area (GMA) and precipitation (GMP) as well as GMP intensity (GMPI) in the mid-Holocene, approximately 6,000 years ago, using all available numerical experiments from the Paleoclimate Modelling Intercomparison Project. Compared to the reference period, both the mid-Holocene GMA and GMP increased in the majority of the 35 models chosen for analysis according to their ability, averaging 5.5 and 4.2 %, respectively, which were mainly due to the increase in monsoon area and precipitation over the boreal land and austral ocean. The mid-Holocene GMPI decreased in most models and by an average of 1.2 %, mainly due to the decrease in monsoon precipitation intensity over the boreal ocean and austral land. The mid-Holocene GMA, GMP, and GMPI all showed opposite changes both between the land and ocean in the northern or southern hemisphere and between the boreal and austral land or ocean. Orbital-induced changes in large-scale meridional temperature gradient and land-sea thermal contrast are the underlying mechanisms, and the presence of an interactive ocean has an amplifying effect in the boreal land monsoon areas overall. Qualitatively, the model-data comparison indicates agreement in the boreal land monsoon areas and South America but disagreement in southern Africa and northern Australia. [ABSTRACT FROM AUTHOR]

Abstract: Many efforts have been made to reconstruct the moisture conditions over China during the mid-Holocene, approximately 6000 calendar years ago. However, most of them have been performed at the single site level or local scale, and the nationwide distribution of the mid-Holocene precipitation and net precipitation (precipitation minus evaporation) changes from both proxy data and simulations remains unclear. Here we first selected 36 out of 51 climate models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) for their demonstrable ability to simulate the baseline climate and for the availability of evaporation data. Our analysis of the ensemble mean results of the 36 models shows that the mid-Holocene annual precipitation, evaporation, and net precipitation were 3.0%, 0.9%, and 6.9% more than the baseline period, respectively, and seasonally all three variables decreased in boreal winter and spring but increased in boreal summer and autumn on the national scale. For that period, both the pattern and magnitude of the above changes differed between the models and the sub-regions, and the interactive ocean effect had little impact overall on the country. Compared with the wetter-than-present climates derived from the records at 64 out of 69 sites across China, the models agreed qualitatively with the multi-proxy data in most parts of China, except Xinjiang and the areas between the middle and lower reaches of the Yangtze and Yellow River valleys, where drier-than-baseline climates were obtained from the 36 models. [Copyright &y& Elsevier]

It has been well documented that vegetation plays an important role in the climate system. However, vegetation is typically kept constant when climate models are used to project anthropogenic climate change under a range of emission scenarios in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios. Here, an atmospheric general circulation model, and an asynchronously coupled system of an atmospheric and an equilibrium terrestrial biosphere model are forced by monthly sea surface temperature and sea ice extent for the periods 2051-2060 and 2090-2098 as projected with 17 atmosphere-ocean general circulation models participating in the IPCC Fourth Assessment Report, and by appropriate atmospheric carbon dioxide concentrations under the A2 emission scenario. The effects of vegetation feedback under future global warming are then investigated. It is found that the simulated composition and distribution of vegetation during 2051-2060 (2090-2098) differ greatly from the present, and global vegetation tends to become denser as expressed by a 21% (36%) increase in global mean leaf area index, which is most pronounced at the middle and high northern latitudes. Vegetation feedback has little effect on globally averaged surface temperature. On a regional scale, however, it induces statistically significant changes in surface temperature, in particular over most parts of continental Eurasia east of about 60°E where annual surface temperature is expected to increase by 0.1-1.0 K, with an average of about 0.4 K for each future period. These changes can mostly be explained by changes in surface albedo resulting from vegetation changes in the context of future global warming. [ABSTRACT FROM AUTHOR]

By analysing a 113–year (1900–2012) observational dataset, it is shown that the interdecadal fluctuation of the summer precipitation over Northeast Asia differs from that in central East Asia during the 20th century, and has experienced three interdecadal shifts in the 1920s, mid‐1960s and late 1990s. That fluctuation coincides well with the multidecadal fluctuation of the sea surface temperature in the North Atlantic, known as the Atlantic Multidecadal Oscillation (AMO). The AMO affects Northeast Asia via a circumglobal teleconnection pattern extending from the North Atlantic to North America. Corresponding with the positive phase of this teleconnection pattern, a tripolar pattern emerges in the Asian–North Pacific sector, with anomalous low pressure over Northeast Asia and high pressure over Lake Baikal and the mid‐latitude western North Pacific. These results suggest that the positive phase of the AMO favours the occurrence of cold vortex over Northeast Asia and anomalous highs over Lake Baikal and the mid‐latitude western North Pacific in summer, which enhances the East Asian summer monsoon and southward intrusion of high‐latitude cold air, and eventually increases the summer precipitation in Northeast Asia. Furthermore, initialized decadal prediction simulations using the CCSM4 model reproduce well the observed variations of the AMO and its associated atmospheric teleconnection but with slightly shifted geographic locations. The simulated anomalous Northeast Asia cold vortex and strong East Asian summer monsoon, lead to above‐normal summer precipitation over Northeast Asia. The modelling results confirm that the multidecadal variability in the North Atlantic can cause the observed interdecadal variations of Northeast Asia summer precipitation. Our results suggest that to understand and predict interdecadal climate change over Northeast Asia, it is important to consider the key role of the AMO. [ABSTRACT FROM AUTHOR]