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Compound wind and precipitation extremes (CWPEs) pose significant threats to natural resources and the socio‐economic security. This study investigates the projected changes and driving factors of CWPEs over Southeast Asia (SEA) based on Coupled Model Intercomparison Project Phase 6 outputs. Results show that the frequency of CWPEs during 2070–2099 is projected to increase by 56.6% (62.2%) under the SSP2‐4.5 (SSP5‐8.5) scenario, while intensity is expected to increase by 11.9% (25.5%). These changes are primarily driven by variations in precipitation, which account for 54.9%–85.7% of the total contribution under the two scenarios mentioned. We further revealed that the probability of high‐frequency (high‐risk) CWPEs will increase by a factor of 2.3 (1.6), with 56.2% (37.3%) of the risk increase is attributable to anthropogenic activities. These findings emphasize the high sensitivity of CWPEs to climate change over SEA, and underscores the importance in informing adaptation strategies for vulnerable regions.

Guided by the target of the Paris Agreement of 2015, it is fundamental to identify regional climate responses to global warming of different magnitudes for Southeast Asia (SEA), a tropical region where human society is particularly vulnerable to climate change. Projected changes in indices characterizing precipitation extremes of the 1.5 °C and 2 °C global warming levels (GWLs) exceeding pre-industrial conditions are analyzed, comparing the reference period (1976-2005) with an ensemble of CORDEX simulations. The results show that projected changes in precipitation extreme indices are significantly amplified over the Indochina Peninsula and the Maritime Continent at both GWLs. The increases of precipitation extremes are essentially affected by enhanced convective precipitation. The number of wet and extremely wet days is increasing more abruptly than both the total and daily average precipitation of all wet days, emphasizing the critical risks linked with extreme precipitation. Additionally, significant changes can also be observed between the GWLs of 1.5 °C and 2 °C, especially over the Maritime Continent, suggesting the high sensitivity of precipitation extremes to the additional 0.5 °C GWL increase. The present study reveals the potential influence of both 1.5 °C and 2 °C GWLs on regional precipitation over SEA, highlights the importance of restricting mean global warming to 1.5 °C above pre-industrial conditions and provides essential information on manageable climate adaptation and mitigation strategies for the developing countries in SEA.

Freezing/thawing indices are important indicators of the dynamics of frozen ground on the Qinghai-Tibet Plateau (QTP), especially in areas with limited observations. Based on the numerical outputs of Community Land Surface Model version 4.5 (CLM4.5) from 1961 to 2010, this study compared the spatial and temporal variations between air freezing/thawing indices (2 m above the ground) and ground surface freezing/thawing indices in permafrost and seasonally frozen ground (SFG) across the QTP after presenting changes in frozen ground distribution in each decade in the context of warming and wetting. The results indicate that an area of 0.60 × 106 km2 of permafrost in the QTP degraded to SFG in the 1960s–2000s, and the primary shrinkage period occurred in the 2000s. The air freezing index (AFI) and ground freezing index (GFI) decreased dramatically at rates of 71.00 °C·d/decade and 34.33 °C·d/decade from 1961 to 2010, respectively. In contrast, the air thawing index (ATI) and ground thawing index (GTI) increased strikingly, with values of 48.13 °C·d/decade and 40.37 °C·d/decade in the past five decades, respectively. Permafrost showed more pronounced changes in freezing/thawing indices since the 1990s compared to SFG. The changes in thermal regimes in frozen ground showed close relations to air warming until the late 1990s, especially in 1998, when the QTP underwent the most progressive warming. However, a sharp increase in the annual precipitation from 1998 began to play a more controlling role in thermal degradation in frozen ground than the air warming in the 2000s. Meanwhile, the following vegetation expansion hiatus further promotes the thermal instability of frozen ground in this highly wet period.

The representation of tropical precipitation is evaluated across three generations of models participating in phases 3, 5, and 6 of the Coupled Model Intercomparison Project (CMIP). Compared to state-of-the-art observations, improvements in tropical precipitation in the CMIP6 models are identified for some metrics, but we find no general improvement in tropical precipitation on different temporal and spatial scales. Our results indicate overall little changes across the CMIP phases for the summer monsoons, the double-ITCZ bias, and the diurnal cycle of tropical precipitation. We find a reduced amount of drizzle events in CMIP6, but tropical precipitation occurs still too frequently. Continuous improvements across the CMIP phases are identified for the number of consecutive dry days, for the representation of modes of variability, namely, the Madden–Julian oscillation and El Niño–Southern Oscillation, and for the trends in dry months in the twentieth century. The observed positive trend in extreme wet months is, however, not captured by any of the CMIP phases, which simulate negative trends for extremely wet months in the twentieth century. The regional biases are larger than a climate change signal one hopes to use the models to identify. Given the pace of climate change as compared to the pace of model improvements to simulate tropical precipitation, we question the past strategy of the development of the present class of global climate models as the mainstay of the scientific response to climate change. We suggest the exploration of alternative approaches such as high-resolution storm-resolving models that can offer better prospects to inform us about how tropical precipitation might change with anthropogenic warming.

Southeast Asia (SEA) is experiencing rapid warming, leading to more extreme heatwaves. Sustained compound heatwaves, with high temperatures during day and at night, pose profound threats in highly vulnerable regions, resulting in great stress on society. We estimated the changes in the compound heatwave characteristics and population exposure over SEA at the end of the 21st century based on the model outputs from the Coupled Model Intercomparison Project Phase 6. Results show that the projected compound heatwaves have significant intensified over SEA linked to increasing greenhouse gas emissions. Contemporary younger generations will face more potential risks than their parents' generation. A child born in the 2010s will experience 1,000 discrete heatwaves in their lifetime, a threefold increase compared with the 1980s. Climate change and population growth combine to drive increased population exposure. The climate effect accounts for 125% in the 0–24‐year‐old cohort, whereas the interaction effect accounts for 85% in the 75+ age group. The relative importance of effects evolves dynamically across age groups, gradually shifting from a predominance of climate effects to a synergy of the climate and population effects. Significant regional inequalities exist in the increased population exposure over SEA. The largest increase occurs in Indonesia, where the aggregate exposure ranges from 45 billion person‐days under the SSP1‐2.6 scenario to 81 and 108 billion person‐days, respectively, in the higher SSP2‐4.5 and SSP5‐8.5 scenarios. The study emphasizes the need for the SEA countries to focus on heat‐stress adaptation strategies, while also working toward fulfilling emission reduction commitments. Plain Language Summary Heatwaves pose significant risks to public health, the economy and the ecological environment. The impacts of compound heatwaves, which combine blazing days with sultry nights, are greater than those of daytime‐ or night‐time‐only heatwaves. Focusing on six Southeast Asian countries at different levels of development, we estimated the number of heatwaves experienced by people spanning different generations over their lifetime, and decomposed the future changes in the population exposure of different age groups. Our results show that the 2010‐generation will experience three times as many compound heatwaves as those born in 1980, which is not only an order of magnitude increase but it will become more extreme when extending the time span. For high‐ to middle‐income countries, such as Singapore and Thailand, the exposure of older people will increase significantly in the future as the population ages. The study highlights the imperativeness for urgent actions required to reduce the future effects of compound heatwaves in SEA. Key Points Compound heatwaves are projected to increase substantially by the end of the 21st century, and will no longer be rare events The intergenerational differences in exposure to compound heatwaves are gradually widening The principal effects responsible for the dramatic increase in population exposure to compound heatwaves vary by age

The interannual variability of precipitation during the summer monsoon transition over the Indochina Peninsula (ICP) is substantially influenced by the sea surface temperature anomalies (SSTAs) of the tropical ocean, showing a robust relationship between April and May (AM) precipitation and the El Niño/Southern Oscillation (ENSO) phenomenon. Dynamic composites and statistical analyses supported by model experiments indicate that the observed anomalous AM precipitation is associated with circulation anomalies over the Pacific and, in addition, affected by the response to the tropical SSTAs forcing from the Indian Ocean (IO): (i) Less (greater) than normal AM precipitation over the ICP occurs during the El Niño (La Niña) years, which is consistent with late (early) Bay of Bengal (BoB) summer monsoon onset. (ii) The dry (wet) AM precipitation years are associated with the anomalous western North Pacific (WNP) anti-cyclone (cyclone) induced by El Niño (La Niña) concurrent with the anti-cyclone (cyclone) over the BoB, suppressing (favoring) the meridional flow of warm and moist air from the Pacific and Indian ocean and thus cutting (providing) moisture supply for the ICP. (iii) The reduced tropical convective activity over Maritime Continent (MC) is related to the weakened local Hadley circulation concurrent with the weakened overturning Walker circulation, and favors a drier than normal AM precipitation over the ICP, to which the wetter years are opposite. These symmetric atmospheric circulation patterns characterizing dry and wet AM precipitation over the ICP are also reproduced by numerical experiments with an atmospheric general circulation model.

To control the growth of CO2 emissions and achieve the goal of carbon peaking, this study carried out a detailed spatio-temporal analysis of carbon emissions in major cities of China on a city-wide and seasonal scale, used carbon emissions as an indicator to explore the impact of COVID-19 on human activities, and thereby studied the urban resilience of different cities. Our research re-vealed that (i) the seasonal patterns of CO2 emissions in major cities of China could be divided into four types: Long High, Summer High, Winter High, and Fluctuations, which was highly related to the power and industrial sectors. (ii) The annual trends, which were strongly affected by the pan-demic, could be divided into four types: Little Impact, First Impact, Second Impact, and Both Impact. (iii) The recovery speed of CO2 emissions reflected urban resilience. Cities with higher levels of de-velopment had a stronger resistance to the pandemic, but a slower recovery speed. Studying the changes in CO2 emissions and their causes can help to make timely policy adjustments during the economic recovery period after the end of the pandemic, provide more references to urban resilience construction, and provide experience for future responses to large-scale emergencies.

Observational evidence has shown that Compound Wind and Precipitation Extremes (CWPEs) can cause substantial disruptions to natural and economic systems under climate change. This study conducts a historical assessment and future projection of CWPEs characteristics in the climate vulnerable region of Southeast Asia (SEA) based on two Shared Socioeconomic Pathways (SSPs) from Scenario Model Intercomparison Project (ScenarioMIP) in Coupled Model Intercomparison Project Phase 6 (CMIP6). Results reveal that the northern Philippines, the eastern and northwestern coastal areas of the Indochina Peninsula have experienced the most frequent, strongest CWPEs during the period of 1985–2014. SEA is projected to experience a frequency increase of 14.4% (22.5%) and intensity increase of 9.4% (19.5%) under the SSP2‐4.5 (SSP5‐8.5) scenario at the end of 21st century (2070–2099). Kalimantan appears to replace the Philippines as the most affected area, particularly under high emission scenario. In addition, the changes in CWPEs are primarily driven by the changes in precipitation, with the average contribution of precipitation changes across the whole region is 62.8% (70.4%) under the SSP2‐4.5 (SSP5‐8.5) scenario. For precipitation uncertainties, the contribution from model uncertainty decreases over time (from 73.9% to 42.7%), while scenario uncertainty increases (from 20.3% to 55.0%). In contrast, for wind projections, model uncertainty remains the dominant factor (from 81.3% to 87.6%) with little change. The present study reveals the high sensitivity of the CWPEs over SEA under global warming and highlighting the risks of future disaster impact in such vulnerable regions. The historical climatological total frequency (in percentage), mean intensity (unitless quantity) and statistical metrics for the characteristics of CWPEs. The statistical metrics are based on the participating CMIP6 ensemble members versus the APHRO observations and ERA5 reanalysis during 1985‐2014.

China’s rapid industrialization and urbanization have led to significant and imbalanced CO2 emissions, putting pressure on achieving sustainable development goals. This study analyzed the CO2 emissions of 31 major cities in China from different sectors (total, power, industry, and transport) from 2019 to 2022. This study constructs a city-scale CO2 emission correlation model to achieve nationwide and urban fine-scale research on CO2 emission spatial networks from different sectors. This study revealed the following: (i) there is an increasing correlation among regions in China, and collaborative governance is crucial; (ii) there are differences in the structure, characteristics, and roles of CO2 emission networks from different sectors; (iii) China’s CO2 emission network is mainly concentrated in the northern and eastern regions, which play an important role in emission reduction; and (iv) the impact factors have different effects on CO2 emissions from different sectors, and we should actively contribute to promoting emission reduction. Correctly understanding the spatial characteristics and influencing factors of CO2 emissions can help us formulate targeted and efficient emission reduction policies.

The Qaidam Basin is a sensitive climate transition zone revealing a wide spectrum of local climates and their variability. In order to obtain an objective and quantitative expression of local climate regions as well as avoid the challenge to pre-define the number of heterogeneous local climates, the ISODATA cluster method is employed to achieve the fine-grained climate divisions of the Qaidam Basin, which can heuristically alter the number of clusters based on the input of monthly temperature and precipitation data. The fine-grained climate classification extends the traditional Köppen climate classification and represents the complex climate transformation processes in terms of fine-grained climate clusters. The following results are observed: (i) The Qaidam Basin is divided into an arid desert basin area and the surrounding alpine mountainous areas. The climate distribution is affected by both the altitude and the dryness ratio, which, employing the Budyko framework, largely characterizes the local energy–water fluxes at the surface and the related vegetation regimes (biomes). The fine-grained climate classification successfully captures their causal relationships and represents them well by the local climates: the climatic spatial differentiation in the mountainous areas is highly consistent with the topography and reveals an elevation-dependent circular distribution from the edges to the center of the basin; the climate heterogeneity within the basin presents a west-to-east meridional distribution due to the combined effect of the mid-latitude westerlies and the Indian monsoon. (ii) The climate gradients are spatially different over the Qaidam Basin. The surrounding mountainous areas have a large climate gradient compared to the inner basin; the southern mountain edge is governed by a more severe climate change than the north-eastern one; and the climate gradient is larger in the eastern than in the western basin. (iii) The lake regions within the basin show an obvious lake effect and reveal a local lake climate. Spatially, a common structure emerges with a dryer-climate zone or watershed embedding a wetter lake-affected area, which appears to migrate eastward becoming stepwise wetter from the very dry center to the wet eastern boundary of the Qaidam basin. This provides a topographically induced insight of the wet climate expansion of initially arid climates and is crucial to improve the Qaidam Basin’s ecological environment. Finally, although this work mainly focuses on the local-scale climates and their variability in the Qaidam Basin, the data-driven cluster methodology for climate refinement is transferable to regional- even global-scale climate studies, which offers broad application prospects.