Under the background of global warming, significant changes have occurred in the regional climate and extreme events in China. A deep understanding of the changing patterns and driving mechanisms of regional climate and extreme events is of great scientific significance for climate change adaptation and disaster risk management. This study reviewed and summarized the latest scientific advancements, and compared the consistency and differences in climate change responses between eastern and western China. It is indicated that since 1961, temperature and precipitation in China have shown an overall increasing trend, with precipitation changes displaying distinct regional characteristics. A notable feature of climate change in western China is "warming-wetting", mainly in Northwest China and the northern Qingzang plateau, while some areas in Southwest China exhibit aridification characteristics of "warming-drying". In eastern China, precipitation has maintained a "southern flood-northern drought" pattern. However, since 2010, this pattern has gradually changed due to a significant increase in precipitation in Northeast and North China. With climate warming, the frequency and intensity of extreme high temperatures, heavy rainfall, and drought events have significantly increased. Human activity, primarily related to greenhouse gas emissions, is the main driving factor behind observed increases in average temperatures and extreme temperatures. Noticeably, internal variability of the climate system has also contributed to changes in regional precipitation. Finally, this study outlines key scientific issues and challenges for future research of climate change in China.

Research on climate change projections aims to provide decision-makers with more reliable and less uncertain information about future climate change. This paper reviews the major progress made in China over the past decade regarding climate change projections, and discusses future perspectives in this field. Climate model projections indicate that both regional average temperatures and precipitation in China will increase, with the largest increases occurring under the scenarios of the highest emissions. In the future, extreme cold events in China are expected to decrease, while extreme heat events will become more frequent; extreme precipitation will continue to rise significantly in intensity and frequency; and compound extreme events will also see a notable increase, in particular the rarest extreme events, which will rise more significantly. Statistical bias-calibration, model weighting, constraint based on detection and attribution, and emergent constraint have been widely applied in regional climate change projections in China. Overall, constrained projections do not alter the qualitative conclusions of the raw model projections, but adjust the magnitude of the projected change. The observational constraint methods have demonstrated the ability to reduce uncertainty in projections across different regions and variables in China. To further advance the regional climate change projection research in China, it is essential to deepen understanding of the climate system and its feedback processes, improve the quality of observational data and the performance of climate model simulations, and enhance the application of emerging technologies such as machine learning.

Research on climate change projections aims to provide decision-makers with more reliable and less uncertain information about future climate change. This paper reviews the major progress made in China over the past decade regarding climate change projections, and discusses future perspectives in this field. Climate model projections indicate that both regional average temperatures and precipitation in China will increase, with the largest increases occurring under the scenarios of the highest emissions. In the future, extreme cold events in China are expected to decrease, while extreme heat events will become more frequent; extreme precipitation will continue to rise significantly in intensity and frequency; and compound extreme events will also see a notable increase, in particular the rarest extreme events, which will rise more significantly. Statistical bias-calibration, model weighting, constraint based on detection and attribution, and emergent constraint have been widely applied in regional climate change projections in China. Overall, constrained projections do not alter the qualitative conclusions of the raw model projections, but adjust the magnitude of the projected change. The observational constraint methods have demonstrated the ability to reduce uncertainty in projections across different regions and variables in China. To further advance the regional climate change projection research in China, it is essential to deepen understanding of the climate system and its feedback processes, improve the quality of observational data and the performance of climate model simulations, and enhance the application of emerging technologies such as machine learning.

This paper reviews the definition and type of droughts, as well as their driving factors, historical changes, attributions and projections based on the Working Group I (WGI) contribution to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) on the physical science basis of climate change. The IPCC AR6 new results show that: (1) The changes in meteorological and agricultural droughts are not significant on a global scale, but display an increasing trend in some regions. The increasing trend shows that anthropogenic climate change plays an important role in exacerbating droughts. For meteorological droughts, the understanding of the influence of human activities is of low confidence. (2) Agricultural and ecological droughts in most regions can be attributed to human activities (medium to high confidence); for hydrological droughts, in addition to human-induced climate change, regional water resources management and land use are also important factors (medium confidence). (3) In the future projections, more regions around the world will experience more severe and frequent drought events in the future. Agricultural and ecological droughts will also become more frequent and intense as the temperature rises. (4) In the analysis of assessment of changes in different types of droughts, the key variable of atmospheric evaporation demand (AED) is emphasized. Changes in AED are not only a direct response to climate warming, but also a driving factor for drought changes, affecting the physiological processes of vegetation. Meanwhile, changes in AED also feedback to evapotranspiration. The interactions between different types of droughts will become more complicated under the background of intensifying climate change. In the future, the research and operational service of droughts in China should deepen our understanding of connections between changes of different types of droughts, strengthen multi-disciplinary cooperation and explore feedback loops between drought changes, local human activities and ecological processes based on multiple datasets and various evidences.

Based on gridded daily in-situ precipitation observations and ERA5 reanalysis data spanning from 1961 to 2021, this study employs an unsupervised deep learning method known as the Self-Organizing Map (SOM) to objectively classify large-scale circulation patterns associated with summer persistent heavy rainfall processes in the Yangtze river basin. Four typical circulation types (P1—P4) are identified, representing distinct configurations of key circulation systems that are closely linked to the formation and distribution of anomalous precipitation. P1 and P3 represent typical single and double blocking circulation patterns at the high latitudes, respectively. In these patterns, the Western Pacific Subtropical High (WPSH) significantly intensifies and westward extends. In contrast, P2 and P4 showcase more prominent features of deepened low-pressure systems in the mid-to-high latitudes. In P2, a broad low trough extends from the lake Balkhash to the west of the lake Baikal, with a ridge to the east of the lake Baikal, forming a typical stable circulation pattern in the Meiyu season. The Yangtze region is under the influence of the low-pressure system, while the WPSH is positioned to the south. P4 shows low and high geopotential height anomalies in the west and east of the lake Balkhash, respectively, along with a cyclonic anomaly in the Yangtze region. The WPSH exhibits a noticeable northward shift in P4. P1 and P2 are supported by cold air from high latitudes, while the cold air support for P3 and P4 are weaker. Additionally, the northward advancement of the East Asian summer monsoon characterized by northward jumps of the WPSH is closely linked to the occurrence of the four circulation types and the position of rain belt. P1 and P2 mainly correspond to persistent heavy precipitation from June to early July, while P3 and P4 mainly correspond to persistent heavy precipitation from early July to August. P1 and P2 result in heavy precipitation to the south of the middle and lower reaches of the Yangtze, whereas the heaviest precipitation centers associated with P2 and P4 respectively lie in the Yangtze river and to the north of the Yangtze. Precipitation intensity corresponding to P1 and P3 also strengthens as the water vapor transport enhances. The stability of these typical circulation patterns is further analyzed. During persistent heavy rainfall processes, persistence is observed on 93.2% of all the corresponding circulation patterns. P1 and P2 typically persist for around 5 days, while P3 and P4 tend to last for approximately 3 days. The long-term trend indicates an increasing frequency of P1 and P3 occurrences, while P2 and P4 are gradually diminishing. This suggests an inclination of persistent heavy rainfall processes in the southern and middle-lower Yangtze river regions from a favorable circulation perspective. In summary, this study reveals several meaningful results, which provide a scientific guidance for clarifying the characteristics and trends of typical circulation patterns corresponding to persistent heavy rainfall.

Under the background of global warming, significant changes have occurred in the regional climate and extreme events in China. A deep understanding of the changing patterns and driving mechanisms of regional climate and extreme events is of great scientific significance for climate change adaptation and disaster risk management. This study reviewed and summarized the latest scientific advancements, and compared the consistency and differences in climate change responses between eastern and western China. It is indicated that since 1961, temperature and precipitation in China have shown an overall increasing trend, with precipitation changes displaying distinct regional characteristics. A notable feature of climate change in western China is “warming–wetting,” mainly in Northwest China and the northern Qinghai–Xizang Plateau, while some areas in Southwest China exhibit aridification characteristics of “warming–drying.” In eastern China, precipitation has maintained a “southern flood–northern drought” pattern. However, since 2010, this pattern has gradually changed due to a significant increase in precipitation in Northeast and North China. With climate warming, the frequency and intensity of extreme high temperatures, heavy rainfall, and drought events have significantly increased. Human activity, primarily related to greenhouse gas emissions, is the main driving factor behind observed increases in average temperatures and extreme temperatures. Noticeably, inter-nal variability of the climate system has also contributed to changes in regional precipitation. Finally, this study outlines key scientific issues and challenges for future research of climate change in China.

Precise drought monitoring is necessary for refined assessment of drought disasters. Usually, the meteorological drought composite index (MCI) is calculated based on long time series data over 30 years so as to fit stable probability distribution of precipitation. In order to fully utilize short-term high-density station data that are usually less than 20 years for drought monitoring, a parameter method is introduced in this study. The parameter method is to calculate the parameters of the probability distribution function of precipitation using data from neighboring long-term stations, and then interpolate them to that of short-term stations, so that MCI of short-term stations can be calculated. In this study, 31 national stations in 9 provinces/regions were selected for cross-checking and analysis of the errors of MCI calculated from the parameter method, as well as the interpolation method and the replacement method. The results show that except in the areas of Northwest China where meteorological stations are comparatively sparse, the MCI calculated by the parameter method is significantly better than that from the other two methods. Compared with the interpolation method, the accuracy of MCI calculated by the parameter method is improved in the central and eastern China, with improved accuracy by over 20% in most parts of North China, Northeast China, Yangtze River basin, Southwest China, and South China. The magnitude of error caused by the parameter method is close to or smaller than that caused by climate change, representing a good stability of the method. During the serious drought in the Yangtze River basin in 2022, comparison of the MCI results from 86 long-term stations and 2688 short-term high-density stations in Jiangxi Province shows that the parameter method used for calculating MCI of short-term stations can create high-resolution map for drought monitoring and provide refined services for drought disaster reduction.

Relatively little is known about the impact of global warming on the tropical cyclone (TC) outflow, despite its large contribution to TC intensity. In this study, based on the International Best Track Archive for Climate Stewardship (IBTrACS) dataset and ERA5 reanalysis data, we show that the TC outflow height has risen significantly (48.20 ± 22.18 m decades⁻¹) in the past decades (1959–2021) over the western North Pacific, and the rising trend tends to be sharper for stronger TCs (the uptrend of severe typhoon is 61.09 ± 40.92 m decades⁻¹). This rising trend of the outflow height explains the contradiction between the decrease trend of the TC outflow temperature and the increase trend of the atmospheric troposphere temperature. Moreover, possible contribution of the TC outflow height uptrend to TC intensity has also been investigated. The results show that the rise of outflow height leads to the decrease of outflow temperature, and thus an increased difference between underlying sea surface temperature (SST) and TC outflow temperature, which eventually favors the increase of TC intensity.