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Understanding future variations and trends of heatwave events has critical implications for the ecosystem and human health. However, the diverse metrics of heatwave affect the comparable assessment of heatwave evolution at regional scales. The inadequate consideration of the enhanced warming trend and local antecedent heat conditions at different climate zones undermines the comprehensive understanding of future heatwave changes. Here, we systematically assess variations and trends in duration, frequency, and intensity of heatwave events in China from 1961 to 2100, using historical observations and climate model simulations from Coupled Model Intercomparison Project Phase 6. The increased rates and trends in the duration and frequency are more evident than those in intensity and severe heatwave days. Regionally, the northern and western regions are projected to suffer longer and more frequent consecutive heatwaves, while southern regions are likely at greater risk of severe heatwave days. A comparison among four scenarios shows that the future heatwave characteristics projected by the high forcing Shared Socioeconomic Pathway (SSP5‐8.5) exhibit substantial intensification than those in other three experiments, imposing intractable dangers to numerous organisms and ecosystems. Under the SSP1‐2.6, the acceleration of all heatwave characteristics is projected to slow down in all regions after 2040. In addition to maximum temperature, temperature advections are projected to contribute to heatwave intensification in western regions. Our results provide a comprehensive assessment of future variations and trends in heatwave events. The comparable future changes across unevenly developed regions are necessary for improving regional adaptive capacity to extreme heat risk. Plain Language Summary: In the past century, China has experienced a clear warming trend. More frequent heatwaves affect crops, vegetations, and water consumption, leading to detrimental impacts on food security and water resource sustainability. Meanwhile, with the rapid development of urbanization and increasing population aging, the high‐temperature vulnerability in China experienced explosive increases. We use historical observations and climate model simulations to quantify the duration, frequency, intensity, and severe heatwave days at regional scales from 1961 to 2100, with consideration of different local antecedent heat conditions at a given station. All regions are projected to experience longer and more frequent heatwaves rather than more intense consecutive heatwaves, while the southern regions will suffer more severe heatwave days compared to those during the historical period. The increased rates of heatwave characteristics are different under a set of future pathways of societal development. The intensification of all heatwave characteristics will be mitigated if the warming is limited below 2°C. Key Points: The increased rates and trends in duration and frequency are more evident than those in intensityThe southern coastal area is projected to suffer more severe heatwave days than other regionsThe acceleration of all heatwave characteristics is projected to slow down in the Shared Socioeconomic Pathway (SSP1‐2.6) scenario after 2040 [ABSTRACT FROM AUTHOR]

Reference evapotranspiration (ET0), which is an indicator of atmospheric evaporation demand over a hypothetical reference surface, is expected to alter along with global climate change. In this study, the changes and driving forces of historical ET0 and its future projections in Xinjiang, China, were comprehensively conducted. The trend analysis revealed that regional ET0 decreased significantly at a rate of −4.1 mm/year2 during 1961–1993 and increased at a rate of 3.4 mm/year2 during 1994–2010. To explore the possible causes, the contributions of major climatic variables to the ET0 trends were derived based on the differential equation method. During 1961–1993, the decreasing trend of ET0 was primarily ascribed to the wind speed. The integrated negative effect from the decrease in wind speed (U) and increase in relative humidity (RH) was more significant than the positive effect from the increase in air temperature (T), resulting in the decrease in ET0. During 1994–2010, combined with increasing T and decreasing RH, the increase in U offset the effect of the net radiation (Rn) decrease and led to an increase in ET0. Future ET0 projections over three periods (2010–2039, 2040–2069, and 2070–2099, which are named as 2020s, 2050s, and 2080s, respectively) were conducted based on the general circulation models under two representative concentration pathways scenarios (RCP4.5 and RCP8.5). A continuous increasing trend in ET0 was demonstrated in the 21st century. The increase in ET0 will increase the irrigated water resource consumption and bring new challenge to water resource management in this area. [ABSTRACT FROM AUTHOR]