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Understanding the link between future changes in East Asian summer monsoon (EASM) and global warming levels is of great importance for regional climate change adaptation and mitigation in East Asia. Here, we analyze the projected changes in EASM circulation and precipitation under different warming levels from 1.5 to 5°C above the preindustrial global mean temperature, using large-ensemble simulations conducted with Canadian Earth System Model version 2. We find that the model projects enhanced monsoon circulation and precipitation with global warming. The 850-hPa meridional winds, precipitation, and 500-hPa vertical ascending motion will be enhanced nonlinearly, while the total column precipitable water will increase quasi-linearly. The increase in precipitable water in the wet EASM region is only slightly greater than global average but the increase in precipitation is much greater than global one, with enhanced 500-hPa vertical ascending motion contrary to global mean. The increased low-level land-sea thermal contrast leads to the enhanced EASM meridional circulation and thus bring a large amount of moisture into Eastern China, providing favorable conditions for additional increase in precipitation. A simplified moisture budget analysis shows that the dynamic component related to strengthening monsoon circulation plays dominant role in the increase in EASM precipitation when the global temperature increases by more than approximately 2°C, while the thermodynamic component caused by increased water vapor is important when the warming is smaller. Plain Language Summary Changes in East Asian summer monsoon (EASM) circulation andprecipitation have great impacts on human society, agriculture and energy in East Asia. Previous studies rarely investigated EASM circulation and precipitation changes under specific global mean temperature increases, such as 1.5 to 5°C of warming. Here, we focus on EASM circulation and precipitation changes linked with different global warming levels. Four EASM metrics (850-hPa meridional wind, precipitation, precipitable water, and 500-hPa vertical velocity) are examined to reflect EASM system changes based on Canadian Earth System Model version 2 large-ensemble runs. We find that EASM low-level meridional wind, precipitation, and midlevel vertical ascending motion will be enhanced nonlinearly with warming, while precipitable water will increase quasi-linearly with warming. The increase in EASM precipitation is greater than global average, accompanied by increasing vertical ascending motion and strengthened southerly winds. When global mean near-surface air temperature increases by more than 2°C, the dynamic component plays dominant role in the increased EASM precipitation, while the thermodynamic factor plays a secondary role. These results provide useful information for developing strategies for climate change policy in East Asia.

 Global warming is associated with substantial increases in heatwave frequency, duration, and amplitude over Southeast Asia. The increase of heatwave amplitude with global mean temperature is quasilinear, and that of heatwave frequency and duration are nonlinear. A warmer future will see a higher risk ratio with rarer extreme heatwave events relative to the current climate.

Increases in the frequency and intensity of heat waves have serious impacts on human health, agriculture, energy and infrastructure. Here we use three simple metrics including the number of heat wave days, the length of heat wave season, and the annual hottest day temperature to characterize future changes in heat wave severity in China, based on large ensemble simulations conducted with the Canadian Earth System Model Version 2 (CanESM2) in the context of emergency preparedness. A heat wave day is defined as a day with daily maximum temperature reaching heat alert level (35°C). We find that global warming is associated with more severe heat waves including more heat wave days, longer heat wave season and higher hottest day temperature, and expansion of regions impacted by heat waves. While the increase in the magnitude of extremes in heat wave metrics with global warming level is close to linear, the increase in the frequency of extremes is much faster. For example, the historically hottest summer in 2013 in Eastern China, which occurs about one in 5 years in the 2013 climate, is projected to become more frequent than one in 2 years under 1.5°C global warming and almost every year would be worse than 2013 under 2°C warming. Additionally, the increase in the frequency of the extreme events is larger for rarer extremes. The frequencies for once-in-5-year, once-in-10-year, and once-in-50-year events increase by 2.5, 3.5, and 5.5 times under 1.5°C global warming, respectively.Plain Language Summary Heat waves have serious impacts on human health, agriculture, energy, and infrastructure. Though a few studies have investigated the future changes in heat waves in China, the heat waves defined in those studies are seldom of direct relevance to emergency preparedness. Here we study changes in heat wave days that are defined as daily maximum temperature above 35°C, a threshold for issuing a heat alert according to China's national Standards. We examine three simple metrics including the annual number of heat wave days, the length of heat wave season, and the annual hottest day temperature based on large ensemble simulations of CanESM2. We find that global warming is associated with more severe heat waves including more heat wave days, longer heat wave season, higher hottest day temperature, and expansion of regions impacted by heat waves. The increase in the heat wave metrics with global warming level is close to linear, while the increase in the frequency of extremes in these metrics is much faster. For example, the once-in-5-year event in the current climate, with a magnitude of the historically hottest summer in 2013 in Eastern China, is projected to become more frequent, to become a once-in-2-year event under 1.5°C global warming and every year event under 2°C global warming.