Increased Population Exposure to Heat and Wet Extremes Moving From Chinese to Global 1.5 or 2.0°C Warming

The Paris Agreement proposed two global warming levels relative to the preindustrial period, with the ideal objective of 1.5 degrees C warming and an upper boundary of 2.0 degrees C. However, the years when the temperature will first reach 1.5 or 2.0 degrees C vary in different regions. Therefore, climate extremes and their population exposure are still not clear at regional or global warming levels. This study investigated climate extremes in China at different Chinese and global warming with 16 CMIP6 models under the middle SSP245 scenario. In China, the year when 1.5 degrees C warming is projected to occur is 2020 and 2035 for 2.0 degrees C warming. These values are more than 10 years earlier than the corresponding global warming levels of 2030 and 2049. Population exposure to percentile-based heat extremes at global 1.5 degrees C warming is projected to greatly increase relative to those when 1.5 degrees C warming occurs in China due to increases in climate extremes, and exposure to absolute heat extreme indices is projected to decrease from Chinese to global 2.0 degrees C warming under the joint impacts of increases in extremes and population decreases. Furthermore, from Chinese to global 1.5 degrees C warming, about 344 million people will experience increased exposure to heat, wet and dry extremes, and around 468 and 371 million people will be affected by increased exposure to heat-wet and heat-dry extremes, respectively. Thus, a more adaptive strategy should be proposed to cope with the future possible natural hazards caused by heat-wet and heat-dry extremes.