Effects of East Asian Anthropogenic Aerosol Emissions Reduction on Summer Extreme Heat Events in Eastern China

Abstract

Since 2013, China has implemented a series of clean air policies to alleviate their air pollution issues. These policies led to a marked reduction of anthropogenic aerosol (AA) emissions in East Asia, making it the most significant emission reduction region in the world. Coincidentally, the frequency and intensity of summer extreme heat events (EHEs) in Eastern China have increased significantly since 2013. The linkage between AA emissions reduction and the increase in EHEs remains unclear. In this study, we investigate the relationship between AA emissions abatement in East Asia and the increase in EHEs in Eastern China from the perspective of atmospheric circulation anomalies based on historical AA single‐forcing simulations from Coupled Model Intercomparison Project Phase 6. The results indicate that the localized AA emissions reduction causes an increase in the shortwave radiation, which warms both the surface and the troposphere in East Asia, leading to a northward shift of the East Asian westerly jet through thermal wind balance and eddy feedbacks. The changes of jet further intensify the sinking motion in Eastern China by triggering anomalous meridional circulation and by guiding the northwestward extension of the Western Pacific subtropical high, which provide favorable conditions for the summer EHEs in Eastern China. The success in reducing regional AA emissions, coupled with the effects of increasing greenhouse gases emissions, could result in additional net warming, which would further exacerbate the challenge for global climate mitigation efforts in the near future.