Contrasting Domestic and Global Impacts of Emission Reductions in China on Tropospheric Ozone

Abstract

Sustained near-surface ozone pollution despite stringent emission controls in China has drawn wide attention. However, how such rapid regional emission reductions affect global tropospheric ozone remains unexplored. Here, using an ensemble of measurements and global model simulations, we find Chinese emission reductions during 2013–2020 have increased domestic surface ozone; particularly in North China, they have decreased the global tropospheric ozone burden by 2.7 Tg (54% of China's anthropogenic contribution and 7% of global anthropogenic contribution in 2019) and ozone radiative forcing by 8.8 mW m⁻² (64% of China's anthropogenic contribution and 9% of global anthropogenic contribution in 2019). Nitrogen oxides (NO_x) associated nonlinear chemistry and height-dependent atmospheric transport patterns primarily cause the contrasting impacts. Future Chinese NO_x emission controls would continue to decrease global tropospheric ozone, while regional surface ozone may still increase unless NO_x reductions exceed ∼53% of the 2019 level. Our results reveal the substantial benefit of regional emission reductions in China on global tropospheric ozone mitigation.