How will China's surface ozone evolve under carbon neutrality target and global climate warming?

Abstract

Surface ozone (O3) has complex relationships with its precursors and is also highly sensitive to meteorological variation and climate change. In China, ground-level ozone pollution remains a persistent air quality concern despite decreasing concentrations of other air pollutants in recent years. China's commitment to achieving carbon neutrality by 2060 is expected to result in unprecedented reductions in air pollutant emissions in the future. This study investigates the combined impacts of anthropogenic emission reductions and future climate change on the evolution of summertime surface O3 under China's carbon neutrality target and the ambitious global 2°C warming scenario. Model simulations reveal an approximately 43% decline (range 31%–49%) in summertime daily maximum 8-hr average (MDA8) O3 in China's six heavily polluted key regions from 2020 to 2060. However, risk of rebound is also projected in some near years due to weather-driven accelerated O3 production rate, enhanced biogenic volatile organic compound (VOC) emissions and atmospheric stagnation, partially offsetting emission reduction benefits. The substantial aerosol reductions (by over 80%) would also enhance MDA8 O3 (up to 10 ppb) from 2020 to 2060 primarily via heterogeneous reactions on aerosols. The high O3-temperature sensitivity poses challenges to O3 mitigation in the short term, with frequent heatwaves or droughts dampening the outcomes of ongoing anthropogenic emission control. In the long term, O3-temperature sensitivity would be reduced by nearly half thanks to continuous anthropogenic emission control, thereby gradually increasing O3 climatic resilience. Quicker and stronger emission control, especially for the anthropogenic VOCs, would significantly mitigate short-term rebound risks.