Investigating the response of China’s surface ozone concentration to the future changes of multiple factors

Abstract. Climate change and associated human response are supposed to greatly alter surface ozone (O₃), an air pollutant generated through photochemical reactions involving both anthropogenic and biogenic precursors. However, a comprehensive evaluation of China’s O₃ response to these multiple changes has been lacking. We present a modelling framework under Shared Socioeconomic Pathways (SSP2-45), incorporating future changes in local and foreign anthropogenic emissions, meteorological conditions, and BVOCs emissions. From the 2020s to 2060s, daily maximum 8-hour average (MDA8) O₃ concentration is simulated to decline by 7.7 ppb in the warm season (April–September) and 1.1 ppb in non-warm season (October–March) over the country, with a substantial reduction in exceedances of national O₃ standards. Notably, O₃ decreases are more pronounced in developed regions such as BTH, YRD, and PRD during warm season, with reductions of 9.7, 14.8, and 12.5 ppb, respectively. Conversely, in non-warm season, the MDA8 O₃ in BTH and YRD will increase by 5.4 and 3.4 ppb, partly attributed to reduced NO_x emissions and thereby weakened titration effect. O₃ pollution will thus expand into the non-warm season in the future. Sensitivity analyses reveal that local emission change will predominantly influence future O₃ distribution and magnitude, with contributions from other factors within ±25 %. Furthermore, the joint impact of multiple factors on O₃ reduction will be larger than the sum of individual factors, due to changes in the O₃ formation regime. This study highlights the necessity of region-specific emission control strategies to mitigate potential O₃ increases during non-warm season and under climate penalty.