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 modeling framework under Shared Socioeconomic Pathways (SSP2-4.5), incorporating future changes in local and foreign anthropogenic emissions, meteorological conditions, and biogenic volatile organic compound (BVOC) emissions. From the 2020s to 2060s, daily maximum 8 h average (MDA8) O3 concentration is simulated to decline by 7.7 ppb in the warm season (April–September) and 1.1 ppb in the 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 Beijing–Tianjin–Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD) during the warm season, with reductions of 9.7, 14.8, and 12.5 ppb, respectively. Conversely, in the non-warm season, the MDA8 O3 in BTH and YRD will increase by 5.5 and 3.3 ppb, partly attributed to reduced NOx emissions and thereby a 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 the non-warm season and under the climate penalty.