City-level synergy and co-benefits of mitigating CO emissions and air pollution in China.

Synergistic control of carbon emissions and pollutant concentrations can efficiently tackle climate change and air pollution. The synergistic performance and co-benefits yielded by controlling these factors are urgent and critical issues in China. Accordingly, a comprehensive indicator for assessing synergistic performance is pioneered, and co-benefits of mitigating CO and PM in Chinese cities are evaluated. Chinese synergistic performance is dominated by CO variations. In 2015-2020, multiple northeastern, central, southern, and eastern cities exhibited synergistic effects by greatly reducing CO emissions. The synergistic performance thereafter leads to co-benefits through environmental and economic feedbacks. The CO and PM controls in Northeast Chinese cities feature the most profound co-benefits of approximate 4800 CNY per capita, with each contributing 72 % and 28 %, respectively, to this total. The findings provide intercity synergistic performance and scientific support for policymaking.