Reply on RC1

Abstract

Regional transport is as much important as local sources that contributing to PM2.5 pollution and causing associated environmental inequality. In the context of future climate change, the effect of the responses of regional transport to the warming meteorology has not been thoroughly investigated. Here we establish cross-province PM2.5 source-receptor matrix in China in 2015 and two climate pathways in 2050s (SSP585 and SSP126), using Community Multi-scale Air Quality model embedded with the Integrated Source Apportionment Method. Results suggest that across-regional transport contributes 27 % - 56.8 % of PM2.5 in five severely polluted regions, which is even more important compared to inner transport within the target region (13.2 % - 20.9 %), especially in Chuanyu and Fenwei regions where suffers large PM2.5 transport (over 50 %) from outside regions. Such results imply that joint-control policy should not only focus on neighboring provinces. Future warming scenario (SSP585) will exacerbate PM2.5 pollution (2 - 5 µg/m3) and also enhance its regional transport (> 3 %) mostly by modulating the across-regional transport rather than inner regional transport. Such enhancement of regional transport of PM2.5 can be significantly weaken (approximately by half) under SSP126 pathway, demonstrating the importance of climate change mitigation on weakening the regional transport of PM2.5 to maximize the co-benefits in both air quality and climate.