Long-term variability in black carbon emissions constrained by gap-filled absorption aerosol optical depth and associated premature mortality in China

Black carbon (BC) plays an important role in air quality, public health, and climate, but its long-term variations in emissions and health effects have been insufficiently understood for China. Here, we present the spatiotemporal evolution of BC emissions and the associated premature mortality in China during 2000-2020 based on an integrated framework combining satellite observations from the Ozone Monitoring Instrument (OMI), an extreme gradient boosting (XGBoost) algorithm, a "top-down" inversion approach, and an exposure-response model. We found that the "bottom-up" approach most likely underestimated BC emissions, particularly in less developed western and remote areas. Pollution controls were estimated to reduce the annual BC emissions by 26 % during 2010-2020, reversing the 8 % growth during 2000-2010. BC emissions in the main coal-producing provinces declined by 2010 but rebounded afterwards. By contrast, provinces with higher economic and urbanization levels experienced emission growth (0.05-0.10 Mg km - 2 yr - 1 ) by 2010 and declined greatly (0.07-0.23 Mg km - 2 yr - 1 ) during 2010-2020. The national annual BC-associated premature mortality ranged between 733 910 (95 % confidence interval: 676 790-800 250) and 937 980 cases (864 510-1 023 400) for different years. The changing BC emissions contributed to an increase of 78 590 cases (72 520-85 600) during 2000-2005 and a decrease of 133 360 cases (123 150-145 180) during 2010-2015. Strategies differentiated by region are needed for further reducing BC emissions and their health and climate impacts.