Integrating emission mitigation with climate dynamics to reduce black carbon deposition in China

Black carbon (BC) deposition poses a critical environmental threat by accelerating cryospheric melt and imposing substantial health risks. However, the drivers governing its long-term dynamics remain poorly quantified, hindering effective environmental governance and sustainable planning. Here, we combine multi-source observations with machine learning to dissect the contributions of emissions and meteorology to BC deposition trends and interannual variability in China during 1980-2022. While emissions dominate multi-decadal trends, a significant multi-year meteorological anomaly temporarily decoupled deposition from emissions beginning in 2003—at which point wet deposition shifted from increasing to decreasing. This reversal preceded sustained emission reductions by several years and occurred five years earlier than the corresponding reversal in dry deposition. Factor separation further demonstrate that meteorological conditions overwhelmingly govern interannual variability across China, accounting for 24.20-54.07% of variance in dry deposition and 55.46-66.65% in wet deposition. Precipitation has emerged as the leading meteorological driver, explaining more variability in wet deposition across most Chinese subregions than any other factor. Our findings demonstrate that climate variability not only regulates year-to-year fluctuations but can reverse long-term deposition trends. This highlights the urgency of incorporating climate uncertainty into emission control strategies and sustainability assessment to achieve a reliable prediction of the environmental impact of BC.