Continuous Reduction of Black Carbon Emissions From China During 2009–2022: Estimates From Observations at Remote Sites in Japan

Abstract To assess the climate impact of black carbon (BC), accurate emission inventories are crucial for climate model simulations. However, bottom‐up emissions inventories have substantial uncertainties regarding anthropogenic BC emissions from China and struggle to capture rapid changes in emissions. Top‐down analysis using atmospheric observations is an useful method to evaluate inventories and to immediately estimate BC emissions. In this study, we estimated the long‐term trend of anthropogenic BC emissions from China for 2009–2022 using observations at remote sites in Japan and a chemical transport model GEOS‐Chem. Our analysis revealed a continuous reduction in Chinese BC emissions of −5.2 ± 0.4% yr −1 after excluding data influenced by wet deposition. This decreasing trend surpassed those of the bottom‐up inventories, which estimated the reduction rates ranging from −2.6% yr −1 to −4.5% yr −1 after 2009. Consequently, the differences between the observation‐based estimates and inventories gradually increased toward the latest years of the inventories. The rapid reduction identified from this observation needs to be reflected in the historical inventory for the Coupled Model Intercomparison Project Phase 7 (CMIP7) to accurately assess the impact of aerosols on past and future climate change.