Evaluation of Black Carbon Concentration Levels and Trends in East Asia from CMIP6 Climate Models: Comparison to Long-Term Observations in Japan and Biases Due to Chinese Emissions.

We evaluated the mass concentration levels and long-term trends of black carbon (BC) in the historical and future scenario simulations using 12 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) for East Asia, the region with the largest anthropogenic emissions. By comparing them with surface observations at two regionally representative sites, Fukue and Noto, for the period of 2009-2020, we found that the CMIP6 multi-model mean was approximately two times higher than the observed BC concentrations and did not reproduce the observed decreasing trend before 2014. Sensitivity simulations of emission inventories using a chemical transport model, GEOSChem, suggested that the overestimation and increasing trend of Chinese BC emissions in the CMIP6 historical inventory (CEDSv2017-05-18) were responsible for the higher concentrations and opposite trends in the CMIP6 BC simulations. The direct radiative effect of BC for CEDS was estimated to be 72% larger in East Asia than that for the ECLIPSEv6b inventory, which reproduced the observed BC concentrations reasonably well. [ABSTRACT FROM AUTHOR]