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.

Automated summary

This study evaluated the mass concentration levels and long-term trends of black carbon (BC) in East Asia using CMIP6 climate models. The results revealed that the models overestimated BC concentrations and did not replicate the observed decreasing trend. Sensitivity simulations using different emission inventories showed that the overestimation of Chinese BC emissions was responsible for these discrepancies.