A Strong Anthropogenic Black Carbon Forcing Constrained by Pollution Trends Over China

Estimates of the effective radiative forcing from aerosol-radiation interaction (ERFari) of anthropogenic Black Carbon (BC) have been disputable and require better constraints. Here we find a substantial decline in atmospheric absorption of -5.79Wm(-2)decade(-1) over eastern central China (ECC) responding to recent anthropogenic BC emission reductions. By combining the observational finding with advances from Coupled Model Intercomparison Project phase6 (CMIP6), we identify an emergent constraint on the ERFari of anthropogenic BC. We show that across CMIP6 models the simulated trends correlate well with simulated annual mean shortwave atmospheric absorption by anthropogenic BC over China. Making use of this emergent relationship allows us to constrain the aerosol absorption optical depth of anthropogenic BC and further provide a constrained range of 2.4-3.0 Wm(-2) for its top-of-atmosphere ERFari over China, higher than existing estimates. Our work supports a strong warming effect of BC over China, and highlights the need to improve BC simulations over source regions.

Automated summary

The decline in atmospheric absorption over eastern central China due to anthropogenic Black Carbon (BC) emissions reduction is identified, and an emergent constraint on the effective radiative forcing from aerosol-radiation interaction (ERFari) of anthropogenic BC is established. The constrained range for the top-of-atmosphere ERFari over China is found to be higher than existing estimates, supporting the strong warming effect of BC over China and highlighting the need to improve BC simulations over source regions.