Uncertainties in anthropogenic aerosol concentrations and direct radiative forcing induced by emission inventories in eastern China

• Uncertainties in aerosol forcing owing to differences in emission inventories were examined.
• Uncertainties in aerosol levels due to emissions are smaller than those caused by model differences.
• Emissions and model differences induce comparable uncertainties in surface nitrate.
• Our estimates of aerosol direct forcing were constrained by observed AOD.

This study quantified the uncertainties in concentrations and direct radiative forcing of anthropogenic aerosols due to emissions in eastern China using a global chemistry–aerosol–climate model. The emission inventories included three global inventories, ACCMIP (Atmospheric Chemistry & Climate Model Intercomparison Project), EDGAR-HTAP (Emission Database for Global Atmospheric Research for Hemispheric Transport of Air Pollution), and EDGAR Version 4.2, and one regional INTEX-B (Intercontinental Chemical Transport Experiment—Phase B) inventory. The uncertainties (a percentage of the standard deviation divided by the mean value across the four inventories) in the regional surface-layer aerosol concentrations due to emissions were 3.9% in sulfate, 40.0% in nitrate, 18.4% in ammonium, 11.1% in POA, 16.7% in SOA and 15.4% in BC. Compared with the ACCMIP model results based on a uniform emission inventory, the impacts of emissions were smaller. One exception is the regional surface-layer nitrate concentration, which had comparable uncertainties due to the emissions (40.0%) and the models (43.8%) because of the complex nitrate chemistry and the highly uncertain NH3 emission. The mean regional aerosol direct forcing at the top of the atmosphere between 1850 and 2006 was − 3.6 Wm− 2 under all-sky conditions and was enhanced up to − 3.83 Wm− 2 after the model assimilated the MODIS find-mode aerosol optical depth (AOD). The impact of the assimilation of absorption AOD is discussed. The uncertainties in aerosol direct forcing were smaller than those of the ACCMIP inter-model results, but still significant. An accurate emission inventory is essential for quantifying the role of aerosols in regional climate.