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The Role of Atmospheric and Oceanic Forcing on the Climate Response to Anthropogenic Aerosols

The climate response to anthropogenic aerosols has a spatial pattern that is distinct from the response to greenhouse gases. This is due to the relatively short lifetime of aerosols in the atmosphere, resulting in spatially varied forcing on the climate. As a result, understanding regional responses to anthropogenic aerosols is important to understanding the total human impact on regional climates. In past studies, some of these regional responses have been linked to aerosol-induced sea surface temperature (SST) changes, while others are linked directly to aerosol forcing on the atmosphere. To further investigate the mechanisms underlying regional responses to aerosol forcing, we ran a set of simulations using a prescribed SST configuration of the Community Earth System Model 1.2/Community Atmosphere Model 5 (CESM1-CAM5). These simulations separately test the impact of changes to aerosol and aerosol precursor emissions and the impact of aerosol-induced SST changes on the climate between 1950-1959 and 2000-2009. We find that the global mean temperature and precipitation response to aerosol forcing is dominated by the SST-mediated response, while the response to emissions dominates in regions with large emission changes such as South and East Asia. Furthermore, we confirm previous results that suggest that aerosol-cloud interactions in CAM5 have a resolution dependence.