The South Asian summer monsoon supplies over 80 % of India'sprecipitation. Industrialization over the past few decades has resulted insevere aerosol pollution in India. Understanding monsoonal sensitivity toaerosol emissions in general circulation models (GCMs) could improvepredictability of observed future precipitation changes. The aims here are(1) to assess the role of aerosols in India's monsoon precipitation and (2)to determine the roles of local and regional emissions. For (1), we studythe Precipitation Driver Response Model Intercomparison Project experiments.We find that the precipitation response to changes in black carbon is highlyuncertain with a large intermodel spread due in part to model differences insimulating changes in cloud vertical profiles. Effects from sulfate areclearer; increased sulfate reduces Indian precipitation, a consistencythrough all of the models studied here. For (2), we study bespokesimulations, with reduced Chinese and/or Indian emissions in three GCMs. Asignificant increase in precipitation (up to ∼20 %) isfound only when both countries' sulfur emissions are regulated, which hasbeen driven in large part by dynamic shifts in the location of convectiveregions in India. These changes have the potential to restore a portion ofthe precipitation losses induced by sulfate forcing over the last fewdecades.
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