The contribution of individual aerosol species and greenhouse gases to
precipitation changes during the South Asian summer monsoon is
uncertain. Mechanisms driving responses to anthropogenic forcings needs
further characterization. We use an atmosphere-only climate model to
simulate the fast response of the summer monsoon to different
anthropogenic aerosol types and to anthropogenic greenhouse gases.
Without normalization, sulfate is the largest driver of precipitation
change between 1850 and 2000, followed by black carbon and greenhouse
gases. Normalized by radiative forcing, the most effective driver is
black carbon. The precipitation and moisture budget responses to
combinations of aerosol species perturbed together scale as a linear
superposition of their individual responses. We use both a
circulation-based and moisture budget-based argument to identify
mechanisms of aerosol and greenhouse gas induced changes to
precipitation, and find that in all cases the dynamic contribution is
the dominant driver to precipitation change in the monsoon region.