Magnitude uncertainty dominates intermodel spread in zonal-mean precipitation response to anthropogenic aerosol increase.

Anthropogenic aerosols are an important driver of historical climate change but the climate response is not fully understood and the climate model simulations suffer large uncertainties. On the basis of a multimodel ensemble of historical aerosol forcing simulation for a period of global aerosol increase during 1965 to 1989, here, we show that the precipitation response shares a common southward displacement of tropical rain bands but the magnitude differs markedly among models, accounting for 76% of the intermodel uncertainty in zonal-mean precipitation change. Our analysis of atmospheric energetics further reveals key mechanisms for magnitude uncertainty: aerosol radiative forcing drives, cloud radiative feedback amplifies, and ocean circulation damps the intermodel uncertainty in cross-equatorial atmospheric energy transport change and the meridional shift of tropical rain bands. This has important implications for understanding and reducing intermodel uncertainty in anthropogenic climate change.