Impact of anthropogenic forcing on the Asian summer monsoon as simulated by eight GCMs

The response of the Asian summer monsoon (ASM) to a transient increase in future anthropogenic radiative forcing is investigated by multi-model global warming experiments. Most models show that, in Asia, the summer monsoon rainfall increases significantly with global warming. On the other hand, the future change in the large-scale flow indicates a weakening of the ASM circulation. Enhanced moisture transport over the Asian summer monsoon region, associated with the increased moisture source from the warmer Indian Ocean, leads to a larger moisture flux convergence, which is responsible for the intensification of the mean rainfall. Pronounced warming over the tropics in the middle-to-upper troposphere causes a reduction in the meridional thermal gradient in the Asian region, which is consistent with the weakened monsoon circulation and eastward shift of the Walker circulation.