Changes in Global Monsoon Precipitation under Global Warming

Monsoons, the most energetic tropical climate system, exert a great social and economic impact upon billions of people around the world. The observational GPCP and CMAP precipitation datasets indicate the consistent increasing trends in both the global monsoon area and total precipitation during the past 30 years (1979–2008). Whether or not this increase trend will continue in the 21st century is further investigated, based on simulations of three high-resolution atmospheric general circulation models that were forced by different future sea surface temperature warming patterns. The results show that the global monsoon area, precipitation and intensity all increase consistently among the model projections. This indicates that the strengthened global monsoon is a robust signal across the models and SST patterns explored so far. The increase of the global monsoon precipitation is attributed to the increases of moisture convergence and surface evaporation. The former is caused by the increase of atmospheric water vapor and the latter is due to the increase of SST. The effect of the moisture and evaporation increase is offset to a certain extent by the weakening of the monsoon circulation.