Does the tropical circulation strengthened or weakened due to global warming?

Changes in rainfall characteristics and the large scale circulation due to increased CO2 emission are analyzed based on projections of 33 CMIP5 models. Results shown that there is an increased risks of extreme rainfall and drought in preferred geographic locations around the world. Specifically, a majority of the models project a consistent response with more heavy precipitation over climatologically wet regions of the deep tropics especially the equatorial Pacific Ocean and the Asian-Australia monsoon regions, and more dry periods over the land areas of the subtropics and the tropical marginal convective zones. In conjunction with the precipitation change, the global circulation is altered featuring a narrowing and deepening of convective zone in the near equatorial regions with increased high clouds, a rise of the center of gravity and acceleration of the upper branch of the Hadley circulation, and an expansion of the subtropics and a poleward shift of the jet stream. Our results suggest that increased risks of severe floods and droughts worldwide induced by increased CO2 emission are connected via a re-adjustment of the global circulation system in a competition for increased availability of atmospheric moisture from global warming.