Anthropogenic forcings, such as greenhouse gases and aerosols, are starting to show their influence on the climate, as evidenced by a global warming trend observed in the past century. The weakening of tropical circulation, a consequence of global warming, has also been found in observations and in 21st-century climate model simulations. It is a common belief that this weakening of tropical circulation is associated with the fact that global-mean precipitation increases more slowly than water vapor. Here we propose a new mechanism for this robust change, which is determined by atmospheric stability associated with depth of convection. Convection tends to extend higher in a warmer climate, due to an uplifting of the tropopause. The higher the convection, the more stable the atmosphere. This leads to a weakening of tropical circulation.

Full Article: http://www.rcec.sinica.edu.tw/~chia/pub.html

Last Updated: 2010-02-03