Tropical rainfall change in warming climate

Global air temperature is projected to rise in response to anthropogenic increase in atmospheric greenhouse gases. Global mean temperature is a convenient index to monitor the climate change but regional patterns of climate change are essential for adaptation. Precipitation change in warming climate, in particular, is to first order spatially variable, causing floods in some places and droughts in some others. This talk discusses recent progress in understanding the dynamics of regional change in tropical rainfall. In particular, the ocean warming pattern and its interaction with the atmosphere are important for changes in tropical convection. A warmer-get-wetter view calls for rainfall increase where the ocean warming exceeds the tropical mean increase, and vice versa. This is supported by analysis of climate model projections of annual rainfall and by observations of the El Nino-Southern Oscillation phenomenon. The ocean warming pattern affects rainfall change because it determines local convective instability and drives low-level circulation changes. We show that the ocean warming pattern accounts for much of the variability among different climate models in rainfall projections.