Decrease in the summer rainfall of the southern United States coast and the Caribbean due to climate change

Simulations from the North American Regional Climate Change Assessment Program (NARCAPP) Geophysical Fluid Dynamics Laboratory (GFDL) AM2.1 timeslice experiment, for current climate (1971-2000) and future climate (2041-2070), were compared and contrasted to assess how May through October accumulated rainfall is responding to climate change along the southern United States coast and in the Caribbean under the Intergovernmental Panel on Climate Change (IPCC) A2 emissions scenario (a scenario of relatively high emissions increase). The simulations were done on a global domain at a horizontal resolution of roughly 50 km.

There is an overall decrease of about 200 mm (30 percent) in the May through October rainfall in the region of the southern United States coast and the Caribbean. The absolute decrease is larger in the regions that receive the most rain. However, proportionally, the decrease is larger in the regions that receive the least rain. For the subregion of Florida, rainfall time series indicate a delay of the region's late wet period in the future climate. This shift needs to be further examined to determine its significance and underlying physical processes. Florida also received less rainfall in future climate, but the standard deviation of the early and late wet periods was found to be larger. This is in accord with the findings of the IPCC of an increase in global extremes as a result of climate change. In a future study, the time series for four other subregions will be analyzed.