NASA released a study predicting that, with increased global warming, areas prone to heavy rains will see increases in rainfall while areas prone to drought will experience even less rainfall. The the announcement of the study released on May 3, 2013 notes:
“The models project for every 1 degree Fahrenheit of carbon dioxide-induced warming, heavy rainfall will increase globally by 3.9 percent and light rain will increase globally by 1 percent. However, total global rainfall is not projected to change much because moderate rainfall will decrease globally by 1.4 percent….Some regions outside the tropics may have no rainfall at all. The models also projected for every degree Fahrenheit of warming, the length of periods with no rain will increase globally by 2.6 percent. ”