Greenhouse Warming Linked to Shifts in December, January, and February Rainfall

Global warming may increase the risk for extreme rainfall and drought according to a NASA-led modeling study. The study shows for the first time how rising carbon dioxide concentrations could affect the entire range of rainfall types on Earth. Analysis of information from 14 climate models indicates wet regions of the world, such as the equatorial Pacific Ocean and the Asian monsoon regions, will likely see increases in heavy precipitation because of warming resulting from projected increases in carbon dioxide levels. Arid land areas outside the tropics and many regions with moderate rainfall could become drier.

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.

This visualization displays areas with no rain (brown), moderate rain (tan), and heavy rain (blue). Very Heavy rainfall (cark blue) is defined as months that receive an average of 0.95 of an inch of rain per day (24 mm/day) every day for the months of June, July, and August. Heavy rainfall is defined as months that receive an average of more than about 0.35 of an inch per day (9 mm/day). Light rain is defined as months that receive an average of less than 0.01 of an inch per day. Moderate rainfall is defined as months that receive an average of between about 0.04 to 0.09 of an inch per day.

See http://www.nasa.gov/topics/earth/features/wetter-wet.html