A warmer atmosphere results in an amplification of the water cycle. Some areas of the world are net importers of rainfall (such as tropical rainforests), while some are net exporters (such as oceans around the tropics). The “amplification” of the cycle means that dry regions become drier, and wet regions become wetter. During the 20th century, total rainfall in the United States increased by about seven percent; the largest increases occurred in the central and eastern regions (net importing regions). Most of this increase in precipitation can be accounted for by heavy and extreme precipitation events becoming even more intense. The amount of rain that falls during the heaviest one percent of rainfall events has increased by 20 percent over the last 100 years.
Seasons: Spring, Summer, Fall, Winter
(Source: United States. Climate Change Science Program. Weather and Climate Extremes in a Changing Climate. Synthesis Assessment Product 3.3: GPO. 2008 and “U.S. Temperature and Precipitation Trends.” U.S. National Oceanic and Atmospheric Administration (NOAA): Climate Prediction Center. 5 January 2005. 26 June 2008 and Soden, B., Wentz, F.J., Santer, B.D. and Zwiers F. “Climatically-Induced Increases in Water Vapor and Precipitation: Causation and Implications.” United States Senate, Washington, D.C. 29 October 2007. Accessed Online 17 December 2007 http://www.ametsoc.org/atmospolicy/ESSSarchiveclimatechange.html>.)