Global warming may lead to an increased risk of extreme rainfall and drought, a NASA study finds.

The results come from an analysis of computer simulations from 14 climate models. The scientists concluded that rising carbon dioxide levels could effect rainfall across all areas of Earth.

"In response to carbon dioxide-induced warming, the global water cycle undergoes a gigantic competition for moisture resulting in a global pattern of increased heavy rain, decreased moderate rain, and prolonged droughts in certain regions," lead author William Lau of NASA's Goddard Space Flight Center in Greenbelt, Md. said.

According to the models, for every one degree of carbon dioxide-induced warming, heavy rainfall will increase by 3.9 percent and light rain will increase by one percent. The projections did not indicate a major change in total global rainfall. Increased heavy rainfall is projected to take place mostly in regions around the equator, especially in the Asian monsoon regions and the Pacific Ocean. The model also indicated that for every one degree Farenheit of warming, the length of time with no rain will increase by 2.6 percent.

"Large changes in moderate rainfall, as well as prolonged no-rain events, can have the most impact on society because they occur in regions where most people live," Lau said. "Ironically, the regions of heavier rainfall, except for the Asian monsoon, may have the smallest societal impact because they usually occur over the ocean."

While the study claims that the models are not very reliable for predicting rainfall amounts in specific areas, they are useful for generating an overall pattern.

"If we look at the entire spectrum of rainfall types we see all the models agree in a very fundamental way — projecting more heavy rain, less moderate rain events, and prolonged droughts," Lau said.