IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability Changes in the occurrence of extremes

Many of the current climate change studies indicate that the frequency in the occurrence of extreme events will increase in the future. Many impacts of climate change will be realised as the result of a change in the frequency of occurrence of extreme weather events such as windstorms, tornados, hail, heatwaves, gales, heavy precipitation or extreme temperatures over a few hours to several days. A limited number of studies on extremes from global models assessed during the AR4 (e.g., Tebaldi et al., 2007) provide estimates of frequency of seasonal temperature and precipitation extreme events as simulated in the present and by the end of 21st century under the A1B emissions scenario. In Central America, the projected time-averaged precipitation decrease is accompanied by more frequent dry extremes in all seasons. In South America, some models anticipate extremely wet seasons in the Amazon region and in southern South America, while others show the opposite tendency.