In recent years there have been a number of prolonged heat waves and heavy rain events, and studies are showing that global climate warming is increasing the risk of extreme rainfall and drought.
To add to the evidence linking climate warming and extreme precipitation and provide a regional as well as global perspective, Lau et al. analyzed projections from 14 different climate models that are part of the CMIP5 project, which is organized by the Intergovernmental Panel on Climate Change in preparation for its upcoming fifth assessment report.
The authors examined not only total rain, but also changes in heavy, moderate, and light rain, as well as drought, on global and regional scales. They find that under a 1 percent per year increase in carbon dioxide emissions, which is comparable to a business-as-usual scenario, the ensemble of models predicts that by the time carbon dioxide emissions triple, globally extremely heavy rain would increase by 100 to 250 percent, moderate rain would decrease by 5 to 10 percent, and light rain would increase by 10 to 15 percent. There would also be a global increase in dry months of up to 16 percent, with the largest risk of drought in areas that are already dry, including northern Africa, southern Africa, and southern Europe, as well as the southwestern United States and Mexico and northeastern Brazil. The increased heavy precipitation would likely be concentrated in wet regions, including the equatorial Pacific Ocean and Asian monsoon areas.
The results add to growing evidence that increased carbon dioxide emissions will change global precipitation patterns. The increased risk of severe floods and droughts globally is associated with an adjustment in the large-scale circulation in response to the heat imbalance induced by global warming.
Article: William K.-M. Lau, H.-T. Wu, K.-M. Kim, A canonical response of precipitation characteristics to global warming from CMIP5 models, Geophysical Research Letters, 2013DOI: 10.1002/grl.50420