Varied Increases in Extreme Rainfall with Global Warming

Intensification of extreme rainfall varies from region to region, study shows.

A new study by researchers from MIT and the Swiss Federal Institute of Technology in Zurich shows that the most extreme rain events in most regions of the world will increase in intensity by 3 to 15 percent, depending on region, for every degree Celsius that the planet warms.

If global average temperatures rise by 4 degrees Celsius over the next hundred years, as many climate models predict given relatively high CO2 emissions, much of North America and Europe would experience increases in the intensity of extreme rainfall of roughly 25 percent.  Some places such as parts of the Asian monsoon region would experience greater increases, while there will be smaller increases in the Mediterranean, South Africa and Australia.

There are a few regions that are projected to experience a decrease in extreme rainfall as the world warms, mostly located over subtropical oceans that lie just outside the tropical, equatorial belt.

The study, published in Nature Climate Change, finds that the varied changes in extreme precipitation from region to region can be explained by different changes in the strength of local wind patterns:  As a region warms due to human-induced emissions of carbon dioxide, winds loft that warm, moisture-laden air up through the atmosphere, where it condenses and rains back down to the surface.  But changes in strength of the local winds also influence the intensity of a region's most extreme rainstorms.

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