More Downpours: Increase in Heaviest Precip Events

Rivers continue to swell in the Ohio and Mississippi Valleys. More than 10 inches of rain fell last week in Arkansas and Louisiana. While the individual weather pattern may allow for heavy rain, the heaviest of this precipitation is increasing as the world warms from climate change.

A warmer world supercharges the water cycle, leading to heavier precipitation. To start, a warmer atmosphere creates more evaporation — for every 1°F of warming, the saturation level is increased by about four percent. With more water evaporating into the atmosphere, there is more available to condense into precipitation, and it’s coming down in bigger downpours. The national map shows where this change has been the most dramatic, indicating that the precipitation in the heaviest one percent of rainfall days is getting heavier.

Science has attributed heavy rain to climate change for decades, but now we can analyze the role of climate change in individual extreme rainfall events.