When It Rains, It Pours: Global Warming and the Rising Frequency of Extreme Precipitation in the United States

Publication Date: December 2007

Publisher: Environment California Research and Policy Center

Author(s): Emily Figdor; Travis Madsen

Research Area: Environment

Keywords: Weather patterns; Global Warming

Type:

Abstract:

Scientists expect that global warming will cause a variety of changes to precipitation patterns in the United States. Many areas will receive increased amounts of rain and snow over the course of a year; some areas will receive less. But
scientists expect that, all across the country, the rainstorms and snowstorms that do occur will be more intense, increasing the risk of flooding and other impacts.

In this report, we evaluate trends in the frequency of storms with extreme levels of rainfall or snowfall across the contiguous United States over the last 60 years. We analyze daily precipitation records spanning from 1948 through 2006 at more than 3,000 weather stations in 48 states.
We then examine patterns in the timing of heavy precipitation relative to the local climate at each weather station.

We find that storms with extreme amounts of rain or snowfall are happening more often across most of America, consistent with the predicted impact of global warming.