Nathan Willcox,
Environment America

New Report: Extreme Downpours Up 24 Percent in U.S.

For Immediate Release

Washington, DC — Storms with heavy rainfall are now 24 percent more frequent in the U.S. than they were 60 years ago, according to a new Environment America report released today. The report makes it clear that the United States is already experiencing extreme downpours much more frequently, consistent with scientists’ predictions about global warming.

“At the rate we’re going, what was once the “storm of the decade” will soon seem like just another downpour,” said Environment America’s Washington, D.C. Director Anna Aurilio. 

Aurilio pointed to the rainstorm that hit Washington, D.C., and much of the east coast in late June, 2006, as an illustration of what more extreme rainstorms could mean for the region. That rainstorm, which broke the one-day, two-day and one-week records for rainfall at Reagan National Airport outside Washington, flooded buildings like IRS, caused mudslides that closed the Capital Beltway, left tens of thousands of homes without power, and even felled a 100-year-old tree on the White House grounds.

“This report demonstrates that we are already seeing the effects of global warming even with a relatively small increase in temperatures. The projected increases are much greater, and the impacts are already much more than was predicted. It is imperative that we begin now to reduce the emissions of heat trapping gases to avoid serious and uncontrollable damage,” said Dr. William Moomaw, Professor of International Environmental Policy; Director of the Center for International Environment and Resource Policy at The Tufts University Fletcher School.

The new Environment America report, "When it Rains, It Pours: Global Warming and the Rising Frequency of Extreme Precipitation in the United States," examines trends in the frequency of large rain and snow events across the continental United States from 1948 to 2006. Using data from 3,000 weather stations and a methodology originally developed by scientists at the National Climatic Data Center and the Illinois State Water Survey, the report identifies storms with the greatest 24-hour precipitation totals at each weather station, and analyzes when those storms occurred.

Nationally, the report shows that storms with extreme precipitation have increased in frequency by 24 percent across the continental United States since 1948. At the state level, 40 states show a significant trend toward more frequent storms with extreme precipitation, while only one state (Oregon) shows a significant decline. 

Key findings in the report include:

  • Storms with extreme precipitation increased in frequency by 24 percent nationally from 1948 to 2006. The New England and Mid-Atlantic regions ranked 1st and 2nd respectively among regions nationwide for the largest increase in the frequency of storms with heavy precipitation.
  • States experiencing an especially high increase in extreme precipitation events during the period studied included Louisiana (52% increase), Massachusetts (67% increase), New Hampshire (83% increase), New York (56% increase), Rhode Island (88% increase) and Vermont (57% increase). 
  • Metropolitan areas showing an especially large increase in the frequency of large storms included Bloomington, IN; Elkhart-Goshen, IN; Baton Rouge, LA; Portland, ME; Jackson, MS; Binghamton, NY; Reading, PA and Williamsport, PA. 

These findings are consistent with the predicted impacts of global warming. Scientists expect some parts of the United States to receive more precipitation as a result of global warming, while other parts receive less. But regardless of the trend in total precipitation, scientists predict that the rain and snow that does fall will be more likely to come in big downpours and heavy snowstorms. 

Environment America was joined by Dr. William Moomaw, Professor of International Environmental Policy and Director of the Center for International Environment and Resources Policy at the Fletcher School at Tufts University, on a teleconference held to release today’s report. 

Environment America’s Aurilio was careful to note that an increase in the frequency of extreme rainstorms does not mean more water will be available. Scientists expect that, as global warming intensifies, longer periods of relative dryness will mark the periods between extreme rainstorms, increasing the risk of drought. For example, the Intergovernmental Panel on Climate Change (IPCC) predicts that, under a scenario of intense warming, the percent of land enduring severe drought globally could be 30 times greater by the end of the century than it is today.

“We can curb the severity of this problem only if our country acts boldly to reduce the pollution that fuels global warming,” said Aurilio.

According to the most recent science, the United States must reduce its total global warming emissions by at least 15 percent by 2020 and by at least 80 percent by 2050 in order to prevent the worst effects of global warming. 

“Steep reductions in global warming pollution are challenging but achievable,” noted Aurilio, “and we already have the energy efficiency and renewable energy technologies we need to get started.”

Tomorrow, the U.S. Senate Environment & Public Works (EPW) Committee is expected to vote on amendments to the “Lieberman-Warner Security Act of 2007” (S. 2191), a global warming bill introduced by Senators Lieberman (Conn.) and Warner (Va.). While recognizing the important efforts of the bill’s supporters on this critical issue, Environment America’s Aurilio said that the legislation must be significantly strengthened to address the challenge of global warming. Specifically, the bill’s current pollution reduction targets fall short of what the science says is necessary to avoid the worst effects of global warming, and the bill gives away far too many subsidies to dirty and dangerous energy sources.

“If we are going to solve the problem of global warming, this bill must be substantially strengthened,” said Aurilio. “Environment America urges the Environment & Public Works Committee to strengthen the bill to require science-based pollution reduction targets, and to limit giveaways to dirty and dangerous energy sources,” concluded Aurilio. 

Aurilio also urged members of Congress to support the Safe Climate Act and Global Warming Pollution Reduction Act—the only legislation in Congress that includes the science-based targets necessary to help protect future generations from the worst effects of global warming.