Global Warming News

Phoenix Arizona—Scientists have said for years that global warming was “loading the dice” when it comes to increasing the frequency of severe storms, and a new Environment Arizona report makes it clear that the Phoenix Metropolitan region is already experiencing extreme downpours much more frequently.  Specifically, the new report found that storms with heavy rainfall are now 43% percent more frequent in the Phoenix region than they were 60 years ago.

“At the rate we’re going, what was once the storm of the decade will soon seem like just another downpour,” said Erik Magnuson, Environment Arizona Program Associate.

Magnuson pointed to the storm that hit Arizona this weekend as an illustration of what more extreme rainstorms could mean for the region. The storm this weekend that dumped anywhere from more than three inches in the northeast valley to more than two inches of rain in Phoenix is an example of new precipitation patterns. Other examples of recent extreme precipitation events include the March 12th 2006 “powerhouse” storm that dumped 2.89 inches on Phoenix and the number one storm in the last ten years that dumped 3.1 inches on October 23 2000.   

“More frequent downpours, fueled by global warming, will leave Arizona even more vulnerable to dangerous flooding in years to come,” said Magnuson.

 The new Environment Arizona 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 for the Mountain Region and Arizona include:
•    Storms with extreme precipitation increased in frequency by 25% percent in the Mountain region from 1948 to 2006.
•    Arizona experienced a 26% percent increase in extreme rainstorms during the period studied.
•    In addition, the Phoenix region shows a significant increase in the frequency of large storms with heavy precipitation, roughly estimated to be a 43% percent increase over the nearly 60-year period.  

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.  


Magnuson 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.
 
“How serious this problem gets is largely within our control – but only if our country acts boldly to reduce the pollution that fuels global warming,” said Magnuson.

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 Magnuson, “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 Climate Security Act of 2007” (S. 2191), a global warming bill introduced by Senators Lieberman (I-CT) and Warner (R-VA).  While recognizing the important efforts of the bill’s supporters on this critical issue, 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.

“In addition to calling for a strengthening of the “America’s Climate Security Act”, our Senators Kyl and McCain and all of our representatives should cosponsor the Global Warming Pollution Reduction Act/Safe Climate Act – the only legislation in Congress that would reduce pollution fast enough to protect future generations from the worst effects of global warming,” concluded Magnuson.


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Environment Arizona is a statewide, citizen-based environmental advocacy organization.