New Report: Extreme Downpours and Snowstorms Up 84 Percent in Vermont

Scientists Link Trend to Global Warming

MONTPELIER, VT—Eleven months after Tropical Storm Irene led to record flooding that devastated much of Vermont, a new report by Environment America Research & Policy Center confirms that extreme rain and snowstorms are happening 84 percent more frequently in Vermont since 1948.

“Irene brought devastation to Vermont, and it’s important to remember that that storm triggered the state’s third major flooding event in a single year,” said Paul Burns, executive director of the Vermont Public Interest Research Group, which released the report locally. “This report proves that the storms really are getting worse, and if we want to reduce the likelihood of more devastating storms in the future, it’s time now to stand up to all those who continue deny science, shirk responsibility and oppose progress on clean energy solutions.”

VPIRG pointed to Tropical Storm Irene that hit Vermont in August of last year as an illustration of what more extreme rainstorms could mean for the state.  That storm, which dumped up to 11 inches of rain on parts of Vermont, resulted in one of the state’s worst natural disasters in over one hundred years.

Based on an analysis of state data from the National Climatic Data Center, the new report found that heavy downpours or snowstorms that used to happen once every 12 months on average in Vermont now happen every 6.5 months on average.  Moreover, the biggest storms are getting bigger.  The largest annual storms in Vermont now produce 35 percent more precipitation, on average than they did 65 years ago.

Scientists have concluded that the rise in the frequency and severity of heavy rainstorms and snowstorms is linked to global warming.  Warming increases evaporation and enables the atmosphere to hold more water, providing more fuel for extreme rainstorms and heavy snowstorms.

The new report, When It Rains, It Pours: Global Warming and the Increase in Extreme Precipitation from 1948 to 2011, examines trends in the frequency of and the total amount of precipitation produced by extreme rain and snow storms across the contiguous United States from 1948 to 2011.  Using data from 3,700 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. The report also examines trends in the amount of precipitation produced by the largest annual storm at each weather station.

“If any of us thought that we could escape the troubles of the world within the borders of this special place, this new data – like Irene last fall – comes as a hard slap across the face,” said noted author, educator and environmentalist, Bill McKibben. “We’ve got to get to work doing all we can to slow the pace of global warming; it’s job one, two and three, for a long time to come.”

Nationally, the report found that storms with extreme precipitation increased in frequency by 30 percent across the contiguous United States from 1948 to 2011. Moreover, the largest annual storms produced 10 percent more precipitation, on average.  At the state level, 43 states show a significant trend toward more frequent storms with extreme precipitation, while only one state (Oregon) shows a significant decline.

Key findings for Vermont and the Region include:

  • Extreme rainstorms and snowstorms are becoming more frequent. Vermont experienced an 84 percent increase in the frequency of storms from 1948 to 2011.  In other words, heavy downpours or snowstorms that happened once every 12 months on average in 1948 now happen every 6.5 months, on average.
  • Storms with extreme precipitation increased in frequency by 85% New England during the period studied.  The New England region ranks first nationwide for the largest increase in the frequency of storms with heavy precipitation.
  • The biggest rainstorms and snowstorms are getting bigger. The amount of precipitation released by the largest annual storms in Vermont increased by 35 percent from 1948 to 2011.

VPIRG was careful to note that an increase in the frequency and severity of extreme rainstorms does not mean more water will be available for human use. Hotter temperatures fuel extreme rainstorms by increasing rates of evaporation. At the same time, however, that evaporation increases soil dryness. Moreover, scientists expect that, as global warming intensifies, longer periods with relatively little precipitation will tend to mark the periods between heavy rainstorms. As a result, droughts are likely to become more frequent and severe in some regions of the United States. Currently, more than half of the lower United States is suffering through prolonged drought, aggravated by the fact that the last six months have been the hottest January-June period on record.

According to the most recent science, the United States must reduce its total global warming emissions by at least 35 percent below 2005 levels by 2020 and by at least 85 percent by 2050 in order to prevent the most devastating consequences of global warming. VPIRG highlighted two proposals from the Obama administration – carbon pollution and fuel efficiency standards for cars and light trucks through model year 2025, and the first ever carbon pollution standards for new power plants – as critical steps toward meeting these pollution reduction targets.

At the state level, Gov. Peter Shumlin released an energy plan last year that calls for Vermont to meet 90 percent of its energy needs with renewable energy by 2050.  In the next 20 years, the administration wants 75 percent of Vermont’s energy to come from renewable sources.  It is considered one of the most ambitious energy plans in the nation.  The Legislature followed up with new legislation this year that will promote the development of relatively small, renewable energy projects through the Standard Offer program. However, industry groups successfully blocked the establishment of a Renewable Portfolio Standard that would have required utilities to buy increasing amounts of energy from renewable sources.

“In Vermont, we’re grateful for the visionary leadership provided by our federal delegation, the Shumlin administration and many state legislators in the fight to stop global warming,” said Burns.  “We’ll need every bit of that leadership in the future if we are to hit our ambitious goals on electricity, transportation and heating.”

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