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Jessica O'Hare,
Environment New Hampshire

New Report: Extreme Downpours More than Double in New Hampshire

Scientists Link Trend to Global Warming
For Immediate Release:

Belmont, NH—After this month’s microburst blew a tree into a Tilton home and damaged 15-20 cars, a new Environment New Hampshire report confirms that the number of extreme rainstorms has doubled in New Hampshire since 1948.  

“As the old saying goes, when it rains, it pours—especially in recent years as bigger storms have hit New Hampshire more often,” said Jessica O’Hare, Advocate for Environment New Hampshire.  “We need to heed scientists’ warnings that this dangerous trend is linked to global warming, and do everything we can to cut carbon pollution today.”  

Based on an analysis of state data from the National Climatic Data Center, the new report found that heavy downpours that used to happen once every 12 months on average in state now happen twice as frequently—5 to 6 months on average.  Moreover, the biggest storms are getting bigger. The largest annual storms in New Hampshire now produce 33% 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.  

“While any single weather event could be mostly due to natural cycles, strong scientific evidence now shows that climate change is playing a growing role in the more intense heat waves and more frequent extreme precipitation events we have been seeing over past decades,” said Jim Rubens for the Union of Concerned Scientists, which advocates for policy changes to reduce air pollution by heat-trapping gasses such as carbon dioxide.

O’Hare pointed to Hurricane Irene that hit Bartlett, NH in August of 2011 as an illustration of what more extreme rainstorms could mean for the state.  Hurricane Irene dumped half a foot of rain in the Western part of the state, led to 275 road closings and left 165,000 people without power

Belmont’s selectwoman, Ruth Mooney commented on the recent downpour in Belmont and Tilton: “As selectwoman for Belmont, I have my neighbors’ safety at heart. The town did a wonderful job responding to the microburst this month, and I say that the damage could have been a lot worse. Every summer, the storms are getting fiercer. That’s why I support programs to reduce carbon emissions are necessary to make sure that our properties in the Lakes Region are secure.”

Key findings for New Hampshire and the New England region include:
•    Extreme rainstorms and snowstorms are becoming more frequent. New Hampshire experienced a 115 percent increase in the frequency of extreme rainstorms from 1948 to 2011.  In other words, heavy downpours or snowstorms that happened once every 12 months on average in 1948 now happen twice as frequently—5 to 6 months, on average.
•    Storms with extreme precipitation increased in frequency by 85 percent in the New England during the period studied.  The region with the largest increase in the frequency of heavy precipitation storms.
•    The biggest rainstorms and snowstorms are getting bigger. The amount of precipitation released by the largest annual storms in New Hampshire increased by 33 percent from 1948 to 2011.

O’Hare 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.

The new Environment New Hampshire 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.

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.  Environment New Hampshire 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, New Hampshire officials are considering ways to improve the Regional Greenhouse Gas Initiative (RGGI), the first-in-the-nation cap on carbon pollution from the power sector that sells permits for carbon emissions and has led to nearly $1 billion in investments in energy efficiency and clean energy solutions in the region.

“How serious this problem gets is largely within our control,” said O’Hare “New Hampshire officials can build on the progress we have made reducing emissions by strengthening the Regional Greenhouse Gas Initiative (RGGI), which has been a key part of our strategy to reduce pollution and shift to clean energy.”