Extreme Downpours and Thunderstorms Up 64 Percent in New York

Scientists Link Trend to Global Warming
For Immediate Release

Less than a year after Hurricane Irene and Tropical Storm Lee created record flooding which devastated New York State, a new Environment New York report confirms that extreme rainstorms and hurricanes are happening 64 percent more frequently in New York since 1948.

“As the old saying goes, when it rains, it pours—especially in recent years as bigger storms have hit New York more often,” said Eric Whalen, Field Organizer for Environment New York.  “We need to pay attention to 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 in New York now happen every 7.3 months on average.  Moreover, the biggest storms are getting bigger.  The largest annual storms in New York now produce an average of 25 percent more precipitation 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 snowstorms. 

Eric Whalen pointed to the rainstorms that hit New York in August and September of 2011 as an illustration of what more extreme precipitation could mean for the state.  Hurricane Irene, which dumped 7.2 inches of rain on the area, led to large scale flooding, the loss of 9 lives in NY, and the shutting down of the NY Metro-Area transportation system.

The new Environment New York 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.

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 New York and the New York Metro-Area include:

  • Extreme rainstorms and snowstorms are becoming more frequent. New York experienced a 64 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 every 7.3 months, on average.
  • Storms with extreme precipitation increased in frequency by 55 percent in the Mid-Atlantic during the period studied.  The Mid-Atlantic region ranks 2nd 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 New York increased by 25 percent from 1948 to 2011. The amount of precipitation released by the largest annual storms in the Mid-Atlantic increased by 23 percent from 1948 to 2011.

Whalen 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.  Environment New York 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 York 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 - but only if we act boldly to reduce the pollution that fuels global warming,” said Eric Whalen. New York officials can build on the progress we have made in 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."