Learning about Our Risks from Hurricane Irene

So how bad was Hurricane Irene? Some commentators seem to think Irene didn’t match up to the media, yet  preliminary assessments suggest Irene will be one of the top 10 costliest hurricanes ever in the United States. New Yorkers are indeed fortunate that the worst case scenario did not play out in their fair city, but that doesn’t mean there were no worst case scenarios elsewhere.

The worst fears about wind intensity did not play out, but a different devastating outcome did occur: Historic inland flooding across a huge swath of the interior Northeast. From New Jersey to Vermont, as much as 12 inches of rain fell in a matter of hours, swelling creeks and streams to well beyond flood stage. Paterson, New Jersey, is still under several feet of water five days after the storm passed and many residents have not be able to return home. Thirteen towns in Vermont were cut off from the outside world, and relief workers were unable to reach one town for days. More than 250 Vermont roadways are damaged and 30 bridges were destroyed.

Route 107, Vermont

The historic flooding in New Jersey and Vermont is an important opportunity to learn even more about our vulnerabilities beyond the coastline and to put a proper price tag on the link between climate change and extreme weather risk. Cynical attempts to downplay Irene’s heavy toll on life, property, and critical infrastructure to distract attention from the serious risks of climate change are callous and irresponsible. Indeed, a scientifically strong link between global warming and heavy precipitation belies this dangerous rhetoric.

Paterson, New Jersey (Source: Los Angeles Times)

We are entering a new climate reality and a new era for extreme weather, and the strongest science we have on the relationship between climate change and hurricanes is on extreme rainfall. The documented increase in heavy downpours in the Northeast and elsewhere is due to increased moisture in the atmosphere thanks to elevated air and ocean temperatures. This process, combined with previous rainfall that saturated the ground in the Northeast, created conditions ripe for historic flooding.

Hurricane Irene calls to mind another recent hurricane where many of the impacts were felt farther inland. In addition to nearly destroying Galveston, Hurricane Ike cut a swath from the Gulf Coast to Michigan in 2008, dropping as much as 7 inches of rain over some inland areas. Ike caused massive power outages and floods that drowned thousands of cattle in Texas and Oklahoma. In Vermont, with its mountainous topography, Irene triggered flash flooding that swept away bridges across the state instead of inundating pastureland. Numerous small streams and brooks swelled, submerging towns and sweeping away houses located nearby (e.g., here and here). In Maine, floods washed away bridges and severed a major trucking route into Canada. Rivers in New York flooded agricultural land, devastating the mostly small, family-owned farms

Tellingly, heavy rainfall—the part of the hurricane-climate change link that scientists understand best—caused the majority of Hurricane Irene’s damage to the interior Northeast. This combination of experience and scientific understanding informs our understanding of climate change risks. The risk posed by extreme rainfall—both from hurricanes and ordinary rain storms—has already increased and will continue to rise in the near future. The dialogue surrounding hurricanes should acknowledge these risks that go beyond simply reporting maximum sustained wind. Irene was not a particularly intense storm based on wind speed, but her huge size and precipitation rates were extraordinary, and sadly, so were the consequences.

Unfortunately, similar devastation could play out in the South over the Labor Day weekend, as a new tropical storm is forming in the Gulf of Mexico. While this storm is not expected to reach hurricane strength, it is very large and could drop up to 20 inches of rain and presents a risk of severe flooding in many inland areas in addition to the coast.

Dan Huber is a Science & Policy Fellow