Hurricane Irene: An Early Taste of Climate Change?

In a year that’s already seen droughts in Texas, floods in Montana, and heat waves across much of the eastern part of the country, you might think US residents have already had their share of weather-related disasters in 2011.  Yet now it looks like densely populated cities on the east coast could face one of the year’s most dangerous weather events yet.

Hurricane Irene, a major tropical storm, has glanced off the North Carolina coast and is predicted to hit New York and other states further north over the course of the next few days.  If it pummels highly populated areas, like New York City, it could cause unprecedented amounts of property damage, and perhaps the loss of hundreds of lives.

But Hurricane Irene is more than a potential catastrophe looming in the immediate future.  Like this year’s floods, droughts, and heat waves, it is also a sample of the kind of extreme weather that is growing more common as a result of climate change.

For years, scientists have warned that global warming and associated regional changes in climate will produce more severe storms—including hurricanes.  Sure enough, the last several years have seen more than their share of tropical storm activity in the Western Atlantic Ocean.  This trend hasn’t registered fully in the public consciousness, because in any particular year stronger tropical storms don’t necessarily translate into more damage from hurricanes.

The destructiveness of the hurricane season depends on where storms land, which varies randomly from year to year.  When Hurricane Katrina hit New Orleans in 2005, the danger posed by hurricanes seared itself into the national consciousness.  On the other hand, last year saw relatively little damage in the US from hurricanes.  Though an unusually large number of storms grew out of the Western Atlantic, by pure luck none hit a US population center.

None of this changes the fact that the number of intense storms has increased dramatically since the middle of last century.  As this has happened, it has become more likely in any given year that a major storm will hit a population center.  That could be what’s about to happen this year, as Hurricane Irene prepares to slam North Carolina and states further north.

Hurricanes have always occurred up and down the east coast of the US, but storms the size of Hurricane Irene are rare in northern latitudes.  The last major hurricane to collide with land as far north as New York was the “Great Storm of 1938,” which hit Long Island and flooded parts of New York City.  Since then the odd Category Two hurricane has made it that far up the coast, but for the most part these storms have steered clear of dense populations.

Hurricane Irene might be about to break that trend.  And while it will probably be smaller than the Great Hurricane of 1938 by the time it reaches Long Island, it has potential to cause far more damage.  That’s because Long Island is a much more populated place than it was in 1938, with low-lying areas highly vulnerable to flooding.

If the worst-case scenario occurs, and Hurricane Irene floods New York City, it will be impossible to put the blame solely on climate change.  However conditions like warmer-than-average waters in the Atlantic, and a 4% increase in atmospheric water vapor due to rising temperatures, have likely helped the storm grow stronger than it would have otherwise.  These conditions, the result of climate change caused by human activity, can be expected to lead to worse storms in the future.

It might be comforting to say that Hurricane Irene can’t be blamed on global warming with certainty—just as it would be nice to dismiss droughts, floods, and heat waves as chance events.  But the truth is a changing climate has produced a world where extreme weather of all types is becoming more common.  Hurricane Irene may be just a preview of things to come.

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