How rare was Superstorm Sandy? A new analysis of historic storms and modeling suggests it was a one-in-700-year event. The fact that it happened at all could mean either that it was just terrible luck to be alive in New Jersey in the century it happened, or that climate change is increasing the chances of such weird storm tracks.
Tropical Storm Sandy collided with the New Jersey shoreline on Oct. 29, 2012, killing more than 100 people and wreaking damages in the tens of billions of dollars. It caused unprecedented flooding by raising waters to more than 14 feet (4.3 meters) above sea level.
What made it so bad was the odd angle at which Sandy hit the New Jersey-New York area. Most tropical storms in the North Atlantic track up the Atlantic coast in a north or northeasternly manner. But Sandy took a hard left and headed to the northwest before it slammed into land. It was, in fact, the only tropical cyclone in history to take that critical, and terrible, route.
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To determine just how uncommon the storm was, researchers Timothy Hall of NASA's Goddard Institute for Space Studies and Adam Sobel of Lamont-Doherty Earth Observatory at Columbia University have looked back at tropical cyclone tracks for the whole North Atlantic from 1950 to 2010. Then they figured out the odds that a Category 1 or greater hurricane with a track like Sandy's could happen again.
What they discovered is that the statistical likelihood of a Sandy is 0.14 per year. In other words, Sandy is a once-in-a-700-year storm. But that's assuming that the climate of 1950 through 2010 continues into the future, which will not be the case.
"The fact that our calculations show Sandy's track to be so rare under long-term average climate conditions implies either that the New York-New Jersey area simply experienced a very rare event (with climate change playing no significant role), or that a climate-change influence increased the probability of its occurrence," wrote the researchers in their just-published paper in the journal Geophysical Research Letters.
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In fact, the loss of Arctic sea ice has been offered up as a cause for the Sandy's weird track. The hypothesis is that as the Arctic gets warmer, the jet stream gets loopier, which can create strange paths just like this one for storms.On the other hand, some climate models fail to show this effect, they report.
What is agreed on by most climate and weather researchers is that global warming is increasing the frequency of intense weather events like Sandy.
"The more certain effect of climate change is through further sea level rise, with a meter or more expected in the next century," Hall and Sobel wrote. "This will exacerbate (tropical cyclone)-induced flooding even if the storms themselves do not change."