It wasn't caused by climate change, but it was a 1-in-700 year storm in other ways and it became the only tropical cyclone in the historical record to do one thing.
The storm brought wind and water to the east coast and more than 100 people died, while tens of billions of dollars in damage were caused. Sandy caused record-breaking flooding in parts of New Jersey, New York, and elsewhere. In lower Manhattan water levels hit 4.28 meters (14.04 feet) above the mean low water level-the highest flood waters in the region since sensors were installed in 1920. One of the drivers behind Sandy's extreme storm surge was the unusual angle Sandy took as it hit the New Jersey coast. Most tropical cyclones in the North Atlantic sweep up the coast on a northward or northeastward track. Sandy, on the other hand, drove into New Jersey traveling toward the northwest - the only tropical cyclone in the historical record to do so.
With this near-perpendicular approach, Sandy's onshore winds had more time to drive a wall of water onto one coastal region, rather than moving along a swath of coastline.
Using information of tropical cyclone tracks for the whole North Atlantic from 1950 to 2010 Hall and Sobel calculate the odds that a similar storm - a category 1 or higher hurricane with an approach angle to New Jersey at least as close to perpendicular as Sandy - could happen again.
According to the authors' statistical model, the occurrence rate of a Sandy-style storm is 0.0014 per year, meaning that if future hurricane activity matches the recent past we should expect a storm like Sandy on average about once every 700 years.
The fact that Sandy happened, the authors say, either means that New York and New Jersey were simply unlucky, or that climate change has increased the probability of Sandy-like storms beyond what can be predicted by steady-climate statistical models.
Citation: Timothy M. Hall and Adam H. Sobel, 'On the Impact Angle of Hurricane Sandy's New Jersey Landfall', Geophysical Research Letters, doi:10.1002/grl.50395
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