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Climate change boosted Hurricane Sandy’s damage by $8 billion, study finds

Scientists have sifted out the role climate change played in making Sandy more destructive

Sandy on Oct. 30, 2012. (NASA)

Hurricane Sandy, which struck coastal New Jersey in October 2012 as a potent cyclone, caused over $60 billion in damage, claiming at least 125 lives in the United States and knocking out power to more than 7 million customers. It was the nation’s most expensive storm since Hurricane Katrina at the time, flooding long stretches of the Mid-Atlantic and sending water gushing into the New York City subway system.

A study published Tuesday in Nature finds that climate change was responsible for at least $8 billion in monetary losses associated with Sandy. The authors found evidence that climate change made the storm’s surge, or rise in ocean water above normally dry land, more severe, increasing the amount of coastline inundation.

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It’s further proof of the rising cost of human-induced climate change, manifest both in the increasing price tag of climate-fueled natural disasters and more subtle changes to everyday life required to adapt to them.

Sandy will be remembered as the widest tropical cyclone on record in the Atlantic, its tropical-storm-force winds at one point expanding outward up to 820 miles from one side of the storm to another. The storm lashed areas from Florida and the Bahamas to northern Maine, even bringing a substantial October snow to the west slopes of the central Appalachians.

In the past, it was said that no single event could be tied to climate change, but increasingly sophisticated modeling technologies coupled with improved physical understanding now permit atmospheric scientists to disentangle a climate signal. In other words, scientists can often re-create an event and determine what aspects of it and its subsequent impact were caused or made worse by climate change.

The authors of the paper acknowledged that the links between climate change and storms like Sandy require more study, and instead focused on coastal flooding. The link between climate change, melting polar ice caps and sea level rise is well-understood and quantified.

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Since 1900, global sea levels have risen by more than seven inches.

That means that a storm now would cause more surge damage than the same storm just a century ago. It’s like living in a house; if your floor gets a bit higher every year, eventually you’re going to hit your head on the ceiling more frequently.

The authors constructed a computer model to simulate Sandy’s impact in a variety of tidal and sea level change scenarios. They cite research that indicates between 87 and 92 percent of observed sea level rise in New York City can be directly linked to human-caused climate change.

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They then used those values and applied them to the sea level rise values observed in New York City, which are somewhat larger than the global average, to obtain estimates of how much sea level rise is attributable to human activities in the Big Apple.

From there, the scientists ran their model and re-created Sandy’s surge with and without the margin of human-caused sea level rise. Even in the most conservative scenario, they found that at least $4.7 billion in damage can be traced back to humans.

There’s a 95 percent chance that the actual value is higher — in the ballpark of $8.1 billion. Some estimates, which were made under the assumption of humans having had an even more substantial impact, peg human-induced climate change as being to blame for up to $14 billion in losses.

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That money isn’t abstract — damages like those that occurred during Sandy are reflected in the price of insurance plans and premiums, particularly for those in vulnerable areas. It’s a real-life cost of climate change that millions of Americans already face.

“Sandy isn’t the only extreme storm that sea level rise due to human-caused global warming has contributed billions in damage to,” Jeff Masters, an atmospheric scientist and longtime weather writer, said in an email. “And it is possible that some of the levee breaches that inundated New Orleans during Hurricane Katrina of 2005, which killed over 1,000 people and caused $170 billion in damage, would not have happened without human-caused sea level rise.”

The findings come at a time punctuated by discussions surrounding the growing impacts climate-fueled natural disasters are having on the U.S. economy, including those from wildfires and drought in the West, more frequent and severe flood events along the Gulf Coast and the uptick in wetter and stronger tropical storms and hurricanes.

A separate study, published Wednesday in the journal Climatic Change, found climate change damages from Hurricane Harvey, which resulted in Texas’s worst flooding disaster on record, totaled $13 billion.

Kerry Emanuel, a hurricane researcher at MIT and pioneer in the field of tropical meteorology, offered stark insight into the concerning conclusions of the Sandy study.

“It drives home how costly small changes in climate can be to a civilization that is so exquisitely fine tuned to the stable climate we enjoyed until we began pouring greenhouse gases into the atmosphere,” he wrote.

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Jason Samenow contributed to this report.