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LONDON, May 25, 2021  We know already that the human cost of climate change is immense. Now we can put a figure on it. Nine years on, New Yorkers have a clearer idea of the direct cost of human-driven climate change to them during just one stormy weekend in October 2012.

With more and worse superstorms probably on the way, we need to know as much as possible. Image: By Zoltan Tasi on Unsplash 

They became poorer by $8.1 billion, say researchers from Princeton, New Brunswick and Hoboken in New Jersey, and Boston in Massachusetts, just because of sea level rise powered first by global heating fuelled by profligate combustion worldwide of coal, oil and gas, and then by a superstorm called Hurricane Sandy.

Researchers can also number the additional people who suffered damages inflicted precisely because of human-driven climate change on that one long, painful weekend: 71,000.

“This study is the first to isolate the human-contributed sea level effects during a coastal storm and put a dollar sign to the additional flooding damage,” said Philip Orton, of Stevens Institute of Technology in Hoboken, one of the authors.

“With coastal flooding increasingly impacting communities and causing widespread destruction, pinpointing the financial toll and lives affected by climate change will hopefully add urgency to our efforts to reduce it.”

“If we were to calculate the cost of climate change across all flooding events that figure would provide clarity on the severe damage we are inflicting on our planet”

There would have been damage anyway: Sandy was a powerful hurricane that slammed into the northeast US coast so hard it set the earthquake alarms ringing. The destruction attributed to Sandy is more than $62 billion, as one of the worst storms in history at the New York bight arrived with the evening high tide to cause devastation and disruption in New York City, New Jersey and Connecticut.

It also killed 43 people in New York City and destroyed thousands of homes and around a quarter of a million cars, vans, buses and trucks.

And now a study in the journal Nature Communications reasons that anthropogenic or human-powered sea level rise must have accounted for at least 13% of the total bill. That is because global heating from greenhouse gas emissions seems to have raised mean sea levels in the New York region by around 10 cms over the last century or so. In fact, Sandy arrived with the highest water level in at least 300 years in the New York metropolitan area.

The researchers set themselves the target of identifying precisely the impact of climate change on sea level rise in that region. To do that, they had to subtract the change that could be explained by coastal subsidence: as a consequence of heavy construction and groundwater abstraction, coastal settlements everywhere are likely to subside.

Knowing the threat

Then they combed maps of the damage, contour data and insurance data to arrive at a specific contribution by sea level rise linked to climate change: at the very least, they judged, $4.7bn, at the most $14bn, and so they compromised on $8bn.

They then numbered the humans who might not have been hit by flooding had there been no climate change: they calculated at least 40,000, and no more than 131,000, before settling on 70,000 additional victims.

Such exercises matter: city planners, coastal defence agencies, insurers and seaside property-holders need to know the scale of extra risk conferred by climate change. There will be more storm damage and flooding, and the new methodology could be adapted to other vulnerable cities.

US coasts already face more frequent floods, rising seas promise more such superstorms and − once again because of global heating − the north-eastern US seaboard can expect to be in the track of fiercer hurricanes.

“If we were to calculate the cost of climate change across all flooding events − both nuisance floods and those caused by extreme storm events − that figure would be enormous,” Dr Orton said. ”It would provide clarity on the severe damage we are inflicting on ourselves and on our planet.” − ClimateNewsNetwork.net

Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.