More than eight billion dollars of the damage caused by Hurricane Sandy along the US northeast coast in 2012 can be blamed exclusively on manmade climate change, according a study released Tuesday.
Sea level rise caused by global warming was also responsible for an additional 36,000 homes being flooded, researchers reported in the journal Nature Communications.
The findings are the first to tease out the dollar value of devastation from the superstorm attributable just to climate change, the authors said, adding that the methods developed can be applied more widely to other cyclones and storm surges.
"If we were to calculate the costs of climate change across all flooding events, that figure would be enormous," said co-author Philip Orton, an associate professor at the Stevens Institute of Technology in New Jersey.
All told, Sandy caused nearly $63 billion (51.5 billion euros) in damages in the tri-state area of New York, New Jersey and Connecticut. It raged for more than a week, killing scores of people in the Caribbean and nearly 150 people in the United States.
"Climate change is already hurting us far more than most of us understand," lead author Ben Strauss, CEO and chief scientist of Climate Central, told AFP.
"We just don't usually do the accounting."
Thousands of people in Hurricane Sandy's path saw their homes suffer expensive and sometimes financially crippling damages purely because of global warming.
"They may not realise it, but they were victims of climate change, full stop," Strauss said.
The study concludes that every centimetre of sea level rise would have translated into roughly an extra billion dollars of damage.
'Low-end estimate'
Oceans have risen more than 3 cm (1.2 inches) in the decade since Sandy, meaning that the same storm today — assuming no change in infrastructure of protection — would inflict a repair bill topping $11 billion.
The estimate is conservative, Strauss said, because it looked only at the impact of climate change on sea level rise, not the storm itself.
Rising temperatures have translated into bigger hurricanes, typhoons and cyclones that hold more water, generate greater wind speeds, and linger longer over land, earlier research has shown.
"It's fair to think of our numbers as low-end estimates that consider only part of warming's effect — and possibly the smaller part," Strauss said.
The study's conclusions were based on a modelling that simulated the effect of various sea levels on impacts from flooding during the storm.
To be sure they were measuring only the influence of manmade climate change, the researchers removed from the equation the impact of natural land subsidence and that part of sea level rise which is due to natural processes.
Expanded to a global scale, the damages due to sea level rise could easily climb into the hundreds of billions of dollars or more over the coming decades.
Earlier research by Strauss found that land that is home to 300 million people could be exposed to annual coastal flooding by 2050, and that land home to 150 million people could be lower than high tides.
These figures are roughly the same regardless of how quickly humanity ramps down carbon emissions.
"But they diverge significantly at the end of this century," Strauss said.
Sharp cuts in carbon pollution over the coming decades could mean 50 million fewer people exposed to coastal flooding in 2100 compared to a scenario in which emissions continue unabated, he said.
