Climate Impacts of Hurricane Harvey: $67 Billion

In a finding that could radically alter future calculations of the social cost of carbon, researchers say new methods of event attribution have now pegged the share of damages from Hurricane Harvey that were caused by global warming at 74.4% of the US$90-billion-plus total—much higher than previous estimates of 22%.

After Harvey ravaged the Caribbean, Texas, and Louisiana in 2017, conventional economics, unequal to the complexity of ascertaining just how much climate change had torqued up the catastrophic storm, put the climate share of the damages at $20 billion. But less than three years later, advances in the science of climate attribution have led researchers in the U.S. and New Zealand to adjust Harvey’s climate damages to a whopping $67 billion, reports the Guardian. The researchers published their findings in April in the journal Climactic Change.

To break down the storm’s damage using the new, more accurate climate attribution tools, the researchers calculated the odds of Hurricane Harvey “happening naturally or under increased carbon dioxide levels, and applied the results to the damage caused,” reports The Guardian. Similar methodology was used in another study published last month in the same journal, which calculated that the droughts that withered New Zealand between 2007 and 2017 “cost the economy about NZ$4.8 billion, of which $800 million was directly linked to climate change.” The authors also determined that, of the $470 million in insured flood losses the country experienced during the same 10 years, $140 million was climate linked.

“We’re pretty sure the climate change-related damages associated with extreme events have been underestimated in most assessments of the social cost of carbon,” said David Frame, professor of climate change at the Victoria University of Wellington and lead author of both studies. “We think this line of research, as it matures, should provide a really valuable input.”

Friederike Otto, director of the Environmental Change Institute at Oxford University, said the new climate attribution methods “could make it possible to generate global estimates of the true cost of climate breakdown, which could have a profound effect on how governments and businesses approach the need to reduce greenhouse gas emissions,” writes The Guardian.

“We have known about the costs of climate change theoretically,” said Otto. “It’s all very well in the abstract, but the global mean temperature does not kill anyone—extreme events cost money and lives. Being able to attribute these impacts to climate change means being able to convey what climate change really means.”

Achieving a more accurate picture “could also help developing countries seeking recognition of the loss and damage they face as a result of climate breakdown, which they argue should spur rich countries to provide more assistance”—likely making loss and damage a key issue at an (eventually rescheduled) COP 26, The Guardian adds.

In a guest post for Carbon Brief, Frame and three other researchers who were involved in the two studies elaborated on the “several ways” their work with climate attribution tools could be used to accelerate climate action. Noting that the significance “is less in the exact numbers and more in the ability to link, more forensically, human influence on the climate to the economic impacts of disasters,” the authors say the revelations of climate attribution could serve as evidence for central banks, insurance companies, policy-makers, climate litigators, and even investors.

“If the social cost of carbon is currently underestimated, and if our new approach can potentially lead to legal actions, then these constitute very powerful arguments for firms to accelerate their divestment initiatives,” they write.