In 2023, the Winooski River in Vermont spilled its banks, kissing the green truss bridge that spanned it. River water poured onto the marble floors of the State House. Up to nine inches of rain fell within 48 hours, causing hundreds of millions of dollars in damage.
A year later, Vermont enacted the Climate Change Superfund Act, which holds oil and gas companies financially responsible for climate damage in the state. Similar legislation passed in New York in 2024 and is pending in California, Maryland, and Massachusetts.
Underpinning the laws is attribution science, which models huge numbers of scenarios using global temperature data to determine the likelihood that extreme weather events like floods or heat waves are related to emissions from burning oil, gas and coal.
A new paper published on Wednesday in the journal Nature expands this type of work to link the emissions from specific emitters to the economic burden of extreme events.
“The oil industry is alarmed by state climate superfund laws and their growing popularity because they are the first policies adopted anywhere in the world that make climate polluters pay a fair share of the enormous damage their products have caused,” said Lee Wasserman, director of the Rockefeller Family Fund, the New York-based charitable foundation that helped created the climate superfund law.
Reaction to the laws was swift. In February, West Virginia and other Republican-led states sued to block New York’s law, saying that only the federal government could regulate emissions. President Trump signed an executive order this month calling the state laws “burdensome and ideologically motivated” and asked Attorney General Pam Bondi to block their enforcement.
For decades, environmental lawyers have been considering how to attribute the harm from greenhouse gas emissions, according to Martin Lockman, a climate law fellow at Columbia University’s Sabin Center.
“Attribution science is incredibly important because it draws a link between specific activities from a company profiting from fossil fuels and specific harms to states and communities,” Mr. Lockman said. “If you cause harm you should be responsible for cleaning it up, it’s as simple as that.”
The new study refines an approach known as “end-to-end” attribution, which links one particular emitter (a company, for instance) to one particular climate-related impact (extreme heat, for example) to a specific damage (a downturn in the global economy).
The study found that Chevron’s emissions had caused up to $3.6 trillion in heat-related losses to global gross domestic product. Christopher Callahan, a postdoctoral earth scientist at Stanford University and an author of the study, said such a high cost was still a gross underestimate of the global impact of burning fossil fuels, especially in poorer, tropical regions that are least responsible for emissions.
“That staggering figure represents damages from just one climate impact,” said Delta Merner, associate director of the Science Hub for Climate Litigation at the Union of Concerned Scientists. “The total harm attributable to major emitters is undoubtedly far greater when the full range of climate hazards is taken into account.”
Theodore J. Boutrous, Jr., a lawyer for the Chevron Corporation said the Nature article “ignores the scientific impossibility of attributing particular climate and weather events to any specific country, company, or energy user. It is part of a misleading advocacy campaign on behalf of wasteful and unconstitutional state lawsuits and energy penalty laws.”
Overall, the paper found that the world would be $28 trillion richer were it not for the extreme heat caused by the emissions from 111 major carbon producers between 1991 and 2020.
Since 2017, more than 100 climate-related lawsuits have been filed each year, according to the new study. But the attribution studies those cases relied on often failed to link emissions to estimated economic damages.
This new framework could provide a function similar to other big damage and loss cases, like holding tobacco companies responsible for lung cancer cases or pharmaceutical companies for opiate addiction.
“Legal scholars have called this kind of attribution the holy grail of climate liability,” said Justin Mankin, a geography professor focused on climate science at Dartmouth College and an author of the Nature paper.
World Weather Attribution, a group run out of Imperial College London, has regularly issued attribution reports over the past decade.
“Sadly we’re still the only ones who really do this, and we’re not an institution, it’s basically a project I do as a university professor working with a team of people,” said Friederike Otto, a physicist who helps to lead World Weather Attribution.
Dr. Callahan and Dr. Mankin used open source tools for their models, and they have made the code and data sources they used to compile the global costs of climate change publicly available on their websites.
“We believe in openly transparent science, especially since the work was paid for by U.S. taxpayers,” said Dr. Mankin, noting that much of the support for the research was financed by the National Science Foundation and NOAA, two of the nation’s largest climate science agencies that have been targeted for funding cuts under the Trump administration.
Extreme weather events continue disrupt communities and strain finances. The 2023 flooding cost Vermont hundreds of millions of dollars, according to Anne Watson, a Vermont state senator who sponsored the bill quantifying the state’s damages between 1995 and 2024. It passed the Legislature last year and the state’s Republican governor allowed it to become law without his signature.
Julie Moore, secretary for the Vermont Agency of Natural Resources, helped organize the request for more information to help the state better understand different approaches to attribution science and how to allocate damages caused by greenhouse gas emissions.
“The charge to us is to adopt rules of how we’ll apply attribution science and ultimately send out cost recovery letters,” Ms. Moore said. The state law says oil and gas corporations will receive letters at the start of 2027.
“The hope is that it’ll result in a significant amount of money coming into Vermont to help both pay for the damage and help us adapt to a hotter, wetter climate that’s a result of this carbon in the atmosphere,” Ms. Watson said. “We need to go to the source of who’s responsible for this.”
