Fossil Fuel Emissions Made Intense Heatwaves 20 to 200x More Likely, Study Finds

Pollution from 180 major fossil fuel and cement companies has made recent heatwaves hotter and more frequent, a new study in the journal Nature finds. Some heatwaves were “statistically improbable” and likely would not have occurred without the companies’ contribution to climate change.

“Events that were near impossible in the past are now occurring,” write the climate researchers at ETH Zurich.

The study tracks emissions from the 180 carbon majors between 2000 and 2023. Climate change made the 213 heatwaves in the study more likely and more intense in that period, compared to a world without climate change. Median or typical heatwaves were 20 times more likely in the first nine years, and 200 times more likely between 2010 and 2019. About a quarter of them “were virtually impossible without climate change.”

The study calculated the overall emissions from the carbon majors and measured that alongside the warming that has been observed. Emissions were broken down and attributed to each carbon major to cover “the emissions associated with the full value chain of their products, including all emissions in line with established accounting and reporting standards” for corporations. The researchers then projected how global warming would have progressed differently if any single company’s emissions had not been produced. From this, they measured the carbon majors’ contribution to climate change, determining how each company was accountable for its influence on heatwaves.

“For each heatwave, we calculate how climate change affected its intensity and likelihood,” lead author Yann Quilcaille, a postdoctoral researcher at ETH Zurich, said in a release. “We identify both the impact of each individual company and the combined effects of other human and natural factors.”

The 14 largest carbon majors contributed the most to the occurrence of heatwaves. But smaller companies still had an effect. “Depending on the carbon major, their individual contribution is high enough to enable the occurrence of 16 to 53 heatwaves that would have been virtually impossible in a preindustrial climate,” the paper states.

The study included publicly traded and state-owned companies, and countries where national fossil fuel production data was available. Collectively, the companies were responsible for 57% of all the carbon dioxide emitted from 1850 to 2023, The Associated Press reports.

The Canadian Press writes that the deadly 2021 heat dome over British Columbia was an estimated 2.3°C hotter because of climate change. Emissions assigned to Cenovus Energy, Suncor Energy, and Canadian Natural Resources Ltd.—three of Canada’s largest oilsands producers—combined to contribute about 0.0073° of that intensity, according to supplementary data published by the authors.

The researchers say their findings are important to fill gaps in climate attribution research, suggesting their method can be used to determine accountability for other natural disasters linked to climate change, like sea level rise, fires, or droughts. The results can also support policy-making, as well as legal challenges against carbon polluters.

Quilcaille said that while individuals burn fossil fuels to fly, drive, and heat their homes, companies should be held to greater accountability because they have pursued their own economic interests to advance their carbon-intensive business models, including by lobbying and spreading disinformation to undermine climate action.

Andrew Gage, staff lawyer with West Coast Environmental Law, who was not connected to the study, told CP that “at some level, we are all collectively responsible for climate change, but at the same time, this type of paper just makes it that much clearer how much more responsible these companies are.”

“The fact that they are not paying any of the costs associated with the harm, and in fact, they’re making record profits selling these products, sort of shows the problems with the way we’ve tackled this legally and economically until now,” said Gage, one of the leads behind WCEL’s Sue Big Oil campaign.

Cover photo:  Jeremy Bezanger/Unsplash