Scientists say the new study could be taken into consideration in legal cases holding companies accountable for their role in climate change.
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Fifty-five heatwaves over the past quarter-century would not have happened without human-caused climate change, according to a study published Wednesday.
Planet-warming emissions from 180 major cement, oil and gas producers contributed significantly to all of the heat events considered in the study, which was published in the journal Nature and examined a set of 213 heatwaves from 2000 to 2023.
The polluters examined in the study include publicly traded and state-owned companies, as well as several countries where fossil fuel production data was available at the national level.
Collectively, these producers are responsible for 57 per cent of all the carbon dioxide that was emitted from 1850 to 2023, the study found.
“It just shows that it’s not that many actors … who are responsible for a very strong fraction of all emissions,” said Sonia Seneviratne, a climate professor at the Swiss university ETH Zurich who was one of the study's contributors.
The set of heatwaves in the study came from the EM-DAT International Disaster Database, which the researchers described as the most widely used global disaster repository. The Nature study examined all of the heatwaves in the database from 2000 to 2023, except for a few that weren’t suitable for their analysis.
Global warming made all 213 of the heatwaves examined more likely, the study found. Out of those, 55 were 10,000 times more likely to have happened than they would have been before industrialisation began accelerating in the 1800s. The calculation is equivalent to saying those 55 heatwaves “would have been virtually impossible” without human-caused climate change, the authors wrote.
“Many of these heatwaves had very strong consequences,” said Seneviratne.
She said the series of heatwaves that struck Europe in 2022, which was linked to tens of thousands of deaths, sticks out in her mind as one of the events with particularly grave consequences.
Scientists calculate how carbon emitters influence heatwaves
Climate scientists can use complex computer programs and historic weather data to calculate the connection between extreme weather events and the planet-warming pollutants humans emit.
Climate change attribution studies often focus on how climate change influenced a specific weather event, but the scientists say this new Nature study is unique because it focuses on the extent to which cement and fossil fuel producers have contributed to heatwaves.
“They are drawing on a pretty well-established field of attribution science now, which has existed for about 20 years,” said Chris Callahan, a climate scientist at Indiana University who was not involved in the study. Callahan has used similar attribution methodologies in his research and said the new study is appropriate and high-quality.
Scientists say the new study could be taken into consideration in legal cases. Globally, dozens of lawsuits have been filed against fossil fuel companies by climate activists, American state governments and others seeking to hold the companies accountable for their role in climate change.
For example, Vermont and New York have passed laws that aim to hold fossil fuel companies accountable for their emissions and the damage caused.
“For a while, it was argued that any individual contributor to climate change was making too small or too diffuse a contribution to ever be linked to any particular impact. And this emerging science, both this paper and others, is showing that that’s not true,” said Callahan.
Justin Mankin, a Dartmouth College climate scientist who wasn't involved in the study, said the findings provide insight into the origins of the heatwaves and how potential hazards from them could be minimised in the future.
“As we contend with these losses, the assessment of who or what’s responsible is going to become really important,” Mankin said. “I think there are some really appropriate questions, like who pays to recoup our losses, given that we’re all being damaged by it.”
