As the world continues to grapple with record-breaking summer temperatures, a groundbreaking scientific study published on September 10, 2025, in the journal Nature has drawn a direct line between the planet’s most punishing heat waves and the pollution emitted by a relatively small group of fossil fuel and cement producers. This research, which spans 213 heat waves worldwide from 2000 to 2023, marks the first time scientists have quantitatively connected the dots between specific companies’ emissions and the worsening intensity and frequency of extreme heat events.
According to the Associated Press, the study found that 55 heat waves over the past quarter-century would not have happened at all without human-driven climate change. That’s not just a statistical quirk—scientists say these 55 events were “virtually impossible” before the industrial era’s surge in carbon emissions. These heat waves, many of which left deadly marks on communities, were made 10,000 times more likely by human-caused global warming, the researchers concluded.
But the findings go further. As reported by CNN, the study’s authors, including climate researcher Yann Quilcaille of ETH Zurich, determined that the 14 largest so-called “carbon majors”—a group that includes oil giants like ExxonMobil and Chevron—are responsible for about half of the increase in heat wave intensity observed over the past two decades. Even the smallest among these major polluters contributed to heat waves that would not have occurred without their emissions. In total, 180 major cement, oil, and gas producers were found to have played a significant role in every one of the 213 heat waves analyzed.
“We establish that the fossil fuel and cement producers substantially contribute to these heatwaves,” Quilcaille wrote in an email to CNN. “We clearly quantify the causal link from their emissions to the intensity and the probability of occurrence of the heatwaves.”
The study’s methodology is notable for its scope and precision. Rather than focusing on isolated events, the research team drew on the EM-DAT International Disaster Database, the world’s most widely used global disaster repository, to examine heat waves that spanned continents and years. By comparing current data to climate conditions before the industrial revolution, the scientists calculated that climate change has increased the median intensity of heat waves by 3.02 degrees Fahrenheit (1.68 degrees Celsius) between 2010 and 2019. Of that increase, 0.85 degrees Fahrenheit (0.47 Celsius) is directly attributed to the emissions of the top 14 carbon majors alone. The remaining 166 carbon majors contributed another 0.68 degrees Fahrenheit (0.38 degrees Celsius).
These numbers aren’t just academic. The consequences of these heat waves have been severe and, in some cases, tragic. Sonia Seneviratne, a climate professor at ETH Zurich and one of the study’s contributors, recalled the devastating European heat waves of 2022, which were linked to tens of thousands of deaths. “Many of these heat waves had very strong consequences,” she told the Los Angeles Times. The research, Seneviratne and her colleagues argue, underscores that a relatively small number of actors are responsible for a disproportionately large share of the world’s carbon emissions—57% of all carbon dioxide released from 1850 to 2023, in fact.
For decades, it was argued that the contributions of any single company or country to climate change were too diffuse to be linked to specific disasters. But as Chris Callahan, a climate scientist at Indiana University who was not involved in the study, told the Los Angeles Times, “this emerging science, both this paper and others, is showing that that’s not true.”
The implications of these findings could be far-reaching, particularly in the legal arena. As reported by Reuters and multiple outlets, dozens of lawsuits have already been filed around the globe by climate activists, state governments, and others seeking to hold fossil fuel companies accountable for their role in climate change. The new study’s detailed quantification of responsibility could provide a scientific backbone for future climate-damage lawsuits, a point emphasized by the inclusion of legal experts on the research team.
Corina Heri, a law professor at Tilburg Law School in Zurich and a coauthor of the study, explained to CNN: “Courts are indicating a willingness to hold carbon majors accountable, but at the same time asking for more scientific certainty, and our study helps to close a part of that gap.” Richard Heede of the Climate Accountability Institute, another coauthor, added, “In our study, we are providing early clues as to the impact of individual fossil fuel companies across their value chain from extraction, processing, distribution, and ultimate combustion of carbon fuels as intended by their global consumers. This study helps lay the foundation of who is at fault, and how to share responsibility.”
The research also highlights the need for even greater scientific precision. Kristina Dahl, vice president for science at Climate Central, called the study “a really compelling piece of work that connects some dots that haven’t been connected before.” However, she and other outside experts noted that the report may actually undercount the number of heat waves in regions like Africa and South America, where such events often go unreported. “While it does give a clear picture of the effect that fossil fuel emissions are having on temperatures around the world, the true impacts are probably much worse,” said Clair Barnes, a climate scientist at the Grantham Institute at Imperial College in the UK.
Looking ahead, the authors suggest that their methodology could be extended to other types of extreme weather events, such as floods and wildfires. The hope is that more robust attribution science will not only inform policy and legal proceedings but also help societies better prepare for, and perhaps mitigate, the hazards of a warming world. Justin Mankin, a climate scientist at Dartmouth College who was not involved in the study, reflected, “As we contend with these losses, the assessment of who or what’s responsible is going to become really important. I think there are some really appropriate questions, like who pays to recoup our losses, given that we’re all being damaged by it.”
With the United Nations and governments worldwide increasingly focused on climate accountability, this latest research may well mark a turning point—not just for the scientific community, but for courts, policymakers, and the public at large. As the heat rises, the search for responsibility, and ultimately solutions, is only intensifying.
