One quarter of more than 200 heat waves that occurred worldwide this century may have been impossible without human-induced global warming. Emissions from the world’s largest fossil fuel and cement companies played a significant role in worsening those events, according to a paper published Wednesday in the journal Nature.
The study is the first to assess the historic impact of climate change on a large series of heat waves. The scientists concluded that emissions from the world’s 180 largest carbon emitters contributed to about half of the increase in intensity of heat waves since preindustrial times. They further determined that 14 of the largest carbon majors, including Exxon Mobil Corp., Saudi Aramco and Gazprom PJSC, played a role in more than 50 heat waves that otherwise would have been almost impossible.
While past studies have mostly looked at emissions from regions and countries, this review focuses on major carbon emitters, said Yann Quilcaille, the report’s lead author and a postdoctoral researcher at ETH Zurich.
“This research is an important step towards accountability,” says Friederike Otto, a professor in climate science at the Imperial College London who wasn’t involved in the study.
Otto is co-founder of World Weather Attribution, a scientific group that pioneered extreme event analysis and whose approach is adopted by the authors of the new study. The latest findings come as the number of climate lawsuits against polluters has surged in recent years, while citizens, communities and states seeking justice have often struggled to prove their case in court.
To help bridge the knowledge gap, scientists are stepping up their efforts to use climate attribution research to examine a wider range of extreme weather events and connect them to specific actors. Earlier this year, a study published in Nature found that Saudi Aramco and Gazprom were each responsible for about $2 trillion of lost global economic growth from extreme heat.
Saudi Aramco declined to comment, while Gazprom and Exxon Mobil haven’t responded to requests for comment.
A growing body of scientific evidence is “opening the door to hold fossil fuel companies responsible” for the harm that their businesses have caused to communities and ecosystems worldwide, Otto said.
In an accompanying essay published in Nature, Karsten Haustein, a Leipzig University climate scientist not involved in the study, wrote that it “is another reminder that denial and anti-science rhetoric won’t make climate liability go away, nor will it reduce the ever-increasing risk to life from heat waves across our planet.”
While heat waves are still considered a natural weather phenomenon, greenhouse gas pollution is making them worse and more frequent. The added heat over time worsens wildfires, droughts, hurricanes and rainfall. Sizzling temperatures also can damage infrastructure, wreak havoc on productivity and increase the health hazards for people. In 2022, heat waves caused more than 60,000 premature deaths across Europe.
To calculate how climate change affects the likelihood and intensity of heat waves, the study’s authors analyzed 213 heat waves between 2000 and 2023 that caused significant social and economic disruptions. As WWA does in their analyses of individual events, the researchers used computer models to simulate how the heat waves would have unfolded under a preindustrial climate, compared with current times.
Their findings show that global warming has made heat waves more likely and more intense, and the situation has worsened over time. To be more specific, the heat waves became 20 times more likely between 2000 and 2009, compared with the preindustrial period between 1850 and 1900, and as much as 200 times more likely between 2010 and 2019.
The team also ran climate models, excluding the emissions of individual carbon majors to specify the effect of a single company on the global average temperature. Once they know how much those carbon majors have contributed to global warming and how the warming affects heat waves, the researchers can then quantify the individual impact from each of the carbon majors to the 213 heat waves recorded in a key international database. For example, fifty-five heat waves were made at least 10,000 times more likely by climate change. Emitters in the former Soviet Union alone made 53 heat waves that much more likely.
The more emissions a company releases, the bigger role it plays in worsening heat waves. But even the smallest polluter of the 180 carbon majors by emissions — Russian coal producer Elgaugol OAO — is responsible for 16 heat waves that would have been virtually impossible in a preindustrial climate, the study finds. Elgaugol hasn’t responded to an emailed request seeking comment.
As bad as this may sound, the actual climate damage caused by the carbon majors may have been even worse. Since many heat waves in parts of the Global South such as Africa and Latin America are underreported and absent from the database, “the study’s findings likely underestimate the true scale of these events, and the real consequences are probably far greater,” Otto said.
Photograph: An Exxon Mobil Corp. refinery at the Port of Rotterdam in Rotterdam, The Netherlands. Photo credit: Peter Boer/Bloomberg