A major study of more than 200 heatwaves this century has found that as many as one in four would not have been possible in a world without human-driven global heating.
Scientists analysed 213 heatwaves between 2000 and 2023, from Europe’s deadly 2003 summer to the record-shattering Pacific Northwest heat dome in 2021, and found every single one was made more intense and more likely by the climate crisis.
The study, published in Nature, also found that a small group of just 14 companies, comprising the world’s biggest fossil fuel and cement producers, were linked to around a third of all the additional heat fuelling today’s extremes.
These companies include Saudi Aramco, ExxonMobil, BP, Shell, Gazprom and the state coal industries in China, Iran and India.
While scientists also stressed that heatwaves are a natural part of the climate system, the evidence shows their intensity and frequency have been radically reshaped by industrial emissions.
“Meta-analysis over time shows that the extremeness of the heatwaves is rising more and more rapidly because of climate change, both in intensity and probability,” the authors wrote.
Researchers found these big emitters could be linked to the occurrence of between 16 and 53 heatwaves that would otherwise have been virtually impossible.
The median estimates indicate that compared to 1850–1900, heatwaves became 20 times more likely between 2000 and 2009 and 200 times more likely from 2010 to 2019 as a result of humanity’s carbon emissions.
The intensity of heatwaves increased by 1.4 C from 2000 to 2009, 1.7 C during 2010 to 2019 and 2.2 C from 2020 to 2023, the study showed.
The findings could have major implications for ongoing climate lawsuits. Courts and policymakers have often struggled to directly connect corporate emissions to specific disasters, but increasing number of studies are now finding data to hold companies directly responsible for extreme weather events.
Such findings can also raise pressure on governments to act faster to cut emissions. The United Nations has repeatedly warned that extreme heat is one of the deadliest consequences of the climate crisis, with the World Health Organisation estimating that heatwaves already kill tens of thousands of people every year. In 2023, heatwaves in Europe alone were found responsible for the deaths of over 40,000 people.
“It is another reminder that denial and anti-science rhetoric will not make climate liability go away, nor will it reduce the ever-increasing risk to life from heatwaves across our planet,” wrote Karsten Haustein from the University of Leipzig in Germany.
