The climate change caused by humans makes heat waves more likely and more intense – and large companies have a decisive part of this. This is the result of a study that evaluated more than 200 heat waves that occurred in different parts of the world between 2000 and 2023. Accordingly, the 180 largest producers of fossil fuels and cement are responsible for half of the increase in heat waves since 1850. The results underline the responsibility of large companies and could offer a basis for future climate laws.
Due to man -made climate change, not only the global average temperatures increase. Extreme weather events such as heat waves, heavy rain or droughts are becoming more common. With the help of climate models, so -called attribution studies can be calculated to what extent an extreme weather event that has occurred can be attributed to climate change and with what probability it would have occurred without anthropogenic greenhouse gas emissions. So far, however, such studies have mainly referred to individual events and gave no broad overview of the whole of such extreme weather and their causes.
Influences of climate change
A team led by Yann Quilcaille from ETH Zurich has now examined 213 heat waves that occurred in different parts of the world between 2000 and 2023. Using climate simulations, they calculated the probability of which corresponding temperatures would have occurred even without the man -made climate change. In these analyzes, they came across a clear trend: “Climate change has made each of these heat waves more likely and more intense, and the situation has worsened over time,” reports Quilcaille.
Compared to the reference period between 1850 and 1900, the likelihood of heat waves between 2000 and 2009 increased 20 times and even 200 times for the period between 2010 and 2019. In addition, between 2000 and 2009 the heat waves were 1.4 degrees Celsius hotter than would have been expected without climate change. Between 2020 and 2023, the influence of climate change even increased the heat wave temperatures by 2.2 degrees Celsius. “A quarter of these heat waves would have been almost impossible in this intensity without the man -made climate change,” reports the team
Responsibility of individual companies
In addition, the researchers calculated the proportion of individual greenhouse gas emitters on the observed trends. To do this, on the basis of production data, they recorded how much carbon dioxide and methane the 180 largest producers of fossil fuels and cement made between 1854 and 2023. “Together, the emissions of these carbon giants alone make up 57 percent of the total cumulative CO2 emissions of humanity since 1850,” report Quilcaille and his colleagues. “Half of these 180 major producers have contributed to the increase in heat wave intensity since 1850.”
14 actors stand out: They have expelled as many emissions as all other 166 companies and are responsible for the appearance of more than 50 heat waves that would otherwise not have taken place in this intensity. The 14 largest carbon giants include producers of fossil fuels from the former Soviet Union, the coal mines of China as well as companies that specialize in promoting and export fossil fuels such as petroleum and natural gas, including Saudi Aramco, Gazprom, Exxonmobil, Chevron, BP and Shell. “While the 14 largest carbon companies have most contributed to the appearance of heat waves, the contributions of smaller actors also play an important role,” emphasizes Quilcaille. Even the smallest of the carbon emitters examined in 180 still bears the responsibility for 16 heat waves, which would not have occurred without the emitted greenhouse gas emissions.
Base for climate lawsuits
“This study is an important step in the direction of responsibility. It once again shows that dangerous changes in the weather events can be associated directly with the emissions of individual fossil fuel companies,” comments Friederike Otto from Imperial College in London, which was not involved in the study. “Many of these large carbon emitters already knew in the 1970s that the combustion of fossil fuels contributes to the warming of the planet. Instead of switching their business models to renewable energies, they have deceived the public about the dangers of their products and used governments that the world remains dependent on fossil fuels.”
From Otto’s point of view, the results of the study could help to ensure that the corporations can be liable for the climate impacts they cause. “A growing number of scientific evidence opens the door to ensure that fossil fuel companies are held responsible for the damage that have caused their products worldwide for communities and ecosystems,” she says. In order to provide further information for political and legal decision -makers, Quilcaille and his team want to examine in future studies for further extreme events such as heavy rain, droughts or fires what proportion individual actors have.
Source: Yann Quilcaille (ETH Zurich) et al., Nature, DOI: 10.1038/S41586-025-09450-9
