That's a bit pricey Can the legal system catch up with climate science? New estimate: Fossil fuel companies have caused trillions of dollars in damages. John Timmer – Apr 23, 2025 5:00 pm | 21 Credit: Marc Guitard Credit: Marc Guitard Story text Size Small Standard Large Width * Standard Wide Links Standard Orange * Subscribers only   Learn more A few decades ago, it wasn't realistic to attribute individual events—even heat waves—to the general warming trend driven by human-caused climate change. Now, there are peer-reviewed methods of rapidly detecting humanity's fingerprints in the wake of weather disasters like hurricanes or climate-driven wildfires. In today's issue of Nature, Dartmouth's Christopher Callahan and Justin Mankin argue that we've reached a similar level of sophistication regarding another key question: What are the economic damages caused by individual climate events? They argue that we can now assign monetary values to the damage caused by emissions that can be traced back to individual companies. They found that "The global economy would be $28 trillion richer ... were it not for the extreme heat caused by the emissions from the 111 carbon majors." They argue that this method might provide legal ammunition for those interested in seeking climate damages in court: "By revealing the human fingerprint on events previously thought to be ‘acts of God,’ attribution science has helped make climate change legally legible." How attribution works The method used by Callahan and Mankin is a variant on standard climate attribution studies. In the standard studies, climate models are run with and without the carbon dioxide that humanity has pumped into the atmosphere through fossil fuels and land use changes. You can then compare the frequency of specific weather events, like the intensity of rainfall from a hurricane or the peak temperatures of a heatwave, both with and without the added CO2. The difference in frequency is an indication of the impact of climate change. But it's possible to repeat the analysis with arbitrary amounts of carbon dioxide. So, the researchers could calculate the estimated emissions from different companies and compare the probabilities of events with and without those emissions. So, for example, Callahan and Mankin calculate the individual contributions of the companies responsible for the most carbon emissions (the "carbon majors" mentioned earlier), such as Chevron or Saudi Aramco. These include both the direct emissions during fossil fuel production, as well as the emissions that result when the products are burned. Similarly, it's possible to calculate the impact of emissions within a limited number of years. For example, Callahan and Mankin note that internal oil company research suggested that climate change would be a problem back around 1980, and calculated the impact of emissions that occurred after people knew they were an issue. So, the approach is extremely flexible. From there, the researchers could use empirical information that links elevated temperatures to economic damage. "Recent peer-reviewed work has used econometrics to infer causal relationships between climate hazards and outcomes such as income loss, reduced agricultural yields, increased human mortality, and depressed economic growth," Callahan and Mankin write. These metrics can be used to estimate the cost of things like flooding, crop losses, and other economic damages. Alternately, the researchers could analyze the impact on individual climate events where the financial costs have been calculated separately. Massive damages To implement their method, the researchers perform lots of individual models, collectively providing the most probable costs and the likely range around them. First, they translate each company's emissions into the impact on the global mean surface temperature. That gets translated to an impact on extreme temperatures, producing an estimate of what the days with the five most extreme temperatures would look like. That, in turn, is translated to economic damages associated with extreme heat. Callahan and Mankin use Chevron as an example. By 2020, Chevron's emissions were responsible for 0.025° C of the warming that year. If you perform a similar analysis for the ears between 1991 and 2020, the researchers come up with a range of damages that runs from a low of about $800 billion all the way up to $3.6 trillion. Most of the damage affected nations in the tropics. Carrying on through the five companies that have led to the most carbon emissions, they calculate that Saudi Aramco, Gazprom, Chevron, and Exxon Mobile have all produced damages of about $2 trillion. BP brings up the rear, with "just" $1.45 trillion in damage. For the full list of 111 carbon majors, Callahan and Mankin place the total damages at roughly $28 trillion. To look at the differences between separate periods, the researchers analyze the impacts in terms of an entity that's responsible for 5 percent of the total carbon emissions—that's roughly a quarter of the US's contributions, or a bit more than the entire contribution of Brazil. For the full period with global temperature records starting in 1850, the damages would be $4.2 trillion. If you start when Exxon's internal research work first highlighted the risk of climate change in 1977, the damage would be $3.3 trillion. If you wait until a clear scientific consensus that it was happening emerged (1990), then the damages would still be $2.5 trillion. (Note that this analysis does not attempt to quantify the benefits of burning fossil fuels during this period. And it also leaves out various non-climate costs, such as the impact of pollution on health.) The analysis of individual events produces smaller, but still striking numbers. For a 2012 heat wave in North America, the researchers place Chevron's share of the damages at just shy of $30 billion. Smaller losses ($28.8 and $3 billion) were associated with heat waves that struck Russia in 2010 and France in 2003. Legal impacts? Callahan and Mankin directly relate this to potential legal liability, arguing that science has progressed to the point where it has something to say about potential liabilities. "To sue over an injury, a litigant typically must demonstrate a causal connection between the action of the defendant and the plaintiff’s injury, sometimes through meeting a ‘but for’ standard: 'but for the actions of the defendant, the plaintiff would not have been injured.'” As they note, this matches up very well with the structure of their analysis, which compares the present climate to one that includes all the emissions "but for" the ones associated with specific companies. But they also note that we're still figuring out what legal standards should be applied, and who should be held liable. For example, a suit in Montana targeted the state for failing to provide its residents with a healthful environment. Other suits have targeted emissions as creating a public nuisance, or companies for misleading their investors by failing to account for climate-related risks. The liability that this study speaks to is not the only option for seeking legal redress. Still, with this work as a guideline, it seems inevitable that someone will attempt to use this to hold oil companies to account. Nature, 2025. DOI: 10.1038/s41586-025-08751-3  (About DOIs). John Timmer Senior Science Editor John Timmer Senior Science Editor John is Ars Technica's science editor. He has a Bachelor of Arts in Biochemistry from Columbia University, and a Ph.D. in Molecular and Cell Biology from the University of California, Berkeley. When physically separated from his keyboard, he tends to seek out a bicycle, or a scenic location for communing with his hiking boots. 21 Comments