Overview

• Climate change increased the likelihood and severity of all 213 heatwaves assessed, with 55 at least 10,000 times more likely than in a preindustrial climate.
• Emissions from 180 named producers explain about half of the rise in heatwave intensity since preindustrial times and account for roughly 57–60% of cumulative CO2 since 1850.
• The 14 largest carbon majors collectively matched the combined impact of the other 166 on intensity, and emissions from any one of the 14 made more than 50 heatwaves virtually impossible.
• Researchers quantified company-level contributions by running models that remove each firm’s emissions and by attributing full value-chain pollution, while noting underreporting in Africa and South America likely understates impacts.
• Legal and policy experts say the findings strengthen the evidentiary basis for climate-liability cases and cost-recovery efforts, even as courts wrestle with jurisdiction and responsibility for end-use emissions.