A previous article focused on the systematic attribution of heatwaves to human-caused climate change. Expanding on this discussion, a new study, “Systematic attribution of heatwaves to the emissions of carbon majors,” heat waves to emissions of major carbon pollutants) goes a step further and specifically quantifies the contribution of particular companies – so-called "major carbon polluters" – to these extreme events. This work represents significant progress in filling the evidence gaps for climate litigation and policy, but also reveals the complexities and obstacles to full attribution of responsibility.

Study focused on the 180 largest fossil fuel and cement producers, which collectively represent 57 % of total cumulative anthropogenic CO2 emissions since 1850 and 75 % emissions from fossil fuels and cement. It was found that emissions from these companies contributed to approximately half the increase in the intensity of heat waves since pre-industrial times and this contribution is constantly increasing. For example, even the smallest of these “major polluters”, Elgaugol, contributed to 16 heat waves (8 %) becoming at least 10,000 times more likely, while the largest emitter, the former Soviet Union, made them this likely in 53 heat waves (25 %).

These findings are crucial because they shift the discussion from a general “human influence” to identifying specific actors and quantifying their contribution to extreme events. This “chain of causation from emitters to extreme climate events” is critically important for legal proceedings seeking compensation for losses and damages or demanding more ambitious climate action from corporations and states.

Despite the groundbreaking nature of the methodology, the study admits several significant limitationsOne of them is incomplete coverage of emissions in the “Carbon Majors” database used. This means that the actual contributions of these companies are likely higher, as the database only covers a portion of the total emissions of fossil fuels and cement.

Another complication is impact of aerosols, which are also released by the burning of fossil fuels. Although aerosols have local and regional cooling effects that could reduce the overall contribution to warming by about 10 %, attributing them to individual companies is extremely challenging. This is due to the complexity of their distribution, regional differences in filtration technologies, and the global trade in fossil fuels. In addition, aerosols are also harmful air pollutants that cause millions of premature deaths annually, but quantifying their health impacts and attributing them to individual emitters is beyond the scope of this study.

The study also highlights that while physical hazards (such as heat waves) can be attributed to climate change and its causes, expanding attribution to social impacts, such as mortality or economic damage, remains a challenge due to the complex nonlinear aspects of vulnerability and exposure that cannot be captured by direct deduction.

In conclusion, this study represents a critically important tool in the arsenal of climate science and legal experts. Systematic attribution of carbon pollutants to extreme heat waves significantly strengthens scientific evidence, which are essential for the equitable sharing of responsibility and financing of adaptation and mitigation measures. However, it also shows that the path to full and comprehensive attribution of all climate change impacts is still fraught with challenges that require further interdisciplinary research and collaboration. JRi

The study was published in the journal Nature.