Increasing likelihood of heat-related mortality events with global warming: a continental epidemiological extreme event attribution study

Heat has become Europe's leading cause of weather-related fatalities, with half of the summer burden attributed to anthropogenic warming. During the record-breaking 2022 summer, more than 11,000 heat-related deaths were estimated to have occurred during a single week. It remains unknown, however, how climate change has influenced the likelihood of this extreme event. Here, by combining well-established Extreme Event Attribution methods with state-of-the-art epidemiological models, we quantify for the first time how global warming has altered the occurrence probabilities of extreme heat-related mortality events such as in the 2022 summer. First, we find that temperature-based extreme event attribution studies are insufficient proxies for accurately attributing associated health impacts. We estimate that 2022-like events are, averaged across Europe, three times [95 % CI 1.02 – 18.6] more likely to occur in 2022 than during pre-industrial times. In Southern Europe, where heat-related mortality rates are already two times higher than the European average, the likelihood of extreme heat-related mortality events has increased even more rapidly, i.e., 2022-like events are associated with a 30-fold [95 % CI 3.8 – 2,354.2] probability surge. Our results highlight that anthropogenic climate change has already substantially increased the probability of extreme heat-related mortality events such as those of the 2022 summer, especially in the South of Europe, and that women and the elderly are the most vulnerable groups. Lastly, we find that 2022-like extreme heat-related mortality events in Europe are expected to occur every eight [95% CI 3.6 – 20.8] years at 1.2 ºC of global warming, every five [95% CI 2.0 – 12.7] years at 1.5 ºC, and every two and a half [95% CI 1.1 – 9.5] years at 2.0 ºC. The study underlines the urgency of implementing mitigation and adaptation measures to limit global warming and reduce the impact of anthropogenic extreme heat on vulnerable populations.