Near-real-time attribution of mortality to extreme heat

Extreme event attribution is a branch of climate science that aims to quantify the extent to which the frequency and intensity of extreme weather events such as heatwaves, cold spells, droughts and floods can be said to have been influenced by human-caused climate change. Extreme heat is the deadliest type of weather, although heat-related illnesses and deaths are not directly captured in death certificates or hospital records, and the risks are rarely appreciated by the public. In this talk we introduce a recent collaboration between scientists at Imperial College London and the London School of Hygiene and Tropical Medicine that brought together established methods from attribution and epidemiology to estimate in near real time the expected number of heat-related deaths in cities across Europe during the summer of 2025, and the proportion of those deaths that can be attributed to human-caused climate change. Across 854 cities in Europe we found an estimated 24,404 (95% interval: 21,968 - 26,806) excess deaths during the summer months, with almost 70% of those attributable to human-caused climate change, although vulnerability to heat varies across the continent. This work received widespread media attention, showing the importance of timely information for public awareness of both the risks to health and the contribution of climate change as the extreme weather unfolded.