Accounting for exposure in 3D spatiotemporally contiguous heatwaves in Europe 1975–2024

Abstract Heatwaves are becoming more common, intense, and widespread as anthropogenic climate change strengthens, increasing their effects on infrastructure, economies, and health. However, material and human effects of heatwaves cannot be adequately captured by their meteorological characteristics alone. In order to address this challenge, we propose a new heatwave index (HWMId_pop), which combines population exposure and meteorological data to provide a more exposure-informed characterization of heatwaves. Heatwaves are detected using a 3D-event framework, which considers heatwaves as spatiotemporal events that transcend conventional, spatially limited definitions. We evaluate this new index by comparing it to the heatwave mortality recorded in the EM-DAT disaster database for Europe from 1975 to 2021. Our results show that HWMId_pop correlates more closely than traditional heatwave indices with mortality data. We also examine trends in several commonly used heatwave indices between 1975 and 2024, finding that our proposed index shows a significant increasing trend. We highlight that the increasing exposed population, driven by the expanding spatial extent of heatwaves and the rising European population, poses growing health risks. Additionally, we argue that this index can be used as a guide to carry out gap-filling in heatwaves impacts databases such as EM-DAT.