Attributing and Projecting Heatwaves Is Hard: We Can Do Better

International audienceExtreme heat is one of the deadliest natural hazards (Harrington & Otto, 2020) and also is one where climate change really is a game changer. For instance, European heatwaves were diagnosed as the deadliest disaster of 2019 (Vautard et al., 2020). The recently released IPCC report concluded that "It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s, with high confidence that human-induced climate change is the main driver of these changes. Some recent hot extremes observed over the past decade would have been extremely unlikely to occur without human influence on the climate system" (Seneviratne et al., 2021). However, challenges arise in the observed trends at the local to regional scales that matter for planning and adaptation. Although changes in heatwaves are widely thought to be simpler to attribute to anthropogenic climate change than precipitation events, there remain significant challenges. Recent work of the World Weather Attribution initiative has highlighted the general issues in attributing regional changes in extreme weather (Philip et al., 2020; van Oldenborgh, van der Wiel, et al., 2021). This paper focuses on the specific problems that can be encountered when attributing the human influence to heatwaves