Maximal reachable temperatures for Western Europe in current climate

Abstract

Human bodies, ecosystems and infrastructures display a non-linear sensibility to extreme temperatures occurring during heatwave events. Preparing for such events entails to know how high surface air temperatures can go. Here we examine the maximal reachable temperatures in Western Europe. Taking the July 2019 record-breaking heatwave as a case study and employing a flow analogues methodology, we find that temperatures exceeding 50 ∘C cannot be ruled out in most urban areas, even under current climate conditions. We analyze changes in the upper bound of surface air temperatures between the past (1940–1980) and present (1981–2021) periods. Our results show that the significant increase in daily maximum temperatures in the present period is only partially explained by the increase of the upper bound. Our results suggest that most of the warming of daily maximum surface temperatures result from strengthened diabatic surface fluxes rather than free troposphere warming.

Western Europe’s extreme July 2019 heatwave in a warmer world

“…Our results point in the same direction. In fact, recent studies suggest that such high values can perhaps not even be excluded for the region in the current climate (Noyelle et al 2023, Zhang andBoos 2023). More research is required to assess the limit of applicability of PGW approaches, and to compare it to other conventional or new methods.…”

“…Because of the large amounts by which existing records were broken, the July heatwave triggered research on the maximum possible temperature in the current climate (Fischer et al 2023, Noyelle et al 2023, Zhang and Boos 2023. Where Fischer et al (2023) used ensemble boosting to find whether the occurred situation could have been more extreme, Zhang and Boos (2023) took a more fundamental approach by testing the hypothesis that the maximum attainable temperature is eventually limited by convective instability between surface and mid-troposphere.…”

“…Where Fischer et al (2023) used ensemble boosting to find whether the occurred situation could have been more extreme, Zhang and Boos (2023) took a more fundamental approach by testing the hypothesis that the maximum attainable temperature is eventually limited by convective instability between surface and mid-troposphere. Noyelle et al (2023) combined this within an analogue framework to unravel the role of thermodynamic and other processes. Both studies concluded that the 50 • C limit cannot be excluded even in the current climate.…”