Attribution of the heavy rainfall events leading to severe flooding in Western Europe during July 2021
Tradowsky, Jordis S.; Philip, Sjoukje Y.; Kreienkamp, Frank; Kew, Sarah F.; Lorenz, Philip; Arrighi, Julie; Bettmann, Thomas; Caluwaerts, Steven; Chan, Steven C.; De Cruz, Lesley; de Vries, Hylke; Demuth, Norbert; Ferrone, Andrew; Fischer, Erich M.; Fowler, Hayley J.; Goergen, Klaus; Heinrich, Dorothy; Henrichs, Yvonne; Kaspar, Frank; Lenderink, Geert; Nilson, Enno; Otto, Friederike E.L.; Ragone, Francesco; Seneviratne, Sonia I.; Singh, Roop K.; Skålevåg, Amalie; Termonia, Piet; Thalheimer, Lisa; van Aalst, Maarten; Van den Bergh, Joris; Van de Vyver, Hans; Vannitsem, Stéphane; van Oldenborgh, Geert Jan; Van Schaeybroeck, Bert; Vautard, Robert; Vonk, Demi; Wanders, Niko
(2023) Climatic Change, volume 176, issue 7
(Article)
Abstract
In July 2021 extreme rainfall across Western Europe caused severe flooding and substantial impacts, including over 200 fatalities and extensive infrastructure damage within Germany and the Benelux countries. After the event, a hydrological assessment and a probabilistic event attribution analysis of rainfall data were initiated and complemented by discussing the
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vulnerability and exposure context. The global mean surface temperature (GMST) served as a covariate in a generalised extreme value distribution fitted to observational and model data, exploiting the dependence on GMST to estimate how anthropogenic climate change affects the likelihood and severity of extreme events. Rainfall accumulations in Ahr/Erft and the Belgian Meuse catchment vastly exceeded previous observed records. In regions of that limited size the robust estimation of return values and the detection and attribution of rainfall trends are challenging. However, for the larger Western European region it was found that, under current climate conditions, on average one rainfall event of this magnitude can be expected every 400 years at any given location. Consequently, within the entire region, events of similar magnitude are expected to occur more frequently than once in 400 years. Anthropogenic climate change has already increased the intensity of the maximum 1-day rainfall event in the summer season by 3–19 %. The likelihood of such an event to occur today compared to a 1.2 ∘ C cooler climate has increased by a factor of 1.2–9. Models indicate that intensity and frequency of such events will further increase with future global warming. While attribution of small-scale events remains challenging, this study shows that there is a robust increase in the likelihood and severity of rainfall events such as the ones causing extreme impacts in July 2021 when considering a larger region.
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Keywords: Ahr, Erft, Extreme event attribution, Flood, Meuse, Rainfall, Global and Planetary Change, Atmospheric Science
ISSN: 0165-0009
Publisher: Springer Netherlands
Note: Funding Information: The authors acknowledge funding from the following sources: Tradowsky: grant 01LP1902B of ClimXtreme (German Federal Ministry of Education Research; BMBF); Chan and Fowler: UKRI FUTURE-STORMS project (NE/R01079X/1); authors associated with the German Federal Institute of Hydrology: German Federal Ministry for Digital and Transport (BMDV) “BMDV Network of Experts”; de Vries and Lenderink: grant agreement No. 776613 of HORIZON 2020 EUCP for HCLIM38 simulations. Computing time for simulations of Forschungszentrum Jülich was granted on the JARA partition of the supercomputer JURECA by the JARA Vergabegremium at the Jülich Supercomputing Centre. Funding Information: We thank Andrew Ciavarella (UK Met Office) for contributing to the WWA report which build the foundation for this work; Matthias Voigt (Federal State Office for the Environment, Rhineland Palatinate, Germany) for the preparation of some CPRCM simulations; Ewelina Walawender (DWD) for preparing Fig. 2 ; Sabrina Wehring (DWD) for preparing Figs. S1 and S2 in the Supplementary Information; Michel Journée (RMI) for the generation of the Belgian Gridded Dataset and the RMI quality-control team for providing the required data on time; Copernicus Climate Change Service (C3S) and ECMWF for providing the ERA5-Reanalysis; the EURO-CORDEX community for RCM simulations which were partly funded by the Copernicus Climate Change Service (C3S) under D34b Lot2041_201802. The results contain modified Copernicus Climate Change Service information 2020. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains. Open Access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2023, The Author(s).
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