Rapid attribution of heavy rainfall events leading to the severe flooding in Western Europe during July 2021

From the 12th to the 15th of July, heavy rainfall associated with cut-off low-pressure system “Bernd” led to severe flooding particularly in the German states North Rhine-Westphalia and Rhineland-Palatinate, as well as in Luxembourg, and along the river Meuse and some of its tributaries in Belgium and the Netherlands. Scientists from Germany, Belgium, the Netherlands, Switzerland, France, Luxembourg, the US and the UK, collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the heavy rainfall causing the severe flooding. Using published peer-reviewed methods, we analysed how human-induced climate change affected maximum 1-day and 2-day rainfall events in the summer season (April-September) in two small regions where the recent flooding has been most severe in the Ahr-Erft region (Germany) and on the Meuse (Belgium) and anywhere over a larger region including Germany, Belgium and the Netherlands.