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

This analysis follows the standard structure of WWA event attribution analysis by defining the event, describing data and models used, assessing trends, attributing the event, synthesis of the results which are put in the context of vulnerability and exposure. The 6th Intergovernmental Panel on Climate Change (IPCC) assessment report (IPCC, 2021) states that extreme precipitation, pluvial and fluvial floods have been observed to increase in Western and Central Europe and will increase with high confidence in case global warming reaches 2 °C, expected to occur by mid-century in case greenhouse gas emissions reduction do not take place quickly. However, attribution of specific local extreme precipitation events to climate change remains difficult due to the high year-to-year or decade-to-decade variability of extreme precipitation. Furthermore, the limited availability of finely-resolved climate model simulations and long-term observations provides challenges to attribution studies of local-scale events

Extreme rainfall occurred in Germany, Belgium, Luxembourg and neighbouring countries during the period 12 to 15 July 2021, leading to severe flooding particularly in North Rhine-Westphalia and Rhineland-Palatinate in Germany and along the river Meuse and some of its tributaries in Belgium and the Netherlands. The flooding resulted in at least 184 fatalities in Germany and 38 in Belgium and considerable damage to infrastructure, including houses, roads, communication, motorways and railway lines as well as bridges. A variety of livelihoods were severely disrupted by the flood event, including local businesses in the affected regions and wine growers that make up the backbone of the Ahr Valley region. Road closures left some places inaccessible for days, cutting off some villages from evacuation routes and other forms of emergency response. The most affected areas are around the rivers Ahr and Erft as well as the Vesdre in the basin of the Meuse. An estimate by the German Insurance Association (GDV) describes the cost of the event at €4.5 to €5.5 billion for Germany alone while damage in Belgium is estimated to exceed €0.35 billion. The devastating impacts of the July 2021 extreme precipitation event that struck Germany and Benelux provides an impetus to carry out an event attribution analysis to investigate the role of anthropogenic climate change in the extreme rainfall event.