Attribution of the 2024 record-breaking precipitation event in Southern Denmark to human-induced climate change

An increase in the frequency and severity of extreme weather events has been reported across the globe. These events threaten society through hazards like floods and droughts, underscoring the need to understand how such risks are evolving in a changing climate. Standardized methods have recently been introduced to assess the potential role of climate change for extreme events. The World Weather Attribution (WWA) offers a probabilistic framework to determine whether changes in the frequency and severity of extremes can be attributed to anthropogenic warming. Here we use this methodology to attribute an unprecedented rainfall event in Southern Denmark to anthropogenic climate change. On September 27, 2024, approx. 145 mm of rainfall fell over the city of Esbjerg, marking the highest daily rainfall on record for September. The event caused widespread flooding, disrupting transportation, damaging infrastructure, and affecting residential areas. This study draws on rainfall observations, reanalysis datasets, and climate model ensembles to assess the role of anthropogenic climate change. Notably, this is the first attribution study to apply ClimEx, a high-resolution, regional single-model initial-condition large ensemble (SMILE). The results of the analysis show that the rainfall event was 60 % (−20 %–540 %) more likely in the current climate compared to a pre-industrial climate, and that the intensity of the event increased by 10.2 % (−3.3 %–25.6 %) due to climate change. Our findings also indicate that the frequency and intensity of such events increase with further warming. Overall, this study highlights how hazards, exposure, and vulnerabilities contribute to risk in cities.