This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In September 2024, Storm Boris brought extreme precipitation and severe flooding to large parts of Central and Eastern Europe. Poland, Czechia and Austria were particularly affected.
In some areas, several hundred millimeters of rain fell within a few days, and numerous rivers burst their banks. Earlier attribution studies had shown that global warming intensified precipitation during Storm Boris. These studies compare the observed event with a counterfactual scenario that largely excludes human influence on the climate.
However, such analyses generally stop at the meteorological event itself and focus on questions such as how much extreme precipitation has intensified. The effects of these changes on flood hazards therefore often remain unclear. "In our study, we have taken this a step further.
Using hydrological models, we investigated how changes in precipitation amounts caused by climate change affect the magnitude of flooding," says lead author Peter Miersch from the UFZ. Although it is known that an increase in precipitation does not necessarily lead to a proportional increase in flood magnitude, the size of this effect for individual events and the extent to which it can be attributed to anthropogenic climate change have so far remained unclear. To investigate this, the researchers combined climate simulations with two different hydrological models in order to trace how rainfall in a catchment generates runoff and ultimately leads to flooding.
The differences were substantial. Without anthropogenic climate change, precipitation during Storm Boris would have been around 6%–9% lower depending on the climate model, but flood peaks would have been 14%–22% lower on average. The study is published in the journal Science Advances.
The reason for this disproportionate increase lies in how catchments respond to additional rainfall. "The soil can initially absorb some of the rain during a heavy rainfall event. But eventually the soil becomes saturated, and every additional millimeter of rain flows directly into the river," explains Miersch.
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