Flooding in the south more likely due to climate change

German Weather Service - Flooding in the south more likely due to climate change

The likelihood of such heavy rainfalls as in late May and early June in South Germany is, according to an analysis, already significantly increased in the context of the climate crisis. Instead of occurring approximately every 42 years as it used to, such rainfalls are now estimated to occur approximately every 30 years in the region, the Regional Climate Office Potsdam of the German Weather Service (DWD) reported.

In a globally two degree warmer future, comparable events in the region are expected to occur on average every 23 to 25 years. However, the computational uncertainties regarding these figures are quite large.

Heavy rainfalls led to landslides and floods in South Germany between May 30 and June 3. In Bavaria and Baden-Württemberg, local record rainfall amounts were measured, particularly affected were the drainage areas of Danube and Neckar, according to the DWD.

Looking back for comparison

The scientists of the meteorological service focused on the drainage areas of the rivers Neckar and Danube, where the strongest rainfalls were measured, in their so-called attribution study. The analysis showed that climate change has increased the likelihood of such or even stronger rainfall events by a factor of approximately 1.4 (range of 0.8 to 4.4). Such an event can therefore occur more frequently today than in a 1.2 degree cooler climate, as it was around the year 1900. The calculations also suggest that the intensity of such a rainfall event has increased in this region by approximately four percent. "Such an event brings about four millimeters (liters per square meter) more rainfall than in a 1.2 degree cooler climate," it was stated.

Water absorbs more easily in warm air

Rising temperatures could theoretically lead to an intensification of rainfalls, as explained in the study. The moisture-holding capacity of air for water vapor increases with rising temperature. "This increased moisture-holding capacity, combined with stronger evaporation over warmer sea surface temperatures, leads to more moisture being taken up in the air over the sea." When these air masses then pass over the continents, they can potentially release more water. "The potential for heavy rainfall therefore increases fundamentally due to climate change."

For an attribution study, meteorological data from the past decades and climate simulations are statistically evaluated. At the beginning of the month, the research consortium Climameter had already presented a similar analysis on the events in South Germany. According to their findings, the rain that caused the floods was up to 10 percent stronger than without human-induced warming.

Even seemingly small amounts of enhanced rainfall can have disproportionately large effects, as the consortium explained. For example, the Ahrtal flood of 2021 was intensified by 3 to 19 percent due to climate change.

1. The climate crisis is significantly influencing the frequency of heavy rainfalls in Potsdam, as reported by the Regional Climate Office of the German Weather Service (DWD).
2. In the future, similar rainfall events in Southern Germany, including regions like Bavaria and Baden-Württemberg, may occur more frequently due to climate change.
3. The Danube and Neckar drainage areas, particularly in Stuttgart, were heavily affected by the heavy rainfalls that led to landslides and flooding in South Germany.
4. The DWD's attribution study on the May-June rainfalls revealed that climate change has increased the likelihood of such events by a factor of approximately 1.4 in the region.
5. Munich, like other parts of Southern Germany, may experience more frequent and intense extreme weather events due to climate change, according to the meteorological data and climate simulations.
6. The warmer temperatures resulting from climate change could potentially intensify rainfalls, as the moisture-holding capacity of air for water vapor increases with rising temperature.
7. Climate change may influence weather patterns in Germany, leading to an increase in the potential for heavy rainfall events, as explained in the study by the meteorological service.
8. The Climameter research consortium found that the rain that caused the floods in South Germany was up to 10 percent stronger than it would have been without human-induced warming.
9. Even seemingly small amounts of enhanced rainfall due to climate change can have disproportionately large effects, as demonstrated by the Ahrtal flood of 2021, which was intensified by 3 to 19 percent due to climate change.
10. The future weather in Germany, including regions like Potsdam and Bavaria, may be influenced by climate change, leading to increased probability of heavy rainfalls and potential flooding events.

Read also:

• Severe flooding continues in southern Germany.
• Floods continue to pose a major threat in southern Germany.
• Rising floods in the southern regions
• Floods: water levels remain critical in many places