Study warns of extreme rainfall Switzerland must prepare for more heavy thunderstorms
Extreme summer rainfall will become more frequent and more intense in the Alps in future. With global warming of two degrees, a research team expects a doubling in the Alpine region.
19.06.2025, 11:19
19.06.2025, 11:26
SDA
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- According to a study by the Universities of Lausanne and Padua, extreme rainfall, which currently only occurs every 50 years, is expected to occur every 25 years in the Alps if the climate warms by two degrees.
- The analysis of 300 mountain weather stations shows that the intensity of summer thunderstorms is already increasing, particularly at higher altitudes.
- This is due to the increased moisture absorption of warm air; just one degree of warming can lead to dangerous flash floods, which makes adjustments such as better drainage systems necessary.
Thunderstorms with such heavy rainfall, which currently only occur once every 50 years on average, occur every 25 years if the climate warms by two degrees, as a study published today in the journal "npj Climate and Atmospheric Science" shows.
"We are already observing an increase in the intensity of summer thunderstorms, and this trend will intensify in the future," said Francesco Mara, a researcher involved in the study, in a statement from the University of Lausanne (Unil). According to the study, the increase will be greater at higher altitudes than at lower altitudes.
300 weather stations analyzed
Researchers from Unil and the University of Padua (Italy) analyzed data from almost 300 mountain weather stations in Switzerland, Germany, Austria, Italy and France.
They focused on record precipitation events lasting between 10 minutes and an hour in the period from 1991 to 2020, as well as the temperatures associated with these events.
In a press release, Unil cited heavy rainfall that flooded the city of Lausanne in June 2018 as an example of such an extreme rainfall event. Within just ten minutes, 41 millimetres of rain fell. Large parts of the city were flooded and the damage caused was estimated at 32 million Swiss francs.
Even one degree is problematic
Even an average temperature rise of one degree can be problematic, the researchers emphasized in a press release from Unil.
"The sudden and massive occurrence of large amounts of water prevents it from seeping into the ground. This can lead to flash floods and debris flows, with corresponding damage to infrastructure and sometimes even fatalities," said Nadav Peleg, first author of the study.
It is therefore crucial to understand how these events could develop with climate change in order to plan suitable adaptation strategies - for example by expanding urban drainage systems.
According to the researchers, the reason for the increase is that warm air can store more moisture. About seven percent more per degree. This increases thunderstorm activity. As the Alpine region is warming faster than the global average, it is particularly affected.
