Climate change tends to make heavy rainfall more intense and more frequent
Published: Sunday, Jul 21st 2024, 09:10
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Climate change has caused heavy precipitation in Switzerland to become more intense and more frequent since 1901. According to the Federal Office of Meteorology, the increases are most likely along the Alpine slopes and in north-eastern Switzerland.
There is a rather low trend for this phenomenon within the Alps, in parts of western Switzerland and in central and southern Ticino, according to a recently published survey by the Federal Office of Meteorology (MeteoSwiss). MeteoSwiss examined the trends in heavy precipitation between 1901 and 2023.
On average, the heaviest daily precipitation per year is now eleven percent more intense than at the beginning of the 20th century. Heavy precipitation, which would occur almost four times a year, is also around 25 percent more frequent on average today than at the beginning of the last century.
The study also examined heavy rainfall events with a duration of ten minutes to five days in detail for the period from 1981 to 2023. The intensity of short precipitation events lasting ten minutes increased by an average of 4.7 percent per decade. The intensity of precipitation lasting up to six hours increased by 2.4 percent. Meanwhile, their frequency hardly changed over the same period.
However, the intensity and frequency of daily and multi-day heavy precipitation has decreased significantly over the past 40 years - contrary to the 120-year trend. The frequency of heavy daily precipitation has decreased by an average of 5.4 percent per decade.
According to MeteoSwiss, the results over the last 120 years are in line with the physical expectation that heavy precipitation will increase as temperatures rise due to climate change. However, the decrease in the frequency and intensity of daily and multi-day heavy precipitation over the last 40 years or so also indicates that the influence of natural variability due to the dominant weather patterns remains significant.
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