August 11, 2017, 6:33 pm
Global warming is altering the timing of floods in Europe, making some rivers swell early and others later than usual, a phenomenon that impacts farming and daily life across the region, researchers said Thursday.
The report in the US journal Science is the largest European study of its kind, and spans 50 years and a vast trove of data from over 4,000 hydrometric stations from 38 countries.
"In the north-east of Europe, Sweden, Finland and the Baltic States, floods now tend to occur one month earlier than in the 1960s and 1970s," said lead author Guenter Bloeschl, a professor at the Institute of Hydraulic Engineering and Water Resources Management at the Vienna University of Technology (TU Wien).
"At that time, they typically occurred in April, today in March. This is because the snow melts earlier in the year than before, as a result of a warming climate."
Winter floods along the Atlantic coast of western Europe tend to occur earlier, almost in the autumn, because maximum soil moisture levels are now reached earlier in the year.
Meanwhile, floods in parts of northern Britain, western Ireland, coastal Scandinavia and northern Germany now tend to occur about two weeks later than they did two decades ago.
Storms hit later in the winter than before, a trend that is likely "associated with a modified air pressure gradient between the equator and the pole, which may also reflect climate warming," said the report.
And as the Mediterranean coast warms, coastal flood events in some regions occur later in the season.
"The timing of the floods throughout Europe over many years gives us a very sensitive tool for deciphering the causes of floods," said Bloeschl.
"We are thus able to identify connections that previously were purely speculative."