North sea storm surges and climate change

Scientists led by Professor Hans von Storch and Dr. Ralf Weiße from the Institute for Coastal Research at the Helmholtz-Zentrum Geesthacht (HZG) have investigated how these two factors have changed over the course of the past century. Working with engineers from the University of Siegen, the scientists have analysed the sea level rise in the German Bight and evaluated all reliable water level measurements. “We wanted to know how and why the intensity and frequency of storm surges has changed in the past,” says Storch. According to the team's analyses, the mean sea level in the German Bight has risen by about 20 centimetres over the past century. Due to rising mean sea levels over the last 50 years, a storm surge similar to the one in 1962, which flooded large parts of Hamburg, would be about ten centimetres higher today. By contrast, the wind climate has not undergone any fundamental change. Although it varies from year to year, the fluctuations fall within the normal range. Compared with the start of the last century, storm seasons today are not marked by a larger number of storms or storms that are more violent than in the past, but this could change in the future, say the coastal researchers at Geesthacht. Furthermore, the sea level will continue to rise as the climate changes. As a result, by the end of the century, storm surges could be 30 to 110 centimetres higher than they are today. Based on current knowledge, flood protection measures will retain their effectiveness through 2030, but will then have to be reassessed. An interactive website run by the HZG’s North German Climate Office provides decision-makers and residents with information on whether new coastal protection measures are required for their regions.

UFZ/FZJ/red.