What Was Previously a Once-in-a-Century Storm Surge Now Occurs Every Eight Years
Storm surges and extreme water levels along coastlines occur significantly more frequently today than at the beginning of the 20th century. A new study in the journal Nature Climate Change shows that what was statistically expected to occur only once every 100 years around 1900 now occurs, in global average, about every eight years. This corresponds to an increase by a factor of about twelve. The team of authors includes Prof. Ben Marzeion from the Institute of Geography and MARUM – Center for Marine Environmental Sciences at the University of Bremen.
A “once-in-a-century event” does not occur regularly every 100 years. Rather, it refers to the statistical probability of occurrence of one percent per year. The study shows that, due to rising sea levels, water levels that were once very rare are now significantly more frequent in many places.
“The factor of twelve is extremely alarming,” says Marzeion. “It shows how much a moderate rise in sea level can alter the frequency of storm surges and extreme water levels.”
Human-Caused Sea Level Rise Is the Decisive Factor
The authors combined tide gauge records with climate model simulations. This allowed them to distinguish the respective contributions of natural fluctuations, local processes such as land uplift or subsidence, and human-induced climate change. Marzeion was responsible for reconstructing the contribution of melting glaciers to sea level rise. The result: Human influence has been the dominant driver of the increase in storm surge events since the 1960s. On its own, human influence has roughly quadrupled the frequency of historical 100-year events.
“Humans are one factor among many,” says Marzeion. “But our study shows that man-made sea-level rise is now the most important reason for the increase in such extreme events.”
The key point is that even a relatively small rise in the mean sea level can have significant consequences. Since 1900, the global mean sea level has risen by about 20 centimeters. This is relevant for storm surges because they start from a higher baseline.
“Many people underestimate what a 20-centimeter rise in sea level means,” says Marzeion. “In the case of a storm surge, these 20 centimeters aren’t just added on top — they shift the entire baseline.”
The study is global in scope, not a local risk assessment for the German North Sea coast. Nevertheless, the results are relevant for northern Germany because they demonstrate how a few centimeters can significantly impact the strain on coastal protection infrastructure.
Ben Marzeion summarizes: “For coastal protection, it is crucial to recognize that historical experience no longer applies. We must respond to this by planning early for adaptation.”
- „Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900“ – Nature Climate Change. DOI: 10.1038/s41558-026-02659-0
Quelle
MARUM – Zentrum für Marine Umweltwissenschaften an der Universität Bremen 2026
