Human-Driven Sea Level Rise Quadruples Coastal Flood Frequency Since 1900, Study Finds

Coastal flooding, once considered unusual, is becoming a more common occurrence worldwide, largely driven by rising sea levels, according to a new international study. The research suggests that the gradual increase in ocean height has fundamentally altered the frequency of exceptionally high sea levels, making damaging coastal floods more common than a century ago.

Published in Nature, the study titled “Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900” highlights that the impact of human-induced sea-level rise is now measurable across much of the global coastline. This is reshaping flood risks in ways that historical observations can already confirm.

Researchers analyzed over a century of sea-level observations from tide gauges globally, integrating them with climate model simulations. Their focus was not just on the total rise in sea level but on the changing frequency of extreme coastal water levels. The study found that events historically considered to have a one-in-100-year probability have dramatically increased in frequency on a global scale.

The analysis indicates that human-driven sea-level rise alone has made these extreme events several times more likely than they were around the start of the 20th century. While factors like tides, storm surges, and local geography still influence coastal flooding, their effects are increasingly amplified by a higher baseline sea level. The study attributes human-driven warming as the primary cause of relative sea-level rise since the 1960s, as warming oceans expand and melting land ice adds water to the sea.