Extreme coastal floods that once struck communities infrequently have grown far more frequent as human-driven climate change raises sea levels, new research published Wednesday shows. The results matter for flood planning and coastal infrastructure decisions amid ongoing planetary warming.
Such floods occur when high tides and storm surges combine with already elevated seas, layered atop natural climate patterns and other human effects. Climate change has intensified storms, increasing flood risks for hundreds of millions in low-lying coastal zones worldwide while causing billions in damage and occasional deaths.
Events with a historical 1 percent annual chance of hitting a coastline are now roughly 12 times more probable on average, per a study in Nature Climate Change. Human-driven climate change alone accounts for about a fourfold rise in likelihood. Researchers examined tide gauge records from over 100 sites and climate models covering 1900 to 2005, noting that later data gaps likely understate current risks.
Human activity has dominated sea level increases since the 1960s, after earlier changes stemmed mostly from natural causes. A companion study in Science Advances found climate change responsible for 58 percent of major flood days between 2000 and 2018, nearly tripling days exceeding extreme levels since the 1970s.
Greenhouse gases from fossil fuel use represent the chief driver, experts said, underscoring the need for stronger coastal protections and adaptation funding as threats continue to grow.
