"Climate change’s rising seas may threaten tens of millions more people than scientists and government planners originally thought because of mistaken research assumptions on how high coastal waters already are, a new study said.
Researchers studied hundreds of scientific studies and hazard assessments, calculating that about 90% of them underestimated baseline coastal water heights by an average of 1 foot (30 centimeters), according to Wednesday’s study in the journal Nature. It’s a far more frequent problem in the Global South, the Pacific and Southeast Asia, and less so in Europe and along Atlantic coasts.
The cause is a mismatch between the way sea and land altitudes are measured, said study co-author Philip Minderhoud, a hydrogeology professor at Wageningen University & Research in the Netherlands. And he attributed that to a “methodological blind spot” between the different ways those two things are measured.
Each way measures their own areas properly, he said. But where sea meets land, there’s a lot of factors that often don’t get accounted for when satellites and land-based models are used. Studies that calculate sea level rise impact usually “do not look at the actual measured sea level so they used this zero-meter” figure as a starting point, said lead author Katharina Seeger of the University of Padua in Italy. In some places in the Indo-Pacific, it’s close to 3 feet (1 meter), Minderhoud said."
Seth Borenstein and Annika Hammerschlag report for the Associated Press March 4, 2026.
