Sea levels aren't just rising—they may already be higher than many scientists have been working with. A new study in Nature says global sea levels have been understated by an average of about 12 inches because most coastal risk studies relied on "geoid" models, which provide an estimate of sea levels based on gravity, rather than direct local measurements. In some parts of the world with complex ocean dynamics, including southeast Asia and the Indo-Pacific, actual levels could be 3 to 5 feet higher than previously assumed, the Guardian reports.
Researchers Philip Minderhoud and Katharina Seeger reviewed 385 peer-reviewed studies published from 2009 to 2025 and found that more than 90% used the indirect method. Once corrected, the numbers shift sharply: after a 1-meter rise in relative sea level, 37% more coastal land worldwide would be below the water line, potentially affecting up to 132 million people. The authors warn that this "interdisciplinary blind spot" feeds into major climate assessments, including recent UN IPCC reports, and are urging a rework of coastal hazard models and policies using their new dataset.
Minderhoud tells the New York Times that he first saw signs of a "widespread mismatch" a decade ago when he was carrying out research in Vietnam's Mekong Delta and observed that the water looked "much higher" than maps indicated. Tulane University geology professor Torbjorn Tornqvist tells the Times that the study is a "wake-up call" with huge implications. "We finally have a really full-blown, robust effort to sort this out and the result, it's somewhat dramatic," Tornqvist says. "It turns out we've been comparing apples to oranges nearly all the time."
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