Study: Seas higher than assumed

ROME, March 5, 2026 — A Nature study says rising seas could threaten tens of millions more people than planners assumed because most coastal hazard research starts from an underestimated baseline, AP News reported, describing findings that the baseline for coastal water heights is higher than many models assume, Deltares said.

Researchers reviewed hundreds of scientific studies and hazard assessments and found roughly 90% underestimated coastal water heights by about 1 foot (30 centimeters), PBS NewsHour, NBC News, and OPB reported.

Why the baseline is wrong

The study attributes the gap to mismatched land-elevation and sea-level measurements, a methodological blind spot that can skew impact estimates when land data are tied to theoretical models instead of measured sea levels, U.S. News reported.

The discrepancies appear most often in the Global South, especially in Southeast Asia and Pacific island regions, where exposure to sea-level rise is already high, AP News and PBS NewsHour reported.

What higher baselines mean

Using a more accurate baseline means that if seas rise by a little more than 3 feet (about 1 meter) by the end of the century, waters could inundate up to 37% more land and threaten 77 million to 132 million more people, NBC News, OPB, and U.S. News said.

Lead author Katharina Seeger of the University of Padua and co-author Philip Minderhoud of Wageningen University & Research said the mismatch between ocean and land reference points can compound planning errors in coastal risk assessments, AP News reported.

Planning implications

Outside experts cited in the coverage said the higher baseline highlights a need for clearer local elevation data and consistent reference points, especially in vulnerable deltas and low-lying coastal plains, PBS NewsHour said.

Some scientists also cautioned that while the measurement gap is real, the implications for impact studies may be less dramatic in places that already use high-quality local data, AP News and OPB reported.

Additional Details Reported

Deltares said its meta-analysis found locally measured sea levels are on average 20 to 30 centimeters higher than geoid-based baselines and that a 1-meter rise could place 31% to 37% more land and 48% to 68% more people below sea level worldwide, especially in the Indo-Pacific, noting the study’s open-access datasets for coastal analysis (Deltares).

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