Sea Level Rise Underestimated in Studies Due to Calculation Error

Coastal sea levels are significantly higher than previously estimated in many parts of the world, according to a study published Wednesday in the journal Nature. Researchers at Wageningen University & Research (WUR) in the Netherlands found that existing scientific assessments underestimate local sea levels by an average of 20 to 30 centimeters, and in some regions, particularly in Southeast Asia and the Pacific, the discrepancy can exceed one meter.

The findings have substantial implications for coastal populations and infrastructure planning. According to WUR calculations, a one-meter sea level rise would submerge coastal strips and river deltas currently home to approximately 130 million people. The study indicates that twice as many people already live below sea level than previously suggested by earlier research.

The research team analyzed 385 scientific publications and discovered that over 90 percent rely on inaccurate models when calculating sea level height. Less than one percent of the studies examined correctly calculated actual coastal sea levels, according to the researchers.

The inaccuracies stem, in part, from the use of outdated calculation methods. These methods often determine sea level height based on satellite measurements of land elevation, data on gravity and Earth’s rotation – known as geoids. This approach fails to adequately account for dynamic factors such as currents, tides, and water temperature, according to the study.

Philip Minderhoud, a lead researcher on the study and an expert in land subsidence and relative sea level rise at Deltares and WUR, described the issue as “a blind spot.” He first recognized the problem approximately ten years ago while visiting the Mekong Delta in Vietnam, an area where numerous rivers flow into the sea. He observed that the water level was considerably higher than indicated on coastal maps, as reported by the Dutch public broadcaster NOS.

The discrepancies are particularly pronounced in regions with complex ocean dynamics, such as those found in Southeast Asia and the Pacific. In these areas, coastal sea levels are estimated to be several meters higher than commonly assumed, the researchers stated.

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) estimates that ocean levels may increase by between 0.28 and 1 meter by 2100, driven primarily by human-induced climate change. However, these projections may be insufficient given the newly identified inaccuracies in current measurement techniques.

Researchers from WUR analyzed peer-reviewed scientific literature published between 2009 and 2025 to calculate the difference between commonly assumed and actual measured coastal sea level, according to a report from AOL.com.

The study’s findings underscore the urgent need for more accurate sea level assessments to inform effective coastal management and adaptation strategies. No immediate response from international bodies or governments has been publicly released following the publication of the Nature study.