New research suggests global sea levels have been underestimated because many studies relied on inaccurate modelling methods rather than direct measurements.
The study, published in Nature, found that ocean levels worldwide are on average about 30 centimetres higher than previously believed.
In some regions of the global south, including Southeast Asia and the Indo-Pacific, sea levels may be 100 to 150 centimetres higher than earlier estimates.
Researchers analysed 385 peer-reviewed scientific studies published between 2009 and 2025 and compared commonly assumed sea level values with actual coastal measurements. The analysis showed that more than 90 percent of the studies relied on land elevation data referenced to global geoid models instead of direct local measurements.
Geoid models estimate global sea levels based on the Earth’s gravity and rotation. However, researchers said these models do not fully account for local factors such as winds, ocean currents, seawater temperature, and salinity, which can influence sea level at specific locations.
As a result, sea levels in earlier studies were undervalued by an average of 24 to 27 centimetres depending on the geoid model used. In some cases, the discrepancies ranged as high as 550 to 760 centimetres.
The research was conducted by Dr. Philip Minderhoud of Wageningen University in the Netherlands and PhD researcher Katharina Seeger.
The findings could have major implications for coastal communities and future climate risk assessments. The researchers estimate that if sea levels rise by one metre, about 37 percent more coastal areas could fall below sea level, potentially affecting up to 132 million people.
The scientists described the issue as an interdisciplinary blind spot and noted that many of the studies they analysed are referenced in recent climate change reports by the Intergovernmental Panel on Climate Change. They called for a reassessment of coastal hazard research methods to ensure climate policies are based on more accurate sea level data.