Average Global Sea Levels Much Higher Than Assumed in Coastal Assessments: Report

A new report by Nature revealed that global sea levels are about 30 cm higher than the estimates in 99% of the global coast hazard assessments. The research conducted by Katharina Seeger, PhD researcher and Dr. Philip S. J. Minderhoud, Associate Professor at Wageningen University in the Netherlands stated that this underestimation happened because the assessment failed to correctly evaluate actual sea level measurements.

The research evaluated 385 peer-reviewed, scientific publications published between 2009 and 2025 and found that less than 1% had correctly assessed where sea levels are today. It also highlighted that most of the research has been widely used to inform major global climate change assessments, including the highly influential reports by the Intergovernmental Panel on Climate Change (IPCC), as well as government policies worldwide. 

The research found that the core flaw in about 90% of the assessments was assuming that coastal sea levels were based on geoid models rather than actual sea-level measurements. The geoid model is a mathematical representation of the Earth’s shape and provides an estimate of global sea levels based on the Earth’s gravity and rotation. As a result, sea levels were undervalued by 24-27cm, depending on the geoid model, with some discrepancies being as high as 550-760cm. 

Higher Risk for Global South Countries 

According to the report, the global south in particular, including Southeast Asia and the Pacific, the actual sea level may be 100-150 cm higher than previously predicted. The research pointed out that after the recalculations, using the correct, real-world sea-level data, the coastal risks were much more extreme. 

The research found that if the sea level rises by 1 metre in the future, 31-37% more land will fall below sea level than earlier studies predicted, about 48-68% more people will find themselves living below sea level, increasing the total number of at-risk individuals to between 77 million and 132 million people globally. In Southeast Asia alone, the estimated land and population at risk nearly doubled by up to 94% and 96%, respectively. 

Call for Systemic Change in Research Standards

The research warned that this “community-wide blind spot” could result in misinformed decision-making for coastal adaptation, climate finance, and mitigation strategies. 

The research also provided ready-to-use corrected global elevation models for the scientific community. It also called for a "systemic change" in research standards, including new peer-review checklists and stricter documentation guidelines for how land and sea data are combined.