A comprehensive review of hundreds of sea level rise studies has found that nearly all of them underestimate the actual height of the oceans by a significant margin – up to 30 centimeters (almost a foot). This means that projections for coastal flooding, submersion of land, and displacement of populations have been dramatically off, putting millions more people at risk than previously understood. The findings, published in Nature on March 4th, expose a systemic error in how researchers have assessed coastal vulnerability for over a decade.
The Scale of the Miscalculation
Researchers Katharina Seeger and Philip Minderhoud of Wageningen University analyzed 385 peer-reviewed studies published between 2009 and 2025, discovering that approximately 99% relied on flawed data. The error stems from a reliance on “geoids” – digital models of Earth’s gravity and rotation – instead of direct, verified sea level measurements. Geoids are useful tools but are prone to inaccuracies in data-sparse regions and fail to account for real-time ocean conditions like currents and tides.
This isn’t just an academic issue. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) has cited 45 of these flawed studies in its Sixth Assessment Report, meaning that global climate policy has been built on incomplete information.
Why This Matters: The Human Cost
An accurate understanding of sea level is critical because even small increases in ocean height have massive consequences. A one-meter rise could displace as many as 132 million people – 68% more than prior estimates suggest. Coastal communities, especially in Southeast Asia and the Indo-Pacific, face an immediate and escalating threat. In some of those regions, current estimates are off by over a meter, meaning the danger is even more extreme than realized.
The underestimation isn’t random. The reliance on geoids creates a consistent bias, particularly in areas where direct measurements are scarce. This has led to a dangerous false sense of security, delaying necessary adaptation measures.
The Root Cause: Data vs. Models
The problem isn’t a lack of tools, but a lack of diligence. Scientists have access to accurate sea level measurements from satellites, tidal gauges, and ocean buoys. However, many studies skipped these crucial data points, opting for the convenience of geoids instead.
“That’s basically what we’ve done unknowingly,” says climate scientist Anders Levermann. “These estimates now tell us that we are much further in the future than we thought we were.”
The few studies that did use verified data—less than 1% of those reviewed—showed significantly more accurate results. The discrepancy varies geographically, with the smallest errors found in North America and Europe, where data coverage is better.
Moving Forward: Correcting the Course
The researchers have released publicly available, high-resolution coastal sea level data to help future studies avoid these errors. The implication is clear: coastal planners must prioritize verified measurements over theoretical models when assessing vulnerability.
The ocean is rising faster and higher than previously believed. Ignoring the corrected data will only exacerbate the consequences. The findings demand a swift shift in methodology to ensure that adaptation strategies are based on reality, not underestimation.
