Sea Level Rise Estimates Dramatically Understated, New Research Reveals
Coastal communities worldwide may be facing a more imminent threat from rising seas than previously understood. A groundbreaking study published March 4 in Nature reveals that hundreds of assessments of sea level rise and coastal flooding have significantly underestimated ocean heights – by as much as 30 centimeters (almost a foot) on average.
The Scale of the Miscalculation
Researchers evaluated 385 peer-reviewed studies published between 2009 and 2025, finding that a staggering 99% incorrectly estimated sea levels. This includes 45 studies referenced in the United Nations’ Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report. The core issue? A reliance on imprecise data known as geoids instead of actual sea-level measurements.
A geoid is a model of Earth’s gravity, representing what the ocean surface would seem like if it were perfectly still. However, geoids don’t account for dynamic factors like ocean currents, winds, and water temperatures, leading to inaccuracies. The study found that measured sea levels are, on average, 24 to 27 centimeters higher than those predicted by geoid-based models.
What Which means for Coastal Populations
The implications of this underestimation are substantial. Researchers estimate that a one-meter rise in sea level – a scenario increasingly likely this century – could now displace 31–37% more land and impact 48–68% more people than previously projected, potentially reaching as many as 132 million individuals.
“Sea level rise is slow but dangerous if you ignore it,” explains climate scientist Anders Levermann of the Potsdam Institute for Climate Research in Germany. “That’s basically what we’ve done unknowingly.”
The Problem with Geoids: A Deeper Dive
Katharina Seeger and Philip Minderhoud of Wageningen University in the Netherlands discovered the widespread error while analyzing studies on sea level rise, storm surges, and other coastal hazards. They found that 90% of the research relied on geoids instead of direct sea-level measurements from sources like satellites, tidal gauges, and ocean buoys. Another 9% improperly aligned existing measurements, and less than 1% used data correctly.
The discrepancy is particularly pronounced in the Indo-Pacific region, where measured sea levels can be more than one meter above geoid estimations. Smaller discrepancies were observed in eastern North America and northern and western Europe.
Correcting the Course: New Data and Future Research
Seeger and Minderhoud have made their coastal sea level data publicly available, integrating the most recent measurements to aid future studies. This data aims to provide a more accurate baseline for assessing coastal vulnerability and informing adaptation strategies.
Coastal geologist Patrick Barnard of the University of California, Santa Cruz, emphasizes the importance of verifying findings from large-scale studies with local data. “The advance of the oceans is even worse than what’s been reported,” he states, urging planners to avoid relying solely on broad estimations without local validation.
Frequently Asked Questions
Q: What is a geoid?
A: A geoid is a model of Earth’s gravity, representing the theoretical shape of the ocean if it were perfectly still. It’s often used as a reference point for measuring elevations, but it doesn’t account for dynamic ocean conditions.
Q: Why is accurate sea level measurement important?
A: Accurate measurements are crucial for assessing coastal vulnerability, planning for sea level rise, and protecting coastal communities, and infrastructure.
Q: What can be done to address the underestimation of sea level rise?
A: Using direct sea-level measurements from sources like satellites and tidal gauges, correcting for geoid inaccuracies, and incorporating regional variations in sea level are essential steps.
Q: How does this impact future climate projections?
A: This research suggests that the impacts of sea level rise may be more severe and occur sooner than previously anticipated, requiring a reassessment of climate adaptation strategies.
Did you recognize? Ocean warming and melting glaciers are the primary drivers of rising sea levels, both direct consequences of climate change.
Pro Tip: When evaluating coastal risk assessments, always check the data sources used and whether direct sea-level measurements were incorporated.
Stay informed about the latest climate research and its implications for your community. Learn more about sea level rise from the United Nations.
