Sea Levels Far Higher Than Previously Understood, Research Finds
A recent study suggests ocean levels are far higher than previously understood, a finding with profound implications for assessing the future impacts of global heating.
Published : March 22, 2026 at 8:43 AM IST
Sea levels around the world are far higher than previously understood, a recent study published in Nature reveals. The authors Katharina Seeger and Philip Minderhoud of Wageningen University in the Netherlands attribute sea level underestimation to inaccurate modelling.
The study uncovered a systematic error in how coastal elevation has been measured. They discovered that more than 90% of studies did not use local, direct measurements of sea levels. Instead, they relied on land elevation measurements referenced against global geoid models—estimates of global sea levels based on Earth's gravity and rotation. Their review finds that the vertical measurements using space-borne elevation models can be off by several metres.
"Through a systematic review evaluating recent Sea Level Rise impacts and coastal hazard assessment studies, we found that these crucial steps were often not considered or performed incorrectly. Rather than considering actual, local sea-level height, coastal sea level is most often assumed to equal (an often outdated) global geoid (or in some instances even ellipsoid), to which open-access global DEMs [digital elevation models] are typically referenced when provided," the researchers said.
The study suggests that ocean levels are far higher than previously understood—a finding with profound implications for assessing the future impacts of global heating and the vulnerability of coastal settlements worldwide.
Globally, the research found that ocean levels are an average of 30 cm higher than previously believed. In some areas of the Global South, including Southeast Asia and the Indo-Pacific region, the discrepancy is even more stark: actual sea levels may be 100–150 cm higher than earlier estimates suggested.
This methodological shortcut introduced a significant error. As Minderhoud explains, "In reality, sea level is influenced by additional factors such as winds, ocean currents, seawater temperature and salinity". By failing to account for these local and regional dynamics, previous research systematically undervalued actual sea levels.
The study combined an analysis of 385 pieces of peer-reviewed scientific literature published between 2009 and 2025 with calculations of the difference between commonly assumed and actually measured coastal sea levels. This comprehensive review revealed systematic underestimation in previous models.
Rising sea levels are already a major threat to coastal communities globally. The UN Intergovernmental Panel on Climate Change (IPCC) currently estimates that by 2100, global mean sea levels may rise by 28–100 cm. The new research suggests that this projection—already alarming—starts from a baseline that is itself significantly higher than previously recognised.
If current ocean levels are already 30–150 cm higher than models assumed, then the impacts of future sea-level rise will be correspondingly more severe. Coastal inundation, saltwater intrusion, erosion, and the displacement of communities will occur sooner and with greater intensity than current projections indicate. For low-lying nations and densely populated coastal regions, the window for adaptation has just narrowed considerably.
These corrections fundamentally alter our understanding of risk. The new calculations reveal that following a relative sea level rise of just 1 metre, an additional 37% more coastal areas will fall below sea level, affecting up to 132 million additional people.
The study contains ready-to-use coastal elevation data across the world, integrated with the latest sea level measurements. It calls for the re-evaluation of existing coastal hazard studies and methodologies to ensure that climate change policies are accurately informed by the true scale of the threat.
The authors conclude their article that, “Our findings may have far-reaching implications for existing coastal adaptation, protection and mitigation strategies, especially those using satellite-derived elevation data as information base.” This work demands an urgent re-evaluation of existing coastal hazard assessments to identify and correct vertical reference and sea-level datum issues. If those flawed assessments have informed current decision-making—and they have—then coastal adaptation strategies must be updated and their implementation timelines expedited.
With the introduction of corrected sea level data for countries like India with densely populated coastal regions and low-lying islands of Lakshadweep and Andaman-Nicobar, vulnerable to sea encroachment, the window for adaptation has just narrowed considerably. The question now is whether policy will catch up to reality before the water does.
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