Overview
- Reviewing 385 papers, the study reports about 90% underestimated present coastal water heights by roughly 20–30 centimeters on average after relying on gravity-based geoids instead of direct measurements.
- Re-basing to observed sea levels suggests a ~1 meter rise this century could inundate up to 37% more land and put an additional 77–132 million people at risk compared with prior estimates.
- The largest discrepancies occur in Southeast Asia and parts of the Pacific, where actual coastal water levels in places are about 1 meter higher than commonly assumed.
- Forty-five of the evaluated studies appear in the IPCC’s Sixth Assessment Report, and the authors have released a global coastal sea-level dataset to support standardized updates.
- Some experts argue many local planners already account for site-specific conditions, while communities such as those in Vanuatu describe present-day shoreline losses as a UNESCO report separately flags ocean-model uncertainties.