Near-Term Future Sea-Level Projections Supported by Extrapolation of Tide-Gauge Observations

Abstract

Global, regional and local sea-level projections rely on complex process-based models of the climate-ocean-cryosphere system. While extrapolation of observational data has been examined on global and regional scales, this approach has not yet been used for the additional complexities of coastal sea-level projections. Here, we evaluate the sea-level trend and acceleration for a global network of 222 tide-gauge observations over 1970–2023, which are then extrapolated to provide local projections up to 2050 and compared with the process-based projections from the Intergovernmental Panel on Climate Change Sixth Assessment Report (AR6). For 2050 relative to 2020, the observation-based and medium-confidence AR6 projections agree within the likely range at 96% of tide-gauge locations. Despite larger spatial variability, the observation-based projections are usually well below the low-likelihood, high-impact AR6 projections. The observation-based projections provide complementary perspectives of near-term local sea-level changes, and this agreement provides increased confidence in the current understanding and projections of sea-level changes over coming decades.