A Global Perspective on Local Sea Level Changes

In 2021, the IPCC published new sea level projections. For the first time, the projections gave insight into expected relative sea level rise locally. A prudent designer of coastal infrastructure will want to know how the local projections compare to local observations. That comparison, to date, has not been made. We compared local projections and observations regarding the rate of rise in 2020. We used two datasets with local sea level information all over the globe. In both datasets, we found approximately 15% of the available sets suitable to establish the rate of rise in 2020. Geographic coverage of the suitable locations is poor, with the majority of suitable locations in the Northern Hemisphere. Latin America and Africa are severely under-represented. Statistical tests were run on all selected datasets, taking acceleration of sea level rise as a hypothesis. In both datasets, approximately 95% of the suitable locations show no statistically significant acceleration of the rate of sea level rise. The investigation suggests that local, non-climatic phenomena are a plausible cause of the accelerated sea level rise observed at the remaining 5% of the suitable locations. On average, the rate of rise projected by the IPCC is biased upward with approximately 2 mm per year in comparison with the observed rate.