Global probabilistic projections of extreme sea levels show intensification of coastal flood hazard

TLDR

Global warming is expected to drive increasing extreme sea levels (ESLs) and flood risk along the world's coastlines. The study presents probabilistic projections of extreme sea levels for the current century, incorporating mean sea level, tides, wind‑waves, and storm surges. The projections account for mean sea level rise, tides, wind‑waves, storm surges, and the dominant drivers of ESL increase—thermal expansion and ice mass loss from glaciers and ice sheets. The study projects a very likely global average 100‑year ESL rise of 34–76 cm under moderate mitigation and 58–172 cm under business‑as‑usual, with tropical coastlines exposed annually to 100‑year events by 2050 and most coastlines by 2100, indicating unprecedented flood risk without adaptation.

Abstract

Global warming is expected to drive increasing extreme sea levels (ESLs) and flood risk along the world's coastlines. In this work we present probabilistic projections of ESLs for the present century taking into consideration changes in mean sea level, tides, wind-waves, and storm surges. Between the year 2000 and 2100 we project a very likely increase of the global average 100-year ESL of 34-76 cm under a moderate-emission-mitigation-policy scenario and of 58-172 cm under a business as usual scenario. Rising ESLs are mostly driven by thermal expansion, followed by contributions from ice mass-loss from glaciers, and ice-sheets in Greenland and Antarctica. Under these scenarios ESL rise would render a large part of the tropics exposed annually to the present-day 100-year event from 2050. By the end of this century this applies to most coastlines around the world, implying unprecedented flood risk levels unless timely adaptation measures are taken.