Future sea level rise dominates changes in worst case extreme sea levels along the global coastline by 2100

We provide the magnitude of a worst case scenario for extreme sea levels (ESLs) along the global coastline by 2100. This worst case scenario for ESLs is calculated as a combination of sea surface height associated with storm surge and wave (100 year return period, the 95th percentile), high tide (the 95th percentile) and a low probability sea level rise scenario (the 95th percentile). Under these conditions, end-of-21st century ESLs have a 5% chance of exceeding 4.2 m (global coastal average), compared to 2.6 m during the baseline period (1980–2014). By 2100 almost 45% of the global coastline would experience ESLs above the global mean of 4.2 m, with up to 9–10 m for the East China Sea, Japan and North European coastal areas. Up to 86% of coastal locations would face ESLs above 3 m (100 year return period) by 2100, compared to 33% currently. Up to 90% of increases in magnitude of ESLs are driven by future sea level rise, compare to 10% associated with changes in storm surges and waves. By 2030–2040 the present-day 100 year return period for ESLs would be experienced at least once a year in tropical areas. This 100-fold increase in frequency will take place on all global coastlines by 2100.