Understanding extreme sea levels for broad-scale coastal impact and adaptation analysis

Source: Nature. Authors: T. Wahl, I.D. Haigh, R.J. Nicholls, A. Arns, S. Dangendorf, J. Hinkel & A.B.A. Slangen

One of the main consequences of mean sea level rise (SLR) on human settlements is an increase in flood risk due to an increase in the intensity and frequency of extreme sea levels (ESL). While substantial research efforts are directed towards quantifying projections and uncertainties of future global and regional SLR, corresponding uncertainties in contemporary ESL have not been assessed and projections are limited. Here we quantify, for the first time at global scale, the uncertainties in present-day ESL estimates, which have by default been ignored in broad-scale sea-level rise impact assessments to date. ESL uncertainties exceed those from global SLR projections and, assuming that we meet the Paris agreement goals, the projected SLR itself by the end of the century in many regions. Both uncertainties in SLR projections and ESL estimates need to be understood and combined to fully assess potential impacts and adaptation needs. Quote from the article:

“Up to 310 million people residing in low elevation coastal zones are already directly or indirectly vulnerable to ESL and coastal storms are causing damages in the order of tens of billion US$ per year. These numbers could increase dramatically with SLR and other changes, leading to annual damages of up to almost 10% of the global gross domestic product in 2100 if no adaptation measures are taken. Hence, there is a need for assessments of potential changes in coastal flood risk and adaptation strategies to manage these risks.”