Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st Century
Global models of tide, storm surge, and wave setup are used to obtain projections of episodic coastal flooding over the coming century. The models are extensively validated against tide gauge data and the impact of uncertainties and assumptions on projections estimated in detail. Global “hotspots” where there is projected to be a significant change in episodic flooding by the end of the century are identified and found to be mostly concentrated in north western Europe and Asia. Results show that for the case of, no coastal protection or adaptation, and a mean RCP8.5 scenario, there will be an increase of 48% of the world’s land area, 52% of the global population and 46% of global assets at risk of flooding by 2100. A total of 68% of the global coastal area flooded will be caused by tide and storm events with 32% due to projected regional sea level rise.
Sea level rise is a well-accepted consequence of climate change1,2,3. Although the focus of the general public often tends to be on the rate and magnitude of increase in mean sea level, the major threats of coastal flooding and erosion are significantly impacted by episodic storm surge and wave setup (the temporary increase in mean water level due to the presence of breaking waves) as well as their time of occurrence in relation to astronomical tide4. As approximately 600 million people live in low elevation coastal zones [i.e. LECZs—coastal regions less than 10 m above mean sea level (MSL)] which generate approximately US$1 trillion of global wealth2,5,6,7, both the environmental and socio-economic impacts associated with episodic coastal flooding can be massive.
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