Global-scale analysis of socioeconomic impacts of coastal flooding over the 21st century

Abstract

Building on a global database of projected extreme coastal flooding over the coming century, an extensive analysis that accounts for both existing levels of coastal defences (structural measures) and two scenarios for future changes in defence levels is undertaken to determine future expected annual people affected (EAPA) and expected annual damage (EAD). A range of plausible future climate change scenarios is considered along with narratives for socioeconomic change. We find that with no further adaptation, global EAPA could increase from 34M people/year in 2015 to 246M people/year by 2100. Global EAD could increase from 0.3% of global GDP today to 2.9% by 2100. If, however, coastal defences are increased at a rate which matches the projected increase in extreme sea level, by 2100, the total EAPA is reduced to 119M people/year and the EAD will be reduced by a factor of almost three to 1.1% of GDP. The impacts of such flooding will disproportionately affect the developing world. By 2100, Asia, West Africa and Egypt will be the regions most impacted. If no adaptation actions are taken, many developing nations will experience EAD greater than 5% of GDP, whilst almost all developed nations will experience EAD less than 3% of GDP.

Exploring spatial feedbacks between adaptation policies and internal migration patterns due to sea-level rise

“…We selected a set of three integrated scenario combinations, ensuring that we covered the uncertainty range with regard to the future amount of SLR (i.e., RCPs), society’s adaptive capacity determined by socioeconomic conditions (i.e., SSPs), and the type of adaptation strategies pursued (i.e., SPAs). Selecting a set of plausible scenario combinations is common practice in supra-national scenario-based modeling studies 15 , 16 , 34 , 62 – 67 . We based our integrated scenario selection on the most plausible SSP-RCP combinations as established in previous work 58 , 110 .…”

“…For this purpose, we employ the current scenario framework in climate change research 57 , 58 , integrating SLR projections based on the representative concentration pathways (RCPs) 59 , population and urbanization projections based on the shared socioeconomic pathways (SSPs) 60 , and shared policy assumptions (SPAs) 61 for coastal adaptation that we have developed specifically for this study (Supplementary Text 1 ). Following common practice in supra-national scenario-based modeling studies 15 , 16 , 34 , 62 – 67 , we use a selected set of plausible integrated scenarios that span the relevant uncertainty range regarding future climatic and socioeconomic conditions.…”

Sea Level Rise in Europe: Observations and projections

“…For instance, the design height of local protective infrastructure may differ from the height of the HCE, and large amplifications of the HCE do not necessarily affect a large fraction of the local population (Rasmussen et al, 2022). Projections of the population affected by changes in extremes (e.g., Haasnoot et al, 2021;Kirezci et al, 2020Kirezci et al, , 2023Rasmussen et al, 2022) or projections of the amplification factors of specifically those ESLs that local coastal protection is designed to withstand (Hermans et al, 2023), help to add context to projections of amplification factors which facilitates translating hazards into impacts (Rasmussen et al, 2022; Sea Level Rise in Europe: impacts and consequences). Policy-relevant information may also be provided by projecting when certain critical increases in the probability of ESLs may be reached instead of how much that probability will increase in 2100 (Rasmussen et al, 2022), akin to the timing of mean SLR milestones (Cooley et al, 2022;Fox-Kemper et al, 2021;Haasnoot et al, 2019;Slangen et al, 2022).…”

Global tropical cyclone extreme wave height climatology

“…In tropical and sub-tropical regions, tropical cyclones (or hurricanes or typhoons) represent the most extreme meteorological forcing events, generating wind speeds in excess of 50 m/s 1 – 4 and ocean significant wave heights in excess of 12 m 5 , 6 . As such, tropical cyclones have important societal impacts, resulting in damage to coastal infrastructure 7 , coastal flooding 8 and beach erosion 9 . Compared to higher latitude storms (extra-tropical cyclones), tropical cyclones are characterized by a relatively small well-formed core with an eye of typical radius from 10 to 40 km 2 , 10 , 11 and an asymmetric vortex wind field.…”