Figure Cross-Chapter BoxSLR.1

Figure Cross-Chapter BoxSLR.1 |  The challenge of coastal adaptation in the era of sea level rise (SLR): (a) typical time scales for the planning, implementation (grey triangles) and operational lifetime of current coastal risk-management measures (blue bars); (b) global sea level projections, which are representative of relative SLR projected for 60–70% of global shorelines, within ±20% errors (WGI AR6 Chapter 9; Fox-Kemper et al., 2021); (c) frequency of illustrative adaptation decisions to +0.5 m of SLR under different SSP-RCP scenarios. In response to accelerated SLR, adaptation either occurs earlier and faster, or accounts for higher amounts of SLR (e.g., to +1 m instead of to +0.5 m). Adaptation to +0.5 m from today’s sea levels have a lifetime of 90 years for SSP1-2.6, but lifetime is reduced to 60 years for SSP5-8.5 and 30 years for a high-end scenario involving low confidence processes. Adaptations to +0.5 m are comparable to, for example, the Thames Barrier in the United Kingdom or the Delta Works in the Netherlands, which primarily had an intended lifetime of 100–200 years. Adaptation measures to +0.2 m may include nourishment or wetland or setback zones.