Figure 4.3 | Additional risk related to sea level rise (SLR) for low-lying coastal areas by the end of the 21st century. Section 4.3.4 provides a synthesis of the assessment methodology and the findings, while SM4.3 provides details. Left-hand panel describes global mean sea level (GMSL) rise observations for the Present-Day (1986–2005) and projections under RCP2.6 and RCP8.5 by 2100 relative to the Present-Day according to advances in this chapter. Relative sea level (RSL) changes at specific locations are represented by the coloured blocs (range of the real-world case studies used) and coloured dotted lines (mean) at the background of the middle panel, which describes risk to illustrative geographies as assessed in this chapter. Each illustrative geography is supported by real-world case studies described in the literature (Box 4.1, 220.127.116.11 and Table SM4.2.5): three for resource-rich coastal cities, three for urban atoll islands, two for large tropical agricultural deltas, five for Arctic communities. N.B. (1): Only Arctic communities remote from regions of rapid glacial-isostatic adjustment have been selected for this assessment. N.B (2): according to the specific scope of the chapter, this assessment focuses on the additional risks due to SLR and does not account for changes in extreme event climatology (Sections 18.104.22.168.1 to 22.214.171.124.3, 126.96.36.199 to 188.8.131.52), which in some cases would imply a different level of risk than assessed here. The middle panel also distinguishes between two adaptation scenarios. (A) ‘No-to- moderate response’ represents a business-as-usual scenario where no major additional adaptation efforts compared to today’s level of effort are implemented (i.e., neither further significant intensification of action nor new types of actions). (B) ‘Maximum potential response’ represents the opposite situation, that is, an ambitious combination of both incremental and transformational adaptation that leads to significant additional efforts compared to today and to (A). Here, the authors assume adaptation implemented at its full potential, that is, the extent of adaptation that is technologically possible, with minimal financial, social and political barriers.