Editing IPCC:AR6/SROCC/Chapter-4 (section)

=== 4.1.3 Sea Level Rise Impacts and Implications for Responses ===

<div id="section-4-1-3sea-level-rise-impacts-and-implications-for-responses-block-1"></div>

Rising mean and increasingly extreme sea level threaten coastal zones through a range of coastal hazards including (i) the permanent submergence of land by higher mean sea levels or mean high tides; (ii) more frequent or intense coastal flooding; (iii) enhanced coastal erosion; (iv) loss and change of coastal ecosystems; (v) salinisation of soils, ground and surface water; and (vi) impeded drainage. At the century scale and without adaptation, the vast majority of low-lying islands, coasts and communities face substantial risk from these coastal hazards, whether they are urban or rural, continental or island, at any latitude, and irrespective of their level of development (Section 4.3.4; Figure 4.3; ''high confidence'' ). In the absence of an ambitious increase in adaptation efforts compared to those currently underway, high to very high risks are expected in many coastal geographies at the upper end of the RCP8.5 ''likely'' range. These include resource-rich coastal cities, urban atoll islands, densely populated deltas, and Arctic communities (Chapter 4 Box 4; Figure 4.3 and Section 4.3.4). At the same time coastal protection is very effective and cost-efficient for cities but not for less densely populated rural areas. Some geographies, such as urban atoll islands and Arctic communities face high risk even under RCP2.6 ( ''medium confidence'' ).

In many places, however, non SLR-related, local environmental and human dimensions of exposure and vulnerability play a critical role in increasing exposure and vulnerability to coastal hazards (Section 4.3.2.5). For example, the ability of morphological and ecological systems (Sections 4.3.3.3 and 4.3.3.5) to protect human settlements and infrastructure by attenuating ESL events and stabilising shorelines is progressively being lost due to coastal squeeze, pollution, habitat degradation and fragmentation (Section 4.3.3.5.4; ''high confidence'' ). Hence, an important near term response to RSL rise is to reduce these adverse environmental and human dimensions of exposure and vulnerability. In addition, the drivers of exposure and vulnerability vary across different coastal contexts ranging from resource-rich cities to small islands (Sections 4.3.3, 4.3.4). Accordingly, effective responses need to be context-specific, and address the locality-specific drivers of risk.

<div id="section-4-1-3sea-level-rise-impacts-and-implications-for-responses-block-2"></div>

<span id="figure-4.3"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 4.3'''

<span id="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-19862005-and-projections-under"></span>
<!-- IMG CAPTION -->
'''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 […]'''
<!-- IMG FILE -->
[[File:24764f4424275dbd01b62a4b9a512a87 IPCC-SROCC-CH_4_SM_4_4-3000x1155.jpg]]

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, 4.3.4.1 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 4.2.3.4.1 to 4.2.3.4.3, 6.3.1.1 to 6.3.1.3), 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.

<!-- END IMG -->
<span id="response-options-governance-challenges-and-ways-forward"></span>