Editing IPCC:AR6/SROCC/SPM (section)

==== Strengthening Response Options ====

'''C.2. The far-reaching services and options provided by ocean and cryosphere-related ecosystems can be supported by protection, restoration, precautionary ecosystem-based management of renewable resource use, and the reduction of pollution and other stressors ( ''high confidence'' ). Integrated water management ( ''medium confidence'' ) and ecosystem-based adaptation ( ''high confidence'' ) approaches lower climate risks locally and provide multiple societal benefits. However, ecological, financial, institutional and governance constraints for such actions exist ( ''high confidence'' ), and in many contexts ecosystem-based adaptation will only be effective under the lowest levels of warming ( ''high confidence'' ). {2.3.1, 2.3.3, 3.2.4, 3.5.2, 3.5.4, 4.4.2, 5.2.2, 5.4.2, 5.5.1, 5.5.2, Figure SPM.5}'''

'''C.2.1''' [[File:c5f1f5f7e69e3c69653136cbc5a42640 SPM-Icon-xxxx.png]] Networks of protected areas help maintain ecosystem services, including carbon uptake and storage, and enable future ecosystem-based adaptation options by facilitating the poleward and altitudinal movements of species, populations, and ecosystems that occur in response to warming and sea level rise ( ''medium confidence'' ). Geographic barriers, ecosystem degradation, habitat fragmentation and barriers to regional cooperation limit the potential for such networks to support future species range shifts in marine, high mountain and polar land regions. ( ''high confidence'' ). {2.3.3, 3.2.3, 3.3.2, 3.5.4, 5.5.2, Box 3.4}

'''C.2.2''' [[File:5f7f347d033531dcf31fbb1ace99b0a7 SPM-Icon-xoxx.png]] Terrestrial and marine habitat restoration, and ecosystem management tools such as assisted species relocation and coral gardening, can be locally effective in enhancing ecosystem-based adaptation ( ''high confidence'' ). Such actions are most successful when they are community-supported, are science-based whilst also using local knowledge and Indigenous knowledge, have long-term support that includes the reduction or removal of non-climatic stressors, and under the lowest levels of warming ( ''high confidence'' ). For example, coral reef restoration options may be ineffective if global warming exceeds 1.5°C, because corals are already at high risk ( ''very high confidence'' ) at current levels of warming. {2.3.3, 4.4.2, 5.3.7, 5.5.1, 5.5.2, Box 5.5, Figure SPM.3}

'''C.2.3''' [[File:37d9ca019c63e0a7a080aaca0b2016e4 SPM-Icon-oxox.png]] Strengthening precautionary approaches, such as rebuilding overexploited or depleted fisheries, and responsiveness of existing fisheries management strategies reduces negative climate change impacts on fisheries, with benefits for regional economies and livelihoods ( ''medium confidence'' ). Fisheries management that regularly assesses and updates measures over time, informed by assessments of future ecosystem trends, reduces risks for fisheries ( ''medium confidence'' ) but has limited ability to address ecosystem change. {3.2.4, 3.5.2, 5.4.2, 5.5.2, 5.5.3, Figure SPM.5}

'''C.2.4''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] Restoration of vegetated coastal ecosystems, such as mangroves, tidal marshes and seagrass meadows (coastal ‘blue carbon’ ecosystems), could provide climate change mitigation through increased carbon uptake and storage of around 0.5% of current global emissions annually ( ''medium confidence'' ). Improved protection and management can reduce carbon emissions from these ecosystems. Together, these actions also have multiple other benefits, such as providing storm protection, improving water quality, and benefiting biodiversity and fisheries ( ''high confidence'' ). Improving the quantification of carbon storage and greenhouse gas fluxes of these coastal ecosystems will reduce current uncertainties around measurement, reporting and verification ( ''high confidence'' ). {Box 4.3, 5.4, 5.5.1, 5.5.2, Annex I: Glossary}

'''C.2.5''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] Ocean renewable energy can support climate change mitigation, and can comprise energy extraction from offshore winds, tides, waves, thermal and salinity gradient and algal biofuels. The emerging demand for alternative energy sources is expected to generate economic opportunities for the ocean renewable energy sector ( ''high confidence'' ), although their potential may also be affected by climate change ( ''low confidence'' ). {5.4.2, 5.5.1, Figure 5.23}

'''C.2.6''' [[File:4d299f9da92412c8279a7422468e6e12 SPM-Icon-xooo.png]] Integrated water management approaches across multiple scales can be effective at addressing impacts and leveraging opportunities from cryosphere changes in high mountain areas. These approaches also support water resource management through the development and optimization of multi-purpose storage and release of water from reservoirs ( ''medium confidence'' ), with consideration of potentially negative impacts to ecosystems and communities. Diversification of tourism activities throughout the year supports adaptation in high mountain economies ( ''medium confidence'' ). {2.3.1, 2.3.5}

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'''C.3. Coastal communities face challenging choices in crafting context-specific and integrated responses to sea level rise that balance costs, benefits and trade-offs of available options and that can be adjusted over time ( ''high confidence'' ). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and retreat, wherever possible, can play important roles in such integrated responses ( ''high confidence'' ). {4.4.2, 4.4.3, 4.4.4, 6.9.1, Cross-Chapter Box 9, Figure SPM.5}'''

'''C.3.1.''' [[File:3dcc514bf2acf9f1b7861bf877ef79a9 SPM-Icon-ooxo.png]] The higher the sea levels rise, the more challenging is coastal protection, mainly due to economic, financial and social barriers rather than due to technical limits ( ''high confidence'' ). In the coming decades, reducing local drivers of exposure and vulnerability such as coastal urbanization and human-induced subsidence constitute effective responses ( ''high confidence'' ). Where space is limited, and the value of exposed assets is high (e.g., in cities), hard protection (e.g., dikes) is ''likely'' to be a cost-efficient response option during the 21st century taking into account the specifics of the context ( ''high confidence'' ), but resource-limited areas may not be able to afford such investments. Where space is available, ecosystem-based adaptation can reduce coastal risk and provide multiple other benefits such as carbon storage, improved water quality, biodiversity conservation and livelihood support ( ''medium confidence'' ). {4.3.2, 4.4.2, Box 4.1, Cross-Chapter Box 9, Figure SPM.5}

'''C.3.2''' [[File:3dcc514bf2acf9f1b7861bf877ef79a9 SPM-Icon-ooxo.png]] Some coastal accommodation measures, such as early warning systems and flood-proofing of buildings, are often both low cost and highly cost-efficient under current sea levels ( ''high confidence'' ). Under projected sea level rise and increase in coastal hazards some of these measures become less effective unless combined with other measures ( ''high confidence'' ). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and planned relocation, if alternative localities are available, can play important roles in such integrated responses ( ''high confidence'' ). Where the community affected is small, or in the aftermath of a disaster, reducing risk by coastal planned relocations is worth considering if safe alternative localities are available. Such planned relocation can be socially, culturally, financially and politically constrained ( ''very high confidence'' ). {4.4.2, Box 4.1, Cross-Chapter Box 9, SPM B3}

'''C.3.3''' [[File:3dcc514bf2acf9f1b7861bf877ef79a9 SPM-Icon-ooxo.png]] Responses to sea level rise and associated risk reduction present society with profound governance challenges, resulting from the uncertainty about the magnitude and rate of future sea level rise, vexing trade-offs between societal goals (e.g., safety, conservation, economic development, intra- and inter-generational equity), limited resources, and conflicting interests and values among diverse stakeholders ( ''high confidence'' ). These challenges can be eased using locally appropriate combinations of decision analysis, land-use planning, public participation, diverse knowledge systems and conflict resolution approaches that are adjusted over time as circumstances change ( ''high confidence'' ). {Cross-Chapter Box 5 in Chapter 1, 4.4.3, 4.4.4, 6.9}

'''C.3.4''' [[File:3dcc514bf2acf9f1b7861bf877ef79a9 SPM-Icon-ooxo.png]] Despite the large uncertainties about the magnitude and rate of post 2050 sea level rise, many coastal decisions with time horizons of decades to over a century are being made now (e.g., critical infrastructure, coastal protection works, city planning) and can be improved by taking relative sea level rise into account, favouring flexible responses (i.e., those that can be adapted over time) supported by monitoring systems for early warning signals, periodically adjusting decisions (i.e., adaptive decision making), using robust decision-making approaches, expert judgement, scenario-building, and multiple knowledge systems ( ''high confidence'' ). The sea level rise range that needs to be considered for planning and implementing coastal responses depends on the risk tolerance of stakeholders. Stakeholders with higher risk tolerance (e.g., those planning for investments that can be very easily adapted to unforeseen conditions) often prefer to use the ''likely'' range of projections, while stakeholders with a lower risk tolerance (e.g., those deciding on critical infrastructure) also consider global and local mean sea level above the upper end of the ''likely'' range (globally 1.1 m under RCP8.5 by 2100) and from methods characterised by lower confidence such as from expert elicitation. {1.8.1, 1.9.2, 4.2.3, 4.4.4, Figure 4.2, Cross-Chapter Box 5 in Chapter 1, Figure SPM.5, SPM B3}

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'''Figure SPM.5 | a, b'''

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'''Figure SPM.5 | Sea level rise risks and responses. The term response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. (a) shows the combined risk of coastal flooding, erosion and salinization for illustrative geographies in 2100, due to changing mean and extreme […]'''
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[[File:7a27bc34a0dcbce2611bddbf41dff53e SROCC_SPM5ab_Final_RGB.jpg]]

Figure SPM.5 | Sea level rise risks and responses. The term response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. (a) shows the combined risk of coastal flooding, erosion and salinization for illustrative geographies in 2100, due to changing mean and extreme sea levels under RCP2.6 and RCP8.5 and under two response scenarios. Risks under RCPs 4.5 and 6.0 were not assessed due to a lack of literature for the assessed geographies. The assessment does not account for changes in extreme sea level beyond those directly induced by mean sea level rise; risk levels could increase if other changes in extreme sea levels were considered (e.g., due to changes in cyclone intensity). Panel a) considers a socioeconomic scenario with relatively stable coastal population density over the century. {SM4.3.2} Risks to illustrative geographies have been assessed based on relative sea level changes projected for a set of specific examples: New York City, Shanghai and Rotterdam for resource-rich coastal cities covering a wide range of response experiences; South Tarawa, Fongafale and Male’ for urban atoll islands; Mekong and Ganges-Brahmaputra-Meghna for large tropical agricultural deltas; and Bykovskiy, Shishmaref, Kivalina, Tuktoyaktuk and Shingle Point for Arctic communities located in regions remote from rapid glacio-isostatic adjustment. {4.2, 4.3.4, SM4.2} The assessment distinguishes between two contrasting response scenarios. “No-to-moderate response” describes efforts as of today (i.e., no further significant action or new types of actions). “Maximum potential response” represents a combination of responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal financial, social and political barriers. The assessment has been conducted for each sea level rise and response scenario, as indicated by the burning embers in the figure; in-between risk levels are interpolated. {4.3.3} The assessment criteria include exposure and vulnerability (density of assets, level of degradation of terrestrial and marine buffer ecosystems), coastal hazards (flooding, shoreline erosion, salinization), in-situ responses (hard engineered coastal defenses, ecosystem restoration or creation of new natural buffers areas, and subsidence management) and planned relocation. Planned relocation refers to managed retreat or resettlement as described in Chapter 4, i.e., proactive and local-scale measures to reduce risk by relocating people, assets and infrastructure. Forced displacement is not considered in this assessment. Panel a) also highlights the relative contributions of in-situ responses and planned relocation to the total risk reduction. (b) schematically illustrates the risk reduction (vertical arrows) and risk delay (horizontal arrows) through mitigation and/or responses to sea level rise. (c) summarizes and assesses responses to sea level rise in terms of their effectiveness, costs, co-benefits, drawbacks, economic efficiency and associated governance challenges. {4.4.2} (d) presents generic steps of an adaptive decision-making approach, as well as key enabling conditions for responses to sea level rise. {4.4.4, 4.4.5}

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'''Figure SPM.5 | c, d'''

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'''Figure SPM.5 | Sea level rise risks and responses. The term response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. (a) shows the combined risk of coastal flooding, erosion and salinization for illustrative geographies in 2100, due to changing mean and extreme […]'''
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[[File:639ee85c6aae6622274d1de479f69a94 SROCC_SPM5cd_Final_RGB-1938x3000.jpg]]

Figure SPM.5 | Sea level rise risks and responses. The term response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. (a) shows the combined risk of coastal flooding, erosion and salinization for illustrative geographies in 2100, due to changing mean and extreme sea levels under RCP2.6 and RCP8.5 and under two response scenarios. Risks under RCPs 4.5 and 6.0 were not assessed due to a lack of literature for the assessed geographies. The assessment does not account for changes in extreme sea level beyond those directly induced by mean sea level rise; risk levels could increase if other changes in extreme sea levels were considered (e.g., due to changes in cyclone intensity). Panel a) considers a socioeconomic scenario with relatively stable coastal population density over the century. {SM4.3.2} Risks to illustrative geographies have been assessed based on relative sea level changes projected for a set of specific examples: New York City, Shanghai and Rotterdam for resource-rich coastal cities covering a wide range of response experiences; South Tarawa, Fongafale and Male’ for urban atoll islands; Mekong and Ganges-Brahmaputra-Meghna for large tropical agricultural deltas; and Bykovskiy, Shishmaref, Kivalina, Tuktoyaktuk and Shingle Point for Arctic communities located in regions remote from rapid glacio-isostatic adjustment. {4.2, 4.3.4, SM4.2} The assessment distinguishes between two contrasting response scenarios. “No-to-moderate response” describes efforts as of today (i.e., no further significant action or new types of actions). “Maximum potential response” represents a combination of responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal financial, social and political barriers. The assessment has been conducted for each sea level rise and response scenario, as indicated by the burning embers in the figure; in-between risk levels are interpolated. {4.3.3} The assessment criteria include exposure and vulnerability (density of assets, level of degradation of terrestrial and marine buffer ecosystems), coastal hazards (flooding, shoreline erosion, salinization), in-situ responses (hard engineered coastal defenses, ecosystem restoration or creation of new natural buffers areas, and subsidence management) and planned relocation. Planned relocation refers to managed retreat or resettlement as described in Chapter 4, i.e., proactive and local-scale measures to reduce risk by relocating people, assets and infrastructure. Forced displacement is not considered in this assessment. Panel a) also highlights the relative contributions of in-situ responses and planned relocation to the total risk reduction. (b) schematically illustrates the risk reduction (vertical arrows) and risk delay (horizontal arrows) through mitigation and/or responses to sea level rise. (c) summarizes and assesses responses to sea level rise in terms of their effectiveness, costs, co-benefits, drawbacks, economic efficiency and associated governance challenges. {4.4.2} (d) presents generic steps of an adaptive decision-making approach, as well as key enabling conditions for responses to sea level rise. {4.4.4, 4.4.5}

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