Editing IPCC:AR6/WGII/Chapter-18 (section)

=== 18.2.4 Climate Change Risks to Development ===

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In the near-term, additional climate change is expected regardless of the scale of greenhouse gas mitigation efforts ( [[#IPCC--2021a|IPCC, 2021a]] ). Across the global scenarios analysed in the AR6, global average temperature changes relative to the reference period 1850–1900 range from 1.2°C to 1.9°C for the period 2021–2040 and 1.2°C to 3.0°C for the period 2041–2060 (WGI AR6 SPM [ [[#IPCC--2021b|IPCC, 2021b]] ], ''very likely'' range). However, the feasibility of emissions pathways (particularly RCP8.5) affect the plausibility of the associated climate projections, potentially lowering the upper end of these ranges because the likelihood of the higher warming levels is a function of the likelihood of the higher emissions scenarios (Riahi et al., 2022) . There is significant overlap between climate scenario ensemble ranges from different emissions scenarios through 2050, more so than through 2100 ( [[#Lee--2021|Lee et al., 2021]] ). There is also overlap between emissions scenario ensembles consistent with different temperature outcomes (Riahi et al., 2022) . Emissions pathway ranges represent uncertainties for policymakers and organisations to consider and manage ( [[#Rose--2018|Rose and Scott, 2018]] , 2020) regarding, among other things, economic growth and structure, available technologies, markets, behavioural dynamics, policies and non-CO 2 climate forcings (Riahi et al., 2022), while climate pathway ranges represent bio-physical climate systems and carbon cycle uncertainties ( [[#Lee--2021|Lee et al., 2021]] ). For all climate projections and variables, there is significant regional heterogeneity and uncertainty in projected climate change ( ''very high confidence'' ) ( [[#IPCC--2021a|IPCC, 2021a]] ). Figure 18.4 apresents examples for average and extreme temperature precipitation change (see also [[#18.5|Section 18.5]] and Tables 18.4–18.5 for more regional detail and ranges of climate outcomes). Higher global warming levels also can affect geographic patterns of change and probability distributions of regional climate outcomes ( [[#Ahmad--2019|Ahmad, 2019]] ). Similarly, for all emissions projections, there is significant regional, sectoral and local heterogeneity and uncertainty regarding potential pathways for climate action (Lecocq et al., 2022; Riahi et al., 2022). Not all uncertainties are represented in projected emissions pathway ensembles, such as policy timing and design (e.g., [[#Rose--2018|Rose and Scott, 2018]] ) or climate projection ensembles.

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'''Figure 18.4 |''' '''Regional projected select climate change and sustainable-development-related climate impact indicators by global warming level.''' Sources: WGI AR6 Interactive Atlas ( https://interactive-atlas.ipcc.ch/ ) and WGII Figures 3.21, 4.17, 5.19, and 6.3. The GWLs shown are multi-model means derived from Hauser et al. (2019) for the respective RCP and SSP and time periods associated with each figure.

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'''Figure 18.4 |''' '''Regional projected select climate change and sustainable-development-related climate impact indicators by global warming level.''' Sources: WGI AR6 Interactive Atlas ( https://interactive-atlas.ipcc.ch/ ) and WGII Figures 3.21, 4.17, 5.19, and 6.3. The GWLs shown are multi-model means derived from Hauser et al. (2019) for the respective RCP and SSP and time periods associated with each figure.

The projected ranges for near- and mid-term global average warming levels are estimated to result in increasing key risks and reasons for concern (Chapter 16). [[IPCC:Wg2:Chapter:Chapter-16|Chapter 16]] developed aggregate ‘Representative Key Risks’ (RKRs) as indicators for subsets of approximately 100 sectoral and regional key risks indicators. The RKRs include risks to coastal socio-ecological systems, terrestrial and ocean ecosystems, critical physical infrastructure, networks and services, living standards and equity, human health, food security, water security, and peace and migration. The majority of these risks are directly linked to sustainable development priorities and the SDGs (Chapters 2 to 16; ( [[#Roy--2018|Roy et al., 2018]] ; [[#IPCC--2019d|IPCC, 2019d]] ; [[#IPCC--2019b|IPCC, 2019b]] ). Therefore, climate risks represent a potential additional challenge to pursuing sustainable development priorities, but also potential opportunities due to geographic variation in climate impacts. In addition, positive synergies have been found between sustainable development and adaptation, but trade-offs are also possible (e.g., [[#Roy--2018|Roy et al., 2018]] ).

For all RKRs, additional global average warming is expected to increase risk. However, the increases vary significantly by RKR, and across the underlying key risks represented within each RKR. Geographic variation in key risk implications is only partially assessed in Chapter 16, but evidence can be drawn from the WGII individual regional chapters. Regionally, key risks are found to be potentially greatest in developing and transition economies ( [[IPCC:Wg2:Chapter:Chapter-16|Chapter 16]] and sectoral chapters), which is also where the least-cost emissions reductions globally are projected to be (Riahi et al., 2022).See Figure 18.4 for an example of key risk geographic heterogeneity (see also [[#18.5|Section 18.5]] for regional detail). [[IPCC:Wg2:Chapter:Chapter-16|Chapter 16]] also maps the RKRs to an updated aggregate ‘Reasons for Concern’ (RFC) framing. Thus, increasing RKR implies increasing RFC associated with unique and threatened systems, extreme weather events, distribution of impacts, global aggregate impacts and large-scale singular events.

Climate risks are found to vary with future warming levels, the development context and trajectory, as well as by the level of investment in adaptation. Together, these three dimensions define risk—with projected climate changes defining the hazard, development defining the exposure, and development and adaptation defining vulnerability. However, how these different dimensions interact and the level of scientific understanding vary significantly among different types of risk. For human systems, in general, the poor and marginalised are found to have greater vulnerability for a given hazard and exposure level. With some level of global average warming expected regardless of mitigation efforts, human and natural systems will be exposed to new conditions, but some level of adaptation should also be expected.

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