Editing IPCC:AR6/WGII/TS (section)

=== TS.AII.2 Assessment of Severity Conditions for Representative Key Risks ===

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Figure TS.AII.1 presents a synthesis of the severity conditions for RKRs by the end of this century. As an illustration of the more specific sets of conditions that result in severe risk for a particular RKR, Figure TS.AII.2 provides examples from individual studies of risks to living standards and the conditions under which they could become severe in terms of aggregate economic output, poverty and livelihoods.

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'''Figure TS.AII.1 |''' '''Synthesis of the severity conditions for Representative Key Risks (RKRs) by the end of this century.''' The figure does not aim to describe severity conditions exhaustively for each RKR, but rather to illustrate the risks highlighted in this report (Sections 16.5.2.3.1 to 16.5.2.3.8). Coloured circles represent the levels of warming (climate), exposure/vulnerability and adaptation that would lead to severe risks for particular key risks and RKRs. Each set of three circles represents a combination of conditions that would lead to severe risk with a particular level of confidence, indicated by the number of black dots to the right of the set, and for a particular scope, indicated by the number of stars to the left of the set. The two scopes are ‘broadly applicable’, meaning applicable pervasively and even globally, and ‘specific’, meaning applicable to particular areas, sectors or groups of people. Details of confidence levels and scopes can be found in [[IPCC:Wg2:Chapter:Chapter-16#16.5.2.3|Section 16.5.2.3]] . In terms of severity condition levels ( [[IPCC:Wg2:Chapter:Chapter-16#16.5.2.3|Section 16.5.2.3]] ), for warming levels (coloured circles labelled ‘C’ in the figure), high refers to climate outcomes consistent with RCP8.5 or higher, low refers to climate outcomes consistent with RCP2.6 or lower, and medium refers to intermediary climate scenarios. Exposure-vulnerability levels are determined relative to the range of future conditions considered in the literature. For adaptation, high refers to near maximum potential and low refers to the continuation of today’s trends. Despite being intertwined in reality, exposure-vulnerability and adaptation conditions are distinguished to help understand their respective contributions to risk severity. { Figure 16.10 }

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'''Figure TS.AII.2 |''' '''Illustrative examples from individual studies of risks to living standards and the conditions under which they could become severe in terms of aggregate economic output, poverty and livelihoods.''' High, medium and low levels of warming, exposure/vulnerability and adaptation are defined as in Figure TS.AII.1. { Figure 16.9 }

The assessment of RKRs demonstrates that severe risk is rarely driven by a single determinant (warming, exposure/vulnerability, adaptation), but rather by a combination of conditions that jointly produce the level of pervasiveness of consequences, irreversibility, thresholds, cascading effects, likelihood of consequences, temporal characteristics of risk and systems’ ability to respond ( ''medium'' to ''high confidence'' ). In other words, climate risk is not a matter of changing hazards (or climatic impact drivers) only but of the confrontation between changing hazards and changing socioecological conditions.

For most RKRs, potentially global and systemically pervasive risks become severe in the case of high levels of warming, combined with high exposure/vulnerability, low adaptation or both ( ''high confidence'' ). Under these conditions there would be severe and pervasive risks to critical infrastructure ( ''high confidence'' ), to human health from heat-related mortality, to low-lying coastal areas, aggregate economic output and livelihoods (all ''medium confidence'' ) from armed conflict ( ''low confidence'' ) and to various aspects of food security (with different levels of confidence). Severe risks interact through cascading effects, potentially causing amplification of RKRs over the course of this century ( ''low evidence, high agreement'' ). (Figure TS.AII.1) { 16.5.2, 16.5.4, Figure 16.10 }

For some RKRs, potentially global and systemically pervasive risks would become severe even with medium to low warming (i.e., 1.5°C–2°C) if exposure/vulnerability is high and/or adaptation is low ( ''medium to high confidence'' ). Under these conditions there would be severe and pervasive risks associated with water scarcity and water-related disasters ( ''high confidence'' ), poverty, involuntary mobility and insular ecosystems and biodiversity hotspots (all ''medium confidence'' ). { 16.5.2 }

All potentially severe risks that apply to particular sectors or groups of people at more specific regional and local levels require high exposure/vulnerability or low adaptation (or both), but they do not necessarily require high warming ( ''high confidence'' ). Under these conditions there would be severe, specific risks to low-lying coastal systems, to people and economies from critical infrastructure disruption, to economic output in developing countries and to livelihoods in climate-sensitive sectors from water-borne diseases, especially in children in low- and middle-income countries, water-related impacts on traditional ways of life and involuntary mobility, for example in small islands and low-lying coastal areas ( ''medium to high confidence'' ). { 16.5.2 }

Some severe impacts are already occurring ( ''high confidence'' ) and will occur in many more systems before mid-century ( ''medium confidence'' ). Tropical and polar low-lying coastal human communities are experiencing severe impacts today ( ''high confidence'' ), and abrupt ecological changes resulting from mass population-level mortality are already being observed following climate extreme events. Some systems will experience severe risks before the end of the century ( ''medium confidence'' ), for example critical infrastructure affected by extreme events ( ''medium confidence'' ). Food security for millions of people, particularly low-income populations, also faces significant risks with moderate to high warming or high vulnerability, with a growing challenge by 2050 in terms of providing nutritious and affordable diets ( ''high confidence'' ). { 16.5.2, 16.5.3 }

In specific systems already marked by high exposure and vulnerability, intensive adaptation efforts will not be sufficient to prevent severe risks from occurring under high levels of warming ( ''low evidence, medium agreement'' ). This is particularly the case for some ecosystems and water-related risks (from water scarcity and to Indigenous and traditional cultures and ways of life). { 16.5.2, 16.5.3 }

Key risks increase the challenges in achieving global sustainability goals ( ''high confidence'' ). The greatest challenges will be from risks to water (RKR-G), living standards (RKR-D), coastal socioecological systems (RKR-A) and peace and human mobility (RKR-H). The most relevant goals are zero hunger (SDG 2), sustainable cities and communities (SDG 11), life below water (SDG 14), decent work and economic growth (SDG 8), and no poverty (SDG 1). Priority areas for regions are indicated by the intersection of hazards, risks and challenges, where, in the near term, challenges to SDGs indicate probable systemic vulnerabilities and issues in responding to climatic hazards ( ''high confidence'' ). { 16.6.1 }

Multiple feedbacks between individual risks exist that have the potential to create cascades and then to amplify systemic risks and impacts far beyond the level of individual RKRs ( ''medium confidence'' ), as also reflected in TS.C.11. These are illustrated in Figure TS.AII.3, panel A at the RKR level, and in Figure TS.AII.3, panel B at the key risk level.

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'''Figure TS.AII.3 |''' '''Illustration of some connections across key risks.''' Panel A describes all the cross-RKR risk cascades that are described in RKR assessments (Sections 16.5.2.3.2 to 16.5.2.3.9). Panel B provides an illustration of such interactions at the key risk level, for example from ecological risk to key dimensions for human societies (building on [[IPCC:Wg2:Chapter:Chapter-16#16.5.2.2|Section 16.5.2.2]] and Table 16.A.4). The arrows are representative of interactions as qualitatively identified; they do not result from any quantitative modelling exercise. { Figure 16.11 }

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