Editing IPCC:AR6/WGII/Chapter-16 (section)

===== Elicitation Methodology =====

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The method used to develop judgements on levels of risk builds on the approach described in WGII AR5 Chapter 19 ( [[#Oppenheimer--2014|Oppenheimer et al., 2014]] ) and outlined in more detail in the work of [[#O’Neill--2017|O’Neill et al. (2017)]] , while integrating advances in the AR6 SRs including expert judgement (SRCCL, [[#Zommers--2020|Zommers et al., 2020]] ). We provide further details on the underlying judgements of risk level compared with previous assessments by indicating key risk criteria associated with each judgement: magnitude of adverse consequences, likelihood of adverse consequences, temporal profile of the risk, and ability to respond to the risk ( [[#16.5.1|Section 16.5.1]] ). The definitions of risk levels used to make the expert judgements are presented in Table 16.7 ( [[#16.5.1|Section 16.5.1]] ).

'''Table 16.7 |''' Definition of risk levels for Reasons for Concern.

{| class="wikitable"
|-
! Level

! Definition

|-
| Undetectable (white)

| No associated impacts are detectable and attributable to climate change.

|-
| Moderate (yellow)

| Associated impacts are both detectable and attributable to climate change with at least ''medium confidence'' , also accounting for the other specific criteria for key risks.

|-
| High (red)

| Severe and widespread impacts that are judged to be high on one or more criteria for assessing key risks.

|-
| Very high (purple)

| Very high risk of severe impacts and the presence of significant irreversibility or the persistence of climate-related hazards, combined with limited ability to adapt due to the nature of the hazard or impacts/risks.

|}

A brief summary of the framework that was used to carry out the risk assessment, synthesis and expert elicitation is presented here, and details are provided in SM16.6. Expert judgements about the qualitatively defined levels of risk (i.e., undetectable, moderate, high, and very high) reached at various levels of global average warming are informed by evidence of observed impacts illustrated in [[#16.2|Section 16.2]] and variations in individual key risks under different scenarios of climate change, socioeconomics and adaptation effort in [[#16.5|Section 16.5]] . We follow the methodological advances from SRCCL [[IPCC:Wg2:Chapter:Chapter-7|Chapter 7]] ( [[#Hurlbert--2019|Hurlbert et al., 2019]] ), which used an expert elicitation protocol for developing the burning embers ( [[#Zommers--2020|Zommers et al., 2020]] ). Specifically, we used expert participants from within the AR6 author team and a protocol based on the modified Delphi technique ( [[#Mukherjee--2015|Mukherjee et al., 2015]] ) and the Sheffield Elicitation Framework ( [[#Oakley--2010|Oakley and O’Hagan, 2010]] ; [[#Gosling--2018|Gosling, 2018]] ). This approach (Figure 16.14) includes a two-round elicitation process with a first round of independent anonymous judgements about the global warming level at which risk levels transition from one to the next, and a final round of group discussion and deliberation to develop consensus. The results are then reported, and additional references are made to findings from other relevant chapters in this report. Then, authors who had not participated in the elicitation as part of independent appraisal review the results.

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'''Figure 16.14 |''' '''Expert elicitation approach for assessment of RFC risk level transitions.''' A more detailed description of the methodology used in this elicitation is provided in SM16.6.

The resulting risk transition or ‘ember’ diagram illustrates the progression of socio-ecological risk from climate change as a function of global temperature change, taking into account the exposure and vulnerability of people and ecosystems, as assessed by literature-based expert judgement. [[#16.6|Section 16.6.3]] presents these diagrams for each RFC, providing information about the most important literature-based evidence that experts used to make their judgements. Similar assessments for selected individual KRs are discussed in Chapters 2, 7, 9, 12, 13 and 14.

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