Editing IPCC:AR6/SR15/Chapter-4 (section)

=== 4.5.1 Assessing Feasibility of Options for Accelerated Transitions ===

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Chapter 2 shows that 1.5°C-consistent pathways involve rapid, global climate responses to reach net zero emissions by mid-century or earlier. Chapter 3 identifies climate change risks and impacts to which the world would need to adapt during these transitions and additional risks and impacts during potential 1.5°C overshoot pathways. The feasibility of these pathways is contingent upon systemic change (Section 4.3) and enabling conditions (Section 4.4), including policy packages. This section assesses the feasibility of options (technologies, actions and measures) that form part of global systems under transition that make up 1.5°C-consistent pathways.

Following the assessment framework developed in Chapter 1, economic and technological, institutional and socio-cultural, and environmental and geophysical feasibility are considered and applied to system transitions (Sections 4.3.1–4.3.4), overarching adaptation options (Section 4.3.5) and carbon dioxide removal (CDR) options (Section 4.3.7). This is done to assess the multidimensional feasibility of mitigation and adaptation options that have seen considerable development and change since AR5. In the case of adaptation, the assessed AR5 options are typically clustered. For example, all options related to energy infrastructure resilience, independently of the generation source, are categorized as ‘resilience of power infrastructure’.

Table 4.10 presents sets of indicators against which the multidimensional feasibility of individual adaptation options relevant to warming of 1.5°C, and mitigation options along 1.5°C-consistent pathways, is assessed.

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'''Table 4.10'''

Sets of indicators against which the feasibility of adaptation and mitigation options are assessed, for each feasibility dimensions. The options are discussed in Sections 4.3.1-4.3.5 and 4.3.7.

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{| class="wikitable"
|-
| Feasibility Dimensions
| Adaptation Indicators
| Mitigation Indicators
|-
| Economic
| Microeconomic viability
Macroeconomic viability

Socio-economic vulnerability reduction potential

Employment &amp; productivity enhancement potential

| Cost-effectiveness
Absence of distributional effects

Employment &amp; productivity enhancement potential

|-
| Technological
| Technical resource availability
Risks mitigation potential

| Technical scalability
Maturity

Simplicity

Absence of risk

|-
| Institutional
| Political acceptability
Legal &amp; regulatory feasibility

Institutional capacity &amp; administrative feasibility

Transparency &amp; accountability potential

| Political acceptability
Legal &amp; administrative feasibility

Institutional capacity

Transparency &amp; accountability potential

|-
| Socio-cultural
| Social co-benefits (health, education)
Socio-cultural acceptability

Social &amp; regional inclusiveness

Intergenerational equity

| Social co-benefits (health, education)
Public acceptance

Social &amp; regional inclusiveness

Intergenerational equity

Human capabilities

|-
| Environmental/Ecological
| Ecological capacity
Adaptive capacity/ resilience building potential

| Reduction of air pollution
Reduction of toxic waste

Reduction of water use

Improved biodiversity

|-
| Geophysical
| Physical feasibility
Land use change enhancement potential

Hazard risk reduction potential

| Physical feasibility (physical potentials)
Limited use of land

Limited use of scarce (geo)physical resources

Global spread

|}
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The feasibility assessment takes the following steps. First, each of the mitigation and adaptation options is assessed along the relevant indicators grouped around six feasibility dimensions: economic, technological, institutional, socio-cultural, environmental/ecological and geophysical. Three types of feasibility groupings were assessed from the underlying literature: first, if the indicator could block the feasibility of this option; second, if the indicator has neither a positive nor a negative effect on the feasibility of the option or the evidence is mixed; and third, if the indicator does not pose any barrier to the feasibility of this option. The full assessment of each option under each indicator, including the literature references on which the assessment is based, can be found in supplementary materials 4.SM.4.2 and 4.SM.4.3. When appropriate, it is indicated that there is no evidence (NE), limited evidence (LE) or that the indicator is not applicable to the option (NA).

Next, for each feasibility dimension and option, the overall feasibility for a given dimension is assessed as the mean of combined scores of the relevant underlying indicators and classified into ‘insignificant barriers’ (2.5 to 3), ‘mixed or moderate but still existent barriers’ (1.5 to 2.5) or ‘significant barriers’ (below 1.5) to feasibility. Indicators assessed as NA, LE or NE are not included in this overall assessment (see supplementary material 4.SM.4.1 for the averaging and weighing guidance).

The results are summarized in Table 4.11 (for mitigation options) and Table 4.12 (for adaptation options) for each of the six feasibility dimensions: where dark shading indicates few feasibility barriers; moderate shading indicates that there are mixed or moderate but still existent barriers, and light shading indicates that multiple barriers, in this dimension, may block implementation.

A three-step process of independent validation and discussion by authors was undertaken to make this assessment as robust as possible within the scope of this Special Report. It must, however, be recognized that this is an indicative assessment at global scale, and both policy and implementation at regional, national and local level would need to adapt and build on this knowledge, within the particular local context and constraints. Some contextual factors are indicated in the rightmost column in Tables 4.11 and 4.12.

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