Editing IPCC:AR6/SYR/Longer-Report (section)

==== 2.3.1. The Gap Between Mitigation Policies, Pledges and Pathways that Limit Warming to 1.5°C or Below 2°C ====

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'''Global GHG emissions in 2030 associated with the implementation of NDCs announced prior to COP26''' '''[[#footnote-066|91]] would make it''' '''''likely''''' '''that warming will exceed 1. 5°C during the 21st century and would make it harder to limit warming below 2°C – if no additional commitments are made or actions taken (Figure 2.5, Table 2.2).''' A substantial ‘emissions gap’ exists as global GHG emissions in 2030 associated with the implementation of NDCs announced prior to COP26 would be similar to or only slightly below 2019 emission levels and higher than those associated with modelled mitigation pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot or to 2°C (&gt;67%), assuming immediate action, which implies deep, rapid, and sustained global GHG emission reductions this decade ( ''high confidence'' ). (Table 2.2, Table 3.1, 4.1). '''[[#footnote-065|92]]''' The magnitude of the emissions gap depends on the global warming level considered and whether only unconditional or also conditional elements of NDCs '''[[#footnote-064|93]]''' are considered ( ''high confidence'' ) (Table 2.2). Modelled pathways that are consistent with NDCs announced prior to COP26 until 2030 and assume no increase in ambition thereafter have higher emissions, leading to a median global warming of 2.8 [2.1 to 3.4]°C by 2100 ( ''medium confidence'' ). If the ‘emission gap’ is not reduced, global GHG emissions in 2030 consistent with NDCs announced prior to COP26 make it ''likely'' that warming will exceed 1.5°C during the 21st century, while limiting warming to 2°C (&gt;67%) would imply an unprecedented acceleration of mitigation efforts during 2030–2050 ( ''medium confidence'' ) (see Section 4.1, Cross-Section Box.2). { ''WGIII SPM B.6, WGIII SPM B.6.1, WGIII SPM B.6.3, WGIII SPM B.6.4, WGIII SPM C.1.1'' }

'''Policies implemented by the end of 2020 are projected to result in higher global GHG emissions in 2030 than those implied by NDCs, i ndicating an ‘implementation gap''' '''[[#footnote-063|94]] ’ (''' '''''high confidence)''''' '''''( Table 2.2, Figure 2.5).''''' Projected global emissions implied by policies implemented by the end of 2020 are 57 (52–60) GtCO 2 -eq in 2030 (Table 2.2). This points to an implementation gap compared with the NDCs of 4 to 7 GtCO 2 -eq in 2030 (Table 2.2); without a strengthening of policies, emissions are projected to rise, leading to a median global warming of 2.2°C to 3.5°C ( ''very likely range'' ) by 2100 ( ''medium confidence'' )(see [[#3.1.1|Section 3.1.1]] ). { ''WGIII SPM B.6.1, WGIII SPM C.1'' }

Projected cumulative future CO 2 emissions over the lifetime of existing fossil fuel infrastructure without additional abatement '''[[#footnote-062|95]]''' exceed the total cumulative net CO 2 emissions in pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot. They are approximately equal to total cumulative net CO 2 emissions in pathways that limit warming to 2°C with a likelihood of 83% '''[[#footnote-061|96]]''' (see Figure 3.5). Limiting warming to 2°C (&gt;67%) or lower will result in stranded assets. About 80% of coal, 50% of gas, and 30% of oil reserves cannot be burned and emitted if warming is limited to 2°C. Significantly more reserves are expected to remain unburned if warming is limited to 1.5°C. ( ''high confidence'' ). { ''WGIII SPM B.7, WGIII Box 6.3'' }

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'''Table 2.2 Projected global emissions in 2030 associated with policies implemented by the end of 2020 and NDCs announced prior to COP26, and associated emissions gaps.''' Emissions projections for 2030 and gross differences in emissions are based on emissions of 52–56 GtCO 2 -eq yr–1 in 2019 as assumed in underlying model studies '''[[#footnote-060|97]]''' . ( ''medium confidence'' ) { ''WGIII Table SPM.1'' } ( ''Table 3.1, Cross-Section Box.2'' ).

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'''Figure 2.5 Global GHG emissions of modelled pathways (funnels in Panel a), and projected emission outcomes from near-term policy assessments for 2030 (Panel b). Panel a''' shows global GHG emissions over 2015-2050 for four types of assessed modelled global pathways:

* Trend from implemented policies: Pathways with projected near-term GHG emissions in line with po licies implemented until the end of 2020 and extended with comparable ambition levels beyond 2030 (29 scenarios across categories C5–C7, WGIII Table SPM.2).
* Limit to 2°C (&gt;67%) or return warming to 1.5°C (&gt;50%) after a high overshoot, NDCs until 2030: Pathways with GHG emissions until 2030 associated with the implementation of NDCs announced prior to COP26, followed by accelerated emissions reductions likely to limit warming to 2°C (C3b, WGIII Table SPM.2) or to return warming to 1.5°C with a probability of 50% or greater after high overshoot (subset of 42 scenarios from C2, WGIII Table SPM.2).
* Limit to 2°C (&gt;67%) with immediate action: Pathways that limit warming to 2°C (&gt;67%) with immediate action after 2020 (C3a, WGIII Table SPM.2).
* Limit to 1.5°C (&gt;50%) with no or limited overshoot: Pathways limiting warming to 1.5°C with no or limited overshoot (C1, WGIII Table SPM.2 C1).

All these pathways assume immediate action after 2020. Past GHG emissions for 2010-2015 used to project global warming outcomes of the modelled pathways are shown by a black line. '''Panel b''' shows a snapshot of the GHG emission ranges of the modelled pathways in 2030 and projected emissions outcomes from near-term policy assessments in 2030 from WGIII Chapter 4.2 (Tables 4.2 and 4.3; median and full range). GHG emissions are CO 2 -equivalent using GWP100 from AR6 WGI. { ''WGIII Figure SPM.4, WGIII 3.5, 4.2, Table 4.2, Table 4.3, Cross-Chapter Box 4 in Chapter 4'' } ( ''Table 3.1, Cross-Section Box.2'' )

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'''Cross-Section Box.1: Understanding Net Zero CO''' '''2''' and Net Zero GHG Emissions

'''Limiting human-caused global warming to a specific level requires limiting cumulative CO''' '''2''' emissions, reaching net zero or net negative CO '''2''' emissions, along with strong reductions in other GHG emissions (see 3.3.2). Future additional warming will depend on future emissions, with total warming dominated by past and future cumulative CO 2 emissions. { ''WGI SPM D.1.1, WGIFigure SPM.4; SR1.5 SPM A.2.2'' } .

'''Reaching net zero CO''' '''2''' emissions is different from reaching net zero GHG emissions. The timing of net zero for a basket of GHGs depends on the emissions metric, such as global warming potential over a 100-year period, chosen to convert non-CO 2 emissions into CO 2 -equivalent ( ''high confidence'' ). However, for a given emissions pathway, the physical climate response is independent of the metric chosen ( ''high confidence'' ). { ''WGI SPM D.1.8; WGIII Box TS.6, WGIII Cross-Chapter Box 2'' }

'''Achieving global net zero GHG emissions requires all remaining CO''' '''2''' and metric-weighted '''[[#footnote-059|98]] non-CO''' '''2''' GHG emissions to be counterbalanced by durably stored CO '''2''' removals ( '''''high confidence).''''' Some non-CO 2 emissions, such as CH 4 and N 2 O from agriculture, cannot be fully eliminated using existing and anticipated technical measures. { ''WGIII SPM C.2.4, WGIII SPM C.11.4, WGIII Cross-Chapter Box 3'' }

'''Global net zero CO''' '''2''' or GHG emissions can be achieved even if some sectors and regions are net emitters, provided that others reach net negative emissions (see Figure 4.1). The potential and cost of achieving net zero or even net negative emissions vary by sector and region. If and when net zero emissions for a given sector or region are reached depends on multiple factors, including the potential to reduce GHG emissions and undertake carbon dioxide removal, the associated costs, and the availability of policy mechanisms to balance emissions and removals between sectors and countries. ( ''high confidence'' ). { ''WGIII Box TS.6, WGIII Cross-Chapter Box 3'' }

'''The adoption and implementation of net zero emission targets by countries and regions also depend on equity and capacity considerations (''' '''''high confidence).''''' The formulation of net zero pathways by countries will benefit from clarity on scope, plans-of-action, and fairness. Achieving net zero emission targets relies on policies, institutions, and milestones against which to track progress. Least-cost global modelled pathways have been shown to distribute the mitigation effort unevenly, and the incorporation of equity principles could change the country-level timing of net zero ( ''high confidence'' ). The Paris Agreement also recognizes that peaking of emissions will occur later in developing countries than developed countries (Article 4.1). { ''WGIII Box TS.6, WGIII Cross-Chapter Box 3, WGIII 14.3'' }

More information on country-level net zero pledges is provided in [[#2.3.1|Section 2.3.1]] , on the timing of global net zero emissions in [[#3.3.2|Section 3.3.2]] , and on sectoral aspects of net zero in Section 4.1.

'''Many countries have signalled an intention to achieve net zero GHG or net zero CO''' '''2''' emissions by around mid-century (Cross-Section Box.1). More than 100 countries have either adopted, announced or are discussing net zero GHG or net zero CO 2 emissions commitments, covering more than two-thirds of global GHG emissions. A growing number of cities are setting climate targets, including net zero GHG targets. Many companies and institutions have also announced net zero emissions targets in recent years. The various net zero emission pledges differ across countries in terms of scope and specificity, and limited policies are to date in place to deliver on them. { ''WGIII SPM C.6.4, WGIII TS.4.1, WGIII Table TS.1, WGIII 13.9, WGIII 14.3, WGIII 14.5'' } .

'''All mitigation strategies face implementation challenges, including technology risks, scaling, and costs (''' '''''high confidence).''''' Almost all mitigation options also face institutional barriers that need to be addressed to enable their application at scale ( ''medium confidence'' ). Current development pathways may create behavioural, spatial, economic and social barriers to accelerated mitigation at all scales ( ''high confidence'' ). Choices made by policymakers, citizens, the private sector and other stakeholders influence societies’ development pathways ( ''high confidence'' ). Structural factors of national circumstances and capabilities (e.g., economic and natural endowments, political systems and cultural factors and gender considerations) affect the breadth and depth of climate governance ( ''medium confidence'' ). The extent to which civil society actors, political actors, businesses, youth, labour, media, Indigenous Peoples, and local communities are engaged influences political support for climate change mitigation and eventual policy outcomes ( ''medium confidence'' ). { ''WGIII SPM C.3.6, WGIII SPM E.1.1, WGIII SPM E.2.1, WGIII SPM E.3.3'' }

'''The adoption of low-emission technologies lags in most developing countries, particularly least developed ones, due in part to weaker enabling conditions, including limited finance, technology development and transfer, and capacity (''' '''''medium confidence).''''' In many countries, especially those with limited institutional capacity, several adverse side-effects have been observed as a result of diffusion of low-emission technology, e.g., low-value employment, and dependency on foreign knowledge and suppliers ( ''medium confidence'' ). Low-emission innovation along with strengthened enabling conditions can reinforce development benefits, which can, in turn, create feedbacks towards greater public support for policy. ( ''medium confidence)'' . Persistent and region-specific barriers also continue to hamper the economic and political feasibility of deploying AFOLU mitigation options ( ''medium confidence'' ). Barriers to implementation of AFOLU mitigation include insufficient institutional and financial support, uncertainty over long-term additionality and trade-offs, weak governance, insecure land ownership, low incomes and the lack of access to alternative sources of income, and the risk of reversal ( ''high confidence'' ). { ''WGIII SPM B.4.2, WGIII SPM C.9.1, WGIII SPM C.9.3'' } .

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