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

=== 4.1 The Timing and Urgency of Climate Action ===

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'''Deep, rapid, and sustained mitigation and accelerated implementation of adaptation reduces the risks of climate change for humans and ecosystems. In modelled pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot and in those that limit warming to 2°C (&gt;67%) and assume immediate action, global GHG emissions are projected to peak in the early 2020s followed by rapid and deep reductions. As adaptation options often have long implementation times, accelerated implementation of adaptation, particularly in this decade, is important to close adaptation gaps. ( '''''high confidence''''' )'''

'''The magnitude and rate of climate change and associated risks depend strongly on near-term mitigation and adaptation actions (''' '''''very high confidence).''''' Global warming is ''more likely than not'' to reach 1.5°C between 2021 and 2040 even under the very low GHG emission scenarios (SSP1-1.9), and. ''likely'' or ''very likely'' to exceed 1.5°C under higher emissions scenarios '''[[#footnote-016|141]]''' . Many adaptation options have medium or high feasibility up to 1.5°C ( ''medium'' to ''high confidence'' , depending on option), but hard limits to adaptation have already been reached in some ecosystems and the effectiveness of adaptation to reduce climate risk will decrease with increasing warming ( ''high confidence'' ). Societal choices and actions implemented in this decade determine the extent to which medium- and long-term pathways will deliver higher or lower climate resilient development ( ''high confidence'' ). Climate resilient development prospects are increasingly limited if current greenhouse gas emissions do not rapidly decline, especially if 1.5°C global warming is exceeded in the near term ( ''high confidence'' ). Without urgent, effective and equitable adaptation and mitigation actions, climate change increasingly threatens the health and livelihoods of people around the globe, ecosystem health, and biodiversity, with severe adverse consequences for current and future generations ( ''high confidence'' ). { ''WGI SPM B.1.3, WGI SPM B.5.1, WGI SPM B.5.2; WGII SPM A, WGII SPM B.4, WGII SPM C.2, WGII SPM C.3.3, WGII Figure SPM.4, WGII SPM D.1, WGII SPM D.5, WGIII SPM D.1.1 SR1.5 SPM D.2.2'' } . ( ''Cross-Section Box.2, Figure 2.1, Figure 2.3'' )

'''In modelled pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot and in those that limit warming to 2°C (&gt;67%), assuming immediate actions , global GHG emissions are projected to peak in the early 2020s followed by rapid and deep GHG emissions reductions (''' '''''high confidence)''''' [[#footnote-015|142]] . In pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot, net global GHG emissions are projected to fall by 43 [34 to 60]% '''[[#footnote-014|143]]''' below 2019 levels by 2030, 60 [49 to 77]% by 2035, 69 [58 to 90]% by 2040 and 84 [73 to 98]% by 2050 ( ''high confidence'' ). ( [[#2.3.1|Section 2.3.1]] , Table 2.2, Figure 2.5, Table 3.1) '''[[#footnote-013|144]]''' . Global modelled pathways that limit warming to 2°C (&gt;67%) have reductions in GHG emissions below 2019 levels of 21 [1 to 42]% by 2030, 35 [22 to 55] % by 2035, 46 [34 to 63] % by 2040 and 64 [53 to 77]% by 2050 '''[[#footnote-012|145]]''' ( ''high confidence'' ). Global GHG emissions associated with NDCs announced prior to COP26 would make it ''likely'' that warming would exceed 1.5°C ( ''high confidence'' ) and limiting warming to 2°C (&gt;67%) would then imply a rapid acceleration of emission reductions during 2030–2050, around 70% faster than in pathways where immediate action is taken to limit warming to 2°C (&gt;67%) ( ''medium confidence'' ) ( [[#2.3.1|Section 2.3.1]] ) Continued investments in unabated high-emitting infrastructure '''[[#footnote-011|146]]''' and limited development and deployment of low-emitting alternatives prior to 2030 would act as barriers to this acceleration and increase feasibility risks ( ''high confidence'' ). { ''WGIII SPM B.6.3, WGIII 3.5.2, WGIII SPM B.6, WGIII SPM B.6., WGIII SPM C.1, WGIII SPM C1.1, WGIII Table SPM.2'' } ( ''Cross-Section Box.2'' )

'''All global modelled pathways that limit warming to 2°C (&gt;67%)''' '''or lower by 2100 involve reductions in both net CO''' '''2''' emissions and non-CO '''2''' emissions (see Figure 3.6) ( '''''high confidence).''''' For example, in pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot, global CH 4 (methane) emissions are reduced by 34 [21 to 57]% below 2019 levels by 2030 and by 44 [31 to 63]% in 2040. ( ''high confidence'' ). Global CH 4 emissions are reduced by 24 [9 to 53]% below 2019 levels by 2030 and by 37 [20 to 60]% in 2040 in modelled pathways that limit warming to 2°C with action starting in 2020 (&gt;67%) ( ''high confidence'' ). { ''WGIII SPM C1.2, WGIII Table SPM.2, WGIII 3.3; SR1.5 SPM C.1, SR1.5 SPM C.1.2'' } . ( ''Cross-Section Box.2'' )

'''All global modelled pathways that limit warming to 2°C (&gt;67%) or lower by 2100 involve GHG emission reductions in all sectors (''' '''''high confidence).''''' The contributions of different sectors vary across modelled mitigation pathways. In most global modelled mitigation pathways, emissions from land-use, land-use change and forestry, via reforestation and reduced deforestation, and from the energy supply sector reach net zero CO 2 emissions earlier than the buildings, industry and transport sectors (Figure 4.1). Strategies can rely on combinations of different options (Figure 4.1, Section 4.5), but doing less in one sector needs to be compensated by further reductions in other sectors if warming is to be limited. ( ''high confidence'' ). { ''WGIII SPM C.3, WGIII SPM C.3.1, WGIII SPM 3.2, WGIII SPM C.3.3'' } ( ''Cross-Section Box.2'' )

'''Without rapid, deep and sustained mitigation and accelerated adaptation actions, losses and damages will continue to increase, including projected adverse impacts in Africa, LDCs, SIDS, Central and South America''' [[#footnote-010|147]] , Asia and the Arctic, and will disproportionately affect the most vulnerable populations ( '''''high confidence)''''' '''''.''''' { ''WGII SPM C.3.5, WGII SPM B.2.4, WGII 12.2, WGII 10. Box 10.6, WGII TS D.7.5, WGII Cross-Chapter Box 6 ES, WGII Global to Regional Atlas Annex A1.15, WGII Global to Regional Atlas Annex A1.27; SR1.5 SPM B.5.3, SR 1.5 SPM B.5.7; SRCCL A.5.6'' } ( ''Figure 3.2; Figure 3.3'' )

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'''Figure 4.1: Sectoral emissions in pathways that limit''' '''warming to 1.5°C.''' '''Panel (a)''' shows sectoral CO 2 and non-CO 2 emissions in global modelled pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot. The horizontal lines illustrate halving 2015 emissions (base year of the pathways) (dashed) and reaching net zero emissions (solid line). The range shows the 5–95th percentile of the emissions across the pathways. The timing strongly differs by sector, with the CO 2 emissions from the electricity/fossil fuel industries sector and land-use change generally reaching net zero earlier. Non-CO 2 emissions from agriculture are also substantially reduced compared to pathways without climate policy but do not typically reach zero. '''Panel (b)''' Although all pathways include strongly reduced emissions, there are different pathways as indicated by the illustrative mitigation pathways used in IPCC WGIII. The pathways emphasise routes consistent with limiting warming to 1.5°C with a high reliance on net negative emissions (IMP-Neg), high resource efficiency (IMP-LD ), a focus on sustainable development (IMP-SP) or renewables (IMP-Ren) and consistent with 2°C based on a less rapid introduction of mitigation measures followed by a subsequent gradual strengthening (IMP-GS). Positive (solid filled bars) and negative emissions (hatched bars) for different illustrative mitigation pathways are compared to GHG emissions from the year 2019. The category “energy supply (including electricity)” includes bioenergy with carbon capture and storage and direct air carbon capture and storage. { WGIII Box TS.5, WGIII 3.3, WGIII 3.4, WGIII 6.6, WGIII 10.3, WGIII 11.3 } ( Cross-Section Box.2 )

[https://www.ipcc.ch/figures/figure-4-1 ]

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