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

==== 4.2.5.1 Overview of Accelerated Mitigation Pathways ====

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The literature reports an increasing number of accelerated mitigation pathways that are beyond NDCs in different regions and countries. There is increasing understanding of the technical content of such pathways, though the literature remains limited on some dimensions, such as demand-side options, systems analysis, or mitigation of AFOLU non-CO 2 GHGs. The present section describes insights from this literature.

Overall, the literature shows that pathways considered consistent with below 2°C (&gt;67%) or 1.5°C (Box 4.2) – including inter alia 80% reduction of GHG emissions in 2050 relative to 1990 or 100% renewable electricity scenarios – are technically feasible ( [[#Lund--2009|Lund and Mathiesen 2009]] ; [[#Mathiesen--2011|Mathiesen et al. 2011]] ; [[#Esteban--2014|Esteban and Portugal-Pereira 2014]] ; [[#Young--2017|Young and Brans 2017]] ; [[#Esteban--2018|Esteban et al. 2018]] ; [[#Child--2019|Child et al. 2019]] ; [[#Hansen--2019|Hansen et al. 2019]] ). They entail increased end-use energy efficiency, significant increases in low-carbon energy, electrification, other new and transformative technologies in demand sectors, adoption of carbon capture and sequestration (CCS) to reduce gross emissions, and contribution to net negative emissions through carbon dioxide removal (CDR) and carbon sinks. For these pathways to be realised, the literature assumes higher carbon prices, combined in policy packages with a range of other policy measures.

The most recent literature also reflects on accelerated mitigation pathways aiming at reaching net zero CO 2 emissions or net zero GHG emissions by 2050 (Section 4.2.4 and Table 4.6; see Glossary entries on ‘net zero CO 2 emissions’ and ‘net zero GHG emissions’). Specific policies, measures and technologies are needed to reach such targets. These include, broadly, decarbonising electricity supply, including through low-carbon energy, radically more efficient use of energy than today; electrification of end-uses (including transport/electric vehicles); dramatically lower use of fossil fuels than today; converting other uses to low- or zero-carbon fuels (e.g., hydrogen, bioenergy, ammonia) in hard-to-decarbonise sectors; and setting ambitious targets to reduce methane and other short-lived climate forcers (SLCFs).

Accelerated mitigation pathways differ by countries, depending inter alia on sources of emissions, mitigation opportunities and economic context. In China, India, Japan and other Southeast Asian countries, more aggressive action related to climate change is also motivated by regional concerns over health and air quality related to air pollutants and SLCFs (Ashina et al. 2012; Aggarwal 2017; [[#Kuramochi--2017|Kuramochi et al. 2017]] ; [[#Xunzhang--2017|Xunzhang et al. 2017]] ; [[#Dhar--2018|Dhar et al. 2018]] ; [[#Jiang--2018|Jiang et al. 2018]] ; [[#Oshiro--2018|Oshiro et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] ; [[#Energy%20Transitions%20Commission%20and%20Rocky%20Mountain%20Institute--2019|Energy Transitions Commission and Rocky Mountain Institute 2019]] ; [[#Khanna--2019|Khanna et al. 2019]] ). Studies of accelerated mitigation pathways in North America tend to focus on power sector and imported fuel decarbonisation in the US , and on electrification and demand-side reductions in Canada ( [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ; [[#Hodson--2018|Hodson et al. 2018]] ; [[#Victor--2018|Victor et al. 2018]] ; [[#Bahn,%C2%A0O.%20and%C2%A0K.%20Vaillancourt--2020|Bahn and Vaillancourt 2020]] ; [[#Hammond--2020|Hammond et al. 2020]] ; [[#Jayadev--2020|Jayadev et al. 2020]] ). In Latin America, many pathways emphasise supply-side mitigation measures, finding that replacing thermal power generation and developing bioenergy (where resources are available) utilisation offers the greatest mitigation opportunities ( [[#Herreras%20Martínez--2015|Herreras Martínez et al. 2015]] ; [[#Nogueira%20de%20Oliveira--2016|Nogueira de Oliveira et al. 2016]] ; Arango-Aramburo et al. 2019; [[#Delgado--2020|Delgado et al. 2020]] ; [[#Lap--2020|Lap et al. 2020]] ). The European Union member states (EU-28) recently announced 2050 climate neutrality goal is explored by pathways that emphasise complete substitution of fossil fuels with electricity generated by low-carbon sources, particularly renewables; demand reductions through efficiency and conservation, and novel fuels and end-use technologies (Prognos et al. 2020). The limited literature so far on Africa’s future pathways suggest those could be shaped by increasing energy access and mitigating the air pollution and health effects of relying on traditional biomass use, as well as cleaner expansion of power supply alongside end-use efficiency improvements ( [[#Hamilton--2017|Hamilton and Kelly 2017]] ; [[#Oyewo--2019|Oyewo et al. 2019]] , 2020; [[#Ven--2019|Ven et al. 2019]] ; [[#Wright--2019|Wright et al. 2019]] ; [[#Forouli--2020|Forouli et al. 2020]] ).

Though they differ across countries, accelerated mitigation pathways share common characteristics as follows. First, energy efficiency, conservation, and reducing energy use in all energy demand sectors (buildings, transport, and industry) are included in nearly all literature that addresses future demand growth (Ashina et al. 2012; [[#Saveyn--2012|Saveyn et al. 2012]] ; [[#Schmid--2012|Schmid and Knopf 2012]] ; [[#Chiodi--2013|Chiodi et al. 2013]] ; [[#Deetman--2013|Deetman et al. 2013]] ; [[#Jiang--2013|Jiang et al. 2013]] ; [[#Thepkhun--2013|Thepkhun et al. 2013]] ; [[#Schiffer--2015|Schiffer 2015]] ; Altieri et al. 2016; [[#Jiang--2016|Jiang et al. 2016]] ; [[#McNeil--2016|McNeil et al. 2016]] ; [[#Nogueira%20de%20Oliveira--2016|Nogueira de Oliveira et al. 2016]] ; [[#Chilvers--2017|Chilvers et al. 2017]] ; [[#Elizondo--2017|Elizondo et al. 2017]] ; [[#Fragkos--2017|Fragkos et al. 2017]] ; [[#Jacobson--2017|Jacobson et al. 2017]] , 2019; [[#Kuramochi--2017|Kuramochi et al. 2017]] ; [[#Oshiro--2017a|Oshiro et al. 2017a]] ; [[#Ouedraogo--2017|Ouedraogo 2017]] ; [[#Shahiduzzaman--2017|Shahiduzzaman and Layton 2017]] ; [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ; [[#Hanaoka--2018|Hanaoka and Masui 2018]] ; [[#Hodson--2018|Hodson et al. 2018]] ; [[#Lee--2018|Lee et al. 2018]] ; Lefèvre et al. [[#Oshiro--2018|Oshiro et al. 2018]] ; 2018; [[#Capros--2019|Capros et al. 2019]] ; [[#Dioha--2019|Dioha et al. 2019]] ; [[#Duscha--2019|Duscha et al. 2019]] ; [[#Khanna--2019|Khanna et al. 2019]] ; [[#Kato--2019|Kato and Kurosawa 2019]] ; [[#Nieves--2019|Nieves et al. 2019]] ; [[#Sugiyama--2019|Sugiyama et al. 2019]] ; [[#Zhou--2019|Zhou et al. 2019]] ; [[#Dioha--2020|Dioha and Kumar 2020]] ).

Similarly, electrification of industrial processes (up to 50% for EU and China) and transport (e.g., 30–60% for trucks in Canada), buildings, and district heating and cooling are commonplace (Ashina et al. 2012; [[#Massetti--2012|Massetti 2012]] ; [[#Saveyn--2012|Saveyn et al. 2012]] ; [[#Chiodi--2013|Chiodi et al. 2013]] ; [[#Deetman--2013|Deetman et al. 2013]] ; [[#Fragkos--2017|Fragkos et al. 2017]] ; [[#Oshiro--2017b|Oshiro et al. 2017b]] ; [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ; [[#Xunzhang--2017|Xunzhang et al. 2017]] ; [[#Jiang--2018|Jiang et al. 2018]] ; [[#Mittal--2018|Mittal et al. 2018]] ; [[#Oshiro--2018|Oshiro et al. 2018]] ; [[#Capros--2019|Capros et al. 2019]] ; [[#Zhou--2019|Zhou et al. 2019]] ; [[#Hammond--2020|Hammond et al. 2020]] ).

Third, lower emissions sources of energy, such as nuclear, renewables, and some biofuels, are seen as necessary in all pathways. However, the extent of deployment depends on resource availability. Some countries have set targets of up to 100% renewable electricity, while others such as Brazil rely on increasing biomass up to 40–45% of total or industry energy consumption by 2050.

Fourth, CCS and CDR are part of many of the national studies reviewed (Ashina et al. 2012; [[#Massetti--2012|Massetti 2012]] ; [[#Jiang--2013|Jiang et al. 2013]] ; [[#Thepkhun--2013|Thepkhun et al. 2013]] ; [[#Herreras%20Martínez--2015|Herreras Martínez et al. 2015]] ; [[#van%20der%20Zwaan--2016|van der Zwaan et al. 2016]] ; [[#Chilvers--2017|Chilvers et al. 2017]] ; [[#Solano%20Rodriguez--2017|Solano Rodriguez et al. 2017]] ; [[#Xunzhang--2017|Xunzhang et al. 2017]] ; [[#Kuramochi--2018|Kuramochi et al. 2018]] ; [[#Mittal--2018|Mittal et al. 2018]] ; [[#Oshiro--2018|Oshiro et al. 2018]] ; [[#Roberts--2018b|Roberts et al. 2018b]] ; [[#Vishwanathan--2018b|Vishwanathan et al. 2018b]] ; [[#Kato--2019|Kato and Kurosawa 2019]] ). CCS helps reduce gross emissions but does not remove CO 2 from the atmosphere, unless combined with bioenergy (BECCS). CO 2 removal from sources with no identified mitigation measures is considered necessary to help achieve economy-wide net negative emissions ( [[#Massetti--2012|Massetti 2012]] ; [[#Deetman--2013|Deetman et al. 2013]] ; [[#Solano%20Rodriguez--2017|Solano Rodriguez et al. 2017]] ).

Each option is assessed in more detail in the following sections.

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