Editing IPCC:AR6/WGIII/Chapter-3 (section)

=== 3.6.3 Aggregate Economic Implication of Mitigation Co-benefits and Trade-offs ===

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Mitigation actions have co-benefits and trade-offs with other sustainable development dimensions ( [[#3.7|Section 3.7]] ) beyond climate change, which imply welfare effects and economic effects, as well as other implications beyond the economic dimension. The majority of quantifications of mitigation costs and benefits synthesized in Sections 3.6.1 and 3.6.2 do not account for these economic benefits and costs associated with co-benefits and trade-offs along mitigation pathways.

Systematic reviews of the literature on co-benefits and trade-offs from mitigation actions have shown that only a small portion of articles provide economic quantifications ( [[#Deng--2017|Deng et al. 2017]] ; [[#Karlsson--2020|Karlsson et al. 2020]] ). Most economic quantifications use monetary valuation approaches. Improved air quality, and associated health effects, are the co-benefit category dominating the literature ( [[#Markandya--2018|Markandya et al. 2018]] ; [[#Vandyck--2018|Vandyck et al. 2018]] ; Scovronick et al. 2019; [[#Howard--2020|Howard et al. 2020]] ; [[#Karlsson--2020|Karlsson et al. 2020]] b; [[#Rauner--2020a|Rauner et al. 2020a]] ,b), but some studies cover other categories, including health effects from diet change ( [[#Springmann--2016b|Springmann et al. 2016b]] ) and biodiversity impacts ( [[#Rauner--2020a|Rauner et al. 2020a]] ). Regarding health effects from air quality improvement and from diet change, co-benefits are shown to be of the same order of magnitude as mitigation costs ( [[#Thompson--2014|Thompson et al. 2014]] ; [[#Springmann--2016a|Springmann et al. 2016a]] ,b; [[#Markandya--2018|Markandya et al. 2018]] ; [[#Scovronick--2019b|Scovronick et al. 2019b]] ; [[#Howard--2020|Howard et al. 2020]] ; [[#Rauner--2020a|Rauner et al. 2020a]] ,b; [[#Liu--2021|Liu et al. 2021]] ; [[#Yang--2021|Yang et al. 2021]] ). Co-benefits from improved air quality are concentrated sooner in time than economic benefits from avoided climate change impacts ( [[#Karlsson--2020|Karlsson et al. 2020]] ), such that when accounting both for positive health impacts from reduced air pollution and for the negative climate effect of reduced cooling aerosols, optimal GHG mitigation pathways exhibit immediate and continual net economic benefits ( [[#Scovronick--2019a|Scovronick et al. 2019a]] ). However, AR6 WGI [[IPCC:Wg3:Chapter:Chapter-6|Chapter 6]] ( [[IPCC:Wg3:Chapter:Chapter-6#6.7.3|Section 6.7.3]] ) shows a delay in air pollution reduction benefits when they come from climate change mitigation policies compared with air pollution reduction policies.

Achieving co-benefits is not automatic but results from coordinated policies and implementation strategies (Clarke et al. 2014; [[#McCollum--2018a|McCollum et al. 2018a]] ). Similarly, avoiding trade-offs requires targeted policies ( [[#van%20Vuuren--2015|van Vuuren et al. 2015]] ; [[#Bertram--2018|Bertram et al. 2018]] ). There is limited evidence of such pathways, but the evidence shows that mitigation pathways designed to reach multiple Sustainable Development Goals instead of focusing exclusively on emissions reductions, result in limited additional costs compared to the increased benefits ( [[#Cameron--2016|Cameron et al. 2016]] ; [[#McCollum--2018b|McCollum et al. 2018b]] ; [[#Fujimori--2020a|Fujimori et al. 2020a]] ; [[#Sognnaes--2021|Sognnaes et al. 2021]] ).

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