Editing IPCC:AR6/WGI/Chapter-6 (section)

== Box 6.2 | SLCF Mitigation and Sustainable Development Goals (SDG) Opportunities ==

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Striving to achieve air-quality and climate targets will bring significant SLCF reductions. These reductions contribute first and foremost to the attainment of SDGs targeting improved human health and sustainable cities (SDGs 3 and 11), specifically related to PM exposure (goals 3.9 and 11.6; [[#Lelieveld--2017|Lelieveld, 2017]] ; [[#Amann--2020|Amann et al., 2020]]), but also access to affordable and clean energy, responsible consumption and production, and climate, as well as reducing nutrient losses and consequently protecting biodiversity (SDG 7, 12, 13, 14 and 15; [[#UNEP--2019|UNEP, 2019]] ; [[#Amann--2020|Amann et al., 2020]]). Furthermore, declining SLCF emissions will result in reduced crop losses (SDG 2; zero hunger) due to decrease of ozone exposure ([[#Feng--2009|Feng and Kobayashi, 2009]] ; [[#Ainsworth--2012|Ainsworth et al., 2012]] ; [[#Emberson--2018|Emberson et al., 2018]]).

However, the design of suitable policies addressing these SDGs can be difficult because of the complexity of linking emissions to impacts on human health, ecosystems, equity, infrastructure and costs. Beyond the fact that several species are co-emitted, interlinkage between species, such as through atmospheric chemistry, can weaken the benefit of emissions reduction efforts. An illustration lies in the recent (2013–2017) reduction of aerosols over China ([[#Silver--2018|Silver et al., 2018]] ; [[#Zheng--2018b|Zheng et al., 2018b]]) resulting from the strategy to improve air quality (‘Clean Air Action’); this has successfully reduced the level of PM <sub>2.54</sub> but has led to a concurrent increase in surface ozone, partly due to declining heterogeneous interactions of ozone precursors with aerosols (K. [[#Li--2019|]] [[#Li--2019|Li et al., 2019]] ; [[#Yu--2019|Yu et al., 2019]]). This side effect on ozone has been addressed since then by amending the legislation to target NMVOC sources, especially solvent use. Complex interactions between anthropogenic and biogenic volatile compounds are also at play and reduction of certain SLCFs could possibly promote new particle formation from organic vapours (e.g., [[#Lehtipalo--2018|Lehtipalo et al., 2018]]). Finally, a recent example of this complexity is the mixed effects on ozone pollution induced by NO <sub>x</sub> decrease during the COVID-19 pandemic (Cross-Chapter Box 6.1). Thus, the climate and air pollution effects of policies depend strongly on the choice of regulated compounds and the degree of reduction. Such policies have to be informed by strong science support, including for example multi-model analyses such as HTAP (UNECE, 2010) and AMAP ([[#AMAP--2015a|AMAP, 2015a]] , b), based on global and regional CCMs. This is essential to capture the complexity and inform the policy development process.

In addition, pursuing SDG objectives, apparently decoupled from air pollution, such as improved waste management, access to clean energy, or improved agricultural practices, would also stimulate and lead to mitigation of SLCFs. Amann et al. (2020) show that a global strategy to achieve the WHO air quality guidelines, cannot only rely on air pollution control but also on a combination of SDG-aligned policies. Such actions would include energy efficiency improvements, increased use of renewables, reduction of methane from waste management and agriculture, and CO <sub>2</sub> and methane due to lower fossil fuel consumption, resulting in climate co-benefits. Consideration of SDGs including local air-quality co-benefits, creates an opportunity to support and gain acceptance for ambitious climate change mitigation ([[#Jakob--2016|Jakob and Steckel, 2016]] ; [[#Stechow--2016|Stechow et al., 2016]] ; [[#Vandyck--2018|Vandyck et al., 2018]]). Such near-term policies targeting SDGs and air quality would enable longer-term transformations necessary to achieve climate goals (Chapter 17, WGIII).
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In summary, there is ''high confidence'' that effective decarbonization strategies could lead to air-quality improvements but are not sufficient to achieve, in the near term, air-quality WHO guideline values set for fine particulate matter, especially in parts of Asia and in some highly polluted regions. Additional policies (e.g., access to clean energy, waste management) envisaged to attain SDGs bring complementary SLCF reduction (''high confidence)'' . Sustained methane mitigation, wherever it occurs, stands out as an option that combines near- and long-term gains on surface temperature (''high confidence'') and leads to an air pollution benefit by reducing ozone levels globally (''high confidence'') ''.''

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