Editing IPCC:AR6/SRCCL/Chapter-5 (section)

==== 5.2.1.1 Short-lived climate pollutants ====

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The important role of short-lived climate pollutants such as ozone and black carbon is increasingly emphasised since they affect agricultural production through direct effects on crops and indirect effects on climate (Emberson et al. 2018 <sup>[[#fn:r170|170]]</sup> ; Lal et al. 2017 <sup>[[#fn:r171|171]]</sup> ; Burney and Ramanathan 2014 <sup>[[#fn:r172|172]]</sup> ; Ghude et al. 2014 <sup>[[#fn:r173|173]]</sup> ) (Chapters 2 and 4). Ozone causes damage to plants through damages to cellular metabolism that influence leaf-level physiology to whole-canopy and root-system processes and feedbacks; these impacts affect leaf-level photosynthesis senescence and carbon assimilation, as well as whole-canopy water and nutrient acquisition and ultimately crop growth and yield (Emberson et al. 2018 <sup>[[#fn:r174|174]]</sup> ).

Using atmospheric chemistry and a global integrated assessment model, Chuwah et al. (2015) <sup>[[#fn:r175|175]]</sup> found that without a large decrease in air pollutant emissions, high ozone concentration could lead to an increase in crop damage of up to 20% in agricultural regions in 2050 compared to projections in which changes in ozone are not accounted for. Higher temperatures are associated with higher ozone concentrations; C3 crops are sensitive to ozone (e.g., soybeans, wheat, rice, oats, green beans, peppers, and some types of cottons) and C4 crops are moderately sensitive (Backlund et al. 2008 <sup>[[#fn:r176|176]]</sup> ).

Methane increases surface ozone which augments warming-induced losses and some quantitative analyses now include climate, long-lived (CO <sub>2</sub> ) and multiple short-lived pollutants (CH <sub>4</sub> , O <sub>3</sub> ) simultaneously (Shindell et al. 2017 <sup>[[#fn:r177|177]]</sup> ; Shindell 2016 <sup>[[#fn:r178|178]]</sup> ). Reduction of tropospheric ozone and black carbon can avoid premature deaths from outdoor air pollution and increases annual crop yields (Shindell et al. 2012 <sup>[[#fn:r179|179]]</sup> ). These actions plus methane reduction can influence climate on shorter time scales than those of carbon dioxide reduction measures. Implementing them substantially reduces the risks of crossing the 2°C threshold and contributes to achievement of the SDGs (Haines et al. 2017 <sup>[[#fn:r180|180]]</sup> ; Shindell et al. 2017 <sup>[[#fn:r181|181]]</sup> ).

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