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

=== 5.2.1 Climate drivers important to food security ===

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Climate drivers relevant to food security and food systems include temperature-related, precipitation-related, and integrated metrics that combine these and other variables. These are projected to affect many aspects of the food security pillars (FAO 2018b <sup>[[#fn:r159|159]]</sup> ) (see Supplementary Material Table SM5.2, and Chapter 6 for assessment of observed and projected climate impacts). Climate drivers relevant to food production and availability may be categorised as modal climate changes (e.g., shifts in climate envelopes causing shifts in cropping varieties planted), seasonal changes (e.g., warming trends extending growing seasons), extreme events (e.g., high temperatures affecting critical growth periods, flooding/droughts), and atmospheric conditions for example, CO <sub>2</sub> concentrations, short-lived climate pollutants (SLCPs), and dust. Water resources for food production will be affected through changing rates of precipitation and evaporation, ground water levels, and dissolved oxygen content (Cruz-Blanco et al. 2015 <sup>[[#fn:r160|160]]</sup> ; Sepulcre-Canto et al. 2014 <sup>[[#fn:r161|161]]</sup> ; Huntington et al. 2017 <sup>[[#fn:r162|162]]</sup> ; Schmidtko et al. 2017 <sup>[[#fn:r163|163]]</sup> ). Potential changes in major modes of climate variability can also have widespread impacts such as those that occurred during late 2015 to early 2016 when a strong El Niño contributed to regional shifts in precipitation in the Sahel region. Significant drought across Ethiopia resulted in widespread crop failure and more than 10 million people in Ethiopia requiring food aid (U.S. Department of State 2016 <sup>[[#fn:r164|164]]</sup> ; Huntington et al. 2017 <sup>[[#fn:r165|165]]</sup> ) (Figure 5.3).

Other variables that affect agricultural production, processing, and/ or transport are solar radiation, wind, humidity, and (in coastal areas) salinisation and storm surge (Mutahara et al. 2016 <sup>[[#fn:r166|166]]</sup> ; Myers et al. 2017 <sup>[[#fn:r167|167]]</sup> ). Extreme climate events resulting in inland and coastal flooding, can affect the ability of people to obtain and prepare food (Rao et al. 2016 <sup>[[#fn:r168|168]]</sup> ; FAO et al. 2018 <sup>[[#fn:r169|169]]</sup> ). For direct effects of atmospheric CO <sub>2</sub> concentrations on crop nutrient status see Section 5.2.4.2.

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'''Figure 5.3'''

<span id="precipitation-anomaly-and-vegetation-response-in-eastern-africa.-a-sep-2015feb-2016-climate-hazards-group-infrared-precipitation-with-station-chirps-precipitation-anomaly-over-africa-relative-to-the-19812010-average-shows-that-large-areas-of-ethiopia-received-less-than-half-of-normal-precipitation.-consequently-widespread-impacts-to-agricultural-productivity-especially-within-pastoral-regions-were-present-across"></span>
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'''Precipitation anomaly and vegetation response in eastern Africa. (a) Sep 2015–Feb 2016 Climate Hazards Group Infrared Precipitation with Station (CHIRPS) precipitation anomaly over Africa relative to the 1981–2010 average shows that large areas of Ethiopia received less than half of normal precipitation. Consequently, widespread impacts to agricultural productivity, especially within pastoral regions, were present across […]'''
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Precipitation anomaly and vegetation response in eastern Africa. (a) Sep 2015–Feb 2016 Climate Hazards Group Infrared Precipitation with Station (CHIRPS) precipitation anomaly over Africa relative to the 1981–2010 average shows that large areas of Ethiopia received less than half of normal precipitation. Consequently, widespread impacts to agricultural productivity, especially within pastoral regions, were present across Ethiopia as evidenced by (d) reduced greenness in remote sensing images. (b) MODIS NDVI anomalies for Sep 2015–Feb 2016 relative to 2000–2015 average are shown for the inset box in (a). (c) Landsat NDVI anomalies for Sep 2015–Feb 2016 relative to 2000–2015 average are shown for the inset box in (b) (Huntington et al. 2017).

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==== 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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