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

=== 6.6.2 Impacts on Natural and Human Systems ===

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Interannual to decadal variability of Indo-Pacific SST variability is ''likely'' to affect extreme hydroclimate in East Africa (Ummenhofer et al., 2018 <sup>[[#fn:r650|650]]</sup> ). The Pacific cooling pattern is often synonymous with predominance of La Niña events in 1998 and 2012 is linked to megadroughts in the USA (Baek et al., 2019 <sup>[[#fn:r651|651]]</sup> ). On decadal to multidecadal time scales, PDO/IPO and Atlantic variability may have impacts on megadroughts in North America (Coats et al., 2016 <sup>[[#fn:r652|652]]</sup> ; Diodato et al., 2019 <sup>[[#fn:r653|653]]</sup> ) and Australia (Vance et al., 2015 <sup>[[#fn:r654|654]]</sup> ) as well as Indian subcontinent (Bao et al., 2015 <sup>[[#fn:r655|655]]</sup> ; Joshi and Rai, 2015 <sup>[[#fn:r656|656]]</sup> ). It is ''likely'' that occurrence of megadroughts in North America and Australia increased (Kiem et al., 2016 <sup>[[#fn:r657|657]]</sup> ; Baek et al., 2019 <sup>[[#fn:r658|658]]</sup> ). PDO and North Pacific Gyre Oscillation may also influence the decadal variability of North Pacific nutrient, chlorophyll and zooplankton taxa (Di Lorenzo et al., 2013).

The Pacific cooling pattern may have significant impacts on terrestrial carbon uptake via teleconnections. The reduced ecosystem respiration due to the smaller warming over land has significantly accelerated the net biome productivity and therefore increased the terrestrial carbon sink (Ballantyne et al., 2017 <sup>[[#fn:r659|659]]</sup> ) and paused the growth rate of atmospheric CO 2 despite increasing anthropogenic carbon emissions (Keenan et al., 2016 <sup>[[#fn:r660|660]]</sup> ). During the 2000s, the global ocean carbon sink has also strengthened (Fay and McKinley, 2013 <sup>[[#fn:r661|661]]</sup> ; Landschützer et al., 2014 <sup>[[#fn:r662|662]]</sup> ; Majkut et al., 2014 <sup>[[#fn:r663|663]]</sup> ; Landschützer et al., 2015 <sup>[[#fn:r664|664]]</sup> ; Munro et al., 2015 <sup>[[#fn:r665|665]]</sup> ), reversing a trend of stagnant or declining carbon uptake during the 1990s. It has been suggested that the upper ocean overturning circulation has weakened during the 2000s thereby decreasing the outgassing of natural CO 2 , especially in the Southern Ocean (Landschützer et al., 2015 <sup>[[#fn:r666|666]]</sup> ), and enhanced the global ocean CO 2 sink (DeVries et al., 2017 <sup>[[#fn:r667|667]]</sup> ). How this is connected to the global warming slowdown is currently unclear.

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