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

===== 5.5.2.2.4 Adjustments due to the zero emissions commitment =====

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Use of TCRE for estimating remaining carbon budgets needs to consider the zero emissions commitment (ZEC), the potential additional warming after a complete cessation of net CO <sub>2</sub> emissions. Based on the ZEC assessment presented in [[IPCC:Wg1:Chapter:Chapter-4#4.7.1.1|Section 4.7.1.1]] , the ZEC’s central value is taken to be zero with a ''likely'' range of ±0.19°C, noting that it might either increase or decrease after half a century. ZEC uncertainty is assessed for a time frame of half a century, as this most appropriately reflects the time between stringent mitigation pathways reaching net zero CO <sub>2</sub> emissions and the end of the century. For shorter time horizons, a similar central zero value applies, but with a smaller range ( [[#MacDougall--2020|MacDougall et al., 2020]] ). Experiments that ramped up and down emissions following a bell-shaped trajectory ( [[#MacDougall--2016a|MacDougall and Knutti, 2016a]] ) show that when annual CO <sub>2</sub> emissions decline to zero at a pace consistent with those currently assumed in mitigation scenarios ( [[#Huppmann--2018|Huppmann et al., 2018]] ; [[#Rogelj--2018b|Rogelj et al., 2018b]] ), the ZEC will already be realized to a large degree at the time of reaching net zero CO <sub>2</sub> emissions ( [[#MacDougall--2020|MacDougall et al., 2020]] ).

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