Editing IPCC:AR6/SYR/SPM (section)

=== Overshoot: Exceeding a Warming Level and Returning ===

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'''B.7 If warming exceeds a specified level such as 1.5°C, it could gradually be reduced again by achieving and sustaining net negative global CO '''''2''''' emissions. This would require additional deployment of carbon dioxide removal, compared to pathways without overshoot, leading to greater feasibility and sustainability concerns. Overshoot entails adverse impacts, some irreversible, and additional risks for human and natural systems, all growing with the magnitude and duration of overshoot. '''''(high confidence)''''' Links to longer report 3.1, 3.3, 3.4, Table 3.1, Figure 3.6'''
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B.7.1 Only a small number of the most ambitious global modelled pathways limit global warming to 1.5°C (&gt;50%) by 2100 without exceeding this level temporarily. Achieving and sustaining net negative global CO 2 emissions, with annual rates of CDR greater than residual CO 2 emissions, would gradually reduce the warming level again ''(high confidence)'' . Adverse impacts that occur during this period of overshoot and cause additional warming via feedback mechanisms, such as increased wildfires, mass mortality of trees, drying of peatlands, and permafrost thawing, weakening natural land carbon sinks and increasing releases of GHGs would make the return more challenging ''(medium confidence)'' . ''[[#box-spm-1|Box SPM.1]] Links to longer report 3.3.2, 3.3.4, Table 3.1, Figure 3.6''

B.7.2 The higher the magnitude and the longer the duration of overshoot, the more ecosystems and societies are exposed to greater and more widespread changes in climatic impact-drivers, increasing risks for many natural and human systems. Compared to pathways without overshoot, societies would face higher risks to infrastructure, low-lying coastal settlements, and associated livelihoods. Overshooting 1.5°C will result in irreversible adverse impacts on certain ecosystems with low resilience, such as polar, mountain, and coastal ecosystems, impacted by ice-sheet, glacier melt, or by accelerating and higher committed sea level rise. ''(high confidence) Links to longer report 3.1.2, 3.3.4''

B.7.3 The larger the overshoot, the more net negative CO 2 emissions would be needed to return to 1.5°C by 2100. Transitioning towards net zero CO 2 emissions faster and reducing non-CO 2 emissions such as methane more rapidly would limit peak warming levels and reduce the requirement for net negative CO 2 emissions, thereby reducing feasibility and sustainability concerns, and social and environmental risks associated with CDR deployment at large scales. ''(high confidence)'' Links to longer report 3.3.3, 3.3.4, 3.4.1, Table 3.1

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