Editing IPCC:AR6/WGIII/Chapter-3 (section)

=== FAQ 3.1 | Is it possible to stabilise warming without net negative CO 2 and GHG emissions? ===

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Yes. Achieving net zero CO 2 emissions and sustaining them into the future is sufficient to stabilise the CO 2 -induced warming signal which scales with the cumulative net amount of CO 2 emissions. At the same time, the warming signal of non-CO 2 GHGs can be stabilised or reduced by declining emissions that lead to stable or slightly declining concentrations in the atmosphere. For short-lived GHGs with atmospheric lifetimes of less than 20 years, this is achieved when residual emissions are reduced to levels that are lower than the natural removal of these gases in the atmosphere. Taken together, mitigation pathways that bring CO 2 emissions to net zero and sustain it, while strongly reducing non-CO 2 GHGs to levels that stabilise or decline their aggregate warming contribution, will stabilise warming without using net negative CO 2 emissions and with positive overall GHG emissions when aggregated using GWP-100. A considerable fraction of pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot and limit warming to 2°C (&gt;67%), respectively, do not or only marginally (&lt;10 GtCO 2 cumulative until 2100) deploy net negative CO 2 emissions (26% and 46%, respectively) and do not reach net zero GHG emissions by the end of the century (48% and 70%, respectively). This is no longer the case in pathways that return warming to 1.5°C (&gt;50%) after a high overshoot (typically &gt;0.1°C). All of these pathways deploy net negative emissions on the order of 360 (60–680) GtCO 2 (median and 5–95th percentile) and 87% achieve net negative GHGs emissions in AR6 GWP-100 before the end of the century. Hence, global net negative CO 2 emissions, and net zero or net negative GHG emissions, are only needed to decline, not to stabilise global warming. The deployment of carbon dioxide removal (CDR) is distinct from the deployment of net negative CO 2 emissions, because it is also used to neutralise residual CO 2 emissions to achieve and sustain net zero CO 2 emissions. CDR deployment can be considerable in pathways without net negative emissions and all pathways limiting warming to 1.5°C use it to some extent.

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