Committed global warming risks triggering multiple climate tipping points

Abrams, Jesse F.; Huntingford, Chris ORCID: https://orcid.org/0000-0002-5941-7770; Williamson, Mark S.; Armstrong McKay, David I.; Boulton, Chris A.; Buxton, Joshua E.; Sakschewski, Boris; Loriani, Sina; Zimm, Caroline; Winkelmann, Ricarda; Lenton, Timothy M.. 2023 Committed global warming risks triggering multiple climate tipping points. Earth's Future, 11 (11), e2022EF003250. 11, pp. https://doi.org/10.1029/2022EF003250

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Abstract/Summary

Many scenarios for limiting global warming to 1.5°C assume planetary-scale carbon dioxide removal sufficient to exceed anthropogenic emissions, resulting in radiative forcing falling and temperatures stabilizing. However, such removal technology may prove unfeasible for technical, environmental, political, or economic reasons, resulting in continuing greenhouse gas emissions from hard-to-mitigate sectors. This may lead to constant concentration scenarios, where net anthropogenic emissions remain non-zero but small, and are roughly balanced by natural carbon sinks. Such a situation would keep atmospheric radiative forcing roughly constant. Fixed radiative forcing creates an equilibrium “committed” warming, captured in the concept of “equilibrium climate sensitivity.” This scenario is rarely analyzed as a potential extension to transient climate scenarios. Here, we aim to understand the planetary response to such fixed concentration commitments, with an emphasis on assessing the resulting likelihood of exceeding temperature thresholds that trigger climate tipping points. We explore transients followed by respective equilibrium committed warming initiated under low to high emission scenarios. We find that the likelihood of crossing the 1.5°C threshold and the 2.0°C threshold is 83% and 55%, respectively, if today's radiative forcing is maintained until achieving equilibrium global warming. Under the scenario that best matches current national commitments (RCP4.5), we estimate that in the transient stage, two tipping points will be crossed. If radiative forcing is then held fixed after the year 2100, a further six tipping point thresholds are crossed. Achieving a trajectory similar to RCP2.6 requires reaching net-zero emissions rapidly, which would greatly reduce the likelihood of tipping events.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2022EF003250
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	2328-4277
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	climate change, tipping point, greenhouse gas, committed warming, irreversibility
NORA Subject Terms:	Earth Sciences Ecology and Environment
Date made live:	15 Nov 2023 15:51 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/536252

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