Drivers of regional variation in the de-emergence of climate change under negative emissions

Douglas, Hunter C., Revell, Laura E., Joshi, Manoj, King, Andrew, Harrington, Luke J. and Frame, David J. (2025) Drivers of regional variation in the de-emergence of climate change under negative emissions. Journal of Climate. ISSN 0894-8755

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Abstract

A central question of climate change impact assessments is identifying when the signal of change emerges from the noise of natural variability, though to date this framework has been almost exclusively applied under warming conditions. In this work, we investigate the phenomenon of de-emergence, where temperatures rise beyond a given threshold and subsequently drop back below that threshold as forcing reverses. Large-scale carbon dioxide removal (CDR), also referred to as negative emissions, has been proposed to lower global-average temperatures and mitigate damage to the Earth system, though the regional effects of this have been under-studied to date. Here, we analyze the results of eight Earth system models (ESM) that participated in the Carbon Dioxide Removal Model Intercomparison Project (CDRMIP). Decades after CO2 concentrations return to pre-industrial levels following a gradual quadrupling, the only regions that most models agree return to pre-industrial temperatures are an area across northwestern Eurasia and a small area off the coast of West Antarctica. Around half of the models project de-emergence for areas of North America and East Asia. We investigate potential causes for these patterns and find that the land areas that cool more also exhibit enhanced latent heat flux, net carbon uptake, and precipitation, implying enhanced evapotranspiration. The region off West Antarctica appears to experience a cooling influence from changes to sea ice and meltwater. Both regions experience changes to cloud radiative effects that cause net cooling. The distribution of de-emergence patterns raises questions about the equity and fairness of overshoot scenarios.

Item Type:	Article
Additional Information:	Data availability statement: The data and code that support the findings of this study will be available at: https://github.com/hdouglas/de-emergence. CMIP6 simulation results are available from: https://esgfnode.llnl.gov/projects/cmip6/ Funding information: H. C. D., L. E. R., L. J. H., and D. J. F. acknowledge funding from the New Zealand Ministry of Business, Innovation and Employment via the Endeavour Fund Whakahura programme (Grant ID: RTVU1906). A. D. K. acknowledges the Australian Government National Environmental Science Program.
Uncontrolled Keywords:	sdg 13 - climate action ,/dk/atira/pure/sustainabledevelopmentgoals/climate_action
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	University of East Anglia Schools > Faculty of Science > Tyndall Centre for Climate Change Research Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Climatic Research Unit
Depositing User:	LivePure Connector
Date Deposited:	04 Feb 2025 16:15
Last Modified:	14 Feb 2025 16:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98365
DOI:	10.1175/JCLI-D-24-0257.1

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