Changes to population-based emergence of climate change from CMIP5 to CMIP6

Douglas, Hunter C., Harrington, Luke J., Joshi, Manoj ORCID:, Hawkins, Ed, Revell, Laura E. and Frame, David J. (2023) Changes to population-based emergence of climate change from CMIP5 to CMIP6. Environmental Research Letters, 18 (1). ISSN 1748-9326

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The Coupled Model Intercomparison Project Phase 6 (CMIP6) model ensemble projects climate change emerging soonest and most strongly at low latitudes, regardless of the emissions pathway taken. In terms of signal-to-noise (S/N) ratios of average annual temperatures, these models project earlier and stronger emergence under the Shared Socio-economic Pathways than the previous generation did under corresponding Representative Concentration Pathways. Spatial patterns of emergence also change between generations of models; under a high emissions scenario, mid-century S/N is lower than previous studies indicated in Central Africa, South Asia, and parts of South America, West Africa, East Asia, and Western Europe, but higher in most other populated areas. We show that these global and regional changes are caused by a combination of higher effective climate sensitivity in the CMIP6 ensemble, as well as changes to emissions pathways, component-wise effective radiative forcing, and region-scale climate responses between model generations. We also present the first population-weighted calculation of climate change emergence for the CMIP6 ensemble, quantifying the number of people exposed to increasing degrees of abnormal temperatures now and into the future. Our results confirm the expected inequity of climate change-related impacts in the decades between now and the 2050 target for net-zero emissions held by many countries. These findings underscore the importance of concurrent investments in both mitigation and adaptation.

Item Type: Article
Additional Information: Author Acknowledgments: We acknowledge funding from the New Zealand Ministry for Business, Innovation & Employment's Endeavour Fund Whakahura programme (Grant ID: RTVU1906). E H is supported by the UK National Centre for Atmospheric Science and by the NERC REAL PROJECTIONS and EMERGENCE projects. We also acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which coordinated and promoted CMIP6. We further thank the climate modelling groups for producing and making available their model output, the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the funding agencies that support CMIP6 and ESGF. Data availability statement: The data that support the findings of this study are openly available at the following URL/DOI: (Douglas 2022). CMIP6 simulation results: CMIP5 simulation results: Emissions data:, IIASA RCP Database, Version 2.05:, IIASA SSP Database, Version 2.0: Global one-eighth degree gridded population dataset, v1.01: Geopolitical boundary shapefiles: (Natural Earth 2021). Human Development Index data: Region masking algorithm: (Hauser 2016). Regridding algorithm: (Zhuang 2020).
Uncontrolled Keywords: climate change emergence,cmip5,cmip6,emissions,inequality,rcps,ssps,public health, environmental and occupational health,environmental science(all),renewable energy, sustainability and the environment,sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/2700/2739
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
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Depositing User: LivePure Connector
Date Deposited: 15 Dec 2022 04:08
Last Modified: 15 Jun 2023 03:32
DOI: 10.1088/1748-9326/aca91e


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