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Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene

Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene
Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene
Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth's history. Previous GMST estimates for the latest Paleocene and early Eocene (∼57 to 48 million years ago) span a wide range (∼9 to 23 ∘C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (∼57 Ma), (2) the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66 % confidence) during the latest Paleocene, PETM, and EECO was 26.3 ∘C (22.3 to 28.3 ∘C), 31.6 ∘C (27.2 to 34.5 ∘C), and 27.0 ∘C (23.2 to 29.7 ∘C), respectively. GMST estimates from the EECO are ∼10 to 16 ∘C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 ∘C higher than pre-industrial). Leveraging the large “signal” associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that “bulk” equilibrium climate sensitivity (ECS; 66 % confidence) during the latest Paleocene, PETM, and EECO is 4.5 ∘C (2.4 to 6.8 ∘C), 3.6 ∘C (2.3 to 4.7 ∘C), and 3.1 ∘C (1.8 to 4.4 ∘C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 ∘C per doubling CO2) but appear incompatible with low ECS values (<1.5 per doubling CO2).
1814-9332
1953-1968
Inglis, Gordon N.
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Bragg, Fran
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Burls, Natalie J.
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Cramwinckel, Margot J.
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Evans, David
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Foster, Gavin L.
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Huber, Matthew
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Lunt, Daniel J.
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Siler, Nicholas
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Steinig, Sebastian
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Tierney, Jessica E.
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Wilkinson, Richard
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Anagnostou, Eleni
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De Boer, Agatha M.
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Dunkley Jones, Tom
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Edgar, Kirsty M.
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Hollis, Christopher J.
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Hutchinson, David K.
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Pancost, Richard D.
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Inglis, Gordon N.
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Bragg, Fran
35391804-f224-4a1b-9c74-b81c226151c0
Burls, Natalie J.
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Cramwinckel, Margot J.
e467976c-be0c-47a5-a7eb-ecfe93048373
Evans, David
e10f6b3a-cbe9-448f-ae28-1eed8e7251aa
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Huber, Matthew
cac8c146-e2e3-4758-9fe9-46aa85e35ad2
Lunt, Daniel J.
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Siler, Nicholas
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Steinig, Sebastian
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Tierney, Jessica E.
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Wilkinson, Richard
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Anagnostou, Eleni
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De Boer, Agatha M.
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Dunkley Jones, Tom
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Edgar, Kirsty M.
7637a79f-afaa-4b62-bbc2-fe2d8bbeaa55
Hollis, Christopher J.
203511ab-eec4-41c5-b718-622189de5dfc
Hutchinson, David K.
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Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1

Inglis, Gordon N., Bragg, Fran, Burls, Natalie J., Cramwinckel, Margot J., Evans, David, Foster, Gavin L., Huber, Matthew, Lunt, Daniel J., Siler, Nicholas, Steinig, Sebastian, Tierney, Jessica E., Wilkinson, Richard, Anagnostou, Eleni, De Boer, Agatha M., Dunkley Jones, Tom, Edgar, Kirsty M., Hollis, Christopher J., Hutchinson, David K. and Pancost, Richard D. (2020) Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene. Climate of the Past, 16 (5), 1953-1968, [1953]. (doi:10.5194/cp-16-1953-2020).

Record type: Article

Abstract

Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth's history. Previous GMST estimates for the latest Paleocene and early Eocene (∼57 to 48 million years ago) span a wide range (∼9 to 23 ∘C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (∼57 Ma), (2) the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66 % confidence) during the latest Paleocene, PETM, and EECO was 26.3 ∘C (22.3 to 28.3 ∘C), 31.6 ∘C (27.2 to 34.5 ∘C), and 27.0 ∘C (23.2 to 29.7 ∘C), respectively. GMST estimates from the EECO are ∼10 to 16 ∘C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 ∘C higher than pre-industrial). Leveraging the large “signal” associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that “bulk” equilibrium climate sensitivity (ECS; 66 % confidence) during the latest Paleocene, PETM, and EECO is 4.5 ∘C (2.4 to 6.8 ∘C), 3.6 ∘C (2.3 to 4.7 ∘C), and 3.1 ∘C (1.8 to 4.4 ∘C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 ∘C per doubling CO2) but appear incompatible with low ECS values (<1.5 per doubling CO2).

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More information

Accepted/In Press date: 2 September 2020
e-pub ahead of print date: 26 October 2020
Published date: 26 October 2020

Identifiers

Local EPrints ID: 443794
URI: http://eprints.soton.ac.uk/id/eprint/443794
ISSN: 1814-9332
PURE UUID: 1ecd38d1-d082-432a-bf9e-4821fc1056a2
ORCID for Margot J. Cramwinckel: ORCID iD orcid.org/0000-0002-6063-836X
ORCID for Gavin L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

Catalogue record

Date deposited: 11 Sep 2020 16:41
Last modified: 26 Nov 2021 03:22

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Contributors

Author: Fran Bragg
Author: Natalie J. Burls
Author: David Evans
Author: Gavin L. Foster ORCID iD
Author: Matthew Huber
Author: Daniel J. Lunt
Author: Nicholas Siler
Author: Sebastian Steinig
Author: Jessica E. Tierney
Author: Richard Wilkinson
Author: Eleni Anagnostou
Author: Agatha M. De Boer
Author: Tom Dunkley Jones
Author: Kirsty M. Edgar
Author: Christopher J. Hollis
Author: David K. Hutchinson
Author: Richard D. Pancost

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