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Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse

Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse
Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse
Despite recent advances, the link between the evolution of atmospheric CO2 and climate during the Eocene greenhouse remains uncertain. In particular, modelling studies suggest that in order to achieve the global warmth that characterised the early Eocene, warmer climates must be more sensitive to CO2 forcing than colder climates. Here, we test this assertion in the geological record by combining a new high-resolution boron isotope-based CO2 record with novel estimates of Global Mean Temperature. We find that Equilibrium Climate Sensitivity (ECS) was indeed higher during the warmest intervals of the Eocene, agreeing well with recent model simulations, and declined through the Eocene as global climate cooled. These observations indicate that the canonical IPCC range of ECS (1.5 to 4.5 °C per doubling) is unlikely to be appropriate for high-CO2 warm climates of the past, and the state dependency of ECS may play an increasingly important role in determining the state of future climate as the Earth continues to warm.
2041-1723
Anagnostou, Eleni
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John, Eleanor H.
c3e52564-92af-4636-84ec-3732a6c1bc05
Babila, Tali
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Sexton, Philip
836b46d0-a948-4366-8cf6-73b7d30e651b
Ridgwell, Andy
769cea5c-e033-456a-8b53-51dfa307dc35
Lunt, Daniel J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Chalk, Thomas
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Pancost, Richard D.
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Foster, Gavin
fbaa7255-7267-4443-a55e-e2a791213022
Anagnostou, Eleni
4527c274-f765-44ce-89ab-0e437aa3d870
John, Eleanor H.
c3e52564-92af-4636-84ec-3732a6c1bc05
Babila, Tali
a59f9473-d145-4d43-92c0-ea682f29fdcc
Sexton, Philip
836b46d0-a948-4366-8cf6-73b7d30e651b
Ridgwell, Andy
769cea5c-e033-456a-8b53-51dfa307dc35
Lunt, Daniel J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Chalk, Thomas
0021bbe6-6ab1-4a30-8542-654d0f2d1a0a
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Foster, Gavin
fbaa7255-7267-4443-a55e-e2a791213022

Anagnostou, Eleni, John, Eleanor H., Babila, Tali, Sexton, Philip, Ridgwell, Andy, Lunt, Daniel J., Pearson, Paul N., Chalk, Thomas, Pancost, Richard D. and Foster, Gavin (2020) Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse. Nature Communications, 11 (1), [4436]. (doi:10.1038/s41467-020-17887-x).

Record type: Article

Abstract

Despite recent advances, the link between the evolution of atmospheric CO2 and climate during the Eocene greenhouse remains uncertain. In particular, modelling studies suggest that in order to achieve the global warmth that characterised the early Eocene, warmer climates must be more sensitive to CO2 forcing than colder climates. Here, we test this assertion in the geological record by combining a new high-resolution boron isotope-based CO2 record with novel estimates of Global Mean Temperature. We find that Equilibrium Climate Sensitivity (ECS) was indeed higher during the warmest intervals of the Eocene, agreeing well with recent model simulations, and declined through the Eocene as global climate cooled. These observations indicate that the canonical IPCC range of ECS (1.5 to 4.5 °C per doubling) is unlikely to be appropriate for high-CO2 warm climates of the past, and the state dependency of ECS may play an increasingly important role in determining the state of future climate as the Earth continues to warm.

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Combined_AnagnostouJuly2020 - Accepted Manuscript
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More information

Accepted/In Press date: 22 July 2020
e-pub ahead of print date: 7 September 2020
Published date: 7 September 2020

Identifiers

Local EPrints ID: 443731
URI: http://eprints.soton.ac.uk/id/eprint/443731
ISSN: 2041-1723
PURE UUID: 40e9af86-1ac0-4928-a87b-6017a7cce79a
ORCID for Tali Babila: ORCID iD orcid.org/0000-0001-9948-9341
ORCID for Thomas Chalk: ORCID iD orcid.org/0000-0002-2880-3847
ORCID for Gavin Foster: ORCID iD orcid.org/0000-0003-3688-9668

Catalogue record

Date deposited: 10 Sep 2020 16:33
Last modified: 26 Nov 2021 06:56

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Contributors

Author: Eleni Anagnostou
Author: Eleanor H. John
Author: Tali Babila ORCID iD
Author: Philip Sexton
Author: Andy Ridgwell
Author: Daniel J. Lunt
Author: Paul N. Pearson
Author: Thomas Chalk ORCID iD
Author: Richard D. Pancost
Author: Gavin Foster ORCID iD

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