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DeepMIP: model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data

DeepMIP: model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data
DeepMIP: model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data
We present results from an ensemble of eight climate models, each of which has carried out simulations of the early Eocene climate optimum (EECO, ∼ 50 million years ago). These simulations have been carried out in the framework of the Deep-Time Model Intercomparison Project (DeepMIP; http://www.deepmip.org, last access: 10 January 2021); thus, all models have been configured with the same paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 ∘C to Eocene warmth. Compared with results from previous studies, the DeepMIP simulations generally show a reduced spread of the global mean surface temperature response across the ensemble for a given atmospheric CO2 concentration as well as an increased climate sensitivity on average. An energy balance analysis of the model ensemble indicates that global mean warming in the Eocene compared with the preindustrial period mostly arises from decreases in emissivity due to the elevated CO2 concentration (and associated water vapour and long-wave cloud feedbacks), whereas the reduction in the Eocene in terms of the meridional temperature gradient is primarily due to emissivity and albedo changes owing to the non-CO2 boundary conditions (i.e. the removal of the Antarctic ice sheet and changes in vegetation). Three of the models (the Community Earth System Model, CESM; the Geophysical Fluid Dynamics Laboratory, GFDL, model; and the Norwegian Earth System Model, NorESM) show results that are consistent with the proxies in terms of the global mean temperature, meridional SST gradient, and CO2, without prescribing changes to model parameters. In addition, many of the models agree well with the first-order spatial patterns in the SST proxies. However, at a more regional scale, the models lack skill. In particular, the modelled anomalies are substantially lower than those indicated by the proxies in the southwest Pacific; here, modelled continental surface air temperature anomalies are more consistent with surface air temperature proxies, implying a possible inconsistency between marine and terrestrial temperatures in either the proxies or models in this region. Our aim is that the documentation of the large-scale features and model–data comparison presented herein will pave the way to further studies that explore aspects of the model simulations in more detail, for example the ocean circulation, hydrological cycle, and modes of variability, and encourage sensitivity studies to aspects such as paleogeography, orbital configuration, and aerosols.
1814-9332
203-227
Lunt, Daniel J.
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Bragg, Fran
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Chan, Wing-Le
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Hutchinson, David K.
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Ladant, Jean-Baptiste
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Morozova, Polina
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Niezgodzki, Igor
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Steinig, Sebastian
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Zhang, Zhongshi
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Zhu, Jiang
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Abe-ouchi, Ayako
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Anagnostou, Eleni
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de Boer, Agatha M.
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Coxall, Helen K.
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Donnadieu, Yannick
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Inglis, Gordon
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Langebroek, Petra
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Lear, Caroline H.
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Hollis, Christopher J.
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Huber, Matthew
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Lunt, Daniel J.
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Bragg, Fran
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Chan, Wing-Le
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Zhang, Zhongshi
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Coxall, Helen K.
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Donnadieu, Yannick
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Foster, Gavin
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Inglis, Gordon
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Knorr, Gregor
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Langebroek, Petra
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Lear, Caroline H.
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Tierney, Jessica E.
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Valdes, Paul J.
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Volodin, Evgeny
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Dunkley Jones, Tom
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Hollis, Christopher J.
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Huber, Matthew
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Otto-Bliesner, Bette L.
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Lunt, Daniel J., Bragg, Fran, Chan, Wing-Le, Hutchinson, David K., Ladant, Jean-Baptiste, Morozova, Polina, Niezgodzki, Igor, Steinig, Sebastian, Zhang, Zhongshi, Zhu, Jiang, Abe-ouchi, Ayako, Anagnostou, Eleni, de Boer, Agatha M., Coxall, Helen K., Donnadieu, Yannick, Foster, Gavin, Inglis, Gordon, Knorr, Gregor, Langebroek, Petra, Lear, Caroline H., Lohmann, Gerrit, Poulsen, Christopher J., Sepulchre, Pierre, Tierney, Jessica E., Valdes, Paul J., Volodin, Evgeny, Dunkley Jones, Tom, Hollis, Christopher J., Huber, Matthew and Otto-Bliesner, Bette L. (2021) DeepMIP: model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data. Climate of the Past, 17 (1), 203-227. (doi:10.5194/cp-17-203-2021).

Record type: Article

Abstract

We present results from an ensemble of eight climate models, each of which has carried out simulations of the early Eocene climate optimum (EECO, ∼ 50 million years ago). These simulations have been carried out in the framework of the Deep-Time Model Intercomparison Project (DeepMIP; http://www.deepmip.org, last access: 10 January 2021); thus, all models have been configured with the same paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 ∘C to Eocene warmth. Compared with results from previous studies, the DeepMIP simulations generally show a reduced spread of the global mean surface temperature response across the ensemble for a given atmospheric CO2 concentration as well as an increased climate sensitivity on average. An energy balance analysis of the model ensemble indicates that global mean warming in the Eocene compared with the preindustrial period mostly arises from decreases in emissivity due to the elevated CO2 concentration (and associated water vapour and long-wave cloud feedbacks), whereas the reduction in the Eocene in terms of the meridional temperature gradient is primarily due to emissivity and albedo changes owing to the non-CO2 boundary conditions (i.e. the removal of the Antarctic ice sheet and changes in vegetation). Three of the models (the Community Earth System Model, CESM; the Geophysical Fluid Dynamics Laboratory, GFDL, model; and the Norwegian Earth System Model, NorESM) show results that are consistent with the proxies in terms of the global mean temperature, meridional SST gradient, and CO2, without prescribing changes to model parameters. In addition, many of the models agree well with the first-order spatial patterns in the SST proxies. However, at a more regional scale, the models lack skill. In particular, the modelled anomalies are substantially lower than those indicated by the proxies in the southwest Pacific; here, modelled continental surface air temperature anomalies are more consistent with surface air temperature proxies, implying a possible inconsistency between marine and terrestrial temperatures in either the proxies or models in this region. Our aim is that the documentation of the large-scale features and model–data comparison presented herein will pave the way to further studies that explore aspects of the model simulations in more detail, for example the ocean circulation, hydrological cycle, and modes of variability, and encourage sensitivity studies to aspects such as paleogeography, orbital configuration, and aerosols.

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Accepted/In Press date: 1 November 2020
e-pub ahead of print date: 15 January 2021

Identifiers

Local EPrints ID: 446554
URI: http://eprints.soton.ac.uk/id/eprint/446554
ISSN: 1814-9332
PURE UUID: 62148f84-9725-4c2b-b6c6-96b03326f5a0
ORCID for Gavin Foster: ORCID iD orcid.org/0000-0003-3688-9668

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Date deposited: 15 Feb 2021 17:30
Last modified: 22 Oct 2021 01:41

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Contributors

Author: Daniel J. Lunt
Author: Fran Bragg
Author: Wing-Le Chan
Author: David K. Hutchinson
Author: Jean-Baptiste Ladant
Author: Polina Morozova
Author: Igor Niezgodzki
Author: Sebastian Steinig
Author: Zhongshi Zhang
Author: Jiang Zhu
Author: Ayako Abe-ouchi
Author: Eleni Anagnostou
Author: Agatha M. de Boer
Author: Helen K. Coxall
Author: Yannick Donnadieu
Author: Gavin Foster ORCID iD
Author: Gordon Inglis
Author: Gregor Knorr
Author: Petra Langebroek
Author: Caroline H. Lear
Author: Gerrit Lohmann
Author: Christopher J. Poulsen
Author: Pierre Sepulchre
Author: Jessica E. Tierney
Author: Paul J. Valdes
Author: Evgeny Volodin
Author: Tom Dunkley Jones
Author: Christopher J. Hollis
Author: Matthew Huber
Author: Bette L. Otto-Bliesner

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