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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  02 Jan 2020

02 Jan 2020

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A revised version of this preprint is currently under review for the journal CP.

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

Daniel J. Lunt1, Fran Bragg1, Wing-Le Chan2, David K. Hutchinson3, Jean-Baptiste Ladant4, Igor Niezgodzki5,6, Sebastian Steinig1, Zhongshi Zhang7,8, Jiang Zhu4, Ayako Abe-Ouchi2, Agatha M. de Boer3, Helen K. Coxall3, Yannick Donnadieu9, Gregor Knorr5, Petra M. Langebroek7, Gerrit Lohmann5, Christopher J. Poulsen4, Pierre Sepulchre10, Jess Tierney11, Paul J. Valdes1, Tom Dunkley Jones12, Christopher J. Hollis13, Matthew Huber14, and Bette L. Otto-Bliesner15 Daniel J. Lunt et al.
  • 1School of Geographical Sciences, University of Bristol, UK
  • 2University of Tokyo, Japan
  • 3Department of Geological Sciences, Stockholm University, Sweden
  • 4University of Michigan, USA
  • 5AWI, Germany
  • 6Institute of Geological Sciences Polish Academy of Sciences, Research Center in Kraków, Biogeosystem Modelling Group, Poland
  • 7NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Norway
  • 8China University of Geoscience (Wuhan), China
  • 9CNRS, France
  • 10Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, France
  • 11University of Arizona, USA
  • 12Birmingham University, UK
  • 13GNS, New Zealand
  • 14Purdue University, USA
  • 15NCAR, USA

Abstract. We present results from an ensemble of seven 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 DeepMIP (, and as such all models have been configured with identical paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 °C to Eocene warmth. Compared to results from previous studies, the DeepMIP simulations show reduced spread of global mean surface temperature response across the ensemble, for a given atmospheric CO2 concentration. In a marked departure from the results from previous simulations, at least two of the DeepMIP models (CESM and GFDL) are consistent with proxy indicators of global mean temperature, and atmospheric CO2, and meridional SST gradients. The best agreement with global SST proxies from these models occurs at CO2 concentrations of around 2400 ppmv. At a more regional scale the models lack skill in reproducing the proxy SSTs, in particular in the southwest Pacific, around New Zealand and south Australia, where the modelled anomalies are substantially less than indicated by the proxies. However, in these regions modelled continental surface air temperature anomalies are consistent with surface air temperature proxies, implying an 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 and aerosols.

Daniel J. Lunt et al.

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Daniel J. Lunt et al.

Daniel J. Lunt et al.


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Publications Copernicus
Short summary
This paper presents the first modelling results from the DeepMIP ( project, in which we present modelling results of the early Eocene Climatic optimum (EECO). We show that, in contrast to previous work, at least two models (CESM and GFDL) produce climate states that are consistent with proxy indicators of sea surface temperature, and achieve this at a CO2 concentration that is consistent with the CO2 proxy record.
This paper presents the first modelling results from the DeepMIP ( project, in...