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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.

Submitted as: research article 02 Jan 2020

Submitted as: research article | 02 Jan 2020

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

A return to large-scale features of Pliocene climate: the Pliocene Model Intercomparison Project Phase 2

Alan M. Haywood1, Julia C. Tindall1, Harry J. Dowsett2, Aisling M. Dolan1, Kevin M. Foley2, Stephen J. Hunter1, Dan J. Hill1, Wing-Le Chan3, Ayako Abe-Ouchi3, Christian Stepanek4, Gerrit Lohmann4, Deepak Chandan5, W. Richard Peltier5, Ning Tan6,7, Camille Contoux7, Gilles Ramstein7, Xiangyu Li8,9, Zhongshi Zhang8,9,10, Chuncheng Guo9, Kerim H. Nisancioglu9, Qiong Zhang11, Qiang Li11, Yoichi Kamae12, Mark A. Chandler13, Linda E. Sohl13, Bette L. Otto-Bliesner14, Ran Feng15, Esther C. Brady14, Anna S. von der Heydt16,17, Michiel L. J. Baatsen17, and Daniel J. Lunt18 Alan M. Haywood et al.
  • 1School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, LS29JT, UK
  • 2Florence Bascom Geoscience Center, U.S. Geological Survey, Reston, VA 20192, USA
  • 3Centre for Earth Surface System Dynamics (CESD), Atmosphere and Ocean Research Institute (AORI), University of Tokyo, Japan
  • 4Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 5Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 6Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
  • 7Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
  • 8Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 9NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • 10Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
  • 11Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 12Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
  • 13CCSR/GISS, Columbia University, New York, USA
  • 14National Center for Atmospheric Research, Boulder, Colorado, USA
  • 15Department of Geosciences, College of Liberal Arts and Sciences, University of Connecticut, Connecticut, USA
  • 16Centre for Complex Systems Science, Utrecht University, Utrecht, The Netherlands
  • 17Institute for Marine and Atmospheric research Utrecht (IMAU), Department of Physics, Utrecht University, Utrecht, The Netherlands
  • 18School of Geographical Sciences, University of Bristol, Bristol, UK

Abstract. The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution and based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.4 and 4.7 °C relative to pre-industrial with a multi-model mean value of 2.8 °C. Annual mean total precipitation rates increase by 6 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases are 1.3 °C greater over the land than over the oceans, and there is a clear pattern of polar amplification with warming polewards of 60° N and 60° S exceeding the global mean warming by a factor of 2.4. In the Atlantic and Pacific Oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. Although there are some modelling constraints, there is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (Equilibrium Climate Sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble earth system response to doubling of CO2 (including ice sheet feedbacks) is approximately 50 % greater than ECS, consistent with results from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea-surface temperatures are used to assess model estimates of ECS and indicate a range in ECS from 2.5 to 4.3 °C. This result is in general accord with the range in ECS presented by previous IPCC Assessment Reports.

Alan M. Haywood et al.

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Alan M. Haywood et al.

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Publications Copernicus
Short summary

The large-scale features of the mid-Pliocene climate, from the 15 models of PlioMIP Phase 2, are presented.

The PlioMIP2 ensemble average climate was ~2.8 °C warmer and experienced ~ 6 % more precipitation than preindustrial, although there are large regional variations.

PlioMIP2 broadly agrees with a new proxy dataset of Pliocene sea surface temperatures. Combining PlioMIP2 and proxy data suggests that a doubling of atmospheric CO2 would increase globally averaged temperature by 2.5–4.3 °C.

The large-scale features of the mid-Pliocene climate, from the 15 models of PlioMIP Phase 2, are...