Clim. Past, 9, 191-209, 2013
www.clim-past.net/9/191/2013/
doi:10.5194/cp-9-191-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Large-scale features of Pliocene climate: results from the Pliocene Model Intercomparison Project
A. M. Haywood1, D. J. Hill1,2, A. M. Dolan1, B. L. Otto-Bliesner3, F. Bragg4, W.-L. Chan5, M. A. Chandler6, C. Contoux7,8, H. J. Dowsett9, A. Jost8, Y. Kamae10, G. Lohmann11, D. J. Lunt4, A. Abe-Ouchi5,12, S. J. Pickering1, G. Ramstein7, N. A. Rosenbloom3, U. Salzmann13, L. Sohl6, C. Stepanek11, H. Ueda10, Q. Yan14, and Z. Zhang14,15
1School of Earth and Environment, Earth and Environment Building, University of Leeds, Leeds, LS2 9JT, UK
2British Geological Survey, Keyworth, Nottingham, UK
3National Center for Atmospheric Research, Boulder, Colorado, USA
4School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK
5Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan
6Columbia University – NASA/GISS, New York, NY, USA
7Laboratoire des Sciences du Climat et de l'Environnement, Saclay, France
8Unité Mixte de Recherche 7619 SISYPHE, Université Pierre-et-Marie Curie Paris VI, Paris, France
9US Geological Survey, MS 926A, 12201 Sunrise Valley Dive, Reston, VA 20192, USA
10Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
11Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
12Research Institute for Global Change, JAMSTEC, Yokohama, Japan
13Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
14Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
15Bjerknes Centre for Climate Research, Bergen, Norway

Abstract. Climate and environments of the mid-Pliocene warm period (3.264 to 3.025 Ma) have been extensively studied. Whilst numerical models have shed light on the nature of climate at the time, uncertainties in their predictions have not been systematically examined. The Pliocene Model Intercomparison Project quantifies uncertainties in model outputs through a coordinated multi-model and multi-model/data intercomparison. Whilst commonalities in model outputs for the Pliocene are clearly evident, we show substantial variation in the sensitivity of models to the implementation of Pliocene boundary conditions. Models appear able to reproduce many regional changes in temperature reconstructed from geological proxies. However, data/model comparison highlights that models potentially underestimate polar amplification. To assert this conclusion with greater confidence, limitations in the time-averaged proxy data currently available must be addressed. Furthermore, sensitivity tests exploring the known unknowns in modelling Pliocene climate specifically relevant to the high latitudes are essential (e.g. palaeogeography, gateways, orbital forcing and trace gasses). Estimates of longer-term sensitivity to CO2 (also known as Earth System Sensitivity; ESS), support previous work suggesting that ESS is greater than Climate Sensitivity (CS), and suggest that the ratio of ESS to CS is between 1 and 2, with a "best" estimate of 1.5.

Citation: Haywood, A. M., Hill, D. J., Dolan, A. M., Otto-Bliesner, B. L., Bragg, F., Chan, W.-L., Chandler, M. A., Contoux, C., Dowsett, H. J., Jost, A., Kamae, Y., Lohmann, G., Lunt, D. J., Abe-Ouchi, A., Pickering, S. J., Ramstein, G., Rosenbloom, N. A., Salzmann, U., Sohl, L., Stepanek, C., Ueda, H., Yan, Q., and Zhang, Z.: Large-scale features of Pliocene climate: results from the Pliocene Model Intercomparison Project, Clim. Past, 9, 191-209, doi:10.5194/cp-9-191-2013, 2013.
 
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