Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 10, 79-90, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Jan 2014
Evaluating the dominant components of warming in Pliocene climate simulations
D. J. Hill1,2, A. M. Haywood1, D. J. Lunt3, S. J. Hunter1, F. J. Bragg3, C. Contoux4,5, C. Stepanek6, L. Sohl7, N. A. Rosenbloom8, W.-L. Chan9, Y. Kamae10, Z. Zhang11,12, A. Abe-Ouchi9,13, M. A. Chandler7, A. Jost5, G. Lohmann6, B. L. Otto-Bliesner8, G. Ramstein4, and H. Ueda10 1School of Earth and Environment, University of Leeds, Leeds, UK
2British Geological Survey, Keyworth, Nottingham, UK
3School of Geographical Sciences, University of Bristol, Bristol, UK
4Laboratoire des Sciences du Climat et de l'Environnement, Saclay, France
5Sisyphe, CNRS/UPMC Univ. Paris 06, Paris, France
6Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
7Columbia University – NASA/GISS, New York, NY, USA
8National Center for Atmospheric Research, Boulder, Colorado, USA
9Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan
10Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
11UniResearch and Bjerknes Centre for Climate Research, Bergen, Norway
12Nansen-zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
13Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
Abstract. The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean–atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene.

Citation: Hill, D. J., Haywood, A. M., Lunt, D. J., Hunter, S. J., Bragg, F. J., Contoux, C., Stepanek, C., Sohl, L., Rosenbloom, N. A., Chan, W.-L., Kamae, Y., Zhang, Z., Abe-Ouchi, A., Chandler, M. A., Jost, A., Lohmann, G., Otto-Bliesner, B. L., Ramstein, G., and Ueda, H.: Evaluating the dominant components of warming in Pliocene climate simulations, Clim. Past, 10, 79-90,, 2014.
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