Articles | Volume 10, issue 11
Geosci. Model Dev., 10, 3979–4003, 2017

Special issue: Paleoclimate Modelling Intercomparison Project phase 4 (PMIP4)...

Geosci. Model Dev., 10, 3979–4003, 2017

Model experiment description paper 07 Nov 2017

Model experiment description paper | 07 Nov 2017

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

Bette L. Otto-Bliesner1, Pascale Braconnot2, Sandy P. Harrison3, Daniel J. Lunt4, Ayako Abe-Ouchi5,6, Samuel Albani7, Patrick J. Bartlein8, Emilie Capron9,10, Anders E. Carlson11, Andrea Dutton12, Hubertus Fischer13, Heiko Goelzer14,15, Aline Govin2, Alan Haywood16, Fortunat Joos13, Allegra N. LeGrande17, William H. Lipscomb18, Gerrit Lohmann19, Natalie Mahowald20, Christoph Nehrbass-Ahles13, Francesco S. R. Pausata21, Jean-Yves Peterschmitt2, Steven J. Phipps22, Hans Renssen23,24, and Qiong Zhang25 Bette L. Otto-Bliesner et al.
  • 1National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, USA
  • 2Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 3Centre for Past Climate Change and School of Archaeology, Geography and Environmental Science (SAGES), University of Reading, Whiteknights, RG6 6AH, Reading, UK
  • 4School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 5Atmosphere Ocean Research Institute, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-20 8564, Japan
  • 6Japan Agency for Marine-Earth Science and Technology, 3173-25 Showamachi, Kanazawa, Yokohama, Kanagawa, 236-0001, Japan
  • 7Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany
  • 8Department of Geography, University of Oregon, Eugene, OR 97403-1251, USA
  • 9Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
  • 10British Antarctic Survey, High Cross Madingley Road, Cambridge CB3 0ET, UK
  • 11College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
  • 12Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA
  • 13Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 14Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, the Netherlands
  • 15Laboratoire de Glaciologie, Université Libre de Bruxelles, CP160/03, Av. F. Roosevelt 50, 1050 Brussels, Belgium
  • 16School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, LS29JT, UK
  • 17NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
  • 18Group T-3, Fluid Dynamics and Solid Mechanics, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
  • 19Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Bussestr. 24, 27570 Bremerhaven, Germany
  • 20Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14850, USA
  • 21Department of Earth and Atmospheric Sciences, University of Quebec in Montreal (UQAM), Montreal, QC, H3C 3P8, Canada
  • 22Institute for Marine and Antarctic Studies, Uinversity of Tasmania, Hobart, Tasmania 7001, Australia
  • 23Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
  • 24Department of Natural Sciences and Environmental Health, University College of Southeast Norway, 3800 Bø i Telemark, Norway
  • 25Department of Physical Geography, Stockholm University, 10691 Stockholm, Sweden

Abstract. Two interglacial epochs are included in the suite of Paleoclimate Modeling Intercomparison Project (PMIP4) simulations in the Coupled Model Intercomparison Project (CMIP6). The experimental protocols for simulations of the mid-Holocene (midHolocene, 6000 years before present) and the Last Interglacial (lig127k, 127 000 years before present) are described here. These equilibrium simulations are designed to examine the impact of changes in orbital forcing at times when atmospheric greenhouse gas levels were similar to those of the preindustrial period and the continental configurations were almost identical to modern ones. These simulations test our understanding of the interplay between radiative forcing and atmospheric circulation, and the connections among large-scale and regional climate changes giving rise to phenomena such as land–sea contrast and high-latitude amplification in temperature changes, and responses of the monsoons, as compared to today. They also provide an opportunity, through carefully designed additional sensitivity experiments, to quantify the strength of atmosphere, ocean, cryosphere, and land-surface feedbacks. Sensitivity experiments are proposed to investigate the role of freshwater forcing in triggering abrupt climate changes within interglacial epochs. These feedback experiments naturally lead to a focus on climate evolution during interglacial periods, which will be examined through transient experiments. Analyses of the sensitivity simulations will also focus on interactions between extratropical and tropical circulation, and the relationship between changes in mean climate state and climate variability on annual to multi-decadal timescales. The comparative abundance of paleoenvironmental data and of quantitative climate reconstructions for the Holocene and Last Interglacial make these two epochs ideal candidates for systematic evaluation of model performance, and such comparisons will shed new light on the importance of external feedbacks (e.g., vegetation, dust) and the ability of state-of-the-art models to simulate climate changes realistically.

Short summary
The PMIP4 and CMIP6 mid-Holocene and Last Interglacial simulations provide an opportunity to examine the impact of two different changes in insolation forcing on climate at times when other forcings were relatively similar to present. This will allow exploration of the role of feedbacks relevant to future projections. Evaluating these simulations using paleoenvironmental data will provide direct out-of-sample tests of the reliability of state-of-the-art models to simulate climate changes.