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

Bette L Otto‐Bliesner ,Jean-Yves Peterschmitt,Andrea Dutton,Steven J Phipps,Fortunat Joos,Francesco S R Pausata,Aline Govin,Sandy P Harrison,Heiko Goelzer,Pascale Braconnot,Gerrit Lohmann,William H Lipscomb,Qiong Zhang,Hubertus Fischer,Samuel Albani,Daniel J Lunt,Patrick J Bartlein,Allegra N Legrande,Anders E Carlson,Christoph Nehrbass-Ahles,H Renssen ,Alan M Haywood ,N M Mahowald ,Ayako Abe‐Ouchi ,Émilie Capron

doi:10.5194/gmd-10-3979-2017

Abstract

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.

Highlights

The modeling of paleoclimate, using physically based tools, has long been used to understand and explain past environmental and climate changes (Kutzbach and Street-Perrott, 1985), and is increasingly seen as a strong out-of-sample test of the models that are used for the projection of future climate changes (Braconnot et al, 2012; Harrison et al, 2014, 2015; Schmidt et al, 2014)
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 and the Last Interglacial 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

Summary

Introduction

The modeling of paleoclimate, using physically based tools, has long been used to understand and explain past environmental and climate changes (Kutzbach and Street-Perrott, 1985), and is increasingly seen as a strong out-of-sample test of the models that are used for the projection of future climate changes (Braconnot et al, 2012; Harrison et al, 2014, 2015; Schmidt et al, 2014). More specific information is given in the contributions for the last millennium (past1000) by Jungclaus et al (2017), for the last glacial maximum (lgm) by Kageyama et al (2017), for the mid-Pliocene warm period (midPliocene-eoi400) by Haywood et al (2016), and the present paper the mid-Holocene (midHolocene) and the previous interglacial (lig127k). Modeling groups are not obliged to run all PMIP4-CMIP6 experiments. It is mandatory, for all participating groups to run at least one of the experiments that were run in previous phases of PMIP (i.e., midHolocene or lgm)

Objectives

Methods

Conclusion