Abstract
Abstract. Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high ( > 800 ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene ( ∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP – the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.
Highlights
There is a large community of Earth scientists with strong interests in “deep-time” palaeoclimates, here defined as climates of the pre-Pliocene
DeepMIP is a working group in the wider Paleoclimate Modelling Intercomparison Project (PMIP4), which itself is a part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6, Eyring et al, 2016)
Within the latest Paleocene and early Eocene, DeepMIP will focus on three periods: 1. The Early Eocene Climatic Optimum (EECO, ∼53–51 Ma) which is the period of greatest sustained (> 1 Myr) warmth in the last 65 million years
Summary
There is a large community of Earth scientists with strong interests in “deep-time” palaeoclimates, here defined as climates of the pre-Pliocene (i.e. prior to ∼ 5 Ma). DeepMIP – the Deeptime Model Intercomparison Project – brings together modellers, the data community, and other scientists into a multidisciplinary international effort dedicated to conceiving, designing, carrying out, analysing, and disseminating an improved understanding of these time periods. The aim will be to effectively characterize our understanding of the palaeoclimate of the chosen interval through the synthesis of climate proxy records, to compare this with the model simulations, and to understand the reasons for the intra- and inter-model and data differences. The ultimate aim is to encourage model development in response to any robust model deficiencies that emerge from the model–data comparison. This is of particular relevance to models that are used for future climate projection, given the relative warmth and high CO2 that characterizes many intervals of deep-time
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