The GFDL Earth system model CM2Mc was run to quasi-equilibrium (3000 to 5000 years) under a broad range of external forcings, in which atmospheric carbon dioxide, orbital parameters and ice sheets were systematically varied over more than 40 combinations. The purpose of these simulations was to map out the expectations of a modern climate model – of the sort used for conducting future climate change scenarios – under conditions that have occurred in the geologically-recent past.
These simulations were described by Galbraith and de Lavergne (Climate Dynamics, 2019). Changes in ocean carbon storage among the simulations were also explored by Eggleston and Galbraith (Biogeosciences, 2018), and Newsom et al. (Earth and Planetary Science Letters, 2021) showed implications for global heat transport and overturning. However, these descriptions only scratch the surface – the output could be used to explore general mechanisms within the climate system, as well as their interactions with global biogeochemistry. The results could also be tested against new paleoclimate observations, to identify aspects of the simulations that are consistent, as well as to identify model biases and shortcomings when confronted with reality.