PlioMIP3 A Science Programme Proposal to the Community

The Pliocene Model Intercomparison Project (PlioMIP) is one of the most successful MIPs in palaeoclimatology. Over two phases since 2008, PlioMIP has co-ordinated the experimental design and publication strategy of the community, which has included an increasing number of climate models and modelling groups from around the world. It has engaged with the palaeo-data community in order to foster new data synthesis, supporting the construction of new model boundary conditions as well as to facilitate new data/model comparisons.

Given the long implementation period for a new phase it is necessary to define the broad parameters of PlioMIP3 now. Here we present different potential components of a new science plan. This incorporates feedback gained from PlioMIP participants following the online PlioMIP2 showcase event in 2021.

PlioMIP3 will continue to have balanced scientific portfolio across both Pliocene for Pliocene and Pliocene for Future agendas. It will continue to carefully consider the competing demands of the overall effort required to complete experiments, and to be a part of the project, versus having the ability to introduce new and existing elements to enhance scientific exploration and understanding of the Pliocene.

We propose the retention of the PlioMIP2 core experiment (Eoi400), but an extension to Core requirements to include either (or both) an experiment focussed on the Early Pliocene, or an alternative Eoi400 simulation. These additions will (a) allow an intercomparison of Early and Late Pliocene warm intervals and help build research connections and synergies with the MioMIP project, and (b) through removal of some of the largest palaeogeographic differences introduced between the PlioMIP2 and 1 (the closure of the Bering Strait and Canadian Archipelago and the exposure of the Sahul and Sunda Shelves), create a time slice simulation for 3.205 Ma (MIS KM5c) with minimal palaeogeographic variations from the modern. This will enhance the palaeo to future scientific connection, and enable an exploration of the significance of palaeogeographic uncertainties on climate simulations.

In addition, we propose a number of optional experiments across 2 tiers of additional activity that incorporate simulations designed to enhance our understanding of Climate Sensitivity, as well as incorporating the radiative forcing potentially stemming from non-CO₂ greenhouse gases. For the first time, we have introduced orbital sensitivity experiments into the science plan examining both Northern Hemisphere minimum and maximum insolation forcing, as well as a specific simulation using dynamic vegetation models. Finally, we have proposed an experiment designed to examine the potential significance of East Antarctic Ice Sheet boundary condition uncertainty, which would help inform a new phase of the Pliocene Ice Sheet Model Intercomparison Project.