Exploring climate sensitivity from Pliocene temperatures

In recent years, simulations of the Paleoclimate Modelling Intercomparison Project (PMIP) of the cold Last Glacial Maximum (LGM) and the warm mid-Pliocene have been used to constrain the equilibrium climate sensitivity (ECS) in an emergent constraint framework. The constraint on ECS arising from Pliocene temperatures is surprisingly robust, as opposed to that based on LGM temperatures. Nevertheless, observational uncertainties on proxy data from the Pliocene are large, in particular at high latitudes. We analyse the sensitivity of the Pliocene-based emergent constraint on ECS to different reconstructions as to verify if the well-constrained ECS is sensitive to the proxy data. We also investigate the boundary conditions of the Pliocene to identify key structural elements which may weaken the emergent constraint relationship. We show that the wider range of ECS in models simulating the Pliocene, as well as numerous sensitivity experiments, is a great advantage for the emergent constraint approach.