Exploring climate sensitivity from Pliocene temperatures

Abstract

<p>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.<span class="Apple-converted-space"> </span>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.</p>

Revisiting a Constraint on Equilibrium Climate Sensitivity From a Last Millennium Perspective

“…Therefore, instead of viewing our study as fully capable of constraining ECS on its own, we contend that our estimates and their associated uncertainties should be regarded as an additional source of knowledge within the existing body of work to generate the most accurate ECS estimate (Sanderson et al., 2021). While this study has exclusively used paleoclimate simulations and reconstructions from the Common Era, there are multiple other past intervals that could be brought to bear on estimates of ECS, including warmer and colder intervals (Renoult, 2022; Tierney et al., 2020; J. Zhu et al., 2020). Combined with additional sources of evidence (e.g., Sherwood et al., 2020), we hope that this work, will contribute to tighter constraints on ECS.…”