Assessment of Equilibrium Climate Sensitivity of the Community Earth System Model Version 2 Through Simulation of the Last Glacial Maximum

Jiang Zhu, Bette L. Otto-Bliesner, Esther C. Brady, Christopher J. Poulsen, Jessica E. Tierney, Marcus Lofverstrom, Pedro DiNezio

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The upper end of the equilibrium climate sensitivity (ECS) has increased substantially in the latest Coupled Model Intercomparison Projects phase 6 with eight models (as of this writing) reporting an ECS > 5°C. The Community Earth System Model version 2 (CESM2) is one such high-ECS model. Here we perform paleoclimate simulations of the Last Glacial Maximum (LGM) using CESM2 to examine whether its high ECS is realistic. We find that the simulated LGM global mean temperature decrease exceeds 11°C, greater than both the cooling estimated from proxies and simulated by an earlier model version (CESM1). The large LGM cooling in CESM2 is attributed to a strong shortwave cloud feedback in the newest atmosphere model. Our results indicate that the high ECS of CESM2 is incompatible with LGM constraints and that the projected future warming in CESM2, and models with a similarly high ECS, is thus likely too large.

Original languageEnglish (US)
Article numbere2020GL091220
JournalGeophysical Research Letters
Volume48
Issue number3
DOIs
StatePublished - Feb 2021

Keywords

  • cloud feedback
  • equilibrium climate sensitivity
  • last glacial maximum

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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