Paleoclimate data provide constraints on climate models’ large-scale response to past CO₂ changes

The paleoclimate record provides a valuable test-bed for evaluating climate models under conditions of significant CO₂ change. This study uses paleoclimate proxy observations to assess climate models across three past time periods: the Last Glacial Maximum (LGM), the mid-Pliocene warm period (MPWP), and the early Eocene climatic optimum (EECO). The CMIP6/PMIP4 ensemble mean accurately simulates global mean surface air temperatures for these periods, showing improvement over CMIP5/PMIP3. However, models with very high or low climate sensitivity deviate from proxy data, highlighting the paleoclimate record's potential for constraining climate sensitivity. Consistency between models and data is also observed regarding polar amplification and land-sea warming contrast. The study emphasizes the importance of incorporating paleoclimate data into model development and evaluation.

Daniel J. Lunt, Bette L. Otto-Bliesner, Chris Brierley, Alan Haywood, Gordon N. Inglis, Kenji Izumi, Masa Kageyama, Darrell Kaufman, Thorsten Mauritsen, Erin L. McClymont, Ulrich Salzmann, Sebastian Steinig, Jessica E. Tierney, Anni Zhao, Jiang Zhu