Fig. 5. Evolving climate sensitivity for the Eocene.

a Calculated ESS (red triangles and error envelope), and ECS (blue triangles and error envelope). See text for relevant methodology. Orange area represents the IPCC range in ECS⁹⁵, and the pink highlighted area the updated 20th century ECS with the addition of state-of-the-art cloud physics⁹⁶. Circles represent estimates from ref. ⁸. b Data-model inter-comparison, with all diamonds representing data. Open diamonds are the data between 39 and 34 Ma, and orange filled diamonds the EOT. Circles⁷ and squares⁶ are all model derived relationships (PI preindustrial). Uncertainties and error envelopes represent 1 s.d. of Monte Carlo propagated uncertainties. c Evolving GMT relationship for the Eocene. GMT is calculated using the BAYSPAR TEX₈₆ record from ODP 959. Error bars represent the calibration and analytical uncertainty on TEX₈₆. For comparison, the GMT estimates from ref. ⁸ are presented with open symbols and red error bars. NB the elevated ECS early in the PETM and ETM 2 are most likely a consequence of slight age model misalignments, or imply non-CO₂ forcing early in these events.