Southern Ocean sea surface temperatures (SST) for the a) Eocene (4x pCO2), b) Oligocene (2x pCO2 model runs), and c) the difference across the transition (2x-4x) showing results for the unscaled multi model ensemble mean. The circles correspond to proxy mean annual air temperature records while the dotted areas show the source area used to compare the model temperature to the proxy record.  d) Summarizing the RMSE for pCO2 model runs for SST, for individual model mapped output see Figure S3. Red lines are the RMSE for each model after the pCO2 scaling for RMSE values see Table S1.