The Eocene-Oligocene Transition (EOT) marks the shift from the greenhouse to icehouse conditions at 34 Ma, when a permanent ice sheet developed on Antarctica. Here we compile published proxy temperature records on and around Antarctica for timeslices defined for the late Eocene (40-34Ma) and early Oligocene (34-30 Ma) bracketing the EOT. Compiled proxy records for mean annual sea surface temperature (SST) cool by on average 1°C and land surface mean air temperature (MAT) by 2°C between the timeslices. Proxy data were compared to climate model simulations for each time interval. We use previous climate model simulations representing pre- and post- EOT, typically forced with a halving of pCO₂ – that results in a larger than expected cooling based on proxies for temperature. We scaled the model outputs to identify the magnitude of pCO₂ change needed to drive a commensurate change in temperature to best fit the temperature proxies. Relative to a post-EOT pCO₂ level of 560 ppmv, this temperature scaling approach indicates a 27% decrease in pCO₂, consistent with carbon dioxide proxy reconstructions. These proxy-model intercomparisons show that pCO₂ is the primary driver of declining temperatures across the EOT, and the magnitude of that forcing was likely consistent with the 200 ppmv estimate from the latest pCO₂ proxy compilations.