Understanding the role of atmospheric CO2 concentration (hereafter aCO2) during past climate warmings requires clear knowledge of how it varies in time relative to temperature. Antarctic ice cores preserve highly resolved records of aCO2 and Antarctic temperature (AT) for the last 800 kyr. Here we propose a revised relative age scale between aCO2 and AT for the last deglacial warming (Termination I, TI) using data from 5 Antarctic ice cores. We infer the phasing between aCO2 and AT at four times when their trends change abruptly. We find no significant lead/lag, with a 1σ accuracy ranging from 160 yr to 90 yr, indicating that aCO2 did not begin to rise hundreds of years after Antarctic temperature, as has been suggested by earlier studies.