Abstract The sequence of events in the global carbon cycle during deglaciations is not entirely understood. Here, we analyze mean ocean δ13 ${delta }^{13}$C and δ18 ${delta }^{18}$O in an updated compilation of foraminiferal stable isotope data comprising 902 time series from 381 sediment cores, with individual records covering intervals within the past 23,000 years. We use changes in mean ocean temperature from ice cores to split δ18 ${delta }^{18}$O into its temperature and seawater components. We show that a 0.48±0.05 $0.48pm 0.05$‰ rise in mean ocean δ13 ${delta }^{13}$C occurred quasi‐synchronously with changes in seawater δ18 ${delta }^{18}$O and is lagging the rise in atmospheric CO2 ${mathrm{C}mathrm{O} }{2}$ during Termination I by ∼2,000 years. Since mean ocean δ13 ${delta }^{13}$C is understood to mainly record net changes in land carbon storage and seawater δ18 ${delta }^{18}$O is mainly depicting the rise in global mean sea level this implies that land carbon changed in‐phase with sea level and not with atmospheric CO2 ${mathrm{C}mathrm{O} }{2}$.