The cause of the glacial/interglacialchange in atmospheric pCO2 is oneof the most interesting aspect inpaleoclimatic research still unknown.Forcing a coupled ocean-atmosphere-biospherebox model of the global carbon cyclewith proxy data over the last glacialtermination we are able to quantitativelyreproduce transient variations in pCO2,d13CO2 and D14C observed in naturalclimate archives. According to ourmodel, a reduction of aeolian ironfertilization in the Southern Oceantriggers the onset of the pCO2increase followed by a breakdownin Southern Ocean stratification.We further deduce that a significantreduction of the thermohalinecirculation during the Younger Dryaswas very unlikely.