The only viable explanations put forth to date for the glacial to interglacial change in atmospheric CO2content suggested from measurements of the CO2content of gas extracted from ice cores involve changes in the ocean's nutrient cycles. Any nutrient change capable of creating the 80 µatm changes in atmosphere CO2pressure suggested by the ice core results also creates significant change in the deep ocean's CO3=content. Evidence from deep sea sediments suggests that these CO3=changes are compensated on the time scale of a few thousand years by reductions or increases in amount of CaCO3accumulating in deep sea sediments. This compensation process has two important consequences. First, it significantly increases the magnitude of the CO2change per unit of nutrient forcing. Second, it causes a delay in the response of the atmospheric CO2change. While the first of these consequences is a boon to those seeking to explain the CO2change, the second may prove to be a curse. The ice core CO2record shows no evidence of a significant lag between the CO2response and the polar warming. In any case it is important that we improve our knowledge of the magnitude and timing of the CaCO3preservation events which mark the close of episodes of glaciation and of the dissolution events which mark the onset of these episodes