Atmospheric carbon dioxide is one of the most important greenhouse gases which changes the radiative balance of the Earth.For the past times we can rely on precise measurements of atmosphericCO2 derived from Antarctic ice cores going 800 000 years back in time.However, so far the dynamics seen in these CO2 records are still notfully understood. In this talk I will introduce what is known from thepaleo data sets (mainly ice core records derived in the European Projectfor Ice Coring in Antarctica EPICA) and how one might interpret theserecords with models of the carbon cycle. The contribution of variousprocesses to the variability in CO2 will be estimated.