CO2 represents the most important greenhouse gas released into the atmosphere as a result of human activity. The majority of our knowledge on the increase in CO2 since the start of the industrialization comes from ice cores, which complement the direct atmospheric CO2 measurements obtained at Mauna Loa since the 1950s. The combined CO2 record shows an unambiguous anthropogenic CO2 increase over the last 150 years from 280 to about 400 ppm in 2014. Values above 300 ppm are unprecedented in the long-term ice core record covering the last 800,000 years, with natural CO2 concentrations varying between interglacial and glacial bounds of about 280 and 180 ppm, respectively (Lüthi et al. 2008, Petit et al. 1999). Moreover, the increase in CO2 concentrations during the last termination shows significant fine structure (Marcott et al. 2014, Monnin et al. 2001), indicating a sequence of events of CO2 release to the atmosphere involving different processes acting at different points in time.