Perturbations in atmospheric CO₂ and in its isotopic composition, e.g., in response to carbon release from the land biosphere or from fossil fuel burning, evolve differently in time. We use an Earth system model of intermediate complexity to show that fluxes to and from the solid Earth play an important role in removing these perturbations from the atmosphere over thousands of years.

A long-standing question in climate science is concerned with what processes contributed to the increase in atmospheric CO₂ after the last ice age. From the range of possible processes we try to constrain the change in carbon storage in the land biosphere. By combining ice core and marine sediment data in a modeling framework we show that the carbon storage in the land biosphere increased largely after the last ice age. This will help to further understand processes at work in the Earth system.

Atmospheric CO₂ is key for climate change. CO₂ is lower during the oldest warm period of the last million years, the interglacials, than during the most recent ones (since 430 000 years ago). This difference has not been explained yet, but could be due to changes of ocean circulation. We test this hypothesis and the role of vegetation and ice sheets using an intermediate complexity model. We show that only small changes of CO₂ can be obtained, underlying missing feedbacks or mechanisms.

Ice cores reveal that atmospheric CO₂ concentration varied synchronously with the global ice volume. Explaining the mechanism of glacial–interglacial variations of atmospheric CO₂ concentrations and the link between CO₂ and ice sheets evolution still remains a challenge. Here using the Earth system model of intermediate complexity we performed for the first time simulations of co-evolution of climate, ice sheets and carbon cycle using the astronomical forcing as the only external forcing.

An Earth system model was set up and applied to evaluate the effects of sea-level change, ocean dynamics, and nutrient utilization on seawater composition and atmospheric pCO₂ over the last glacial cycle. The model results strongly suggest that global sea-level change contributed significantly to the slow glacial decline in atmospheric pCO₂ and the gradual pCO₂ increase over the Holocene whereas the rapid deglacial pCO₂ rise was induced by fast changes in ocean dynamics and nutrient utilization.