This study simulates long-term future climate scenarios to assess the persistence of CO₂ emissions in the atmosphere. Results show that the land stores 4 %–13 % of emissions after 100 kyr and that the removal timescale of CO₂ for silicate weathering is shorter than previously expected. Our study highlights the importance of adding model complexity to the global carbon cycle in Earth system models for improved predictions of long-term atmospheric CO₂ concentration.

Using an Earth system model that can simulate Dansgaard–Oeschger-like events, we show that conditions under which millennial-scale climate variability occurs are related to the integrated surface buoyancy flux over the northern North Atlantic. This newly defined buoyancy measure explains why millennial-scale climate variability arising from abrupt changes in the Atlantic meridional overturning circulation occurred for mid-glacial conditions but not for interglacial or full glacial conditions.

Using a fast Earth system model we trace the stability landscape of the Atlantic meridional overturning circulation in the combined freshwater forcing–atmospheric CO₂ space. We find four different Atlantic meridional overturning circulation states that are stable under different conditions and a generally increasing equilibrium Atlantic meridional overturning circulation strength with increasing CO₂ concentrations.

To trigger glacial inception, the summer maximum insolation at high latitudes in the Northern Hemisphere must be lower than a critical value. This value is not constant but depends on the atmospheric CO₂ concentration. Paleoclimatic data do not give enough information to derive the relationship between the critical threshold and CO₂. However, knowledge of such a relation is important for predicting future glaciations and the impact anthropogenic CO₂ emissions might have on them.

We present transient simulations of the last glacial inception with the coupled climate–ice sheet model CLIMBER-X showing a rapid increase in Northern Hemisphere ice sheet area and a sea level drop by ~ 35 m, with the vegetation feedback playing a key role. Overall, our simulations confirm and refine previous results showing that climate-vegetation–cryosphere–carbon cycle feedbacks play a fundamental role in the transition from interglacial to glacial states.