| Summary: | Trends in the atmospheric concentration of CO 2 during three recent interglacials – the Holocene, the Eemian and Marine Isotope Stage (MIS) 11 – are investigated using an earth system model of intermediate complexity, which we extended with process-based modules to consider two slow carbon cycle processes – peat accumulation and shallow-water CaCO 3 sedimentation (coral reef formation). For all three interglacials, model simulations considering peat accumulation and shallow-water CaCO 3 sedimentation substantially improve the agreement between model results and ice core CO 2 reconstructions in comparison to a carbon cycle set-up neglecting these processes. This enables us to model the trends in atmospheric CO 2 , with modelled trends similar to the ice core data, forcing the model only with orbital and sea level changes. During the Holocene, anthropogenic CO 2 emissions are required to match the observed rise in atmospheric CO 2 after 3 ka BP but are not relevant before this time. Our model experiments show a considerable improvement in the modelled CO 2 trends by the inclusion of the slow carbon cycle processes, allowing us to explain the CO 2 evolution during the Holocene and two recent interglacials consistently using an identical model set-up.
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