Soil carbon-concentration and carbon-climate feedbacks in CMIP6 Earth system models

Achieving climate targets requires mitigation against climate change, but also understanding of the response of land and ocean carbon systems. In this context, global soil carbon stocks and its response to environmental changes is key. In this presentation, the global soil carbon feedbacks to both changes in atmospheric CO₂ and associated climate changes for Earth system models (ESMs) in CMIP6 are quantified. A standard approach is used to calculate the carbon cycle feedbacks, which are defined as soil specific carbon-concentration (β_s) and carbon-climate (γ_s) feedback parameters. Amongst CMIP6 ESMs, it is shown that the sensitivity to CO₂ is found to dominate global soil carbon changes at least up to a doubling of atmospheric CO₂. However, the sensitivity of soil carbon to climate change is found to become an increasingly important source of uncertainty under higher atmospheric CO₂ concentrations.