Carbon cycle feedbacks represent large uncertainties on climate change projections, and the response
of soil carbon to climate change contributes the greatest uncertainty to this. Future changes in soil
carbon depend on changes in litter and root inputs from plants, and especially on reductions in the
turnover time of soil carbon ...
Carbon cycle feedbacks represent large uncertainties on climate change projections, and the response
of soil carbon to climate change contributes the greatest uncertainty to this. Future changes in soil
carbon depend on changes in litter and root inputs from plants, and especially on reductions in the
turnover time of soil carbon (τs) with warming. The latter represents the change in soil carbon
due to the response of soil turnover time (∆Cs,τ), and can be diagnosed from projections made with
Earth System Models (ESMs). It is found to span a large range even at the Paris Agreement Target
of 2◦C global warming. We use the spatial variability of τs inferred from observations to obtain a
constraint on ∆Cs,τ . This spatial emergent constraint allows us to greatly reduce the uncertainty in
∆Cs,τ at 2◦C global warming. We do likewise for other levels of global warming to derive a best
estimate for the effective sensitivity of τs to global warming, and derive a q10 equivalent value for
heterotrophic respiration.