Quantifying negative radiative forcing of non-permanent and permanent soil carbon sinks

Summary

Reversibility of soil carbon sinks is a major obstacle in assigning soil carbon sequestration as negative emission technology and it is still unclear how a non-permanent CO2 removal shall be accounted for. In this study, we combine various scenarios of reversible and non-reversible soil carbon sinks with atmospheric CO2 impulse response functions and calculations of the resulting radiative forcing. A time horizon of up to 500 years was considered. Results show that any soil carbon sink generates negative radiative forcing (i.e., cooling) when aggregated over longer time scales. Whereas also non-permanent CO2 removals from the atmosphere provide negative average radiative forcing, their effect is substantially smaller than that of permanent removals of the same magnitude. We show that the a