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

Summary

This modelling study addresses a critical gap in climate policy by quantifying how soil carbon sequestration generates negative radiative forcing (climate cooling) when assessed over extended time horizons. The authors demonstrate that whilst non-permanent soil carbon removals do provide climate benefits, their effect is substantially smaller than permanent removals of equivalent magnitude. They propose a simple, quantitative metric—average annual soil organic carbon balance—that enables unbiased assessment and comparison of soil carbon mitigation projects, with potential application to climate policy guidance and carbon markets.

UK applicability

The findings are directly applicable to UK soil carbon policy and carbon market design, particularly for assessing the climate mitigation value of UK agricultural and land management practices. The proposed metrics framework may inform future UK climate commitments and voluntary carbon scheme standards that account for soil carbon sequestration.

Key measures

Radiative forcing (W/m²); soil organic carbon balance; atmospheric CO₂ impulse response functions; time-integrated radiative forcing over 500-year horizon

Outcomes reported

The study quantified negative radiative forcing (cooling effect) generated by soil carbon sinks over a 500-year time horizon, comparing reversible versus non-reversible carbon removal scenarios. Results demonstrated that average annual soil organic carbon balance over the integrated time window is the primary determinant of radiative forcing, independent of sink longevity or carbon gain/loss rates.

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