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

Summary

This modelling study addresses a critical gap in climate policy: how to account for non-permanent soil carbon removals as a negative emissions technology. By integrating soil carbon scenarios with radiative forcing calculations over extended timescales, the authors demonstrate that whilst non-permanent CO₂ removals do produce cooling effects, their climate benefit is substantially smaller than equivalent permanent removals. The work proposes a quantitative framework based on average annual carbon balance that may support transparent assessment and comparison of soil carbon mitigation projects.

UK applicability

The findings are directly applicable to UK soil carbon accounting and climate policy, particularly regarding the design of soil carbon markets and the assessment of agricultural sequestration schemes. The suggested metrics could inform guidance for UK-based soil carbon projects and compliance with carbon accounting standards.

Key measures

Radiative forcing (W m⁻²), soil carbon sequestration rates, atmospheric CO₂ impulse response, time-integrated climate impact over 500 years

Outcomes reported

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

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