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 reversibility affects the cooling potential of soil carbon sequestration. Using impulse response functions and radiative forcing calculations over 500 years, the authors show that while all soil carbon sinks generate negative forcing (cooling), non-permanent removals deliver substantially smaller effects than permanent ones of equivalent magnitude. The work proposes a simple, quantitative framework—based on average annual carbon balance—to enable fair comparison and assessment of soil carbon mitigation projects for policy and market purposes.

UK applicability

The framework developed is universally applicable and could inform UK soil carbon markets, agricultural policy, and voluntary carbon schemes by providing an evidence-based method to value and compare soil carbon projects. However, the study does not address UK-specific soil conditions, farming systems, or carbon sequestration rates, so local validation would support deployment in UK climate and agriculture policy.

Key measures

Radiative forcing (in watts per square metre); atmospheric CO₂ impulse response functions; soil organic carbon balance over integrated time windows; comparison of permanent versus non-permanent carbon sink scenarios

Outcomes reported

The study quantified negative radiative forcing (cooling effect) generated by soil carbon sinks over a 500-year time horizon, comparing reversible (non-permanent) and non-reversible (permanent) carbon removal scenarios. It established 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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