37 Year Soil Experiment Shows Warming Unlocks Stable Carbon, Accelerating Climate Change

A 37 year soil warming experiment at Harvard Forest found that even stable soil carbon, once thought to be protected, breaks down as temperatures rise. Researchers kept soil 5 degrees Celsius above ambient for nearly four decades and observed that microbes began decomposing long lasting carbon stores during the fourth decade, releasing extra CO2. This finding suggests a stronger climate feedback loop than previously modeled. As the planet warms, soils may release more carbon, which in turn adds to atmospheric CO2 and drives further warming. The study, published in Science of the Total Environment, highlights the need to include this process in climate models for more accurate projections. For carbon markets and climate policy, this implies that natural carbon sinks like forest soils may be less reliable under sustained warming. Projects relying on soil carbon sequestration could face higher reversal risks, and models used for carbon accounting may need updating to reflect this newly observed vulnerability.