Scientists Discover "Organic Carbon Thermostat" Accelerating Climate Stabilization

Recent research has unveiled a potent natural feedback mechanism, termed the "organic carbon thermostat," which accelerates Earth's carbon sequestration processes, potentially stabilizing the climate more rapidly than previously understood.

This newly identified process operates alongside the well-known silicate weathering feedback, significantly reducing the time required for atmospheric carbon dioxide (CO₂) removal—from over 500,000 years to possibly just 100,000 years. Initiated by increased phosphorus input into oceans during warming periods, this mechanism stimulates phytoplankton blooms, leading to enhanced carbon burial on the seafloor. While offering insights into Earth's long-term climate regulation, researchers caution that it won't mitigate near-term global warming risks.

Background on Earth's Climate Regulation

Earth's climate stability over geological timescales is maintained through natural feedback mechanisms that regulate atmospheric CO₂ levels. The primary known process is silicate weathering, where the chemical breakdown of silicate minerals in rocks consumes atmospheric CO₂, forming bicarbonate ions that eventually precipitate as carbonate minerals in the ocean, effectively sequestering carbon. This process operates over hundreds of thousands to millions of years, acting as a long-term climate thermostat.

Discovery of the Organic Carbon Thermostat

Recent research has identified an additional, potent feedback mechanism termed the "organic carbon thermostat," which accelerates Earth's natural carbon sequestration processes. This mechanism involves the phosphorus cycle and its impact on oceanic phytoplankton dynamics. In warmer climates, increased weathering of phosphorus-bearing minerals releases more phosphorus into rivers and oceans. This nutrient influx stimulates phytoplankton blooms; upon their death, these organisms sink, depositing organic carbon on the seafloor. Warmer, oxygen-depleted waters enhance this cycle by recycling phosphorus back into the water column, sustaining phytoplankton growth and accelerating carbon burial. This feedback loop can significantly reduce the time required for atmospheric CO₂ removal, potentially stabilizing the climate more rapidly than previously understood.

Implications for Climate Change Mitigation

While the organic carbon thermostat suggests a natural mechanism that could counteract human-driven CO₂ emissions more swiftly, researchers caution that it won't mitigate near-term global warming risks. Historical evidence indicates that such processes have triggered extreme cooling episodes, though a similar scenario is unlikely today due to current oceanic oxygen levels. Understanding this mechanism adds a crucial layer to our comprehension of Earth's long-term climate regulation systems.

Expert Insights

"There are definitely times in Earth's history when a lot of organic carbon has been deposited," said Ridgwell. "We've sort of known that there must be other things going on [besides silicate weathering], but it's much more complex to put in a model."

Conclusion

The identification of the organic carbon thermostat provides valuable insights into Earth's complex climate regulation mechanisms. While it offers hope for natural processes that can mitigate atmospheric CO₂ levels, it also underscores the importance of understanding and managing human-induced climate change to prevent unintended consequences.