Introduction: A New Twist in Earth’s Climate Regulation
Scientists have long studied how Earth maintains climate balance over geological timescales. A recently highlighted finding suggests there isn’t just one thermostat at work—there could be a hidden, supercharged mechanism that accelerates the burial of carbon beneath the seafloor. If true, this could cause the next ice age to arrive on time, rather than be delayed by human-driven climate change.
The Established Thermostat: Silicate Weathering
For decades, researchers have described the silicate weathering feedback as Earth’s primary long-term climate regulator. When atmospheric CO2 rises, the warming climate accelerates the weathering of silicate rocks. This process pulls CO2 from the atmosphere, stores it in oceans and rocks, and, over millions of years, tends to cool the planet back toward baseline levels. Conversely, cooler periods slow this process. While powerful, this thermostat operates on slow scales, often requiring up to a million years to rebalance following perturbations.
A Second Thermostat Emerges: Organic Carbon Burial in the Ocean
In a collaboration that blends geologic history with advanced climate modeling, researchers uncovered evidence for a second, faster mechanism rooted in the phosphorus cycle. The idea began with an examination of how much organic carbon was preserved in ocean sediments after past volcanic and warming episodes. They found that huge amounts of organic carbon could be buried on the seafloor under certain conditions, acting as a potent sink for atmospheric CO2.
Key to this second thermostat is the phosphorus cycle. Weathering of phosphate-containing rocks releases phosphorus into rivers and oceans, fueling phytoplankton growth. When phytoplankton die, they contribute organic carbon and phosphorus to sediments. Warmer oceans, which hold less dissolved oxygen, can recycle phosphorus back into the water while still burying organic carbon deeper in sediments. This combination can accelerate CO2 removal from the atmosphere and cool the planet—much faster than the silicate weathering feedback alone.
How the Two Thermostats Interact
The researchers describe the organic carbon thermostat as a “supercharged” version of the phosphorus cycle. With abundant nutrients available, ocean biology thrives and drives a strong, rapid sequestration of carbon in sediments. This process can dampen atmospheric CO2 far more quickly than previously thought possible. If activated in the near future, it could negate much of the warming caused by human emissions on short to medium timescales, but it also risks overshooting, potentially accelerating a move toward glaciation.
What This Means for the Next Ice Age
Current models have suggested that Earth’s next glacial period could be pushed back by tens of thousands of years due to ongoing climate change. The new work posits that the organic carbon thermostat might compensate for some of that delay by locking away CO2 faster than expected. The fate of Earth’s climate then hinges on how these feedbacks balance with ongoing anthropogenic emissions and natural volcanic activity.
Experts caution that the mechanism is not a shield for today’s populations. Dr. Dominik Hülse emphasizes that while this thermostat could influence long-term cycles, it does not mitigate the immediate impacts of warming. “It’s not to say that we will be safe from global warming in the next 100 or even 1,000 years,” he noted.
Looking Ahead: Research and Implications
Researchers stress that more work is needed to quantify the conditions under which the organic carbon thermostat dominates and how it interacts with the silicate weathering feedback. If validated, these insights could refine long-range climate forecasts, improve paleo-climate reconstructions, and influence how we think about future CO2 trajectories.
In the end, Earth’s climate system may be regulated by multiple, overlapping thermostats, each with its own tempo and tipping points. The question now is when and how these mechanisms will synchronize in a changing world.
