Scientists Identify Earth’s Natural Climate Thermostat

Scientists have uncovered a previously hidden feedback loop that may explain how Earth has maintained a relatively stable climate for tens of millions of years. The new research shows that fluctuations in sea level alter the amount of phosphate that reaches the open ocean, a key nutrient that fuels marine productivity.

The study finds that when sea levels rise, more phosphate is delivered to the ocean, boosting the growth of phytoplankton and other organisms that sequester carbon. The resulting increase in organic matter that sinks to the seafloor enhances the burial of carbon, effectively removing carbon dioxide from the atmosphere and exerting a cooling influence on the planet. Conversely, falling sea levels reduce phosphate input, diminishing carbon burial and allowing atmospheric CO₂ to rise.

By linking sea‑level dynamics to nutrient fluxes and long‑term carbon sequestration, the research provides a mechanistic explanation for Earth's long‑term climate stability. The discovery underscores the importance of geological and biological interactions in regulating atmospheric composition over deep time.