By Abbas Nazil
Researchers have discovered a powerful natural mechanism that may cause Earth to “overcorrect” for rising carbon dioxide levels, potentially ensuring that the next ice age arrives on schedule instead of being delayed by tens of thousands of years.
The study, published in Science on September 25, reveals that rising atmospheric CO₂ could activate a newly identified “supercharged thermostat” that buries massive amounts of carbon beneath the ocean floor far faster than scientists previously thought possible.
This natural process, driven by the movement of phosphorus from land to sea, could remove human-emitted carbon within 100,000 years, much quicker than the previously known “lazy thermostat” linked to silicate weathering, which takes up to a million years to achieve a similar balance.
According to co-author Andy Ridgwell, a geology professor at the University of California, Riverside, both thermostats might work together, with the phosphorus-based mechanism ensuring that the next glacial cycle starts on time despite current global warming trends.
However, this discovery offers no immediate relief for humanity.
Co-author Dominik Hülse of the University of Bremen cautioned that the mechanism operates over geological timescales and cannot protect us from the impacts of global warming within the next few centuries.
The concept of Earth regulating its own climate is not new.
For decades, scientists have known about the silicate weathering feedback, a process where rain absorbs CO₂, reacts with silicate rocks, and eventually traps carbon in ocean sediments as limestone and chalk.
This cycle stabilizes atmospheric CO₂ levels but moves too slowly to explain the rapid changes seen in glacial and interglacial periods.
The new study suggests a second, faster thermostat powered by the phosphorus cycle.
When rocks containing phosphorus-rich minerals weather due to rainfall, the nutrient flows into rivers and eventually into the ocean.
There, it fuels the growth of phytoplankton, microscopic organisms that absorb CO₂ during photosynthesis.
When phytoplankton die, they sink to the seafloor, burying carbon and phosphorus in sediments.
In warmer conditions, oceans hold less oxygen, releasing phosphorus back into the water but continuing to bury carbon, leading to an efficient feedback loop.
This recycling of phosphorus keeps ocean productivity high, drawing even more CO₂ out of the atmosphere and cooling the planet.
Ridgwell described this as a “supercharged” version of Earth’s natural climate regulation, one that could cause the planet to cool more aggressively after a period of warming.
In extreme past events, this overcorrection might have even triggered snowball Earth episodes.
Although modern oceans are oxygen-rich enough to prevent such an outcome today, researchers believe this feedback could help counteract the current delay in the planet’s natural ice age cycle.
Previous models predicted that human activity might postpone the next ice age by tens of thousands of years, but this mechanism could restore the timeline.
“Whatever delay we’ll end up with for the next ice age,” Ridgwell said, “thinking about this mechanism might bring it back forward again.
One is going to start at some point for sure; it’s all about when it starts.”