Earth's Climate System: When Overshooting Becomes a Risk
New research from UC Riverside has revealed that Earth's natural climate regulation mechanisms may not be as gentle as once believed. Instead of gradually stabilizing the planet’s temperature, these systems can overcorrect during periods of warming, triggering dramatic cooling that could plunge the world into another ice age.
The Traditional Climate Thermostat
For decades, scientists described Earth's climate stability as regulated by slow geological weathering. Rainwater absorbs carbon dioxide from the atmosphere and dissolves exposed silicate rocks, neutralizing greenhouse gas accumulation. This carbon then travels to the ocean and is sequestered in limestones and seashells, keeping atmospheric CO₂ levels—and thus planetary temperatures—relatively stable over millions of years.
A Feedback Loop With a Twist
The UC Riverside study, published in Science, finds that an overlooked loop amplifies climate shifts dramatically. As CO₂ levels rise and the climate warms, more nutrients like phosphorus wash into the ocean, fueling explosive plankton blooms. These plankton absorb carbon dioxide, and when they die, they sink and bury that carbon in the ocean floor. Initially, this looks like a powerful counterweight to warming.
But the feedback does not stop there. Increased plankton activity strips oxygen from the oceans. In lower oxygen conditions, phosphorus recycles more efficiently but is less likely to be buried. This fuels even more plankton, setting off cycles that further reduce ocean oxygen. The end result is runaway carbon burial, rapidly cooling the planet far below its initial temperature—sometimes to the extent of initiating planetary-scale ice ages.
Explaining Ancient Extreme Ice Ages
This mechanism explains why episodes like “Snowball Earth”—where almost the entire planet was covered in ice—were possible. Gentle climate regulation cannot account for such extremes. The UC Riverside team’s computer models show that under certain conditions, such overshooting can occur, dramatically flipping the planet from hot to frozen in geological time
Modern Implications and Timeline
Lower oxygen in past geological eras made this climate system even more erratic, resulting in more severe ancient ice ages. Today’s higher atmospheric oxygen damps the effect, but does not eliminate it. The study warns that present-day warming could still trigger a much milder, but rapid onset of a new ice age—potentially starting anywhere from 50,000 to 200,000 years in the future. Nevertheless, this process will not help counteract climate change quickly enough for modern society.
“The Earth will eventually cool back down, in however wobbly a way, but not fast enough to help us out in this lifetime,” said lead author Andy Ridgwell. The priority remains to limit ongoing warming rather than relying on distant, unpredictable planetary mechanisms to restore balance.
Conclusion
Earth’s climate system is more erratic and powerful than previously thought. While long-term natural cycles may eventually rebalance temperatures, the feedbacks triggered by carbon burial and oxygen depletion in oceans show our climate thermostat is prone to overshooting, with ice age risks lurking far into the future. For now, science urges action to control our emissions and avoid destabilizing the climate to dangerous extremes