Could global warming trigger a runaway cooling cycle into an ice age?

Science · Published 25 October 2026 Swipe more like this →

In short: The Earth's climate is governed by complex feedback loops that can sometimes overcorrect. While we often think of warming as a linear process, new research suggests that extreme heat could actually trigger biological mechanisms that bury carbon so rapidly they might plunge the planet back into a deep freeze.

For decades, the prevailing scientific consensus was that Earth's climate is stabilized by rock weathering. In this process, rain absorbs atmospheric CO2 and reacts with silicate rocks like granite. This chemical reaction breaks down the minerals, carrying dissolved material and carbon into the oceans where they form limestone and shells, locking carbon away for millions of years. As temperatures rise, weathering speeds up, theoretically acting as a thermostat to cool the planet back down.

However, researchers at UC Riverside have identified a missing feedback loop that could cause the system to overshoot this balance. They found that increased rainfall during warming periods carries more nutrients, such as phosphorus, into the oceans. This fuels massive blooms of plankton—microscopic organisms that absorb CO2 via photosynthesis. When these plankton die, they sink and bury carbon in ocean sediments. In warmer conditions, this process can spiral out of control; the massive growth of plankton can deplete oxygen levels in the water, leading to even more rapid carbon burial.

This mechanism may explain why some ancient ice ages were so severe that snow and ice covered nearly the entire planet—a level of freezing that simple rock weathering cannot account for. While this doesn't negate modern climate change, it suggests a potential 'overshoot' where warming triggers a biological cooling response. Interestingly, recent data on the Barnes Ice Cap shows that while a new glacial period began roughly 2,000 years ago, human-induced global warming by the 1960s was sufficient to halt and reverse that growth.

The mystery of atmospheric methane adds another layer of complexity. Since 2006, methane levels have been rapidly increasing without slowing down. Whether this spike is driven by human activity or signals a larger planetary shift toward an ice age termination event remains a subject of active scientific inquiry.

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