Human‑Driven Warming Could Paradoxically Push Earth Toward a Far‑Future Ice Age

Warming today could set the stage for extreme cooling far in the future

Earth’s climate has swung dramatically over its 4.6‑billion‑year history. Slow geochemical processes such as silicate weathering have long acted as a planetary thermostat, drawing down atmospheric CO2 when the planet warms and returning it toward equilibrium. A new study, however, warns that biological and oceanic feedbacks amplified by human‑caused warming could overcompensate and, on geological timescales, drive the planet into a pronounced cooling phase.

What the study found

Researchers from the University of Bremen and the University of California, Riverside modeled how warmer oceans and altered nutrient cycles might change marine productivity. They found that increased surface temperatures and greater nutrient availability — particularly phosphorus — could spur larger and more frequent algal blooms. When those algae die, a greater fraction of organic carbon can sink to the seafloor and be buried in sediments, locking CO2 out of the atmosphere for very long periods.

“With the silicate weathering alone, we were unable to simulate such extreme values,” said co‑author Dominik Hülse (UC Riverside), illustrating that combined oceanic and biological feedbacks can, in some model scenarios, outpace the slow rock weathering that normally stabilizes climate.

How an overcorrection could unfold

Under the model’s stronger feedback scenarios, amplified carbon burial by marine organisms triggers progressive drops in atmospheric CO2. That cooling reduces surface temperatures, which can further alter ocean circulation and nutrient distributions in ways that sustain high burial rates. Over tens to hundreds of thousands of years, this runaway sequestration could produce an ice‑age‑scale cooling event.

Importantly, the study’s authors stress that modern atmospheric oxygen levels are much higher than during Earth’s most extreme deep freezes, such as the Cryogenian, making a complete global "snowball Earth" unlikely. Even so, a significant long‑term cooling episode would have major implications for global ecosystems and the climate regime.

Why this doesn’t solve today’s climate crisis

These feedbacks operate on geological timescales. Even if they eventually reduce global temperatures, that process would take far longer than the timeframes relevant to human societies and ecosystems. The paper’s authors — including Andy Ridgwell and Dominik Hülse — emphasize that this long‑term natural balancing offers no near‑term relief from current warming and its impacts.

Bottom line: Warming today could set in motion oceanic and biological feedbacks that over centuries to millennia lock more carbon into the deep ocean, potentially leading to substantial cooling many tens to hundreds of thousands of years from now. That distant possibility underscores, rather than diminishes, the urgent need to reduce emissions now.

Study published in Science. Authors affiliated with the University of Bremen and UC Riverside.