Global Warming May Overshoot and Trigger the Next Ice Age, Say Scientists

Scientists have discovered a missing link in Earth's carbon cycle, which could help to explain the ice ages. When it gets warmer, nutrient-laden runoff from the land fuels plankton blooms in the sea that bury huge quantities of carbon there, thus drawing down atmospheric CO₂. In low-oxygen settings, this feedback can ratchet up more strongly, causing the planet to fall far colder than its initial state. This process won't turn the tide on modern climate change anytime soon, but it might help explain some of Earth's most extreme ice ages in the past, when nearly all of the planet was covered with ice and snow.

Ocean Nutrient Feedback Found to Amplify Climate Extremes, Potentially Triggering Ice Ages

According to a UC Riverside report, researchers identified a critical gap in how Earth's carbon recycling was understood. The researchers discovered that as atmospheric CO₂ levels increase, nutrient runoff encourages the growth of plankton, whose decay reduces oxygen levels. It is this recycling of phosphorus that fuels yet more blooms, which in turn store even more carbon in the sediments, and take us closer to a cooler planet. In their computer simulations, the team found that this feedback can push the temperatures down to levels that can set off ice ages, especially under conditions of low atmospheric oxygen, such as in the early history of Earth.

Scientists believed rock weathering stabilised climate by absorbing CO₂, but ancient ice ages reveal ocean nutrient feedback amplifies climate extremes beyond this process.

Earth's Climate “Thermostat” Can Overshoot, But Immediate CO₂ Reductions Remain Crucial, Scientists Warn

UC Riverside's Ridgwell likened Earth's climate to an overcooling thermostat, with warming potentially triggering future cooling and possible ice ages.

Ridgwell stressed urgent climate action, as human CO₂ emissions heat Earth faster than slow natural cooling, requiring immediate emission reductions to prevent catastrophe.