Scientists have long known that rock weathering acts as a natural thermostat, slowly pulling CO2 out of the atmosphere over millions of years. A new study in Nature Communications complicates that picture — and the implications for modern climate change are worth paying attention to.
Researchers from the University of Oxford, led by Madeleine Stow, looked at a warming event from 183 million years ago called the Toarcian Ocean Anoxic Event. Triggered by massive volcanic eruptions across what’s now South Africa and Antarctica, it caused 6 to 7 degrees Celsius of global warming and wiped out coral reefs and marine species.
Here’s the twist: while rock weathering removes CO2, eroding organic carbon from sediments releases it. The team found that during the Toarcian event, this organic carbon weathering actually amplified the warming — creating a feedback loop that made a bad situation worse.
They used a clever technique involving rhenium isotopes in seabed sediments to measure how much organic carbon was oxidized during the event. The isotope ratio acts like a chemical fingerprint of ancient carbon cycling.
Does this mean the same thing is happening now? Maybe. As modern temperatures rise, more organic carbon in eroding soils and sediments could be releasing additional CO2 — adding to the warming we’re already causing. But the researchers caution that the geological past doesn’t map neatly onto the present.
