Rock weathering may be more complicated than Earth’s “thermostat” model suggests. Research discussed by Bob Hilton and skeptical views from Rugenstein point to a feedback loop where weathering of organic carbon can amplify warming triggered by volcanic CO2—whi
For a planet that relies on chemistry to keep itself in check, Earth’s climate “thermostat” has always sounded like a tidy system: when CO2 rises, silicate minerals weather and pull that carbon back down, helping prevent runaway warming.
But Hilton’s work nudges that comfort. “Lo and behold, we end up finding that we can explain this apparent discrepancy,” Hilton said. The core idea is stark in its implications: weathering of organic carbon amplified the warming initiated by volcanic CO2. In other words, the planet warmed more than it would have if only the volcanic CO2 had been emitted.
That isn’t just a detail for geochemists to argue over—it goes to the heart of how Earth responds to big pushes of CO2 from deep time. In the lab, the preparation looks simple enough: acid-digested rock samples were being prepared for analysis using column chromatography. Those samples. associated with the research being discussed. are part of the effort to understand what carbon is released and what pathways drive the planet’s response.
Still, the argument is far from settled. Rugenstein is skeptical of how much CO2 the weathering itself would actually release. “Their estimates of the total amount of carbon delivered by this feedback are enormous,” Rugenstein said. “I find it difficult to believe that these carbon fluxes are going to be as big as they think they are.”.
So where does that leave Earth’s “thermostat”? The question lands hard because the widely accepted view is that weathering of rock—specifically silicate minerals—reduces atmospheric CO2 and prevents runaway global warming.
Hilton doesn’t discard that foundation. “Silicate weathering is still playing a major role. We’re not challenging that,” he said. But the new picture, as Hilton and Rugenstein describe it, shifts the pressure inside the system: “It means that silicate weathering has to work harder.”
Rugenstein makes the tradeoff even clearer: “While [organic carbon weathering] could be a big positive feedback. in the end. that tells you that the silicate weathering feedback has to be even stronger. ” he said. The climate problem then becomes a competition. How much organic carbon-rich sediment is exposed on land determines the strength of the push from organic carbon weathering.
There is also a limit built into the chemistry of supply. “At some point. you’re going to run out of organic carbon to oxidize. and that’s then going to place a hard limit on the strength of this feedback. ” Rugenstein said. Against that shrinking fuel, the supply for silicate weathering looks far less constrained. “In contrast, the volume of silicate minerals available to weather and draw down CO2 is much greater,” Rugenstein said. “That’s why that feedback ultimately is a stronger one—we have a much bigger buffer to play with.”.
Put together. the back-and-forth between these processes turns the planet’s response to CO2 into something less automatic than the thermostat metaphor suggests. If organic carbon weathering can temporarily add CO2 to the atmosphere during major warming events. the “cooling” machinery driven by silicate weathering has to compensate more aggressively.
The implications for humans are described as long-term, small, and uncertain. The study suggests the feedback is likely to apply to other climate warming events. “including our own today.” Hilton foresees organic carbon weathering adding CO2 to the atmosphere over the next few centuries. with a small amplifying effect to human-caused warming. “It’s not disaster stations,” Hilton said. “But it is an amount of carbon that could be released at a rate more than it is right now. and that does eat into our carbon budget.”.
In the end. the tension in this research isn’t just whether organic carbon weathering happens—it’s how big it really is. and how the balance between two competing weathering pathways plays out under pressure. The lab work points to a mechanism; the debate over scale points to uncertainty; and the stakes come down to what that means for the carbon budget we’re trying to protect.
rock weathering organic carbon weathering silicate weathering volcanic CO2 climate thermostat column chromatography carbon budget positive feedback global warming