A study reveals that weathering of organic carbon can release CO2, amplifying warming, while silicate weathering still draws down CO2 but must work harder. This adds a small amplifying effect to human-caused warming over centuries.
<p>Since the <a href="https://ajsonline.org/article/60278-the-carbonate-silicate-geochemical-cycle-and-its-effect-on-atmospheric-carbon-dioxide-over-the-past-100-million-years">early 1980s</a>, Earth scientists have understood that erosion and weathering of rock slowly removes CO<sub>2</sub> from the atmosphere, regulating Earth’s climate on geological timescales. But <a href="https://www.nature.com/articles/s41586-023-06581-9">recent studies</a> have shown that erosion can also <em>emit</em> CO<sub>2</sub> by oxidizing organic carbon contained in eroding sediments. It hasn’t been clear how this competition between <em>removal</em> by rock weathering and <em>emission</em> by organic carbon weathering ends up affecting Earth’s climate.</p>
<p><a href="https://www.nature.com/articles/s41467-026-71533-6">A new study</a> in the journal Nature Communications uses the geological past to test how these competing effects added up. Doctor Madeleine Stow of the University of Oxford, with colleagues from across the UK and France, examined a volcanically triggered episode of global warming that happened in the early part of the Jurassic period, 183 million years ago, known as the “Toarcian Ocean Anoxic Event.”</p>
<p>They found that eroding organic carbon amplified climate warming at the time, suggesting that the same process may apply to modern climate change. But the extent to which the <a href="https://en.wikipedia.org/wiki/The_Tempest">past is prologue</a> is uncertain.</p><p><a href="https://arstechnica.com/science/2026/06/feedbacks-upon-feedbacks-rock-weathering-and-the-climate/">Read full article</a></p>
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# Feedbacks upon feedbacks: Rock weathering and the climate
Source: [https://arstechnica.com/science/2026/06/feedbacks-upon-feedbacks-rock-weathering-and-the-climate/](https://arstechnica.com/science/2026/06/feedbacks-upon-feedbacks-rock-weathering-and-the-climate/)
“Lo and behold, we end up finding that we can explain this apparent discrepancy,” said Hilton\. In other words, weathering of organic carbon amplified the warming initiated by volcanic CO2, so the planet warmed more than it would have if only the volcanic CO2had been emitted\.
[](https://cdn.arstechnica.net/wp-content/uploads/2026/06/column-chemistry.png)
Acid\-digested rock samples being prepared for analysis using column chromatography\.
Credit: Bob Hilton
Acid\-digested rock samples being prepared for analysis using column chromatography\.Credit: Bob Hilton
But Rugenstein is skeptical of the amount of CO2released by the weathering\. “Their estimates of the total amount of carbon delivered by this feedback are enormous,” said Rugenstein\. “I find it difficult to believe that these carbon fluxes are going to be as big as they think they are\.”
## Where does that leave Earth’s “thermostat”?
If rock weathering*emits*CO2, where does this leave our widely accepted understanding of Earth’s climate “thermostat,” where weathering of rock \(specifically weathering of silicate minerals\)*reduces*atmospheric CO2, preventing runaway global warming?
“Silicate weathering is still playing a major role\. We’re not challenging that,” said Hilton\. “It means that silicate weathering has to work harder\.”
“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,” said Rugenstein\.
The strength of the competition between silicate weathering and organic carbon weathering depends on the amount of organic\-carbon\-rich sediment that’s exposed on land\. “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,” said Rugenstein\.
By contrast, the volume of silicate minerals available to weather and draw down CO2is much greater\. “That’s why that feedback ultimately is a stronger one—we have a much bigger buffer to play with,” said Rugenstein\.
## A small, long\-term uncertain impact for humans
The study suggests that this feedback is likely to apply to other climate warming events, including our own today\. Hilton foresees organic carbon weathering adding CO2to the atmosphere over the next few centuries, with a small amplifying effect to human\-caused warming\. “It’s not disaster stations,” said Hilton, “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\.”
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