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 CO 2 , so the planet warmed more than it would have if only the volcanic CO 2 had been emitted. 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 CO 2 released 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 CO 2 , where does this leave our widely accepted understanding of Earth’s climate “thermostat,” where weathering of rock (specifically weathering of silicate minerals) reduces atmospheric CO 2 , 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. …