A new study in Nature Communications uses geological evidence from the Jurassic period to examine a critical climate feedback: rock weathering. While it is well known that weathering of silicate rocks slowly removes CO2 from the atmosphere over geological timescales, the erosion of organic carbon contained in sediments can also release CO2. The study, led by the University of Oxford, found that during a volcanic warming event 183 million years ago, the oxidation of organic carbon in eroding rocks amplified the warming. The researchers used rhenium isotopes in ancient seabed sediments as a tracer to measure how much organic carbon was weathered on land during the Toarcian Ocean Anoxic Event. They found that as the climate heated up, organic carbon weathering intensified, creating a positive feedback loop that worsened the warming. This suggests that similar processes could play a role in modern climate change, though the extent of the impact remains uncertain. The study highlights the complexity of natural carbon cycles and the importance of understanding all sources and sinks of CO2.
