New Paleozoic atmospheric pCO2 records based on C3 land plants

Atmospheric CO₂ is the most important long-lived greenhouse gas that regulates the Earth's climate. To date, there are only ~100 reconstructed pCO₂ data from proxies based on stomata, paleosol carbonate and phytane across in the Paleozoic. The scarcity of Paleozoic pCO₂ proxy data limits our understanding of the role of CO₂in major climatic and biotic events. Here, we utilize new compilations (n> 700) of the stable carbon isotope records of C₃land plants (δ¹³C_plants) in its various forms (well-preserved leaf cuticles, pollen grains, bulk organic matter within the sediments, kerogen, charcoal, and individual organic compounds) in Paleozoic sediments (420 to 251 Ma), as well as marine carbonate (δ¹³C_carb) to reconstruct a new high-resolution atmospheric pCO₂. We find that the Paleozoic pCO₂ ranges from ~150 to >6000 ppm with high values (>1000 ppm) corresponding to three major intervals (the Early Devonian, the Late Devonian, and the Lopingian), whereas pCO₂ values less than 300 ppm are associated with the late Paleozoic Ice Age. These variations in Paleozoic atmospheric pCO₂ are mainly controlled by the imbalance between volcanic degassing and silicate weathering. The silicate weathering feedback strength during the evolution of C₃land plant is evaluated using the new pCO₂ data.