• DOI:10.1029/2018PA003356
• Corpus ID: 130296033

Multiple Proxy Estimates of Atmospheric CO2 From an Early Paleocene Rainforest

@article{Kowalczyk2018MultiplePE,
  title={Multiple Proxy Estimates of Atmospheric CO2 From an Early Paleocene Rainforest},
  author={Jennifer B. Kowalczyk and Dana L. Royer and Ian M. Miller and Clive W. Anderson and David J. Beerling and Peter J. S. Franks and Michaela Grein and Wilfried Konrad and Anita Roth-Nebelsick and Samuel A. Bowring and Kirk R. Johnson and Jahandar Ramezani},
  journal={Paleoceanography and Paleoclimatology},
  year={2018},
  volume={33},
  pages={1427 - 1438}
}

• J. Kowalczyk, D. Royer, +9 authors J. Ramezani
• Published 1 December 2018
• Environmental Science, Geography, Geology
• Paleoceanography and Paleoclimatology

Proxy estimates of atmospheric CO2 are necessary to reconstruct Earth's climate history. Confidence in paleo‐CO2 estimates can be increased by comparing results from multiple proxies at a single site, but so far this strategy has been implemented only for marine‐based techniques. Here we present CO2 estimates for the well‐studied early Paleocene Castle Rock site in Colorado using four paleobotanical proxies. Median estimates range from 470 to 813 ppm, demonstrating fair correspondence. The synthesis yields a median of 616 ppm (352–1110 ppm at 95% confidence), considerably higher than previous early Paleocene CO2 estimates (~300 ppm). Ash bed geochronology by the high‐precision U‐Pb method places the Castle Rock assemblage at 63.844 ± 0.097 Ma (fully propagated 2σ error). When these results are placed into the broader context of other Cenozoic CO2 estimates from plant‐gas‐exchange approaches and coeval estimates of global mean surface temperature, a pattern emerges of an Earth system sensitivity around 3 °C per CO2 doubling during the Paleocene and Eocene, a time with little land ice, then steepening to >7 °C after the Eocene once land ice was present on Antarctica.