D. O. Breecker et al., PNAS 107 (2010), Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100

Proceedings of the National Academy of Sciences, 107(2) (2010) 576-580; doi: 10.1073/pnas.0902323106

Atmospheric CO₂ concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100

1. D. O. Breecker¹,², 
2. Z. D. Sharp and 
3. L. D. McFadden

+Author Affiliations

1. MSC03-2040, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131

1. Edited by Thure E. Cerling, University of Utah, Salt Lake City, UT, and approved October 22, 2009 (received for review March 5, 2009)

Abstract

Quantifying atmospheric CO₂ concentrations ([CO₂]_atm) during Earth’s ancient greenhouse episodes is essential for accurately predicting the response of future climate to elevated CO₂ levels. Empirical estimates of [CO₂]_atm during Paleozoic and Mesozoic greenhouse climates are based primarily on the carbon isotope composition of calcium carbonate in fossil soils. We report that greenhouse [CO₂]_atm have been significantly overestimated because previously assumed soil CO₂ concentrations during carbonate formation are too high. More accurate [CO₂]_atm, resulting from better constraints on soil CO₂, indicate that large (1,000s of ppmV) fluctuations in [CO₂]_atm did not characterize ancient climates and that past greenhouse climates were accompanied by concentrations similar to those projected for A.D. 2100.

Link:  http://www.pnas.org/content/107/2/576.abstract