Earth Syst. Dynam. Discuss., 2, 211-240, 2011
www.earth-syst-dynam-discuss.net/2/211/2011/
doi:10.5194/esdd-2-211-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Earth System Dynamics (ESD). A final paper in ESD is not foreseen.
Geologic constraints on earth system sensitivity to CO2 during the Cretaceous and early Paleogene
D. L. Royer1, M. Pagani2, and D. J. Beerling3
1Department of Earth and Environmental Sciences and College of the Environment, Wesleyan University, Middletown, Connecticut, 06459, USA
2Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA
3Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK

Abstract. Earth system sensitivity (ESS) is the long-term (>103 yr) equilibrium temperature response to doubled CO2. ESS has climate policy implications because global temperatures are not expected to decline appreciably for at least 103 yr, even if anthropogenic greenhouse-gas emissions drop to zero. We report quantitative ESS estimates of 3 °C or higher for much of the Cretaceous and early Paleogene based on paleo-reconstructions of CO2 and temperature. These estimates are generally higher than climate sensitivities simulated from global climate models for the same ancient periods (~3 °C). We conclude that climate models do not capture the full suite of positive climate feedbacks during greenhouse worlds. These absent feedbacks are probably related to clouds, trace greenhouse gases, seasonal snow cover, and/or vegetation, especially in polar regions. Continued warming in the coming decades as anthropogenic greenhouse gases accumulate in the atmosphere ensures that characterizing and quantifying these positive climate feedbacks will become a scientific challenge of increasing priority.

Citation: Royer, D. L., Pagani, M., and Beerling, D. J.: Geologic constraints on earth system sensitivity to CO2 during the Cretaceous and early Paleogene, Earth Syst. Dynam. Discuss., 2, 211-240, doi:10.5194/esdd-2-211-2011, 2011.
 
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