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Past extreme warming events linked to massive carbon release from thawing permafrost


A Corrigendum to this article was published on 22 August 2012


Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend1. The first and largest of these events, the Palaeocene–Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification2 and an increase in global temperature of about 5 °C within a few thousand years3. Although various explanations for the PETM have been proposed4,5,6, a satisfactory model that accounts for the source, magnitude and timing of carbon release at the PETM and successive hyperthermals remains elusive. Here we use a new astronomically calibrated cyclostratigraphic record from central Italy7 to show that the Early Eocene hyperthermals occurred during orbits with a combination of high eccentricity and high obliquity. Corresponding climate–ecosystem–soil simulations accounting for rising concentrations of background greenhouse gases8 and orbital forcing show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of petagrams (1015 grams) of carbon to the atmosphere–ocean system, once a long-term warming threshold had been reached just before the PETM. Replenishment of permafrost soil carbon stocks following peak warming probably contributed to the rapid recovery from each event9, while providing a sensitive carbon reservoir for the next hyperthermal10. As background temperatures continued to rise following the PETM, the areal extent of permafrost steadily declined, resulting in an incrementally smaller available carbon pool and smaller hyperthermals at each successive orbital forcing maximum. A mechanism linking Earth’s orbital properties with release of soil carbon from permafrost provides a unifying model accounting for the salient features of the hyperthermals.

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Figure 1: Orbital phasing of Early Eocene hyperthermals.
Figure 2: Climate-biome and permafrost simulations in response to increasing background GHG levels and orbital forcing.


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This work was funded by the US National Science Foundation under award ATM-0513402/0513421 to R.M.D. and D.P., and EAR-0628358 to M.P. D.J.B. acknowledges support from a Royal Society-Wolfson Research Merit Award.

Author information




R.M.D. conceived the permafrost–hyperthermal model with input from S.G., M.P., D.T., D.P. and D.J.B. S.G. developed the cyclostratigraphic framework and performed MTM and SSA analyses. R.M.D., D.T. and D.P. designed the numerical modelling scheme and D.T. analysed the GCM results. D.J.B. and R.M.D. developed the changing GHG concentration scenarios for the model simulations. K.S. and T.Z. refined the carbon calculations. R.M.D. was the primary author and all co-authors contributed to the writing and response to reviewers.

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Correspondence to Robert M. DeConto.

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The authors declare no competing financial interests.

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Supplementary Information

This file contains Supplementary Methods, Supplementary Figures 1-13, Supplementary Table 1 and additional references. This file was replaced on 22 August 2012, as Supplementary Table 1 contained incorrect data – see the corrigendum 11424 linked to the this paper for details. (PDF 4161 kb)

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DeConto, R., Galeotti, S., Pagani, M. et al. Past extreme warming events linked to massive carbon release from thawing permafrost. Nature 484, 87–91 (2012).

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