Methane outbursts from seafloor deposits are unlikely to have been the sole cause of an extreme episode of global warming around the time of the Palaeocene–Eocene Thermal Maximum some 55 million years ago.
Karla Panchuk of Pennsylvania State University, University Park, and her colleagues configured an Earth-system model with early Eocene geography to assess the involvement of potential carbon sources with distinct isotopic signatures.
Methane could have produced an observed negative carbon-13 isotope bump, but couldn't have caused the calcium carbonate dissolution in the oceans estimated from sediment layers. The team suggests that a carbon pulse of at least 6,800 gigatonnes — three times what methane could produce — is needed to reconcile the observations.
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Palaeoclimate: Methane didn't act alone. Nature 453, 260 (2008). https://doi.org/10.1038/453260c
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DOI: https://doi.org/10.1038/453260c
