Everybody’s talking about methane…

It actually started 16 years ago when Gerald R. Dickens and his colleagues published their paper on oceanic methane hydrate dissociation and the Palaeocene-Eocene Thermal Maximum (PETM). Their hypothesis that release of methane gas stored in oceanic sediments was the cause of the negative carbon-isotope excursion at the end of the Palaeocene and hence the trigger of the global warming recorded at the PETM, got scientists working on climate change and mass extinction around the world to suddenly set their old theories aside and focus on this new one.

Burning natural gas which consists of methane to 80% (Left) and a methane molecule (right).

Today, it seems, everybody’s talking about methane, CH4, this very potent greenhouse gas. From methane stored in clathrates underneath the ocean floor, or frozen by permafrost in the circum- Arctic or Antarctic tundra ( e.g. De Conti et al. 2012), to cattle or even farting dinosaurs during the Mesozoic, it poses a severe threat to life on Earth if released in large quantities. Hence, many scientific papers (see e.g. Payne et al. 2004 and references therein, and Ruhl et al. 2011) have argued that methane must have played a role in the end-Permian and end-Triassic mass extinctions, which are both associated with negative carbon-isotope excursions indicating input of light carbon (carbondioxide or methane from volcanoes or other sources).

My colleagues and I have studied the Triassic-Jurassic (T/J) boundary of the Denmark and compared that to a well known T/J boundary succession in England. In these two areas the carbon-isotope records exhibit three negative excursions separated by two intervals with more positive carbon-isotope values. What we have found is that the most profound floral changes on land and amongst organisms in the epicontinental sea that once covered these two areas, commenced within the first positive interval, i.e. between the first negative carbon-isotope peak and the second (most prominent) one. At the same level as the second negative carbon-isotope peak, which has been attributed to methane injection by e.g. Ruhl et al. 2011, the flora does not seem to be affected but is instead recovering, while organisms in the ocean continue to suffer. Hence our study suggests a more complex scenario…

You can read our paper (or just the abstract) or the press release.


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