Cooling the Cretaceous greenhouse



The Earth may not have been such a hot greenhouse world during the Jurassic and Cretaceous periods, suggests a study. The research reconciles records of ancient climate and atmospheric carbon dioxide levels with our understanding of how the two are linked.

Marine data indicate a series of cold spells during the time of the dinosaurs, but these did not seem to tally with records of high carbon dioxide levels, which would suggest higher temperatures and ‘greenhouse’ conditions.

David Beerling and colleagues studied the fossilized remains of ancient liverworts and, using the isotopic composition of the fossils, they reconstructed atmospheric CO2 levels for the period between 200 and 60 million years ago. The new records show lower and more variable CO2 concentrations than previous estimates. These results suggest that carbon dioxide was in fact the main driver of long-term climate change during this period, and that the previously unexplained cold periods were tied to natural decreases in atmospheric CO2 concentration.

Author contact:
David Beerling (University of Sheffield, Sheffield, UK)
Tel: +44 114 222 4359; E-mail: D.J.beerling@Sheffield.ac.uk