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Greenhouse of the dinosaurs

Press release issued: 12 October 2001

Greenhouse of the dinosaurs

New evidence has come to light that the world of the dinosaurs and early mammals was heated by the greenhouse effect. An international team led by Dr Paul Pearson at the University of Bristol has found evidence that tropical ocean temperatures were over 30 degrees centigrade in the Late Cretaceous and Eocene periods. Today, open ocean temperatures rarely reach this level.

The study, reported in Nature on October 4, overturns an earlier theory that a different arrangement of ocean currents warmed the poles at the same time as cooling the tropics. Instead, it seems the world as a whole was hotter. This result fits with earlier findings by the Bristol researchers that carbon dioxide levels were once much higher than today and would have trapped more heat at the Earth's surface.

Temperatures were measured by analysing the chemical composition of fossil plankton shells extracted from mud deposited on the ancient seabed. The scientists collected samples from remote locations in Tanzania, Mexico and elsewhere.

"Previous workers have applied the same oxygen isotope technique and reported relatively cool temperatures," said Dr Pearson.

"But they were misled by the poor preservation of their fossils. Only exquisitely preserved samples reveal the real temperature, which was often surprisingly hot."

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Copyright: 2001 The University of Bristol, UK
Updated: Friday, 12-Oct-2001 13:35:47 BST

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