Thursday, December 29, 2005

Dinosaurs cooked by global warming

Fresh fossil leaves analysis shows there was a sudden and dramatic rise in carbon dioxide in the Earth's atmosphere 65 million years ago. It's what killed the dinosaurs, say researchers. C02 was injected into the atmosphere in vast amounts by the impact of an asteroid striking CO2 rich limestone rock and the ensuing blistering heatwave that followed raised global temperatures by as much as 7.5 Celsius making it impossible for the ancient reptiles and countless other lifeforms to survive. CO2 levels were estimsted to be four to five times higher for 10,000 years after the impact

The researchers from the University of Sheffield, UK, and Southwest Texas State University and Pennsylvania State University, US, studied the fossilised pores of leaf of gingkoes and ferns that grew around the time of the dinosaurs' demise. The number of carbon dioxide-absorbing pores in the fossils reflects the amount of carbon dioxide in the air: the fewer the pores, the more carbon dioxide.

By using computer simulations and doing real experiments on plants, the scientists can show there was a sudden, five-fold increase in CO2 at the end of the Cretaceous.

This can only be explained, they believe, by the sudden vaporisation of between 6,400 and 13,000 billion tonnes of carbon - a substantial component of the limestone rocks that lined the shallow sea that existed at Chicxulub 65 million years ago.

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