A previously unexploited source of information is now throwing new light on Earth's climate during the age of dinosaurs. Fossilized dinosaur teeth show that concentrations of carbon dioxide in the atmosphere during the Mesozoic Era, i.e., 252 to 66 million years ago, were far higher than they are today. This has been determined by researchers at the universities in Göttingen, Mainz, and Bochum following the analysis of oxygen isotopes in the dental enamel of dinosaur teeth.