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 (JGU) and Bochum following the analysis of oxygen isotopes in dental enamel of dinosaur teeth. The scientists used a new innovative technique to detect the relative ratios of all three natural oxygen isotopes, opening up new prospects for geological climate research. In addition, the isotope data shows that the primary production of all plants at the time was double that of the current yield.