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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.
"One hundred and fifty million years ago the carbon dioxide level in the atmosphere was almost ten times what its pre-industrial level was, and more than ten times the 180 ppm that carbon dioxide got down to during the ice ages of the last one million years."