Courtesy of Dr. Steven C. Clemens, Geology Department Brown University

This represents the atmospheric carbon dioxide in parts per million by volume from the early 60's to mid 90's.

The seasonal CO2 record Keeling, C.D., and T.P. Whorf. 1998. Atmospheric CO2 records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A.