Portrait of Professor Charles D. Keeling (April 20, 1928 - June 20, 2005), American oceanographer and climate scientist. Keeling was the first to confirm, by measurement, the gradual accumulation of carbon dioxide (CO2) in the Earth's atmosphere, thus alerting the world to the anthropogenic contribution to the greenhouse effect and global warming. The data set that shows this change in CO2 levels is known as the "Keeling Curve." Previously, it had been thought that the excess CO2 would be absorbed by the oceans. This photograph was taken in March 1992 in Keeling's laboratory at the Scripps Institution of Oceanography, San Diego, California.