Portrait of Professor Charles D Keeling (b.1928), the US oceanographer and climate scientist. Keeling was the first to confirm, by measurement, the gradual accumulation of carbon dioxide (CO2) in the Earth's atmosphere. The data set that shows this change is known as the "Keeling Curve". Previously, it had been thought that the excess CO2 would be absorbed by the oceans. This worldwide increase in CO2 concentration is thought to cause 'global warming', a rise in the Earth's mean temperature by the 'Greenhouse Effect'. This photograph was taken in March 1992 in Keeling's laboratory at the Scripps Institution of Oceanography, San Diego, USA.