BBC: The Keeling Curve may be scarcely known outside scientific circles, but the jagged upward slope showing rising carbon dioxide (CO2) levels in the atmosphere has become one of the most famous graphs in science, and a potent symbol of our times.It was 50 years ago that a young American scientist, Charles David Keeling, began tracking very precise measurements of CO2 in the Earth’s atmosphere at two of the world’s last wildernesses - the South Pole and the summit of the Mauna Loa volcano in Hawaii.His remarkable data set sounded some of the first alarm bells over the build-up of the gas in the atmosphere, and has led to the tracking of greenhouse gases worldwide.