Keeling Curve

The Keeling Curve is a graph of the accumulation of carbon dioxide in the Earth's atmosphere based on continuous measurements taken at the Mauna Loa Observatory on the island of Hawaii from 1958 to the present day. The curve is named for the scientist Charles David Keeling, who started the monitoring program and supervised it until his death in 2005. Keeling's measurements showed the first significant evidence of rapidly increasing carbon dioxide (CO2) levels in the atmosphere. According to Naomi Oreskes, Professor of History of Science at Harvard University, the Keeling curve is one of the most important scientific works of the 20th century. Many scientists credit the Keeling curve with first bringing the world's attention to the current increase of in the atmosphere. Prior to the 1950s, measurements of atmospheric concentrations had been taken on an ad hoc basis at a variety of locations. In 1938, engineer and amateur meteorologist Guy Stewart Callendar compared datasets of atmospheric from Kew in 1898–1901, which averaged 274 parts per million by volume (ppmv), and from the eastern United States in 1936–1938, which averaged 310 ppmv, and concluded that concentrations were rising due to anthropogenic emissions. However, Callendar's findings were not widely accepted by the scientific community due to the patchy nature of the measurements. Charles David Keeling, of Scripps Institution of Oceanography at UC San Diego, was the first person to make frequent regular measurements of atmospheric CO2 concentrations in Antarctica, and on Mauna Loa, Hawaii from March 1958 onwards. Keeling had previously tested and employed measurement techniques at locations including Big Sur near Monterey, rain forests of the Olympic Peninsula in Washington state, and high mountain forests in Arizona. He observed strong diurnal behavior of CO2, with excess CO2 at night due to respiration by plants and soils, and afternoon values representative of the "free atmosphere" over the Northern hemisphere.