U.S. scientist Charles Keeling measures carbon dioxide in the atmosphere

U.S. scientist Charles Keeling sets up stations to measure carbon dioxide concentrations in the atmosphere at the South Pole and at Mauna Loa, Hawaii. The measurements have shown a steady rise.

Roger Revelle, the Director of Scripps Institution of Oceanography, based at La Jolla, California, persuaded Dr. Keeling to continue his work there. Revelle was also one of the founders of the International Geophysical Year (IGY) in 1957-58 and Keeling received IGY funding to establish a base on Mauna Loa in Hawaii, two miles (3,000 m) above sea level.

Dr. Keeling started collecting carbon dioxide samples at the base in 1958. By 1960, he had established that there are strong seasonal variations in carbon dioxide levels with peak levels reached in the late northern hemisphere winter. A reduction in carbon dioxide followed during spring and early summer each year as plant growth increased in the land-rich northern hemisphere. In 1961, Keeling produced data showing that carbon dioxide levels were rising steadily in what became known as the "Keeling Curve".

In the early 1960s, the National Science Foundation stopped supporting his research, calling the outcome "routine". Despite this lack of interest, the Foundation used Keeling's research in its warning in 1963 of a greenhouse effect. A 1965 report from President Johnson's Science Advisory Committee similarly warned of the dangers of the greenhouse effect.

The data collection started by Dr. Keeling and continued at Mauna Loa is the longest continuous record of atmospheric carbon dioxide in the world and is considered a reliable indicator of the global trend in the mid-level troposphere. Dr Keeling's research shows that the atmospheric concentration of carbon dioxide has grown from 315 parts per million (ppm) in 1958 to 380 (ppm) in 2005 with increases correlated to fossil fuel emissions. There has also been an increase in seasonal variation in samples from the late 20th century and early 21st century.