The concentration of atmospheric carbon dioxide at Mauna Loa Observatory, Hawaii is reported for eight years (1964–1971) of a long term program to document the effects of the combustion of coal, petroleum, and natural gas on the distribution of CO2 in the atmosphere. The new data, when combined with earlier data, indicate that the annual average CO2 concentration rose 3.4% between 1959 and 1971. The rate of rise, however, has not been steady. In the mid-1960's it declined. Recently it has accelerated. Similar changes in rate have been observed at the South Pole and are evidently a global phenomenon.