Little did Dave Keeling know then that he had laid the basis for his remarkable career investigating the global behaviour of atmospheric CO₂.

In 1956 Dave Keeling's measurements came to the attention of Harry Wexler at the US weather bureau and Roger Revelle at Scripps Institution of Oceanography. To both these organizations he proposed a global program based on infrared gas analyzers to measure the atmospheric CO₂ concentration at several remote locations around the world including the South Pole station and at Mauna Loa in Hawaii. The proposal was supported by and became one of the features of the International Geophysical Year (IGY) beginning in July 1957 and ending in December 1958.

Using IGY funds from the Weather Bureau, Dave Keeling bought four infrared gas analyzers from the Applied Physics Corporation. One of these was installed at Mauna Loa in March 1958 and on the first day of operation recorded an atmospheric CO₂ concentration of 313 ppm.

To Dave Keeling's surprise, however, the CO₂ concentration at Mauna Loa had risen by 1ppm in April 1958 to a maximum in May when it began to decline reaching a minimum in October. After this the concentration increased again and repeated the same seasonal pattern in 1959. In Dave Keeling's words "We were witnessing for the first time nature's withdrawing CO₂ from the air for plant growth during summer and returning it each succeeding winter" In 1959 the average concentration had increased and increased still further in 1960 as shown in the graph.

Dave Keeling's analytical skills and dedication had paid off with two dramatic discoveries: firstly, of the natural seasonal "breathing" of the planet and secondly, of the rise in atmospheric CO₂ due to the combustion of fossil fuels by industry and to land use changes. Published in the 1960 Tellus Article, "The concentration and isotopic abundances of carbon dioxide in the atmosphere" (pdf), these significant findings marked the beginning of the now world famous "Keeling Curve" which extends for almost 5 decades and represents one of the most important geophysical records ever made.