Keeling developed the first instrument that could measure carbon dioxide in atmospheric samples with consistently reliable accuracy, and in 1958 began collecting carbon dioxide samples from a base he established at Mauna Loa, Hawaii, two miles (3000 m) above sea level. From this data he established what became known as the Keeling Curve, a graph of the accumulation of carbon dioxide in the Earth's atmosphere. In this transcription of Keeling's text from a symposium on atmospheric polution in April 25, 1969 Keeling presented irrefutable observational data documenting the progressive rise of CO2 in Earth's atmosphere from the mid-1800s to 1970. The first publication of the Keeling Curve appears on p. 14, figure 7.
Keeling began his paper as follows: "I originally proposed as the title of this talk: 'If carbon dioxide from fossil fuels is changing man's environment, what will we do about it?' It was my meaning to inquire into what might be the response of scientists, philosophers, and decision-makers if specialists assert that accelerated use of fossil fuels may be harmful. I was requested to modify the title to read 'Is Co2 from fossil fuel changing man's environment?' either because a shorter title might suggest a shorter more acceptable talk, or because I obviously cannot answer the first question. I cannot answer the second question either; but I will not give you my views on both questions." He ended his paper with, "If the human race survives into the twenty-first century with the vast population increase that now seems inevitable, the people living then, along with their other troubles, may also face the threat of climatic change brought about by an uncontrolled increase in atmospheric CO2 from fossil fuels."
Digital facsimile from nsdl.library.cornell.edu at this link.
(Thanks to Juan Weiss for this reference and its interpretation.)