In the United States, the first concerns about the ramifications of continued greenhouse gases can be traced to the late 1950s. In 1957, Roger Revelle, Scripps Institute of Oceanography, and Hans Suess, University of Chicago, suggested that the burning of fossil fuels would lead to significant increases in atmospheric carbon dioxide (CO₂) concentrations and that humans were engaged in a “large-scale geophysical experiment” with long-term consequences (Revelle and Suess 1957). Charles David Keeling, Scripps Institute of Oceanography, began taking regular measurement of CO₂ that same year at the Mauna Loa Observatory as part of the International Geo-physical Year in 1957-1958. Keeling’s early data showed a cyclical nature to annual Northern Hemisphere atmospheric composition that corresponds to the terrestrial “respiration” of the planet, as well as an overall upward trend superimposed on top of that cycle (Keeling et al. 1976, 1982).

In 1965, a report of the President’s Science Advisory Committee (PSAC 1965) made clear that there was a sound basis for linking human activities to the increasing CO₂ concentration and that this would lead to global warming (Table 1.2). The panel recommended augmented research efforts and attention to this environmental issue. By the early 1970s, a number of international groups, including several that advised the United Nations, had come to the same conclusion. As recommended, U.S. research efforts were intensified during the 1970s. At the same time, several additional activities concluded that humans were indeed in the process of altering the Earth’s