In 1966 scientists begin to investigate the historical climate of the earth, as well as historical levels of carbon dioxide, by drilling ice cores in Greenland and in Antarctica. Information trapped in successive layers of ice provides the answers scientists have been seeking. In between the layers are tiny bubbles of atmosphere which are analyzed for specific content of greenhouse gases. Based on this information, paleoclimatologists plot the change in the earth’s climate for the last 400,000 years. The data the ice cores yield is shocking in its specificity. They show cyclical changes in carbon dioxide concentrations in the atmosphere over time. These changes are constant and predictable for most of the historical period studied. At one point in the record, however, the cyclical data come to an abrupt end and a steady, ever increasing level of carbon dioxide concentration builds in a predictable curve. That point of change: 1750 - The beginning of the Industrial Revolution.