Scientists use ice core samples to obtain temperatures of the earth from 400,000 years ago! The third of five lessons instructs pupils to interpret historical climate data to see changes over time. In part I, participants interpret graphs of temperature data from 400,000 years ago; in part II, they analyze data from 10,000 years ago to the present; and in part III, they tie it all together by looking at carbon dioxide concentrations over the past 400,000 years. They finish by comparing their results to climate changes.