In this Second Annual Keeling Lecture from Scripps Institution of Oceanography at UC San Diego, Lonnie G. Thompson, distinguished professor of earth sciences at Ohio State University and recipient of both the National Medal of Science and the Tyler Prize for Environmental Achievement, provides insight into the convincing evidence of climate change provided by glaciers and polar ice-caps, and the implications that inaction in the face of this rapid change will have on societies on a global scale. (#20913)