This video segment adapted from NOVA scienceNOW profiles glaciologist Lonnie Thompson and his research into tropical mountain glaciers as a way to understand climate history. Beginning in the 1970s, Thompson recognized that tropical ice cores contain information relating to tropical climate phenomena, including El Niño events and monsoons. These phenomena are not archived in ice from polar regions. Thompson explains that his archive of ice cores is full of clues that, taken together with records collected from around the world, can help scientists create a timeline that tells Earth's "climate story."