Polar ice sheets are sensitive indicators of current climate and also preserve evidence of past climate conditions. Scientists studying Earth's climate history core thousands of meters deep into ancient ice to retrieve gas bubbles trapped in ice sheets. Ice cores help reconstruct climatic conditions from hundreds of thousands of years ago. Join Dr. Jeff Severinghaus as he explains how gas bubbles are trapped, how they provide detailed chemical clues to the past and how they are helping to shape future climate scenarios. (#13815)