Satellite data from a mission measuring infrared energy reveal just how differently—and how dramatically—surface temperatures swing across two full years at the poles. In this animation, surface temperatures across the Arctic and Antarctic pulse between cold (dark blue) and milder to warm (lighter blue to red). Surface temperatures, and how they fluctuate, offer a window into Earth’s energy budget, the net flow of energy into and out of the Earth system. Sunlight absorbed by the surface is re-radiated as infrared heat, which bounces between Earth’s surface and atmosphere before escaping to space. Maps courtesy of Chad Greene, NASA/JPL, using data from NASA’s PREFIRE mission.