Black soot may contribute to melting glaciers and other ice on the planet and eventually a warmer Earth. Traveling potentially thousands of miles from its sources on air currents, this pollution eventually settles out of the air, onto land and into the oceans. On ice and snow, it darkens normally bright surfaces. Just as a white shirt keeps a person cooler in the summer than a black shirt, the vast stretches of polar ice covering much of the planet's top and bottom reflect large amounts of solar radiation falling on the planet's surface, helping regulate Earth's temperature. Soot lowers this albedo, or reflectivity, and the ice retains more heat, leading to increased melting. Soot-darkened ice retains more light, contributing to the process. As light is absorbed, the environment is heated, thus intensifying a feedback loop: a warmer planet yields more ice melting and thus an even warmer planet. Note: This is the standard definition version MPEG of the Ice Albedo (soot case) Animation. Animator: Susan Twardy (HTSI). Scientist: James Hansen (NASA/GSFC GISS). Writer: Kathryn A. Stofer.