Since the 1960s scientists have thought melting Arctic sea ice amplifies global warming by decreasing Arctic albedo—that's the percentage of solar radiation that a surface reflects back into space. Arctic albedo has declined 4 percent since 1979, twice as fast as previous models suggested. As ice melts, less sunlight is reflected back into space, which exposes more dark water, which absorbs more sunlight, which melts more ice. In addition, scientists are studying how deposits of black carbon, a component of soot, are darkening the reflective surfaces and may also be contributing to lost albedo. The albedo loss is described in an article in the Proceedings of the National Academy of Science by Kristina Pistone, et al. and in a Live Science report by Laura Poppick.