Albedo

Albedo is a measure of surface reflectivity; in case of the Earth, it says how much sunlight (energy) is reflected back to space – it is a ratio of irradiance reflected to the irradiance received by a surface. Albedo has a cooling effect. It depends mostly on colour of surface (dark coloured surfaces absorb more energy than light coloured surfaces, for example water surface has lower albedo than sea ice).

Scientists based at the University of California, San Diego have analyzed Arctic satellite data from 1979 to 2011, and have found that average Arctic albedo levels have decreased from 52 percent to 48 percent since 1979, because of declining of Arctic sea ice.