The sources of interannual variability in planetary albedo were identified through regression analysis. In a global sense, more than 90% of the variability can be linearly related to surface albedo fluctuations and cloud fluctuations. In snow and ice-covered regions, the surface accounts for more than 50% of the variability, due to large surface albedo variability associated with snow and ice fluctuations. Over snow and ice-free areas, however, the cloud contribution overwhelms the surface contribution during all seasons. The importance of surface fluctuations in generating planetary albedo variability in the cryosphere zones implies any change in surface albedo will significantly modify solar radiation. The retreat of northern hemisphere snow cover and Arctic sea ice have been recently observed by satellites. This is associated with a large-scale warming in the northern hemisphere, and the decrease in surface albedo associated with it may result in more warming by increasing the amount of the solar radiation absorbed by the surface-atmosphere system. This supports the idea that surface albedo feedback amplifies the initial perturbation of the climate system and thus acts as a positive feedback in climate change.
Supplementary URL: