Snow darkening effect, Colorado Rockies. This view shows extreme dust deposition from the deserts of the Colorado Plateau onto the Colorado Rockies snowpack in 2009. The viewpoint is from the high point of the Senator Beck Basin in the San Juan Mountains, Colorado, USA. This is an example of the 'snow darkening effect' (SDE), where snow albedo drops (here to about 30 percent) as dust and pollution (light-absorbing aerosols) settle on snow. This more than doubles the absorption of sunlight, leading to increase melting of snow and ice. This is an important effect observed in climate change, leading to increased warming at the Earth's surface.