The decline in snow and ice surface cover in the Northern Hemisphere between 1979 and 2008 has led to a reduction in the cooling associated with these bright surface covers reflecting sunlight back to space, according to a study published online this week in Nature Geoscience. The contributions from snow on land and sea ice to this decline in cooling were roughly equal.

Mark Flanner and colleagues used remote sensing and field observations to assess the influence of snow and ice in the Northern Hemisphere on the balance at the top of the atmosphere between incoming radiation from the Sun and outgoing radiation from the Earth back into space. The resulting warming feedback from the decline in highly reflecting regions covered by snow and ice is substantially larger than comparable assessments from climate models.