Over the past decade or more, other teams have tracked the decline of snow and ice cover in the Northern Hemisphere, the northward march at high latitudes of vegetation typically found farther south, and other changes that suggest the feedback has kicked in.
This latest study says "yes, the feedback is working as we suspected it would be," says Dr. Serreze, who was not part of the team conducting the research. "But it also argues that maybe the feedback is stronger than we thought it would be."
That last point will likely be challenged, he adds, as part of the scientific process.
"Putting numbers to these feedbacks is a tough thing to do," he says. Still, "this is an important paper. I see this as a significant advance in climate science."
As one of the world's two deep-freeze thermostats, Antarctica is still chiller-in-chief. But because the Arctic is warmer than its southern counterpart, small changes in temperatures at the top of the world have a relatively larger effect on ice and snow cover, researchers say.
Mark Flanner, a climate researcher at the University of Michigan who led the team, says the goal of the new study was to provide a reality check on global climate models' representations of the impact that declining snow and ice has on the Earth's so-called radiation budget. The radiation budget is a kind of bookkeeping process that tries to account for all the sunlight Earth receives and either reflects or converts into heat.
Using satellite measurements as well as field measurements of the extent of snow and ice cover, the team teased out details of seasonal patterns in the amount of solar radiation the Northern Hemisphere's snow and ice reflect.