Pinning down the size of this effect – one of three major feedbacks in the global climate process – is important in understanding how much the global climate could warm in response to rising concentrations of greenhouse gases that human activities have pumped into the atmosphere, explains Mark Serreze, director of the National Snow and Ice Data Center in Boulder, Colo.
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.