One of the most pressing predictions that must be made in climate science concerns the rate of polar melting. As they warm—and the Arctic and Antarctic regions have heated up faster than most of the rest of the planet—the glaciers of Greenland and Antarctica are melting and flowing into the ocean, which then raises sea levels. The ability to accurately project just how rapidly polar ice will melt as temperatures rise would enable policymakers to prepare coastal cities like New York and Shanghai for rising seas—and maybe, it might just scare them enough to actually take steps to combat climate change. The problem is that ice is a tricky thing, and modeling melt rates remains an inexact science—so much so that in the most recent assessment by the Intergovernmental Panel on Climate Change (IPCC), scientists actually chose not to include potential accelerations in polar melt when calculating sea level rise over the next century, which they estimated at just 7 to 23 inches by 2100. Not exactly scary.
But here’s something that really is frightening. A new study presented by the International Arctic Monitoring and Assessment Program has found that feedback loops are already accelerating warming in the far North, which will rapidly increase the rate of ice melt. As a result, the panel now estimates that sea levels could rise by as much as 5.2 ft. by the end of the century. From the report:
The greatest increase in surface air temperature has happened in autumn, in regions where sea ice has disappeared by the end of summer. This suggests that the sea is absorbing more of the sun’s energy during the summer because of the loss of ice cover. The extra energy is being released as heat in autumn, further warming the Arctic lower atmosphere. Over land, the number of days with snow cover has changed mostly in spring. Early snow melt is accelerated by earlier and stronger warming of land surfaces that are no longer snow-covered.
These processes are termed “feedbacks.” Snow feedbacks are well known. The sea-ice feedback has been anticipated by climate scientists, but clear evidence for it has only been observed in the Arctic in the past five years.
Here’s how the feedback works: ice, being white, tends to reflect sunlight, thus cooling the lower atmosphere. But as temperatures rise thanks to climate change, and more of that ice melts, sunlight begins striking the dark open ocean, which absorbs the light rather than reflects it. That increases the rate of warming in the lower atmosphere, which leads to more ice melting, which exposes more ocean and so on and so on. “Parts of Greenland have started to change in ways that are a shock to many of us,” says Gordon Hamilton, an associate research professor at the University of Maine’s Climate Change Institute. “Not only has the extent of melting increased a lot, but the length of the melting season has increased a lot as well.”
The report was released Wednesday at a meeting of nearly 400 scientists in Copenhagen who now have the responsibility to explain what these results mean for the climate. From the Associated Press:
James White, of the University of Colorado at Boulder, told fellow researchers to use simple words and focus on the big picture when describing their research to a wider audience. Focusing too much on details could blur the basic science, he said: “If you put more greenhouse gases in the atmosphere, it will get warmer.”
Prominent U.S. climate scientist Robert Corell said researchers must try to reach out to all parts of society to spread awareness of the global implications of the Arctic melt.
“Stop speaking in code. Rather than ‘anthropogenic,’ you could say ‘human caused,’” Corell said.
Of course, it will ultimately be policymakers who bear the responsibility for actually doing something about the big melt, and they’ll have a chance soon—next week foreign ministers from the U.S., Canada, Norway, Iceland, Denmark, Sweden, Finland and Russia will gather in Greenland for an Arctic Council meeting. The representatives there will talk about the possibility of shipping in the Arctic—a side effect of the big melt—and discuss controlling some short-lived pollutants like black carbon that can be particularly dangerous to the Arctic. The Arctic Council—like most international groups—has little in the way of actual authority, and action on climate change still remains the province of individual nations—not all of which are on board. But “this report is an alarm bell that only adds to the concern,” says Rafe Pomerance, the former deputy assistant secretary of state for environment and development. We can’t say we weren’t warned.