http://news.nationalgeographic.com/2015/12/151223-Arctic-ice-climate-change-global-warming-geoengineering-science/
Santa's Home Is Melting. Will We Ever Bring It Back? By Tim Folger, National Geographic PUBLISHED DECEMBER 23, 2015 In Barrow, Alaska, where the ice broke up early this year and the migration of bearded seals was perturbed, a boy looks out to sea after a failed seal hunt. PHOTOGRAPH BY KATIE ORLINSKY, NATIONAL GEOGRAPHIC Vast and white, easily visible from space, Earth’s Arctic ice cap seems such a permanent fixture—a frozen country at the top of the world—that the idea that it could ever vanish almost defies comprehension. But by the middle of the century most of it will in fact vanish, thanks to our burning of fossil fuels. The North Pole and most of the ocean around it will be free of sea ice in summer for the first time in thousands of years. Will we ever bring the ice back? That’s the question a team of researchers from Columbia University pondered in a presentation last week at the annual meeting of the American Geophysical Union in San Francisco. It’s not as academic as it sounds. Most climate models suggest that our efforts to limit carbon dioxide emissions—starting with the steps agreed to in Paris on December 12—will not be enough to keep Earth from warming more than 2 degrees Celsius. To prevent even worse impacts than the loss of Arctic ice, by late in this century we’ll have to not only shut down emissions, but find a way to clean up massive amounts of carbon dioxide that we’ve already put in the atmosphere. That technology, once developed, would give us the ability to cool the planet—which would put the future of the Arctic in play again. “The basic message,” says oceanographer Stephanie Pfirman of Columbia, “is that we will be able to bring the ice back as long as we bring the [planet’s] temperature down.” Sea ice breaks up in the spring around Baffin Island. As the planet warms, the area north of Baffin and Ellesmere Islands is where ice may endure the longest, into the second half of this century. PHOTOGRAPH BY PAUL NICKLEN, NATIONAL GEOGRAPHIC CREATIVE The question is, will future generations, accustomed to a warmer world and an open Arctic, want to cover it with ice again? A Two-Way Street The Arctic Ocean still freezes over most of its surface every winter, but an increasing area of that ice is so thin that it melts again the following summer. Since the first satellite measurements in 1979, the extent of the ice in September, when it reaches its annual minimum, has shrunk by more than 11 percent per decade. (Read about a research ship that locked itself in the ice last winter.) The ice helps cool the Arctic by reflecting most incoming sunlight back to space— so as it shrinks, the warming and the melting accelerate. That feedback is one reason the Arctic is warming twice as fast as the rest of the globe. (Check out a graphic that explains the loss of ice.) If we pull carbon dioxide out of the atmosphere—if the planet cools in a global sense—the sea ice ought to rebound almost instantly, certainly within a few years. —Robert Newton, Columbia University And because of that feedback, many researchers have assumed that once the perennial sea ice was gone, it wouldn’t come back. “People thought if we got rid of the sea ice and had this big black ocean surface up there absorbing a lot of sunlight, we would never be able to restore the ice cover,” Pfirman says. The warmer sea surface would still freeze in winter, but the ice would never get thick enough to survive the summer. But research cited by Pfirman and her colleagues indicates that Arctic ice could prove to be more resilient, and the loss of ice more reversible, than some models have predicted. Ice-free water absorbs more sunlight, but it also radiates away more heat. There doesn’t seem to be a temperature threshold that’s a point of no return. “Both from the paleontological records and from the [computer] model runs going forward, it does seem that the ice responds very quickly to the surface air temperature,” says Robert Newton, an oceanographer at Columbia and one of Pfirman’s coauthors. “If we pull carbon dioxide out of the atmosphere—if the planet cools in a global sense—the sea ice ought to rebound almost instantly, certainly within a few years.” To Chill or Not To Chill The Paris climate agreement aims to keep global warming below 2 degrees Celsius. But even if the world meets that ambitious goal, the Arctic is still likely to warm by at least 4 degrees. The impact on the region’s people and wildlife, from Inuit hunters to polar bears to ice algae, will be enormous. Many ice-dependent species may not survive in the new, blue Arctic. But researchers don’t expect all the ice to disappear by mid-century. In the "last ice" area off northernmost Canada and Greenland, a small remnant of a few hundred thousand square miles may linger into the 2070s or 2080s. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
