Global Warming

The Warming of Greenland

. . . All over Greenland and the Arctic, rising temperatures are not simply melting ice; they are changing the very geography of coastlines. Nunataks — “lonely mountains” in Inuit — that were encased in the margins of Greenland’s ice sheet are being freed of their age-old bonds, exposing a new chain of islands, and a new opportunity for Arctic explorers to write their names on the landscape. . . .

. . . The abrupt acceleration of melting in Greenland has taken climate scientists by surprise. Tidewater glaciers, which discharge ice into the oceans as they break up in the process called calving, have doubled and tripled in speed all over Greenland. Ice shelves are breaking up, and summertime “glacial earthquakes” have been detected within the ice sheet.

“The general thinking until very recently was that ice sheets don’t react very quickly to climate,” said Martin Truffer, a glaciologist at the University of Alaska at Fairbanks. “But that thinking is changing right now, because we’re seeing things that people have thought are impossible.” . . .

. . . There is no consensus on how much Greenland’s ice will melt in the near future, Dr. Alley said, and no computer model that can accurately predict the future of the ice sheet. Yet given the acceleration of tidewater-glacier melting, a sea-level rise of a foot or two in the coming decades is entirely possible, he said. That bodes ill for island nations and those who live near the coast. . . .

When Being Green Raises the Heat

. . . Trees don’t just absorb carbon dioxide — they soak up the sun’s heating rays, too. Forests tend to be darker than farms and pastures and therefore tend to absorb more sunlight. This has a warming influence that appears to cancel, on average, the cooling influence of the forest’s carbon storage. This effect is most pronounced in snowy areas — snow on bare ground reflects far more sunlight back to space than does a snowed-in forest — so forests in areas with seasonal snow cover can be strongly warming.

In contrast, tropical forests appear to be doubly valuable to the earth’s climate system. Not only do they store copious amounts of carbon, the roots of tropical trees reach down deep, drawing up water that they evaporate through their leaves. In the atmosphere, this water may form clouds that reflect sunlight back to space, helping to cool the earth. . . .