A boat skims through the melting ice in the Ilulissat fiord, on the western coast of Greenland, in 2008. The glacier is the most active in the Northern Hemisphere, producing 10 percent of Greenland's icebergs, or some 20 million tons of ice per day. But experts say the glacier is in bad shape because of climate change.
Steen Ulrik Johannessen/AFP/Getty Images
A general view of the Aletsch Glacier on April 21, 2007, near Brig, Switzerland, the largest glacier in the Alps. Unseasonably warm weather with temperatures up to 77 degrees Fahrenheit across Switzerland let snow melt, even at Alpine altitudes.
Johannes Simon/Getty Images
This Sept. 16 image released by NASA shows the amount of summer sea ice in the Arctic, at center in white, and the 1979 to 2000 average extent for the day shown, with the yellow line. Scientists say sea ice in the Arctic shrank to an all-time low of 1.32 million square miles on Sept. 16, smashing old records for the critical climate indicator.
In this combination of photos, American physicist David Wineland (left) speaks at a news conference in Boulder, Colo., and French physicist Serge Haroche speaks to the media in Paris after they were named winners of the 2012 Nobel Prize in physics.
Ed Andrieski, Michel Euler/AP
Researchers say that springtime snow is melting in the Arctic even faster than Arctic ice. That means less sunlight is reflected off the surface. Bare land absorbs more solar energy, which can contribute to rising temperatures on Earth. Above, a musher races along the Iditarod in the Alaskan tundra in 2007.
A man stands in a fountain in Washington Square Park on July 18, in New York City. Temperatures were expected in the upper 90's during another heat wave in the city.
Mario Tama/Getty Images