This aerial photograph, taken Aug. 17, 2007, shows melting glaciers near Ilulissat in Greenland. According to the AFP, Greenland's glaciers are melting at a faster rate than ever, some moving up to 38 yards a day. Michael Kappeler/AFP/Getty Images/Newscom/File
A melting glacier is seen below Mount Edith Cavell in Jasper, Alberta, Canada. Newscom/File
Icebergs calved from Helheim glacier float in Sermilik Fjord on the south-eastern coast of Greenland in this August 19 photo. The southeastern coast of Greenland is the focus for Greenpeace's three-month Arctic Meltdown Tour. The Greenpeace ship Arctic Sunrise is currently supporting a team of independent glaciologists and oceanographers as they seek to explain and bring attention to the accelerating Arctic ice melt.
A combination photograph shows a historic image taken in 1928 (top) of the Upsala Glacier in Patagonia, Argentina, contrasted with a 2004 photograph (bottom) with a similiar view of the Glacier. The pictures illustrate the extent to which climate change has caused the ice to melt away during the past 80 years. Greenpeace/Beltra/Reuters/File
Patterns made by melt rivers and pieces of ice that form the edges of the retreated glacier of Frederikshab Isblink are seen in Frederikshab Isblink, Greenland.
Polar bears are seen floating on ice in the Chukhi Sea in Alaska. Polar bears are vulnerable in much of their current range due to rising temperatures from global warming. Melting of the bears' sea ice habitat makes it more difficult for them to find food. Zuma/Newscom/File
People take pictures of a banner displayed by Greenpeace activists on Gorner Glacier in Zermatt, South Switzerland, on August 25.
Water flows from a melting glacier in the Swiss Alps in Arolla, near Sion, on June 29, 2008. Glaciers and mountain snow are melting earlier in the year than usual, meaning the water has already gone when millions of people need it during the drier summer months. Denis Balibouse/Reuters/File
A melt lake lying on the surface of the Humboldt glacier is pictured on July 31. Nick Cobbing/Greenpeace/Reuters
Ice calves from the north side of the Perito Moreno glacier into Argentine Lake, in the Parque Nacional Los Glaciares, 50 miles west of the city of El Calafate, Argentina, on March 26, 2007. The Perito Moreno glacier is one of only three Patagonian glaciers that are not retreating. Periodically the glacier advances over the L-shaped lake forming a natural dam which separates the two halves of the lake when it reaches the opposite shore. Other glaciers are in the process of retreat due to global warming. Enrique Marcarian/Reuters
Seagulls stand on an iceberg floating in a fjord near Ilulissat, Greenland, on August 16, 2007. Michael Kappeler/AFP/Pool/Newscom/File
Water is seen falling from a glacier in this undated photograph. Newscom/File
Retreating alpine glaciers in a warming world may seem to have an obvious connection. But glaciers respond to environmental changes, well, glacially. At any point, it's hard to tell how much of a glacier's retreat is due to human-triggered factors now and how much is due to natural factors that might have held sway years ago, researchers say.