Sept. 24, 2007 -- As more than 150 nations participate in today's United Nations conference on global warming, scientists have confirmed that a clear passage has opened across the Arctic Sea for the first time in recorded history.
Last week, U.S. scientists reported that warmer temperatures have shrunk the Arctic ice cap to its smallest size in history — with the great melting uncovering vast stretches of the Arctic Ocean and opening up a northwest shipping lane mariners have been dreaming about since Christopher Columbus discovered America.
Researchers fear sea levels could be rising much faster than first thought with some scientists predicting an ice-free Arctic by the summer of 2100.
Watch a video of Bill Blakemore's tour of the ice wonders of Greenland here.
Greenland Becomes More Green, Less White
Greenland has become an international symbol of rapid glacial melting. Icebergs once the size of skyscrapers are increasingly shedding from the country's ice sheet.
Jakobshavn glacier, Greenland's "galloping glacier," has become infamous for its rapid shrinking -- it has retreated nine miles in only five years.
More scientists are beginning to believe that glacial melt may leave cities including Boston, Seattle and Galveston, Texas, submerged due to rising sea levels, devastating hundreds of millions of people on the world's coastlines by mid-century.
The sea level increase is an effect of global warming that is affecting all seven continents.
The global ice-melting problem has increased so greatly that in one day a glacier can dump out into the ocean as much water as New York City uses annually.
In 2006, researchers confirmed that Greenland's glaciers are melting at double the rate of the what they were five years ago. Scientists report that the fjord and Jakobshavn glacier are now pouring out some 20 million tons of frozen water into the ocean every day.