Last fall, it was just a puddle of melted ice, high on the Belvedere Glacier in the Italian Alps.
Today it is an icy lake — 34 acres and growing. A local mayor at first dubbed it "the Fleeting Lake," but it is not living up to its name. It shows no sign of disappearing on its own.
In the valley below is the resort town of Macugnaga, with some 700 residents. Italian engineers have now embarked on an ambitious project to drain the lake and prevent a potential flood.
Some 200 people are involved — volunteers along with army and civil protection officials. Ten pumps have been helicoptered up to the glacier, 8,200 feet above sea level.
Engineers are now waiting for the weather to clear. When it does, they will begin draining the new lake into a basin lower on the mountain.
In the meantime, video cameras track the water level around the clock and transmit the images to a control room in Macugnaga.
Town officials say there is no immediate danger. Early in the week, 15 people were evacuated, but were allowed to return to their homes a few days later. Other officials worry that the media attention will frighten away tourists.
Glaciers Retreating Worldwide
Climate scientists say it's difficult to pinpoint the reason any particular glacier will start to melt because conditions vary from place to place.
"However, this particular glacier, the fact that it is melting, is consistent with what's happening all around the world," says David Rind, climate researcher at NASA's Goddard Institute for Space Studies.
Climate scientists say glaciers all around the world are now retreating. Montana's Glacier National Park had more than 150 glaciers when it was inaugurated a century ago. Today it has only 37.
It's a pattern that is seen not only in the Rockies, but also in the Andes and the Himalayas. In Africa, the snows of Kilimanjaro, made famous by Hemingway, are disappearing. The mountain's permanent ice cap has shrunk by more than 80 percent in the last century and some scientists predict it will disappear entirely before the decade is out.
"People think of glaciers as perhaps the canary in the coal mine," Rind says.
Mountian glaciers, especially in the tropics, are more sensitive to temperature change than the ice at the poles, he says, and the fact that they are melting now, after being stable for the last 10,000 years, is a sign that the earth really is getting warmer.
The glaciers are a precious resource in parts of the world. In Pakistan and the surrounding regions, hundreds of millions of people depend on glaciers for fresh water.
"The real problem with global warming is what will happen to water, already under pressure due to population growth," Rind says. "Water is an irreplaceable resource. If you don't have it you can't substitute anything else."
In the Italian Alps, the problem is not too little water, but too much. And local officials are now just waiting for a break in the weather to rid themselves of an unwanted and potentially dangerous lake high above their heads.
ABCNEWS' Ned Potter contributed to this report.