Columbia Glacier - Alaska
Southeastern Alaska is famous for tidewater glaciers: big icefields spilling from mountains directly to the sea. While some continue to advance, the 2,000-square-kilometer Columbia Glacier, which sweeps from the Chugach Mountains into Prince William Sound, has been decreasing in size with great rapidity over the past several decades. After a long period of stability, it shrank from 41 miles long in 1980 to 33 in 2001. Icebergs calved from its retreating snout pose a threat to shipping.
Furtwangler - Tanzania
The Furtwangler Glacier and other icefields on Mount Kilimanjaro, the highest peak in Africa, have garnered much attention in recent years. Their substantial retreat has special poetic resonance, as one of Ernest Hemingway's most famous short stories, "The Snows of Kilimanjaro," celebrated the remote whiteness of the 19,330-foot stratovolcano. About 82 percent of Kilimanjaro's glacial extent was lost between 1912 and 2000. However, rising temperatures might not be the primary culprit. Some evidence points to declines in precipitation and cloudiness. Whatever the cause, the glaciers appear to be ever-hastening toward oblivion--they may be gone within decades.
Gangotri Glacier - India
Gangotri Glacier spills northwest out of the Himalaya Range in northeastern India. One of the largest icefields in this greatest of Earth's mountain systems, the 18-mile Gangotri births the Ganges River, sacred to Hindus and water supply to millions. Like other Himalayan glaciers, the Gangotri has been on the retreat in recent decades, receding 3,785 feet between 1936 and 1996--and more than 251 feet between 1996 and 1999 alone. The United Nations notes that the Himalayas and the other great uplifts surrounding the Tibetan Plateau furnish the water for 40 percent of the world's population. The rapid disappearance of their glaciers has major repercussions.
Pastoruri Glacier - Peru
Pastoruri belongs to the most extensive chain of glaciers in the tropics: the icefields of Peru's Cordillera Blanca (White Range). In 2007, fast-receding Pastoruri split into two portions, and its last ice cave collapsed. As in the Himalayas, the glaciers of Cordillera Blanca and other ranges of the Andes are immensely important to large human populations in surrounding lowlands. The White Range's glaciers provide drinking and irrigation water and hydropower to the Rio Santa Valley below.
Trift Glacier - Switzerland
The retreat of Alpine glaciers like the Trift will have a major impact on the dense human populations around this iconic chain as well. Scientists predict the majority of glaciers in the Alps may disappear by 2050--a threat not only to the region's water supply but also its massive skiing industry. Between 2004 and 2005, the Trift Glacier, located in central Switzerland, decamped more than 600 feet.