Researchers found that the melting altitude of one of Everest’s glaciers had risen about 50 meters (165 feet) over a period of two years, more than twice as fast as usual. They also reported that a large, high-altitude cliff observed in 2002 seemed to have disappeared. On the Nepal side of the mountain, similar melting has occurred. In 2002, the U.N. warned that 40 Himalayan glacial lakes were on the verge of bursting and endangering nearby residents, as a result of global warming.

Three-quarters of the world’s fresh water is stored in glacial ice, especially in mountain areas, and released slowly into rivers during dry or hot months.

Some scientists say global warming could increase the average global temperature by 1.4 to 5.8 degrees Celsius (2.5 to 10.5 degrees Fahrenheit) over the next century, with catastrophic results, such as glaciers retreating, causing oceans to rise and flooding lowlands around the world.