The Everest research is partly funded by the IPCC, which is trying to make amends for an embarrassing mistake. In 2010, the U.N. organization retracted a forecast that Himalayan glaciers could disappear by 2035. The IPCC said the forecast, made in its 2007 assessment report, was unfounded and based on an error.
The worldwide brouhaha that followed admission of the error highlighted the paucity of knowledge about climate change in the world’s greatest mountain range.
Few weather stations operate in the Himalayas, and most of the land is inaccessible to scientists, cleaved off from civilization by rugged peaks. There are few roads, and transportation across the mountain range by helicopter is dangerous and expensive, with few flat strips to land planes on.
Himalayan countries and nongovernmental organizations have started new measurement and research projects on glaciers throughout the Himalayas during the past few years.
Other researchers have been using data from the NASA satellites—the Gravity Recovery and Climate Experiment (GRACE), a two-satellite system started in 2002, and the Ice, Cloud, and land Elevation Satellite (ICESat), which was launched in 2003—to estimate changes in ice cover around the world, including in the Himalayas.
The satellite projects are providing scientists with more information than they could ever have hoped to have acquired by trekking out onto the glaciers to take measurements the old-fashioned way.
Tobias Bolch, a University of Zurich glaciologist who has conducted fieldwork in the Himalayas and who co-authored the Science paper, says most Himalayan glaciers, on average, “have certainly lost mass or retreated quite strongly” since the middle of the 19th century. What’s more, “there is an increasing trend of a glacial retreat in recent decades.”
Not all of the water is making it out to sea. Vast volumes are trapped in pits that were scoured out of the mountainsides as glaciers grew and crept downward. These pits are turning into lakebeds as the glaciers retreat.
Many of the glacial lakes are held in place by piles of gravel and boulders known as moraines that were bulldozed into place by the leading edge of the glaciers. The melt water is trapped behind the moraine, and the lake keeps growing as the glacier shrinks. “This is very unstable,” says Pradeep Mool, a geomorphologist at the Kathmandu, Nepal-based nonprofit International Centre for Integrated Mountain Development.
Such hazards became clear in 1977 when a glacial lake below the peak of Mt. Ama Dablam in eastern Nepal overtopped a moraine, triggering a flood that claimed three lives. Similar accidents have occurred since then, including another in Nepal in 1980 that destroyed villages more than 40 miles from the rupture.
An inventory published in 2011 by Mool and his colleagues identified 1,466 glacial lakes in Nepal alone. Several are deeper than 250 feet. Because of the rugged Himalayan terrain, it’s impossible or prohibitively expensive to drain the glacial lakes.
The flood hazards are prevalent throughout the mountain range. More than 150 glacial lakes have been identified in India, 16 of which were classified in 2010 as being potentially dangerous. The rupture of such lakes, perhaps triggered by an earthquake in the seismically active region, could be catastrophic.
Flash-flood risks ranked negligibly low among the manifold dangers faced 60 years ago by Hillary and Norgay. But villagers throughout the Himalayas now live in fear of being flooded by the remnants of the region’s vanishing ice and snow.