Scores of mountain lakes may burst their banks in the next 10 years because of global warming, sending millions of gallons of floodwaters swirling down valleys and endangering tens of thousands of lives, scientists warned Tuesday.
Research released today by the United Nations Environment Program (UNEP) shows that lakes in the Himalayas are rapidly filling with icy water as rising temperatures accelerate the melting of glaciers and snowfields.
The agency pinpointed 24 glacial lakes in Nepal and 24 in Bhutan "that have become potentially dangerous" due to a regional increase in average air temperatures of 1.8 degrees Fahrenheit since the 1970s.
"We have evidence that any of these lakes in Nepal and Bhutan could, unless urgent action is taken, burst its banks in as little as five years time with potentially catastrophic results for people and property hundreds of kilometers downstream," said Surendra Shrestha, regional coordinator for UNEP's early warning division.
"These are the ones we know about. Who knows how many others, elsewhere in the Himalayas and across the world, are in a similar critical state?" Shrestha added, noting that since less than 10 percent of the Himalayan region had been assessed, there could be areas where the risk is great but as yet unknown. Surveys were planned for China, Pakistan, and Central Asia.
Work is already under way to lower the level of one of the Nepali lakes considered most at risk, according to Pradeep Mool, a remote-sensing expert with the International Center for Integrated Mountain Development, which carried out the research with UNEP.
As a result of the melting of a nearby glacier, he said, the Tsho Rolpa Lake had grown from 0.23 square kilometers in the late 1950s to 1.4 square kilometers today. A flood could inflict serious damage as far as the village of Tribeni, some 108 kilometers away, threatening about 10,000 people. Engineers were working to lower its level by 30 meters, and a network of sensors and sirens had been linked from the lake to villages at risk from its floodwaters.
UNEP experts say millions of dollars are urgently needed to carry out similar work on scores of other glacial lakes if disasters are to be averted. Mool emphasized that although glacial lake bursts were not a new phenomenon, there was evidence that they had been occurring more frequently in the past 30 years, the period during which glaciers had been retreating faster than ever before in recorded history.
The warning about glacial lakes coincides with a meeting this week of a UN-sponsored body, the Intergovernmental Panel on Climate Change, that in the last four years has played a key role in confirming the existence of "new and stronger evidence" that most of the global warming observed over the last 50 years is attributable to human activities, such as the burning of oil.
"Greenhouse gases," such as naturally-produced carbon-dioxide, methane, and nitrous oxide, along with artificially-generated hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, had been at the center of a fierce debate over whether the Earth's natural cooling system was being directly slowed down by a range of industrial processes.
Speaking on the eve of the April 17-20 meeting in Geneva, the 19th meeting of the Panel, Klaus Toepfer, UNEP's executive director, said, "Climate change is the biggest threat facing humankind, with extreme weather events, droughts and rises in disease forecast for many parts of the globe over the coming decades."
"If...glaciers continue to retreat at the rates being seen in places like the Himalayas, then many rivers and freshwater systems could run dry, threatening drinking water supplies as well as fisheries and wildlife," said Toepfer. "We now have another compelling reason to act to reduce emissions of carbon dioxide and other greenhouse gases."
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