At nearly 13,000 feet above sea level, in the shadow of a sharp Himalayan peak, a wall of black ice oozes in the sunshine. A tumbling stone breaks the silence of the mountains, or water gurgles under the ground, a sign that the glacier is melting from inside. Where it empties out — scientists call it the snout — a noisy, frothy stream rushes down to meet the river Ganges.

D.P. Dobhal, a glaciologist who has spent the last three years climbing and poking the Chorabari glacier, stands at the edge of the snout and points ahead. Three years ago, the snout was roughly 90 feet farther away. On a map drawn in 1962, it was plotted 860 feet from here. Mr. Dobhal marked the spot with a Stonehenge-like pile of rocks.

Mr. Dobhal’s steep and solitary quest — to measure the changes in the glacier’s size and volume — points to a looming worldwide concern, with particularly serious repercussions for India and its neighbors. The thousands of glaciers studded across 1,500 miles of the Himalayas make up the savings account of South Asia’s water supply, feeding more than a dozen major rivers and sustaining a billion people downstream. Their apparent retreat threatens to bear heavily on everything from the region’s drinking water supply to agricultural production to disease and floods.

Indian glaciers are among the least studied in the world, lacking the decades of data that scientists need to deduce trends. Nevertheless, the nascent research offers a snapshot of the consequences of global warming for this country and raises vital questions about how India will respond to them.

According to Mr. Dobhal’s measurements, the Chorabari’s snout has retreated 29.5 feet every year for the last three years, and while that is too short a time to draw scientific conclusions about the glacier’s health, it conforms to a disquieting pattern of glacial retreat across the Himalayas.

A recent study by the Indian Space Research Organization, using satellite imaging to gauge the changes to 466 glaciers, has found more than a 20 percent reduction in size from 1962 to 2001, with bigger glaciers breaking into smaller pieces, each one retreating faster than its parent. A separate study found the Parbati glacier, one of the largest in the area, to be retreating by 170 feet a year during the 1990s. Another glacier that Mr. Dobhal has tracked, known as Dokriani, lost 20 percent of its size in three decades. Between 1991 and 1995, its snout inched back 55 feet each year.

Similar losses are being seen around the world. Lonnie G. Thompson, a glaciologist at Ohio State University, found a 22 percent loss of ice on the Qori Kalis glacier in Peru between 1963 and 2002. He called it “a repeating theme whether you are in tropical Andes, the Himalayas or Kilimanjaro in Africa.”

The Chorabari, sweeping down from Kedarnath peak across 2.3 square miles, is relatively lucky. It is blessed with a thick cover of rocks and boulders, which acts as a sort of insulation and slows the melting. Since Mr. Dobhal began collecting data here in 2003, the Chorabari has been shedding its weight — that is to say, melting faster than the rate at which snow and ice accumulates, and as a result, thinning out by roughly five feet each year. The snow line, in addition, is gradually moving higher.

A vast and ancient sheet of ice, a glacier is in effect the planet’s most sensitive organ, like an aging knee that feels the onset of winter. Its upper reaches accumulate snow and ice when it is cold; its lower reaches melt when it is warm. Its long-term survival depends on the balance between the buildup and the melting. Glaciers worldwide serve as a barometer for global warming, which has, according to a report this year by the Intergovernmental Panel on Climate Change, been spurred in recent decades by rising levels of greenhouse gas emissions.

Even the Himalayas have grown measurably warmer. A recent study found that mean air temperature in the northwestern Himalayan range had risen by 2.2 degrees Celsius in the last two decades, a rate considerably higher than the rate of increase over the last 100 years.

In its report, the international panel predicted that as these glaciers melt, they would increase the likelihood of flooding over the next three decades and then, as they recede, dry up the rivers that they feed. “In the course of the century,” it warned darkly, “water supply stored in glaciers and snow cover are projected to decline, reducing water availability in regions supplied by meltwater from major mountain ranges, where more than one-sixth of the world population currently lives.”
(By SOMINI SENGUPTA, The New York Times, 17/07/2007)