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Charting unknown waters

The behaviour of Himalayan glaciers is beset with uncertainty but the region’s water availability remains a critical issue. Navin Singh Khadka reports.

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In the wake of the recent controversy over the retreat of Himalayan glaciers, in which the United Nations' climate-science body admitted that it was an error to assert that they would disappear by 2035, water availability has emerged as a key issue with even more uncertainty. Receding Himalayan glaciers grabbed headlines because they feed major rivers in south Asia and some parts of south-east Asia, which is home to a sizeable proportion of the planet's population. If the glaciers significantly retreated or even disappeared, it would be an issue of life and death for many millions of people who depend on these rivers.

But now that the Intergovernmental Panel on Climate Change (IPCC) has said that it was a mistake to say the glaciers will be gone in a matter of decades, does that mean water is not a worrying issue any more? Many scientists believe it is even more worrying given the uncertainty surrounding the future impacts of climate change in a region not only of high population, but also of high population growth.

The broad consensus is that glaciers themselves are indeed retreating, although the rate of the recession may be debatable. However, there are other climate-influenced factors that affect river flows, such as changes in precipitation, snowfall and regional temperature. “There has been too much focus on glaciers whereas there are other factors like precipitation and snowfall that affect the levels of waters in rivers downstream the eastern Himalayas,” says Mats Eriksson, a senior hydrologist with the Nepal-based International Centre for Integrated Mountain Development (ICIMOD), which has carried out several studies on the glaciers in the Hindu Kush Himalayas.

Below the eastern part of the Himalayas are major rivers like the Ganges and the Brahmaputra, as well as their tributaries. These are vital lifelines for millions of people in India, Bangladesh, Nepal, Bhutan and Tibet. A recent study for the World Bank has shown that the volume of water resulting from glacial melt in Nepal makes up less than 5% of the flow of rivers leaving the country and contributing to the Ganges downstream. “That is, about 95% or more of the river flow is the result of rain and melting seasonal snow,” says the report’s co-author, Richard Armstrong, a glaciologist from the University of Colorado at Boulder in the United States.

If that is true, rivers downstream of the eastern Himalayas will hardly be affected, even if the glaciers recede or disappear. However, would the other contributing factors to the rivers’ flow, such as precipitation and snowfall, remain the same in the changing climate? No, say scientists, but whether that will lead to rise or fall of river levels – and by how much and when – are the questions still waiting to be answered.

“We are seeing some changes in the monsoon,” Eriksson says of the seasonal precipitation system that shapes the climate in this part of the region. “Last year, for example, the monsoon arrived one month late in Nepal and then some places saw 80 millimetres of water in a day during the delayed rainy season. But there has been no consistent measurement of precipitation and temperature and there is a lack of proper studies.”

Some scientists believe absorption of solar radiation by aerosols (dust particles and carbon soots) can heat the atmosphere and accelerate regional impacts of global warming, which in turn affect water resources. William Lau, who heads the atmospheric sciences branch at US space agency NASA’s Goddard Space Flight Center, carried out a study in India last year and found that, as a result of aerosols, regional temperature was rising much faster than expected. And that, he said, could influence the monsoon systems, resulting in less water availability in the region.

But Armstrong says a warming climate could also mean a stronger monsoon bringing more precipitation that could increase stream flows. “Having said that, it should be noted that future precipitation patterns predicted by climate models are highly variable and there is a very little regional agreement among the models,” he says.

High variability is also an issue with the flow of rivers in the western Himalayas that do not fall within the monsoon regime. “There is no clear-cut signal as there is a large variation between average annual flows,” says Arshad Muhammad Khan, a physicist who heads the Global Change Impact Studies Centre in Pakistan. “For example, in the Indus River, the maximum flow is twice that of the minimum.” Unlike the Ganges, rivers like the Indus in the western part of the Himalayas are heavily dependent on glaciers, as this region does not get monsoon rains. But even here, glacial status is not reported to be uniform.

Some scientists say increasing temperature has meant that glaciers don't get enough snowfall during winter and therefore river flow during summer is dwindling. “We have seen the decline in the flow of the Indus, Chenab and Jhelum rivers,” says professor Mohammad Sultan Bhat of Kashmir University, who has conducted field studies with India's flood and irrigation department. “We have recorded a decrease of 40% in the flow of Jhelum's tributary river … that is fed by the receding Kolahi glacier.” But Kenneth Hewitt, a glaciologist from Canada who has been doing field studies in Pakistan's Karakoram mountains, told BBC News last October that he had seen at least half a dozen glaciers there advancing since he saw them five years ago.

With glaciers offering such complex pictures, combined with increasingly complicated precipitation and temperature patterns, the region's river systems that depend on all these factors cannot be simpler. Politics and geography, experts say, have made understanding the situation even more difficult. “Some countries in the region are not willing to share water-related data because they regard it as confidential,” says Eriksson of ICIMOD. “Since it is difficult to access them, proper studies on water availability remain a major challenge.”


Navin Singh Khadka is a journalist with the BBC Nepali service. He has a sustained interest in environment, with a focus on climate change vis-a-vis Himalayan ecology.


An earlier version of this report appeared on the BBC on January 27, 2010.

Homepage image by James C Farmer

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匿名 | Anonymous

“未知”或许是好事

科学研究最忌讳以偏概全,无法实事求是。这就是为什么最近一系列被媒体捅出来的关于气候变化的质疑受到广泛的讨论。基于自身条件所限,民众没有别的方法,只能选择相信科学家。如果科学家因为种种原因,信口雌黄,或者只为了某种利益有意忽视真相的另一面,被揭穿后,这种无条件的信任就崩溃了。

因此我宁愿听到科学家说“事情很复杂,我们还在研究”,也不希望他们斩钉截铁的下定论:“是的,2035年,冰川就消失了。”

Perhaps the "Unknown" Is a Good Thing

More than anything, scientific research tries to avoid taking a part for the whole. This is why recently the questioning of climate change has received so much media attention. Because of our own limitations, people can do nothing but choose which scientists to believe. And if scientists, for whatever reason, make unfounded claims or intentionally ignore facts for some other gain, when they are exposed, this unconditional confidence in them will collapse.

This is why I would rather hear them say, "It's a very complicated issue, we still have more research to do." And by the same token, I wouldn't want them to reach an unequivocal conclusion: "Yes, in 2035, the glaciers will have disappeared."
Comment translated by Clay Baylor

Default avatar
匿名 | Anonymous

喀喇昆仑—喜马拉雅的冰川变化

我认同卡加德先生对于这个复杂而且充满矛盾的讨论的平衡性评估。
我要澄清一下他所引用的我的评论。尤其涉及到喀喇昆仑中部的两个盆地和2005年到2009年期间前进的高纬度冰川。实际上它们是过去十年里我在喀喇昆仑山最高处的“穆斯塔卡”观察到的30多座冰川的一部分,包括长度从小型到中级(10-40千米)的冰川。在喀喇昆仑最大的冰川上我只观察到了冰体加厚或者冰体边缘冰碛过度堆积的广泛迹象,但这看上去似乎是还未影响到(可能会,也可能不会)遥远终点的扩散证据。
我再加一句,直到最近,我的观察依然遭到了甚至是工作在其他地区的冰川学家的挑战和质疑,但是现在看来却是被接受的。然而,证据似乎很明显,在亚洲高地和世界的大多数其他地区冰川覆盖正在减少。在两者任意一种情况下,气候变化都是关键所在,只是比之前的想法更加复杂。

Glacier change in the Karakoram Himlaya

I commend Mr Khadka on a balanced assessment of a complicated and, of late, badly conflicted discussion.

I would just clarify the comment of mine he cited. It referred specifically to observations in two basins of the central Karakoram and high altitude glaciers which had advance between 2005 and 2009. In fact they are part of more than 30 glaciers I have observed advancing in the past decade in the highest "Mustag" part of the Karakoram in involve small to intermediate glaciers (10-40km) in length. On the largest Karakoram glaciers I have only observed widespread evidence of thickening of the ice or over-riding of the ice margin moraines, but this seemed evidence of expansion which has not yet (and may or may not?) affect the distant termini.
Let me add that until quite recently, my observations were challenged or dismissed by even by glaciologists working in other regions, but now seem to be accepted. However, the evidence seems clear that the ice cover is diminishing in most other regions of High asia and the world. In either case, climate change is the key, just more complicated than fomerly thought.