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In Nepal it's easy to gauge the threat of warming, where the vanishing glaciers can be seen with one's own eyes. But downstream, in the farmland and cities of India, Bangladesh, Pakistan and China, the consequences are both more dire and less evident. According to the estimate of an Indian researcher, melt from the glaciers of the Himalayas supplies the rivers of Asia with more than 300 million cu. ft. of water every year as much as 50% of the water flow of some major rivers (like the Indus, which irrigates India and Pakistan), according to the International Center for Integrated Mountain Development, an advocacy group based in Kathmandu, Nepal. Although more-rapid melting from warming would increase that water flow in the short term, potentially aiding agriculture, it would be like making ever larger withdrawals out of a limited bank account: eventually it will run dry. Given how fickle the monsoon can be and the additional risk of climate change weakening those vital rains the water tower of the Himalayas becomes all the more important. "It is the ice melt from these glaciers that sustains irrigation," says Lester Brown, president of the Earth Policy Institute. "The melting of these glaciers is the most massive threat to food security that we have ever projected."
It is also a threat to global security. In developing nations such as China and India, growing prosperity means ever greater demand for and potential battles over water. For countries that have long grappled with famine, that's a frightening possibility and one that could trigger international conflict. The rivers of the Himalayas crisscross international borders, while the mountains are shared by several nations. Already China has come under fire from its neighbors for damming rivers that eventually flow into other nations. And while security experts point out that cross-border conflict over water has been relatively rare even India and Pakistan have so far managed to share the Indus water scarcity has frequently led to internal civil conflict. In a water-stressed region with nuclear capabilities, it could be disastrous to let the most valuable commodity become rarer still. "Climate change is a real specter that we don't fully understand yet," says the IWMI's Chartres. "The impacts already seem to be stronger than we expected, and we could have real difficulties in the developing world."
The Search for Science
The trouble is that while melting glaciers remain a leading indicator of climate change, determining exactly how quickly they're melting has been difficult, especially in the remote Himalayas. Data on the ground remain thin, and records may go back only a few decades or are all but nonexistent in the case of many glaciers. Nor does it help that the nations that share the Himalayas do so jealously. India does not allow Chinese researchers to visit its glaciers, China is sensitive because of concerns over Tibet, and India and Pakistan cooperate little on science or almost anything else.
There is, unsurprisingly, active scientific disagreement about the impact of climate change on the glaciers. An Indian-government-backed report published in October claimed that many Indian glaciers are stable or that the rate of retreat has slowed in recent years, despite clear warming. Critics pointed out that the report was not peer-reviewed in a scientific journal and had major data gaps. But the lack of clarity makes it that much more difficult for policymakers to craft the right response. "The Himalayan data just isn't there," says Richard Armstrong, a senior research scientist at the National Snow and Ice Data Center in Boulder, Colo., who is skeptical that the glaciers are receding rapidly. "These glaciers are at a very high altitude, and what precipitation they get tends to fall as snow, which can add to their mass. There's a tendency to oversimplify."
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