It's well below freezing as Renoj Thayyen climbs to the weather station high up in India's Karakoram mountains, his Koflach boots crunching shin-deep into the snow.
The 50-year-old hydrologist has been making this trip to study water and weather patterns across the Himalaya and Karakoram ranges every few months for nearly three decades. What he has recorded alarms his fellow scientists and the governments they advise.
Reaching a hut at 15,500 feet (4,700 meters), Thayyen plugs in a rectangular device like an outsized USB and downloads six months of data, from gauges of atmospheric temperature and sun duration to depth of snowfall. Water discharge readings are relayed from the bed of a glacier nearby.
The measurements add to a body of evidence that global warming is disturbing water cycles on the roof of the world, and in unpredictable ways. Snow cover is shrinking, glaciers are melting, the monsoon season changing and permafrost is at risk, all with drastic consequences for a region whose ice fields hold the largest freshwater reserves outside the poles.
"Winter temperatures are rising and glaciers are losing mass," said Thayyen of India's National Institute of Hydrology as he transferred the data to his laptop. "That is impacting water resources in this area." And the people who depend upon them, since in the upper valleys of the Indus River, "more than elsewhere, glacial meltwater is also linked with livelihoods."
The shifting dynamics miles above sea level are starting to wreak havoc far below in a river basin twice the size of France. Extreme flooding and drought in recent years has sparked a national emergency in Pakistan, which depends on the Indus for 90% of its food production, and across the border in India, where crop failures have led to a surge in farmer suicides.
The Himalayas supply water to some 1.3 billion people in eight countries. And while the main nations at risk should be cooperating to mitigate the impact on hundreds of millions of people who depend on water from the mountains for survival, the opposite is happening. The rush to secure water resources adds to tensions in a region where the world's two most populous countries, China and India, sit upriver from a host of smaller neighbors, and where India and Pakistan are avowed enemies. Water is becoming weaponized as a result.
Prayer flags snap in the icy wind at the Khardung la pass, 2,000 feet above the weather station. A Buddhist shrine overlooks an excavator clearing snow for the few private vehicles and army convoys headed to Siachen, part of India's permanent military presence in the disputed frontier region. India and Pakistan have fought over this inhospitable terrain intermittently since 1984, with the loss of more than 2,000 lives, as much to the weather as weapons. Siachen, as well as being one of the largest glaciers in the Karakoram, is considered the highest battleground on earth.
The Nubra valley beyond was once a part of the ancient Silk Road trading route that connected Asia with Persia and Europe. Now it is a staging post in the inexorable advance of climate change.
This Indian part of the Tibetan plateau is a high altitude desert with little rain and scant vegetation. It isn't equipped for the increased precipitation being experienced. Sudden deluges killed more than 170 people here a decade ago, but population pressures mean new settlements keep spreading across the flood plains regardless.
Sitting in her new house near the confluence of the Nubra and Shyok rivers—both of which feed the Indus—Sonam Wangmo, 55, recalls the night her field and home of three decades were washed away. "All we had left were the clothes we were wearing," she said. Flash floods were rare in her childhood, but they have been upending lives in India's Himalayas almost every year for the past decade. That pattern is forecast to accelerate.
Water from glacial melt is lost through sudden floods in the Indus Valley. By 2050, temperatures across the Hindu Kush Himalaya region stretching from Afghanistan to northern Myanmar are expected to rise by some 1-2 degrees Celsius—in some places by as much as 4-5 degrees—causing more snow and glacier melt. A study published by Columbia University's Lamont-Doherty Earth Observatory found that Himalayan glaciers melted twice as quickly in 2000-2016 as they did from 1975 to 2000.
That water is lost through sudden floods. But what's more worrying to Wangmo is that winters are now warmer, bringing less snow and hence less water in the summer months for valleys like hers that rely on the meltwaters for irrigation and farming.
The upper Indus basin is at particular risk. But it is not alone. According to the United Nations, the entire Hindu Kush Himalaya is warming three times faster than the global average. Those mountains feed the 10 largest river systems in Asia, providing drinking water, irrigation, energy, industry and sanitation for some 1.3 billion people.
Melting glaciers "are the biggest economic, human and national-security threat Pakistan will ever face," said Lahore-based climate policy consultant Dawar Butt.
India, Pakistan and Bangladesh are all victims of global warming, which makes them reliant on a worldwide reduction in harmful emissions blamed for rising temperatures. To some extent they can only prepare for the worst. Yet each is also contributing to the warming by building coal-fired power capacity—as is China, which is both the source of the region's great rivers and the world's biggest emitter.
The Indus valley is one of six cradles of world civilization, all centered on rivers. Ancient Egypt had the Nile, Mesopotamia the Tigris and Euphrates. Pakistan, Afghanistan and India benefited from the great fertile plain formed by the Indus and the Ganges.
Despite a shared heritage stretching into antiquity, Pakistan and India have been at loggerheads since Partition in 1947. However, a treaty brokered by the World Bank in 1960 recognized the importance of the Indus to both nations, and set out the distribution of waters.
Indian Prime Minister Narendra Modi's Hindu nationalist administration has threatened to divert what it claims is its share of Indus water from Pakistan as a retaliatory measure for terrorist attacks, especially in the disputed Kashmir region, which India says are orchestrated by Pakistan and which Islamabad denies. That represents an unprecedented threat to the accord.
"Up until the 2000s, the Indus water treaty was the one positive thing in the equation between India and Pakistan. But in the last 10 years, that has changed," said Gareth Price, senior research fellow on the Asia-Pacific Programme at Chatham House in London. "Water seems to have become part of the armoury for India to respond to Pakistan."
In an air conditioned office more than 700 miles south of Siachen, an official in India's water ministry reads reports of water loss in the Indus with concern.
As political pressure to make water a diplomatic tool increases, India is trying to find ways to renegotiate the Indus treaty. The accord covers the water distribution and sharing rights of six rivers in the basin. Pakistan was allotted three western rivers—the Indus, Jhelum and Chenab—while India retained the Sutlej, Beas and Ravi that flow eastward. Under the treaty, India can use, though not store, some water from the western rivers for irrigation purposes.
According to the official in Delhi, it is well within India's rights to develop hydroelectric capacity and use waters even from those rivers allotted to Pakistan without abrogating the treaty. Pakistan has become used to taking more water than its share, the official said. It is a stance reflected in demands by India's ruling Bharatiya Janata Party, and channelled by Modi during a campaign event before local elections in the northern state of Haryana in October.
"For the last 70 years, the waters that belonged to India and farmers of Haryana were going to Pakistan. Modi will stop it and bring it to your households," the prime minister said, adding that work to achieve those ends had begun. "Modi will fight your battle." Modi's office did not immediately respond to an email seeking comments on whether he would renegotiate the treaty.
India's attitude compounds what for Pakistan is already a national emergency. Agriculture accounts for more than 20% of the economy, with most food produced on farmland fed by the Indus. Prime Minister Imran Khan told the UN Climate Action Summit in New York in September that Pakistan "faces a clear and present danger from the changing climate, especially in terms of water stress and food security."
Pakistan is hardly blameless: as well as an addiction to coal, it wastes much of the water it has. Still, Islamabad is taking steps in the country's defense, setting up an "early warning system" to detect surges from melting glaciers. But it is largely at the mercy of others.
"We are directly impacted by climate change and it has to do with what is happening up north," said Malik Amin Aslam, the prime minister's advisor on climate change.
Over coming decades, Pakistan faces massive increases in river flows that will inundate farmland, destroy villages and obliterate infrastructure—followed by drought. Aslam says "the only reasonable way forward" is for the eight countries affected to expand the Indus treaty to take into account climate change, the shared nature of the underground aquifer and the roles of China and Afghanistan, neither of which was party to the original agreement.
Current politics rules that out, however. Bhutan, Nepal and other "small countries" support the idea, just not India under "this extremist government," he said. "It is like India has got the tap control on Pakistan, whereas China has the tap control on India."
On India's northeastern border, there is no treaty determining water sharing with China. Instead, India pays Beijing to supply data on cross-border flows. That includes readings on the Brahmaputra, a river sacred to Hindus, which after surfacing in Tibet travels across northern India to merge with the Ganges in Bangladesh.
During flood season, from May 15 to October 15, China sends India data on rainfall, water levels and discharge twice daily, at 8am and 8pm Beijing time. In case of emergencies such as landslides or cloud bursts, China will supply near real-time data to enable warnings and disaster management, according to another Indian government official with knowledge of the arrangement, who asked not to be named due to its political sensitivity. The system has worked well so far, said the official—with the exception of 2017.
That was the year of a military standoff between India and China, when Beijing sent troops into a strategic sliver of Bhutan overlooking Indian territory, prompting Delhi to respond. The tensions lasted for almost three months, all during the peak flood season, before the soldiers were stood down. China blamed technical problems for not transmitting data to India, saying that measuring stations had been washed away. Beijing stands ready to continue to cooperate on flood reporting with India "in the spirit of humanitarianism and goodwill," China's Ministry of Water Resources said in June.
China now plans some nine hydropower projects on the Brahmaputra, and as many as 40 on its tributaries, according to the Indian official. Beijing has said it has no plans to divert waters. But if they do, said the official, India could have problems.
Bangladesh, meanwhile, is closely watching activities upstream. It too is facing the prospect of increased floods as well as worse "drought-like conditions," said Ainun Nishat, who has represented Bangladesh in UN climate negotiations for more than a decade.
Once synonymous with inundation, Bangladesh has invested over years in flood management infrastructure. Still, the Brahmaputra at the point it enters Bangladesh from India recorded its highest ever level last year, breaching dykes built to prevent flooding.
"During the flood period, we're always at risk. And the flood level has become erratic due to climate change," said Nishat. He recommends an international agreement "on how China is managing the whole thing."
Time is on no-one's side. The International Centre for Integrated Mountain Development in Nepal predicts the Himalayas could lose 64% of their ice by 2100—within a human lifetime.
Those on the front lines are already adapting to change. C. P Dorjay, 52, a businessman in Leh, across the Karakorum pass from China, recalls sledding to the bazaar as a child. That is no longer possible. As the snow retreats, some rivers have more water while streams vanish, marshes dry up and springs disappear.
The only hope, said Dorjay, is to plan for a future with less water. Even then, the outlook is bleak. "We depend totally on glaciers and snowfall," he said. "If glaciers vanish, how do we survive?"