If you’ve never experienced altitude headaches, try imagining a crazed medieval executioner squeezing a cord around your skull, perhaps using some primitive vice contraption to ensure the pressure never eases. After a four-day trek up mountain paths filled with evil little leeches and lavishly expansive cowpats, that torturer was at his most energetic as I sat in Furdiki Sherpa’s kitchen hut, 50km west of Mount Everest in the Nepali Himalaya.
Furdiki had never had to worry much about anything so feeble as altitude sickness. At 74, she’d spent her entire life in the village of Na Gaun, 4,180 metres above sea level. This made her an invaluable witness on the story that had brought me to her village: the huge, hazardous growth of the nearby glacial lake of Tsho Rolpa.
As indicators of global warming, the world’s glaciers are hard to beat. While scientists are confident that heatwaves and tropical storms will grow in severity as temperatures warm, attributing the causes of specific events is fraught with difficulty. In contrast, the inexorable melting of the mountain glaciers and polar ice sheets looks like the world's biggest smoking gun. The glaciers are shrinking at a bewildering pace of about 335 billion tonnes a year, according to a recent study in Nature. That’s over 10,000 tonnes a second.
All this melting ice is creating severe dangers for the world’s low-lying islands and coastal cities, which could be inundated by resulting sea level rise. But there are some equally terrifying – and in many cases much more acute – threats to the communities right by the source of the problem, living on the slopes below the world’s mountain glaciers.
Na Gaun was the stuff of Nepalese tourism brochures, a scattering of tiny homes with sloping roofs, towered over by dark timeless mountains. Between the houses stretched dry stone walls, built to restrain the village’s population of cows, yaks and naks (female yaks to you and me – though never referred to so disrespectfully by any Nepali). It was hard to see that the walls were serving much purpose, given the imperiousness with which the animals sauntered through the village lanes.
While the mountains dominated the skyline, when I stood among Furdiki’s half-dozen cows in the small grass yard outside her home, it was something else that caught my eye: the grey rim of Tsho Rolpa, a heavy crescent resting amid the peaks to our east.
All that stood between the lake’s 85 million cubic metres of water and Furdiki’s home — and the homes of her neighbours, and all the other settlements I’d trekked through on the way up — was a fragile natural dam of ancient rubble riddled with air pockets and lumps of ice in what one researcher described to me as a “Swiss cheese kind of structure”.
With hundreds of these lakes scattered across Nepal, as well as Tibet and Pakistan, scientists have been scrambling to figure out the risks to downstream communities of an increase in outburst floods as their volume surges. Unhappily, there have been several recent examples for them to study. In 2016, an outburst flood in Tibet swept over the border towards the Nepalese border village of Tatopani, destroying homes and much of a nearby hydroelectric plant. Pakistan’s northern Chitral region has been hit by a series of such floods, with the most recent one coming just this month – damaging homes and infrastructure, and reportedly leaving prime minister Imran Khan’s sister stranded during her summer holiday.
Furdiki settled into a low stool next to her stove chimney to recount her local lake’s astonishing growth. Under a bright purple fleece she wore traditional mountain costume, with a coarse striped apron and silver-buckled belt over a kind of kimono with white trim. Her face was deeply creased by the mountain climate, and by a broad grin that exploded across her face at the slightest provocation. Years of biting winter cold had given her cheeks a permanent blush that glowed under her turquoise eyes.
As a girl, Furdiki had spent two months each monsoon season chaperoning her family’s livestock in the pastures that then surrounded Tsho Rolpa, sleeping in huts alongside the other village youth. “Back then the lake was so small – about the distance from from here to that house,” she said, pointing through her window to a house just a few minutes' walk away. “We used to lead the animals back and forth across the glacier.” But each rainy season, Furdiki would return to find the pasture shrunken, the ice scaled back, the lake enlarged.
Now, Tsho Rolpa is well over two miles long, and even to get close to the glacier – as I was to discover – takes several hours of fairly full-on exertion. A few weeks before my visit, a UK-Nepalese team of researchers had visited the site and warned that the glacier feeding the lake was retreating at a pace of 60 metres per year, with the lake now stretching across 1.6 square kilometres - the size of 148 football pitches. The researchers urged the construction of new monitoring systems, warning of “catastrophic” flood impacts for up to 6,000 households in villages including Na Gaun.
The valley already has a system of sensors and sirens, designed to warn residents of an outburst – although it would give people in Na Gaun just 10 minutes to flee their homes before the water hit. Yet Furdiki refused to share the scientists’ view of the lake as a fearsome liability for her community. She had watched the village’s population shrivel to a small fraction of its size in her youth, and nearly all those left were in old age or near it. All seven of her children had gone to seek higher incomes in the capital city of Kathmandu, and rarely undertook the exhausting mountain trek required to see their parents.
The only thing now breathing life into this ageing community, Furdiki said, was its lake. The more Tsho Rolpa grew, the more it caught the attention of trekkers and researchers, who were sustaining two lodges in the village. If the flow of visitors continued to grow, Furdiki hoped it might give her children a reason to come back to their home village.
It was a perplexing thought – foreign visitors coming to gawp at a huge natural hazard, rejuvenating a village that could ultimately be destroyed by the object of their curiosity. But having come all this way, I could hardly skip the big attraction.
“No way,” said Laxmi, my mountain guide. We were sitting at the top of a cliff above the lake’s western edge, at the end of a trail that had been curtailed by a series of landslides. The far end of the lake, where the amputated glacier sat, was more than a mile away as the crow flies – and unlike the crow, we’d need to clamber several hundred metres up a steep incline, potentially to find that there was no way down the other side.
Even from this vantage point, the view was impressive. The lake stretched below us, a dirty greenish-grey, looking something like the world’s biggest concrete slick. There were no people or animals in sight, and the silence was total but for a faint wind whisking through the valley, the distant chirp of birds and the hum of drifting insects. On the lake’s opposing side were banks of loose grey stone displaced by landslides, which gave way a few dozen metres up to solid, hulking black Himalayan rock that rose almost vertically until it vanished in thick cloud. I was suddenly intensely aware of the immense age of this mountain range, which has been growing ever since India began pushing its way into Eurasia 50 million years ago. But with the arrival of Tsho Rolpa, even this lofty, desolate landscape was now being reshaped at speed by the byproducts of modern industry. And to fully grasp the pace of that change, I would need to see the melting glacier.
I suspect I hadn’t given Laxmi much cause for confidence in my mountaineering prowess in the prior few days, especially after I started tottering drunkenly on the blisters from my rented boots. But eventually he relented, tired of my pleading, and we set out up the steep stope of Tsho Rolpa’s high western bank. The climb was as hairy as Laxmi had warned: well over an hour of uphill clambering inside the clouds, such an eerie and disorienting experience that it felt like welcome company when, near the highest point of our climb, Laxmi pointed out the paw prints of a carnivorous snow leopard.
Just as we bent to look at the prints, we jumped at what sounded like a sudden burst of cannonfire, booming up from below. It was the decomposing glacier, a large block of it falling into the lake, and as I picked my way downwards through the clouds, trying not to slip on the jagged carpet of loose stone, that truncated ice body came into view.
It was like peering into the mouth of a giant made of ice whose tongue had been hacked off, leaving only a useless root that was now rotting away. The melt was fastest near the water surface, creating looming overhangs that looked like they must splinter and drop into the lake any minute. Which of course they were doing, in a sporadic rhythm, from small pieces spattering apologetically down, to the larger chunks producing those artillery sounds that echoed high in the surrounding hills. Having reached the water they spread and drifted, each slowly melting and making its small contribution to the lake’s growth. Behind the glacier’s jagged face its interior was a bright bubblegum blue, offset by the dusty grey of the debris that lay on its roof, carpeting a still vast expanse of ice that stretched back far onto the slope behind it.
I stood at the edge of the lake’s loose western moraine, as close to the glacier as I could get without surfing a tide of rubble down the sheer slope that began a few feet away. Perhaps too close, I realised, as a bunch of nearby rocks moved, unbalanced by melting chunks of ice beneath them, and started a little landslide down into the lake. I took a few steps back and returned to staring at the slowly vanishing glacier, far older than modern civilisation but destined to be wiped away by it. It seemed only a matter of time — perhaps decades, perhaps days — until this grotesque process reached its natural conclusion, with a violent escape of water triggered by an avalanche or landslide, or simply by the gradual weakening of the lake’s walls under growing water pressure.
Not that such dark prognostications would wash with Furdiki, whose relentless good cheer left no room for visions of destruction. In his 2013 book Hyperobjects, the philosopher Timothy Morton argued that the forecast impact of global warming was something on a scale so enormous, so divorced from our experience of the world to date, that we humans just aren’t really built to process it. For Furdiki, the sudden destruction of the village where she had spent her entire life was perhaps a notion no less overwhelming.
“I’ve been saying the same thing to all those scientists who came here,” she told me with her enormous kindly smile. “I’ve lived here over seventy years and that lake has never burst out. Not once!”