Kanchha, our Sherpa guide, took off at an unexpectedly fast pace along what seemed little more than a dry and dusty yak track. We chased after him as best we could, affected as we were by the combination of altitude and the large lunch we had just consumed at the teahouse at Thokla.

Our destination was Chola Tsho, a large glacial lake contained in a valley formed by two comparatively minor peaks, Awi (17,208 feet) and Arakam Tse (21,073 feet), and held in place by the Chola glacier. The trail undulated radically (ironically, the locals call this type of terrain “Sherpa flat”), and so it took us close to 40 minutes to walk the 1.5 miles around the hill to the lake. I had read several articles about the effects of climate change on glacial lakes in this region and was keen to visit one myself to try to understand the problem.

I was in Nepal, trekking in the Himalayas toward the base camp at Mount Everest. Since I was a boy growing up in England, I had dreamed of walking through these mountains and maybe even one day of climbing to the top of some of the highest peaks on Earth. Now I was here, on a site visit exploring the possibilities of establishing a program to bring students and alumni to this magnificent place.

The scale and beauty of the Khumbu region was beyond anything I had experienced elsewhere, and while I relished each beautiful day of hiking, it was clear that this region is suffering from the effects of global climate change. It reminded me of the canary in the coalmine; changes in this highly sensitive region appear to presage significant global changes that might dramatically affect all human existence.

Average temperatures in Nepal have risen 1.8oF between 1971 and 1994, with the most extreme increases noted during the dry winter months. This was twice that of similar mid-latitude Northern Hemisphere warming trends over the same time period and was especially great in the Himalayan ranges where we were hiking.

Chola Tsho sits at an altitude of 15,150 feet, and we were several hundred feet higher up the hill, yet even in early December the skies were clear and the daytime temperature reached the mid-60s. Although extremely comfortable and photogenic, this did not feel right.

Anecdotal reports, both published and from our guides, suggest that snowfall amounts at higher elevations between November and January have decreased significantly over recent years, and that the monsoon season, normally between May and September, is becoming less reliable. In other words, it seemed as though we were witnessing the effects of climate change firsthand.

It was not just the smaller peaks that were showing signs of stress; even the summit of Everest itself is affected. According to published witness reports by Apa Sherpa, who in 2011 at the age of 50 climbed Everest for a record 21st time, there is less snow on the mountain. “The snow along the slopes had melted, exposing the bare rocks underneath, which made it very difficult for us to walk up the slope, as there was no snow to dig our crampons into,” he said. “This has made the trail very dangerous for all climbers."

Apa reports that some expeditions no longer have to melt snow for drinking and cooking at Camp 2 at 21,300 feet, and that he saw running water around Camp 4 on the South Col at 26,000 feet for the first time in 2009. He describes that weather patterns have changed dramatically in the foothills, too, and that potato yields and yak numbers have declined.

Other crops now grow at higher altitudes and have longer growing seasons than in the past. On our trek from Lukla (9,400 feet) to Namche Bazaar (11,280 feet) a few days earlier, we had passed many gardens with healthy crops of cabbage, garlic and bok choy growing far later in the season than they used to, according to our guides. Mosquitoes were found in Namche for the first time in 2008, and there are even reports of houseflies at Everest Base Camp at 17,300 feet. Similarly, we were surprised to see a butterfly hitchhike on the sleeve of one of the Sherpa at 15,000 feet during one of our hikes.

All these observations are consistent with the effects of climate change in this region.

At that moment, the milky green waters of Chola Tsho faced us. Like other glacial lakes in the region, it has been growing as a result of increased snowmelt from the surrounding peaks and from the retreating glacier itself. If trends continue, it seems likely that the moraine dam holding the lake in place will fail, releasing a massive inland tsunami of water and rock to wash down the valley toward the small town of Pheriche.

In the next valley to the southeast, an even more dangerous lake, Imja Tsho, sits at the base of Imja Tse (Island Peak). This lake, now up to a mile and a half long, over a quarter mile wide and 300 feet deep and the fastest growing major glacial lake in Nepal, is the subject of intense international scrutiny by scientists seeking to understand the nature of the risk.

If—or is it when—the lake bursts through its moraine dam, a wall of rock, mud and water will sweep down the valley, destroying homes and land for a generation. The town of Dingboche, where we stayed for two nights to acclimate to the high altitude, is in the path of this predicted GLOF and would undoubtedly be completely destroyed. Following similar warnings a few years ago, some residents moved their livestock to higher ground and evacuated the town. As described to us by our guides, they returned after a few days without incident but remain uneasy about the prospects of a catastrophe.

Chola and Imja are just two lakes that threaten this region. Seven miles to the west of Chola Tsho lies the Gokyo valley and the Ngozumpa glacier, which flows from Cho Oyo, at 26,906 feet the world’s sixth tallest mountain. The moraine field at the southern end of the glacier has created Spillway Lake, which has the potential to reach four miles long, six-tenths of a mile wide and 350 feet deep. This lake, fed by a series of smaller lakes sitting on the surface of ice interconnected by caverns and subglacial streams, has been observed to drain and refill within a matter of days as ice melts upstream.

Significant though these local changes are, they pale next to the loss of the Himalayan glacial system as a whole. Here, glaciers are retreating faster than anywhere else on earth, and predictions suggest they may all disappear within 50 years. It is estimated that 1.3 billion people live in regions affected by the Himalayan system, either in flood-prone areas or through their reliance on reliable glacier-derived fresh water. Huge areas of Asia could become uninhabitable if these rivers of ice are lost.

We had spent close to an hour overseeing Chola Tsho, taking photos and considering how change will surely come to this region, before our guide, with a grin on his face, brought us back to task. We had to get moving if we were to reach our destination at Lobuche, two miles and another 1,500 feet higher up the track to the north, before the sun set behind Cholatse.

Under the clear, warm skies of December, watching rivers roar downstream carrying melt water from Everest south to the plains of Nepal and beyond, I was struck by conflicting feelings of privilege, awe, guilt and humility. As we climbed up a steep slope to rejoin the trail, struggling once again to keep up, I thought about how long this unique environment could stay the way it is. How was it that the Sherpa we met were so friendly and welcoming and seemed not to harbor any grudge against the outside world that caused these problems? Could local solutions to relieve glacial lake pressures be developed in time to avoid catastrophe? Were global solutions to combat climate change even possible in this hyper-political world? What could I do?

Back in the United States, with time to reflect on these experiences, I think the best thing that I can do is tell people what I learned: that the canary isn’t doing so well these days.

Images by author.