On a postcard day in 2021, Tenzing Gyalzen Sherpa crested the Balcony, a windswept rest spot high on Mount Everest’s Southeast Ridge. In front of his crampons, half-buried in the hardened snow, were the remains of the world’s highest weather station.
When the station was first assembled and bolted to the rock, it looked like an elaborate backyard antenna festooned with bird-feeders and weathervanes. In reality, it was $30,000 of precision instruments designed to measure wind, humidity, temperature, solar radiation, and barometric pressure. Now, the mangled seven-foot-tall mast lay on its side, embedded in ice.
Tenzing, a 31-year-old electrician and mountain guide, removed his phone from his down suit and began taking pictures of the scene. The Balcony Station had stopped transmitting on January 20, 2020—seven months after it was installed. It was one of five automatic weather stations placed in May 2019 as part of a partnership between the National Geographic Society, Tribhuvan University in Kathmandu, and the Nepal government, with funding from Rolex.
Kneeling in the snow next to the wrecked station, Tenzing removed a screwdriver and wrench from his pack and began to unfasten a small gray pelican case that was bolted to the mast. In it was a data logger that contained the last data the station had collected before succumbing to the extreme conditions.
For climate scientists Tom Matthews and Baker Perry, co-leaders of the project, the readings the station broadcasted via satellite link have provided a trove of insights into the meteorological “hidden realm” of the world’s highest mountain and the surrounding Hindu Kush Himalaya. As the 2019 and 2020 data continue to be analyzed, they're yielding surprising conclusions across a diverse field of studies, from human physiology to questions of long-term water supplies and seasonal crop cycles.
In particular, the stations have revealed that high-altitude snow and ice were disappearing much faster than previously assumed.
“The summit of Mount Everest may well be the sunniest place on earth,” Matthews says. When all that energy is reflected or absorbed into the mountain’s surface, it causes solid ice to transform directly to vapor, producing significant losses of the ice mass—even at temperatures well below zero.
“Effectively, there’s more melting going on than we knew at high altitude, which affects our estimates of how much snow there is," Matthews explains. "And that can cascade into estimates of how sensitive glaciers are to temperature change.”
From the weather stations' data, the team also gleaned new information relevant to the hundreds of mountaineers who come to Everest every year. For example, Matthews discovered that the amount of oxygen available to climbers on the upper slopes varies considerably with the weather.
Altogether, the network was gathering information that could directly impact not only the lives of mountaineers and Sherpas, but also the 1.6 billion people who rely on fresh water from the region—until its components began to fail.
At about the same time the Balcony Station stopped transmitting, the wind sensors below it—at the next highest station, on the South Col—went offline as well. “We saw a gust of about 150-odd-miles an hour right before, so there’s no wondering what happened,” Matthews says.
But before the technology could be repaired, COVID halted all activity on the south side of Mount Everest in 2020. And so it wasn’t until last year that Tenzing and another Sherpa could finally visit the Everest network for its first official maintenance.
At the lower stations, they installed new sensors, replaced batteries, and inspected fittings and bolts. Tenzing then proceeded up to the Balcony Station to assess the damage and retrieve its data logger.
But he wasn’t done. The team was already planning the mangled equipment's replacement, an improved weather station, and Tenzing was to survey a new, higher location for it. He continued upward until he reached Bishop Rock, a landmark named for Barry Bishop, a member of the first U.S. expedition to summit Everest, in 1963 (and a former National Geographic editor). At 8,810 meters, it's about 40 vertical meters below the summit—and the planned site for the new highest station.
Weather station test lab
The term “automated weather station” is a bit of a misnomer since every weather station must be regularly maintained by human technicians. Against the weather, any moving part will eventually fail.
Ask Keith Garrett. As director of technology at the Mount Washington Weather Observatory in New Hampshire, Garrett maintains a network of 18 automated weather stations across the White Mountains. Sitting in the trajectory of three major storm tracks and only 100 miles from the North Atlantic, Mount Washington routinely records winds in excess of 100 miles an hour during more than 100 days a year.
“We’ll see temperature sensors ripped clean off, with the radiation shield shattered,” Garrett says. “Pretty much, I’m trying to think of something that has not broken.”
All this made Mount Washington an ideal testing ground for the team building version two of the Everest weather stations.
Violent winds were a key factor the Everest engineering team had to consider. Part of the benefit of putting a weather station near the mountain's summit is that it can actually measure the lower part of the jet stream—but that also means the wind sensors have to be able to endure sustained periods of hurricane-force winds.
And yet, a station's wind sensors generally are among its most vulnerable instruments. “With propeller-driven anemometers, they require regular maintenance. The bearings wear out, the assembly itself can fail, the propellers break—especially under heavy icing,” Garrett says.
By far the least problematic wind sensor is a Pitot Tube anemometer, a device invented in the 18th century by French engineer Henri Pitot. Today, its modern iterations are omnipresent in the aviation industry in the form of narrow metal tubes that protrude from wings and noses of aircraft.
“The benefit of the Pitot sensor is that it’s got no moving parts,” Baker Perry explains. But it also has a downside: The sensor can only monitor wind from a 40-degree width in a fixed direction and must be facing the prevailing wind. And since everything must be carried by hand up the mountain, weight is a major issue. So, working in collaboration with the National Geographic team, Garrett radically stripped-down existing Pitot technology, reducing a 44-pound system to less than five.
After a winter of testing on the summit of Mount Washington, the new sensor seemed viable. It only needed to be carried to the roof of the world and installed.
New and improved, higher up
This spring, Tenzing, Perry, and Matthews returned to Everest. With them were 12 other Sherpa, most of whom had participated in the original weather station expedition. The team assembled at base camp, along with hundreds of recreational mountaineers and guides who congregated for the main 2022 climbing season.
The new station they brought to install on Bishop Rock included several upgraded components, including Garrett’s ultralight Pitot Tube wind sensor design. Their plan was to remove the destroyed station at the Balcony and assemble the new one at the Bishop Rock site Tenzing had scouted out the year before.
This would be no small effort and not without risk, but Tenzing and all the Sherpas working on the mountain recognized that the weather stations provided several direct benefits. Weather data is essential to any big mountain climb, helping guides plan expeditions and keep clients safe. Then if things do go wrong and a climber must be rescued, providing real-time data to helicopter pilots and rescuers increases the odds of success exponentially. Tenzing puts it simply: “We save more climbers' lives."
On the morning of May 9, team members began to arrive at Bishop Rock at 9 a.m. The wind raked over Everest at 40 miles an hour, pushing the windchill down to 40 degrees below Celsius.
As the team started to set up the new weather station, Matthews found the fingers on his right hand were wooden with frostbite; he could offer no real help. But the Sherpa guides had been preparing for this moment since 2019. Eight team members each climbed with a 24-volt battery in their down suit to warm them for drilling the vital anchor bolts.
In the biting, gusty air, the successful installation took about two and a half hours, an hour longer than the team had hoped. Tenzing completed the final wiring to power up the station.
By the time Tenzing, Matthews, and their Sherpa colleagues made it back down to base camp several hours later, the new station was already sending data. “We have a good chance of measuring a full winter’s wind,” Matthews reflects. “That would be fascinating.”
Meanwhile, news had broken that a Chinese team of scientists had installed their own network of seven weather stations on Everest. It was on the north side of the mountain, the opposite side from the climb Tenzing, Matthews, and Baker led. And the altitude of the highest station in the Chinese network? It's reported to be roughly the same elevation as Bishop Rock. Just a stone’s throw from the summit.
Does this mean that there’s a new international race to put weather stations on the world’s highest mountain? Matthews downplays such talk. “I believe more information coming from Everest is far better for everyone,” he says.