[The most commonly accepted figure for Mount Everest’s height is 29,029 feet, a measurement that dates to the 1950s. Some scientists believe that the world’s highest mountain may have shrunk slightly after a powerful earthquake struck Nepal in 2015.]
By Joanna Slater
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An
aerial view of Mount Everest in April. (Sarah Lai/AFP/Getty Images)
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KATHMANDU,
Nepal — When Khim Lal Gautam
reached the top of Mount Everest at 3 a.m. on May 22, it was dark, windy and
lethally cold.
Gautam carried some unusual baggage — a
ground-penetrating radar and a top-of-the-line satellite navigation device.
Unlike most climbers, he and his team remained at the summit for nearly two
hours so they could take the measurements they needed. Gautam suffered a
serious case of frostbite, and his colleague nearly died of a lack of oxygen
while descending.
But they completed their mission: to obtain
crucial pieces of data that will help determine Mount Everest’s true height.
The most commonly accepted figure for Mount
Everest’s height is 29,029 feet, a measurement that dates to the 1950s. Some
scientists believe that the world’s highest mountain may have shrunk slightly after
a powerful earthquake struck Nepal in 2015.
Now, for the first time, Nepal has sent its
own teams outfitted with the latest surveying technology to come up with a new
measurement of the peak. The two-year, $1.3 million effort is driven both by
patriotism and scientific inquiry, experts say.
The southern flank of Mount Everest “belongs
to Nepal, but for 170 years foreigners have been measuring its height,” said
Roger Bilham, a geologist at the University of Colorado. The current project
could be “the most accurate measurement ever made.”
Sometime early next year, the new height will
emerge from a modest cluster of offices on the ground floor of a government
building in Kathmandu, home to the country’s Survey Department. Susheel Dangol,
the chief survey officer, recently installed a keypad-entry system for his
department just to safeguard the Everest data.
“Everyone is curious about the project,” he
said with a grin. During an interview, his cellphone rang with a call from a
senior official in the country’s Land Ministry inquiring about the progress of
the work. Dangol has developed a stock response to those who ask about the
final figure: At the moment, I’m unable to say.
Dangol, 38, oversees a team of 80 people who
have hiked, driven and helicoptered across Nepal to gather the data required
for an updated measurement. Among their challenges: transporting a $200,000
Canadian-made gravimeter — which measures the force of gravity at a given
location — along juddering Himalayan roads to nearly 300 different spots.
The question of Everest’s height is
intimately linked to its modern history. It is known in Nepal as Sagarmatha and
in Tibet as Chomolungma. The search for the mountain’s English name began after
it was declared the world’s highest peak by surveyors in India in 1856. (Its
namesake is George Everest, the prior chief surveyor of India, but even he
wasn’t crazy about having the mountain named after him.)
Dangol’s team is tackling its task with two
methods. The first is to measure Everest the old-fashioned way using
trigonometry. Such calculations produced the first-ever tally of Everest’s
height, as well as the measurement taken in the 1950s by an Indian team that
serves as the current standard.
But that technique will serve as “a check, a
redundancy,” said Christopher Pearson, a research fellow at the University of
Otago in New Zealand who consulted with Nepal on the project. The pathbreaking
part of the effort will come through the second method, which relies on a
combination of readings from a satellite navigation system and a complex model
of sea level.
Enter Gautam, a 15-year veteran of the survey
department. The 35-year-old had already summitted Everest once before in 2011.
This time, however, his four-person team was carrying 90 pounds of equipment in
addition to their regular climbing gear. They planned their ascent to arrive at
the summit in the middle of the night so their work would not be disturbed by
other climbers.
While most climbers limit their time at the
roof of the world to descend quickly from the “death zone,” Gautam and his team
“did not have that privilege,” he recalled. They stayed at the summit for an
hour and 45 minutes, taking readings with a Global Navigation Satellite System
device and a ground-penetrating radar that can gauge the difference between the
actual rock summit and the snow that covers it.
Wearing bulky mittens against the extreme
cold, Gautam and his team couldn’t operate the small knobs on their equipment.
So they took off the mittens and worked in fleece gloves instead. For weeks
afterward, Gautam had no sensation in his fingers. The frigid temperatures also
damaged his feet: He lost the tip of his left big toe to frostbite and now
wears only sandals, rather than shoes.
On the descent, all their food and water was
gone, and Gautam’s colleague ran out of oxygen, a life-threatening situation.
Their climbing guide managed to borrow a bottle from another Sherpa who was
heading up the mountain, Gautam said, saving his colleague’s life.
Although the data they carried with them on
the way down weighed nothing, “its preciousness made it so heavy,” said Gautam.
Yet the satellite readings from the Everest
expedition are not sufficient. They give the mountain’s “ellipsoidal” height —
the height of the summit above a smoothed geometric model of the Earth. The
readings do not reveal an object’s precise height above sea level.
Judging exactly where sea level would begin
beneath Everest’s massive tons of rock turns out to be a key question.
Generating the model of sea level required lugging a gravimeter, which is
carried in a large suitcase-like box, to 297 spots in Nepal. “We have to be
cautious and drive slowly,” Dangol said. At each measuring point, the machine
must be calibrated before taking readings for two sessions of three minutes
each.
The data collection will be completed next
month, Dangol said. Then the processing will begin: six people, sitting in a
room equipped with high-speed computers and specialized software, for three to
four months, checking and rechecking the figures. It will be a “closed camp,”
Dangol said. Not even he will know the results at first.
Nepal’s effort has been “incredible,” said
Pearson, the surveying expert in New Zealand. “Staggeringly, it has all worked,
and they have all the information they need to get an accurate height.”
Dangol is already looking forward to next
year, when Nepal plans to unveil Everest’s new height — both the rock height
and the snow height, down to the centimeter. That will be “kind of like a
thesis defense,” he said.
Even the loss of part of his toe did not dull
Gautam’s pride in his work. “We are so happy because we finished our difficult
task,” he said. “I was ready to take [a] risk for the nation.”
Ankit Adhikari contributed to this report.
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