Mount Everest stands 8,848.86m tall, Nepal and China announces

By Pradeep Bashyal | BBC News Nepali (Read this in Hindi & Nepali)

The world’s highest peak Mount Everest is 8,848.86 meters tall, Nepal and China jointly announced on Tuesday.

The new height of the mountain at the border of two countries is 86 centimeters taller than previously accepted height of 8,848 meters. The height also includes the snow cap.

In a written message, President of Nepal Mrs. Bidhya Devi Bhandari announced: “At this historic moment, after having measured and jointly processed the survey data by the respective survey departments of our two countries, I am pleased to join your excellency [Chinese president Xi Jinping] disclose height of 8,848.86 meters as the new height of Mount Sagarmatha/ Chomolongma."

Mount Everest is called Sagarmatha in Nepal and Chomolongma in Tibet.

Teams of surveyors from Nepal and China separately measured the height of the Everest. Until now, China had put the height at 4m lower than globally accepted height determined by the Survey of India during British colonial rule.

The measurement of the mountain was initiated by Nepal in 2017 after the huge earthquake in 2015 that was said to have a significant impact to the top of the world.

Known as Chomolungma in Tibet, the highest mountain spreads across the two nations, but its peak lies within Nepal's territory.

Despite having several measurements in the past, this is the first time Nepal has measured the height of the Everest on its own.

Later, China initiated a similar survey and both Nepal and China had agreed to share data and key findings in a joint statement signed by President Bidhya Devi Bhandari and her counterpart Xi Jinping in 2019.

A year later, the two sides made an official announcement.

Process

In the spring of 2019, two Nepali surveyors reached the summit of Mount Everest.

Reaching atop is drastically different than what is perceived in general.

A majority of the climbers tend to conquer the Everest when their mind and body turn lethargic.

A team led by surveyor Khimlal Gautam had a duty to be performed at the top despite mental and physical lethargy that summiteers report after reaching the top.

"For summiteers, scaling the highest peak means a great accomplishment. For us, it was just the beginning," Gautam had told the BBC upon his return.

His team spent around two hours at the top of the world placing a GPS tracking device, which cost him his toe due to frostbite.   

The device would synchronize with another 8 global navigation satellite system (GNNS) placed over different points across Nepal.

At the summit, the GPS antenna would record their precise position based on the satellite network.

Peter Hale Molnar, distinguished professor of Geological Sciences at the University of Colorado Boulder said, "With GPS, one can measure the distance to the center of the earth with an uncertainty of a centimeter or less. We measure heights relative to sea level. Measuring what sea level would be under Everest is hard."

Due to earth gravity-related with uneven mass distribution of earth, practically there isn't the same sea level.

The lead surveyor Gautam said, "Therefore, this is the most probable value. But given our unique approach and technology, we claim this is the most accurate height measured so far."

As a significant part of survey, the team had spent more than a double of anticipated time to get large range of data.

"Unlike other survey of the Everest in the past and even of Chinese this time, we choose 3AM in the morning to minimize errors that could have caused due to sunlight in the day time," Gautam added. 

Roger Bilham, the professor Emeritus of Geological sciences at University of Colorado Boulder has been long involved in the region and with some of the previous surveys.

He told BBC News Nepali: "The Nepal surveyors have very precisely corrected for the geoid using gravity and spirit leveling data unavailable to previous surveyors."

According to Gautam, the figure announced today is the ‘most authentic’, especially as there are multiple measurement techniques involved.

Apart from the modern GPS survey, the team also conducted the ‘old-school’ leveling survey, a popular method in the 19th century, when the height of the summit was measured relative to the sea-level.

According to Professor Roger, in 1857, sea level was measured in Karachi and Calcutta for one month, based on which, heights of several points in Bihar, India were measured. These points in Bihar were used to measure the height of the summit using triangulation.

The results of both the methods - GPS survey and leveling survey - were used to triangulate and validate the new height of the Everest, Gautam said.

China has previously conducted two height measurements of Mount Everest – first in 1975 and then in 2005. China had been showing Everest’s height as 8,844.43 (excluding the snow cap).

Members of the Chinese survey team installed a GPS device on the summit but they used China’s BeiDou navigation satellite system, believed to be a rival to the US-owned GPS.

Need to re-measure height

The Himalaya has been formed by a series of earthquakes since the collision of India and Asia approx 50 million years ago.

During the 2015 earthquake, Nepal at the longitude of the Himalaya, contracted north-south by up to one meter; the mountains north of the Kathmandu Valley rose by about one meter, according to Mike Searle, professor of Earth Sciences at the University of Oxford.

In this survey, Nepal government officials say that they have taken the reference of snowcap while measuring the Everest.

Mike Searle however added, "The snowcap on top of the Everest varies by meters every season. During the monsoon, snowfall can add two or more meters onto the summit, although usually, the west to east jet stream winds blast this off quickly."

"The height measurements are from permanent GPS station drilled and bolted into the rock. There is one just below the summit, one on the Hillary Step, and South Col, and from base camp downwards many more, these were originally put in by the Americans and National Geographic."

Prestigious Affair

One of the least developed economies Nepal had no option but to trust 'outsiders' to scale what it believes its measure treasure.

Without prior experience, the team had few textbook references, according to Nepali officials.

"With very limited resources it was quite a challenge. All we had was a sense of responsibility and quest for ownership. We wanted to end our reliance on outsiders," surveyor Gautam said.

"This was Nepal's team effort. Many of us used brains but personally, we risked our lives to make this happen."

The task might be tedious but its cost experts say isn’t that hefty. Equipment alone roughly costs one hundred thousand dollars.

"All it needs is an organization, energy, and competence," Professor Roger added. According to him, the figure achieved by Nepal's survey team is reliable as they have been ‘cautiously optimistic that they will improve on previous measurements’.

"Nepal's survey department is competent and keen to repeat the measurements of its mountain”

After the first scientific measurement of the Everest done by British India 161 years ago, this is Nepal's first own measurement of its mountain.

There have been a few measurements by several foreign teams. For instance, the northern half of the mountain was first measured by the British in the 1920s and then by the Chinese in the 1960s.

In 1999, National Geographic Society had come up with a height measuring 8,850 meters. But, Nepal didn’t own up this finding.