Why Does Everyone Climb Everest in May?

The AP reported this morning that three climbers who attempted to scale Mount Everest this weekend died and that two more were still missing. But about 150 climbers managed to summit the world's highest peak on either day?including a 73-year-old who became the oldest woman to reach the zenith.?

Why is everyone ascending Everest in May? To find out, and to get other answers to our questions about Everest, we talked to John All, a geographer at Western Kentucky University. All climbed Everest in 2010 via the Northeast ridge and has spent a year collecting data on climate change at Nepal's base camp.

Why You Should Go In May

It comes down to snow, temperature, and wind. "Mount Everest protrudes into the stratosphere, and most of the year the summit is buffeted by winds of over 100 miles per hour that will kill a climber in minutes or even hurtle them into the void," All told Popular Mechanics. "It is only during the onset or cession of the Asian Monsoon that these winds die down and allow climbers short seven- to 10-day windows to climb the mountain."

The highest recorded wind speed at the summit was a 175 mph in February 2004. For reference, a Category 5 hurricane has sustained wind speeds of at least 157 mph. Throughout the winter, hurricane-force winds pummel the summit for three days out of four.

The two windows in which those wild winds die down happen in May and September. But snow falls during the September calm, so fresh snow drifts offset the break from the wind. That's why so many people try the ascent in May, All says.

The monsoon season also provides survivable temperatures. The Everest summit temperature ranges from an average of minus 4 F to minus 31 F, but the temperature is generally warmer as the winds blow more gently from the end of May until the third week of October, according to weather reports.?

How Much Gear Is Up There?

"Not much anymore," All says. Climbers and sherpas get paid for every empty oxygen bottle that they bring down, and expeditions these days are cleaner than they used to be.?

And How Many Bodies Are There?

According to a study published in the British Medical Journal in 2008, from 1921 to 2006, there may have been 192 deaths above the 26,247-foot mark. That gives the summit a 1.3 percent mortality rate, the study found.

All says he saw bodies starting at about 27,890 feet. "I didn't see any until I hit the Northeast ridge, then there are probably five or six within 5 meters of the route and 10 within 10 meters of the route," he says.?

"The sherpas don't want to touch them. It's a religious issue. And you can't carry them down because you're close to dying yourself. It would take tens of thousands of dollars to bring them down. You'd have to have an entire expedition to get a body down. It would take five strong climbers at a?minimum."?

Do We Really Know How Tall Everest Is?

There's no question that Everest is the tallest point on the planet. "It has been measured dozens of times by every conceivable technology: Ultra-accurate GPS, laser, radar, and simple surveying," All says. "Now the only question remaining is what is its official elevation. Is it where the surface (snow) is located, or is it actually the rock itself, which is several meters lower? Either way, it is substantially higher than anything else on Earth."

In 1856, nearly 150 years before anyone measured the peak with GPS, Everest's original surveyors calculated the peak's height with remarkable accuracy. The Great Trigonometric Survey, which included the mountain namesake George Everest, put the summit at 29,002 ft.

Yet, as All says, the elevation is still not a settled issue. Mount Everest is 29,035 feet, according to measurements that National Geographic's team took on its Millennium Expedition in 1999. But ask China and Nepal and they might say that Everest is 29,028 feet. Earlier surveys established that height, and it falls within the National Geographic expedition's margin of error.?

Why can't surveyors do better? One big confounding factor is that scientists measure elevation about sea level, and sea level is not constant. It varies slightly around the world and it changes with tides, so the best practice is to agree on an average and measure from there. Another issue is plate tectonics. Everest rides the edge of a plate that is thrusting upward. Its height may be changing constantly.?

Another National Geographic expedition is on Everest now and they might settle the question of the peak's rock height. The team of North Face climbers and geologists from Montana State University plan to drill through the ice to the rock and take GPS measurements.

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