Killer weather on Mount Everest

From Montreal, at a joint meeting of the American and Canadian Geophysical Unions

In May 1996, eight climbers attempting to reach the peak of Mount Everest died. An analysis of weather patterns at the time suggests that a sudden drop in barometric pressure may have played a significant role in the tragedy.

During the first week of that month, Mount Everest lay beneath a zone of abnormally high atmospheric pressure, says Kent Moore, a physicist at the University of Toronto. When wind speeds dropped on the evening of May 9, mountaineers from two expeditions left their 8,000-meter-high base camp and headed for the 8,848-m summit. On the afternoon of May 10, a storm with near-hurricane-force winds engulfed the peak and trapped 26 climbers on the slopes.

By May 11, the previous week’s high barometric pressure had plummeted by about 5 percent. Although that may not sound like much, atop Mount Everest it’s enough to reduce a climber’s oxygen intake by 14 percent. For mountaineers already near their limits of endurance, the adverse effects of the pressure drop probably compounded the insults of fatigue, high winds, and extremely cold temperatures. Eight climbers didn’t make it back alive, a tragedy chronicled in Jon Krakauer’s 1997 book Into Thin Air (Villard).

Moore’s analysis suggests that the sudden drops in barometric pressure on Mount Everest in springtime are associated with jet streaks, which are areas of higher-than-average wind speed within the jet stream that steers storm systems through the Himalayan region each spring. If confirmed, this linkage could open a way to forecast significant drops in barometric pressure, possibly preventing some climbing catastrophes, says Moore.