There’s good news and bad news at Denali, North America’s tallest mountain.

The bad news is that the 66 tons of frozen feces left by climbers on the Alaska summit is expected to start melting out of the glacier sometime in the coming decades and potentially as soon as this summer, a process that’s speeding up in part due to global warming.

The good news is that this year, for the first time, the guide companies that lead many of the 1,200 climbers who attempt the summit each year have voluntarily decided to start packing out their human waste. This comes just a year after the National Park Service instituted a policy that all such waste below 14,000 feet must be carried off the mountain.

“Climbers and particularly guide services are really embracing the new policy and are even exceeding it. It has become kind of an informal badge of merit to carry off all your waste,” said Michael Loso, a National Park Service glaciologist who’s been studying the problem of climber excrement on the mountain for close to a decade.

Denali is a majestic mountain about five hours north of Anchorage, Alaska. At 20,300 feet, it's visible from the city on clear days. It's one of the Seven Summits, the highest mountains on each of the seven continents. Conquering them all is considered a major mountaineering challenge in the climbing world.

The poop problem is very real. Climbers scaling Denali, previously known as Mount McKinley, generate close to 2 metric tons of human waste each year, according to the National Park Service. (The average human “deposit” weighs half a pound and the average length of a climber's stay on the mountain is 18 days, which is how researchers got the figure of 66 tons over the course of the past century.)

Initially, human waste was left in snow pits on the Kahiltna glacier, the most common route up, or thrown into deep crevasses at higher elevations. It was believed that the waste would be ground up in the ice over time.

It turns out that what goes around comes around, even in a glacier, Loso said. He performed several experiments that show the buried feces eventually resurface farther downstream on the surface of the glacier, where they begin to melt.

This is true of all glaciers, which are really extremely slow-moving rivers of ice, though the process seems to be speeding up.

Research by the National Park Service found that in the past 50 years, the area covered by ice within the Alaskan parks has diminished by 8 percent.

“We have lost more glacier cover in the Alaskan national parks than there is area in the whole state of Rhode Island,” said Loso.

“One of the consequences of warming temperatures is that the surface of the glacier is melting more quickly,” he said.

This means that waste deposited at the lowest climbing camp on the mountain could start reappearing soon, maybe even this climbing season, which begins in April. Waste deposited higher up the mountain will take longer to appear.

“That could be as much as two to three centuries,” Loso said.

Park Service staff are keeping their eyes open, but they’re not making special trips to look for excrement.

“We don’t choose to spend our limited funding to just hunt for it all summer long,” Loso said.

Still pretty yucky

Denali has to deal with excrement. On Mount Everest, melting glaciers are exposing the bodies of climbers who had long been buried in the snow and ice. Because elevations are lower on Denali, most climbers who die on the mountain are carried off to be buried.

A 40-some-year trip through a glacier doesn’t make human waste any less gross. Loso’s research suggests that, in general, the bacteria and other bugs that live in feces survive after being buried in the snow or dropped in a crevasse. Tests of the rivers into which the glacier melts found fecal coliform bacteria, albeit in amounts well below the standard for recreational lakes and rivers.

It won't be pleasant for whoever finds that emerging poop.

“The waste will emerge at the surface not very different from when it was buried. It will be smushed and have been frozen and be really wet. It will be biologically active, so the E. coli that was in the waste when it was buried will be alive and well. We expect it to still smell bad and look bad,” Loso said.

Packing it out

The National Parks Service realized there was a poop problem on Denali years ago. In 2001, it launched a pilot program with the American Alpine Club climbing group to test small, lightweight portable toilets called Clean Mountain Cans.

These reusable bucket-size containers hold 1.8 gallons of solid waste and are lined with a biodegradable bag.

But no urine, notes Joe Horiskey, director of RMI Expeditions. “If you urinate in the CMC, it’s going to freeze and increase the weight.”

After years of testing, last year’s climbing season was the first in which all climbers were required to pack out their excrement below 14,000 feet. Above that, they are allowed to throw the frozen bags into one designated area in a deep ice crevasse.

But for this year’s climbing season, six of the seven guide companies – which take about 50 percent of climbers up the mountain – have voluntarily committed to packing out all their waste, said Tucker Chenoweth, a mountaineering ranger at Denali with the National Park Service.

That means carrying cans of excrement all the way to the summit and back. It’s something the guide companies have been doing informally for a while, but now they're making the leap into total removal.

It’s not the easiest thing to do, said Todd Burleson, president of Alpine Ascents International.

“You’re already carrying 100 pounds and then you’re adding another 20 pounds of feces. But it’s the right thing to do,” he said.

Chenoweth says a lot of individual climbers, especially Americans, are also packing out all their waste.

“There’s a pretty strong ‘Leave no trace’ ethic among U.S. climbing and outdoors folks. It’s kind of part of the deal,” he said.

'The best thing for the mountain'

So how do you deal with 21 days' worth of poop? Very carefully.

Each climber is assigned their own Clean Mountain Can by the Park Service before they fly up to base camp at 7,200 feet.

From the moment they touch down on the mountain, all solid waste goes into that can. No trash or wet wipes are allowed, though toilet paper is OK.

“We say about 12 uses is a full can. It weighs somewhere between 10 and 15 pounds when full,” Chenoweth said.

Guides delicately note that up on the mountain, where climbers are eating mostly freeze-dried food, bathroom needs are a little different than down below.

“It might not be an ‘everyday’ thing,” Horiskey said.

The cans are equipped with a gas release valve, so the lid doesn’t pop off when they’re flown off the mountain from base camp.

On the lower part of the climb, climbers use sleds to hold their gear, which includes the cans. Due to the altitude, the cans' contents freeze, so they're not smelly.

On the last leg of the climb, the sleds aren’t used and the cans are strapped to climbers’ backpacks.

“This is something we will all be getting used to,” Horiskey said. “But it’s the best thing for the mountain. It’s just what we’re going to have to do.”