Right this minute, groups of slightly wind-burned climbers are chilling (literally) more than halfway up the south side of Mount Everest, letting their bodies adjust to the altitude and awaiting the chance to aim for the summit. They are part of the first spring expeditions from the Nepal side since a horrific avalanche killed 16 Sherpa guides last April and wiped out the crowded spring climbing season on the mountain’s most popular route.

(See: Mount Everest, in 3.8 billion pixels)

Their experience is different this year than it would’ve been last year in many ways. Here are six reasons why:

The climbing is tougher

Last April’s avalanche occurred at the western edge of the Khumbu Icefall, a narrow, steep portion of the Khumbu Glacier that is dotted with deep crevasses and huge ice formations. To get to the summit from Nepal, you have to get through the glacier one way or another. The western edge is a relatively quick and easy path, but it is susceptible to ice blocks breaking free from cliffs thousands of feet above, which is what happened last year.

This spring, climbers will take a more difficult but less avalanche-prone path closer to the middle and eastern side of the icefall. This path is steeper and slower, with deeper crevasses and more vertical ladders over ice cliffs.

The “new” route is actually an old route that fell out of favor in the 1990s when commercial expeditions became big business.

A climber makes his way down from the summit of Mount Everest. (Alpenglow Expeditions via AP)

The route may (or may not) be safer

Nepali authorities deemed the middle route safer because avalanches are less likely along this path, a major concern for Sherpa mountain workers, who make several dozen trips through the icefall ferrying supplies to and from Base Camp each spring. (By contrast, an average climber makes four to eight trips through the icefall while going up and down to acclimatize to the altitude before the final summit push.)

(Read: How dangerous is the Sherpas' work on Everest?)

However, the middle of the icefall has its own dangers.

The glacier moves more quickly in the middle, usually three to six feet per day. House- and car-size ice formations called seracs dot the terrain and can crack and collapse at any time. Fixed ropes and ladders that are secure one day can be dislodged the next, and new crevasses can open up, requiring additional ladders and ropes. During the 2011 season, for instance, just 23 ladders were needed in the icefall at the start of the season compared with 58 at the end, said Adrian Ballinger of Alpenglow Expeditions, who cited safety as the main reason he moved his Everest climbers to the Tibet side this year.

Medical help is closer

Nepali officials beefed up medical staff on the mountain for the spring season this year. The Himalayan Rescue Association Nepal said it will have four doctors at the Base Camp emergency tent and should be able to airlift sick or injured climbers off some parts of the mountain within 90 minutes.

The price is steeper

Not surprisingly, changes on the mountain mean expeditions cost more. Prices vary wildly from less than $30,000 for bare-bones trips to more than $100,000 for amenity-filled luxury excursions. (Veteran mountaineering journalist Alan Arnette estimated that even a solo trip without a guide or supplemental oxygen would probably cost $25,000.)

This year, nearly everyone will pay at least a little bit more in at least these key areas:

Permit fees — The Nepali government said it cut fees from $25,000 per foreign climber to $11,000, which is technically true, although several expedition leaders said few, if any, climbers ever paid $25,000. Nearly everyone took advantage of a group package, which made the true cost about $10,000 per person. This year, that option doesn’t exist, and the fee is a flat $11,000.

Worker insurance premiums — In response to Sherpa demands after the 2014 avalanche, the Nepali government raised the required insurance coverage scale for mountain workers. Life insurance increased 50 percent to $15,000 for high-altitude workers, and medical insurance will rise by 33 percent to $4,000, costs that are paid by expeditions. Western expeditions eager to attract and keep the most experienced Sherpas provide even more insurance (and higher pay).

The terrain is rockier

This is not so much a year-over-year change as a decade-over-decade one, according to longtime climbers and guides. While heavy snow is still common, Everest in general is getting drier, less snowy and more rocky than in decades past. Its glaciers have shrunk by more than 13 percent over the past 50 years, according to research presented at a world geophysics conference in 2013.

Climbers didn’t need scientists to tell them that.

“The first time I went on the Khumbu Icefall was 1988, and it didn’t seem to be as big a monster to get through,” said guide Lydia Bradey, who that year became the first woman to reach the summit without bottled oxygen. She summited again in 2008 and 2013 and was surprised by the difference in terrain. She said the rocks are now so close to the surface that it can take twice as long to get from Base Camp to Camp II.

Same for the notoriously steep Lhotse Face, which confounds less experienced climbers who are not used to wearing spiked metal crampons over their boots.

“As the years go by, the west face of Lhotse is becoming drier and less covered in snow, and the terrain is becoming icier and harder and even with some rocks,” Bradey said. “You’re climbing little tiny sections of ice with fixed ropes. … The west face of Lhotse is becoming a harder beast to get up.”

A porter carries crates containing oxygen tanks on his way to the Everest Base Camp. (AP)

The summit is higher

You can add a few millimeters to that official height of 29,029 feet. According to the U.S. Geological Survey, the mountain is probably about two- to four-tenths of an inch higher this year than last.

Blame plate tectonics.

Geologists disagree about how many millions of years ago the Himalayas were formed, but they are mostly united about how: As the Indian Plate crashed northward into the Eurasian Plate, the edges were forced up. (Everest climbers may see fossils of coral and other sea creatures when they cross a face of sedimentary rock known as Yellow Band at about 25,000 feet.)

Because the Indian Plate is still slowly moving, Mount Everest grows by two- to four-tenths of an inch each year.

Read more stories:

How dangerous is the Sherpas' work on Everest?

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