(CNN) - An experienced mountaineer, Adrian Ballinger knows about the dangers of Everest better than most. He's spent 12 seasons as a guide on the world's highest peak and has summited it eight times -- once without supplementary oxygen, which almost cost him his life.
"I really think if Everest had been 15 feet higher, I wouldn't have summited and got down alive," Ballinger tells CNN.
The mountain's ruthless nature has been laid bare in recent months. Poor weather has restricted the time frame for summit attempts, as well as making living conditions and Base Camp preparation even more challenging.
The death toll of 11 -- exacerbated by severe weather and queues to the summit -- already makes this season the fourth deadliest on record, according to Nepal's Tourism department.
Ballinger, who runs a guiding company called Alpenglow Expeditions, has had first-hand experience of the crowding that has taken place in order reach the top of Everest.
"We saw close to 100 other climbers also moving into camp getting ready to summit on May 23," Ballinger says of a day that saw deaths at the top of the mountain.
"To me as a guide, there's no way I would send my team up with 100 other climbers into the 'death zone' above 26,000 feet."
The "death zone" is a mountaineering term that describes altitudes over 8,000 meters where the human body is exposed to insufficient levels of oxygen.
Five years ago Ballinger's company presciently moved from the Nepal side of Everest -- where images of a long, snaking queue up to the summit last month went viral -- to the Tibetan side of the mountain, which he believes is better regulated by local authorities. Of the 11 deaths this year, nine came on the Nepal side.
"We ended up holding our team for a full 24 hours at the highest camp," adds Ballinger, recalling what happened last month.
"We had additional oxygen brought up so we can make sure our team stayed safe and comfortable. It was worth the risk of the next day being bad versus going with 100 people which is just an obvious terrible decision from a mountain guiding perspective."
Danduraj Ghimire, director general of Nepal's Tourism Department, told CNN that poor conditions has been to blame for the number of deaths, forcing climbers to try and rush up and down the mountain during short windows of good weather.
He also added that inexperienced high-altitude workers were not to blame for the deaths, but that inexperienced climbers were more of a problem.
"There's only so much we can do to stop inexperienced climbers," he said. "This is something that the climbers need to ask themselves: am I confident enough to try Everest? Am I experienced enough?
"Climbing Everest is not a luxury, it's not a joke. Because of the challenging weather and the altitude, it's about a matter of life and death."
However, Ballinger says that inexperienced guides have contributed to a "herd mentality" at the top of the mountain.
"The realities of capitalism and commercialism [mean that] 80% of the market is this lower budget market, $25,000 to $35,000 trips. The only way to offer a $30,000 trip on Everest is to massively cut corners," he says, pointing to the need for trained Sherpas and mountain guides.
Sherpas, native Himalayan mountaineers, help climbers set up camp, ensure loads are evenly distributed, and take responsibility for the trekking group's safety. They are, in short, the best ally for foreign climbers.
"When you cut those things, I think you lose a lot of the decision-making ability that's necessary when you have a holiday season like this one when conditions are really difficult," says Ballinger.
To summit Everest doesn't only require the know-how of a local guide as well as extreme physical and mental endurance.
Meticulous preparation is also essential. Ahead of an Everest summit attempt, for example, Ballinger would sleep in an altitude tent at home in California to simulate the low-oxygen conditions on the mountain.
Only a few hundred people have ever climbed Everest without oxygen. Ballinger failed his first attempt on Everest in 2016, but was successful in 2017 -- something he says is the proudest achievement of his career.
"It took me two years of very dedicated work to train my body and my mind and get the right day and adjust my metabolism to be successful up there," he says.
"In terms of your lifestyle [in the Himalayas], everything changes. We live in tents, it's difficult to eat, difficult to sleep. We constantly deal with what I would call low-grade suffering, almost like a hangover."
'The savage mountain'
This July, Ballinger is trying to climb K2 -- the world's second highest mountain -- without oxygen. According to renowned Alpinist and mountain chronicler Alan Arnette, fewer than 200 people have ever summited both K2 and Everest, with or without oxygen.
Nicknamed "the savage mountain," K2 sits on the border of Pakistani-Controlled Kashmir and China in the Karakoram Range. Its routes and camps are exposed to rock falls and avalanches, while steep slopes and an unforgiving climate mean far fewer mountaineers venture to climb it.
Arnette calculates that there have been 379 summits of K2 and 85 deaths through 2019 -- a rate of 22% compared to 3% on Everest. For every four climbers that have scaled the mountain, one has died trying. It is also the world's only peak over 8,000m never to have to been climbed during winter.
"One of the things I'm hopeful about is that on Everest, I found the last 200 meters to be excruciatingly painful and difficult without oxygen, but I felt pretty good to 8,500m or 8,600m," says Ballinger.
"Hopefully the slightly lower elevation of K2 [8,611m] actually works well for my body and I can move well all the way to the summit.
"Really the only thing that can make you safer on K2 with that rock fall and avalanche hazard is to move faster. I've worked for over a year to be as strong and healthy and fit as I possibly can be to hopefully climb fast."
Introduced to rock climbing at the age of 11 when his family moved from England to Massachusetts, Ballinger has been a full-time guide for the past 15 years and has climbed on five continents, constantly seeking new challenges in different locations.
His vocation involves an element of risk taking, and the thoughts of his friends, family, and partner Emily Harrington -- who is also a professional climber -- are very much part of his approach when he takes on new challenges.
"What I feel is how often I'm willing to take risks," says Ballinger. "A real awareness of that risk and thinking about how often I'm willing to step into that real and why it's worth it.
"I'm very open to talking about it with my friends and my family and with Emily."
For her own part, Harrington is fully aware of the dangers posed by climbing big mountains.
The couple recently launched their own YouTube channel -- DangerStikTV -- that follows their lives together and on opposite sides of the world.
In one episode, Harrington tearfully considers the prospect of being apart and reflects that K2 is "probably one of the more dangerous things Adrian's ever done."
In another, they both come to terms with losing teammates to an avalanche in Canada: "It makes me think of Adrian a lot," says Harrington. "It makes me think of K2."
She is pursuing her own goals that are hardly risk-averse. A five-time US national climbing champion and two-time North American champion, Harrington is training to free climb El Capitan -- Yosemite's imposing, 3,200-feet rock face -- in a single day.
Free climbing uses ropes, harnesses and belays only as a means of protection, rather than to assist upward progress.
El Capitan has gained plenty of attention recently after Alex Honnold -- who has recently been partnering with Harrington on climbs -- scaled the rock face without ropes or harnesses, a death-defying feat that was captured in the Oscar-winning documentary "Free Solo."
El Cap, which soars above a thick row of trees in Yosemite, is uniquely exposed. Just to look up at it is dizzying enough, let alone clawing at its vertical surface with your hands and feet, the safety of ground thousands of feet below you.
'Afraid of heights'
Every time she faces a big wall like El Cap, Harrington says that the same human fears start to creep in.
"I've always actually been afraid of exposure and a little bit afraid of heights," she tells CNN. "When I was a kid, it was really hard for me to get through the process of falling.
"I feel like every time I go to El Capitan, I have to go through the same process I did when I was 12 years old -- learning how to take a fall onto a rope.
"It's taken years and years for me to realize that to be afraid is okay. Back when I was younger it was something that angered and frustrated me about myself, I would get really upset and down on myself.
"Now it's something I'm more willing to accept and just sit with it and accept that it's a part of me and it's something that I have to move through really slowly."
She says climbing -- and the practice of following a well-rehearsed route -- becomes almost meditative and that she conquers her fears on big walls by absorbing herself in the process.
"When I'm actually climbing, it's far easier for me because that is my comfort zone. Being on the wall, holding onto something, moving over the stone -- that is very comfortable for me," she says.
"When I'm in that world I can focus a lot more. With all the other logistics involved ... you spend a lot of time actually not climbing and that for me is the scary part.
"Climbing is massively mental. There's so much mental strength that's required and belief in oneself and confidence that's required in order to do the things that we do ... I think that a lot of times we forget about that side of things and performance in an athlete."
Harrington and Ballinger, who met on Everest in 2012, might be the closest thing the sport of climbing has to a "power couple." To use that tag, however, risks glamorizing this gritty pair.
Opposite sides of the world
They spend four to six months of the year apart, and while one dangles from ropes on a soaring Californian rock face, the other battles unforgiving storms and energy-sapping altitudes on the world's highest peaks in the Himalayas and the Karakoram Range.
Communication occurs between -- or sometimes during -- these climbs, depending on whether a sketchy mobile signal allows it.
It's hardly a relationship built on convenience, nor is it one that escapes the clutches of everyday life.
They're buying a house together in California -- logistically tricky when they're on opposite sides of the world -- and have to fulfill duties for their respective sponsors -- Eddie Bauer for Ballinger and North Face for Harrington.
"Emily and I spend a lot of time talking about climbing, but we also spent a lot of time not talking about climbing," says Ballinger.
"So much of what we love doing together is actually not our profession. We love cooking, we love spending time on Lake Tahoe, we love traveling to places we haven't been to before.
"We're both learning to fly airplanes now -- lots of different things that I think are really important for the health of our relationship."
Leading mountaineer Alan Arnette has written extensively about Everest and K2 and analyzed climbing data of the two mountains. CNN's graphic is based on Arnette's research.
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