"I figured I was dead. I would just keep falling and never wake up."

This is how John All, co-author of Icefall: Adventures at the Wild Edges of Our Dangerous, Changing Planet, describes the moment after he plunged 70 feet into a crevasse in the Himalayas. Alone, and with a dislocated shoulder, he had to haul himself from ledge to ledge toward the surface, using only one arm.

But this is more than just another life or death adventure in the mountains, another 127 Hours or Into Thin Air. In addition to being an accomplished mountaineer, All is a scientist who uses his skills to reach places most people fear to tread, in order to bring back data that is helping us understand how climate change is altering the world’s highest peaks.

When National Geographic caught up with him at his home in Bellingham, near Seattle, All explained how he survived his fall into the crevasse, why climate change is making climbing more dangerous, and why it’s vital for scientists to get up in the mountains.

View Images Courtesy John All

“I had dug myself out of my own grave,” you wrote after that terrifying ordeal in the Himalayas. Talk us through the incident.

[Laughs] That’s a big question! Everest had been closed after an avalanche, so we had moved to Mount Himlung, a mountain near Annapurna on the border between Tibet and Nepal. Because of the accident on Everest, we were down to just three people and one of them was not feeling well. Jake, the other climber with me, agreed to take her down. So I had the difficult choice of staying up there alone, which is never ideal. But I thought, “We've got an established camp, I walked around, it looked pretty safe.” I thought it would be alright.

The morning after they headed out, I went to get some water to boil to make coffee and to collect some snow samples. It was bright sunlight so I went out with a light jacket and no headlamp or satellite phone. There was not a hint of a crevasse. But as I was about to take a sample I suddenly had that free-falling feeling. It's pitch black, and I feel my face smashing into the ice. The suddenness was overwhelming. I went from bright sunlight to pitch black as my world collapsed.

I figured I was dead. I would just keep falling and never wake up. But suddenly I was stopped. It was like a miracle. But once I started looking around, realizing where I was at, I knew I was dead. My legs were dangling over the edge. Just my upper body was on the block of ice that was holding me up. I couldn't get up because I had ripped my arm out of its socket and broken all the bones in my shoulder and arm.

It was like a meat locker. I could feel the cold penetrating my bones already. Because the rest of the team had just headed down, I knew they needed to recover and then would need a day to get back up. It would be a minimum of two days, and I knew I wouldn't live that long.

That's when I pulled my research camera out and started talking to myself about all my options. I take photos of everything I do because, if I'm working in Africa and I need to recall a detail, that's going to be the best way to do it. I was also thinking about my mom and my friends and family and realized that just talking wouldn’t convey what was happening to me nearly as well. So I started recording things.

It was too soft and steep to go straight, so I had to head to the right, climbing with one arm. I had my ice tools so I would place one as far as I could reach, pull on it, then reach back and grab the one behind, and move it forward, climbing from ledge to ledge. It would take me ten to fifteen minutes of climbing over the void before I’d hit another ledge. Every time I stopped, I would take a video. There were four or five major ledges on the way out and I had to climb hundreds of feet to my right, in order to go those 70 feet up.

View Images John All broke 15 bones, dislocated his shoulder, and suffered from internal bleeding. He was rescued one day after his fall and transported to a hospital in Kathmandu. Photograph by Niranjan Shrestha, AP

When I finally got out, I thought I would feel relieved. But I'd spent every bit of my energy, all my heart and soul, getting to the surface. I tried to stand up but I just fell to the ground. That's when I realized I was not saved. I still had to crawl back to my tent. So it was elation, but a fearful elation, because I knew there was still a lot to do.

The worst part was, I had a canteen of water. I hadn’t drunk any for 24 hours and I had been working really hard. So I was dying of thirst. But there was no way to open it with one hand. I tried my teeth and my ice axes, everything. But I just had to listen to the water sloshing about in the canteen all night while I had this incredible thirst.

As a young man you were a scientist first and a mountaineer in your spare time. The two halves of your life came together in the American Climber Science Program. Talk about its creation and goals.

Just prior to creating the program I'd been in Nepal on a Fulbright, teaching Nepali graduate students how to collect data in the mountains. I realized there was this big gap. There were lots of scientific questions in the mountains but it's a dangerous place and difficult for people to access. So there was a lot of data that wasn't being collected.

Being a climber and knowing lots of really great climbers, as well as working with the American Alpine Club, which focuses on conservation efforts, I realized that if we could bring these two groups together it would allow safe travel for noble scientific goals. There aren’t too many people who have taken the time to become both a really good climber and a really good scientist. Most scientists, or most climbers, focus on that single passion, so I’m sort of unique in that I have pursued both fully.

The goal of the program is to take advantage of climbing expeditions better. Normally, when you have a scientist going to the mountains, he might be a glaciologist and so he goes in and collects glacial data. I didn't think that was very efficient. What I wanted was get a glaciologist to work with a geologist, to work with an ecologist: lots of “ologists” with different expertise working together to look at the impact of climate change on these systems.

View Images Thomas F. Hornbein and William F. Unsoeld pause on the West Ridge of Mount Everest in 1963. Photograph by Barry Bishop, Nat Geo Image Collection

You write, “Mountains have always been unstable. But in recent years, climate and weather changes have made climbing seem even more like roulette.” Explain some of those changes taking place on Everest, and other mountains, and how it affects mountaineers.

When you look at climate change, the evidence in the mountains is overwhelming. They're changing so fast. Glaciers that are tens of thousands of years old are retreating up the mountain and disappearing before our eyes. Those changes are unprecedented. If you had a ticket anywhere on earth to see the impact of climate change at its most dramatic, there's no doubt it’s the mountain ranges.

Several famous climbing routes around the world are no longer in existence, like the Petit Dru, in Chamonix, France, also known as the American Route. Basically, the entire chunk of rock people used to climb disintegrated a few years ago. Similarly, the West Ridge on Mount Everest, which was first climbed by an American, can’t be climbed anymore because the ice has all melted. This is happening around the world.

Your latest venture is the Mountain Environments Research Institute. Talk about its mission—and whether you are concerned about President Trump’s plans to slash funding on climate change science?

In terms of our mission, it's to take the next step. Scientists have created niches. They know what they're doing in terms of how they want to approach science. But we need to have more people in the mountains and access to data, for now and the future. The Mountain Environment Research Institute is intended to train the next generation. We focus on three things: science, societies, and skills. What is the physical science of glacial retreat geology and who are the societies in these mountains that are affected? What can they inform us about how to better adapt? The final one is skills, which means avalanche awareness and wilderness medicine, all the things people need to go out into the wild and survive.

In terms of President Trump, politics changes in the wind. Trump won't be here forever, but fundamentally changing the planet we live on is forever. And I feel like there's an overwhelming desire across the political spectrum to understand what's happening. So, short term, yeah, the funding is difficult. But in the long term, this is the only planet we have and we’re changing it at an amazing rate. Pretty much everyone recognizes that. So, he’s a minority voice.

View Images After a massive rockfall, climbers can no longer follow the American Route up the Petit Dru in Chamonix, France. Photograph by Philippe Desmazes, AFP/Getty

Some people regard the idea of focusing on adapting to climate change, rather than preventing it, as a kind of capitulation. You disagree, don’t you?

If we want to stop climate change utterly, we will have to stop all use of fossil fuels. And that won’t happen in the near future. We depend on them for fighting fires, for ambulances, for power or food production. So we have to have two approaches. The first is political, to find ways to use fewer fossil fuels. The more important thing is recognizing that the world will continue changing and that we can adapt to those changes. Turning away from the problem won’t work in a crevasse and it’s not going to work for our future. We've got to find a way to survive and flourish in our environment.

One of the main things I try to do is look at what's happening both from a physical standpoint but also how societies are adapting. How people in Central America deal with frequent hurricanes because people in Florida are going to have to deal with more frequent hurricanes; or how people in Africa deal with drought, because people in Texas are going to have to deal with drought. There are analogues and parallels for all the changes that are occurring around the world.

You are sometimes asked to give motivational speeches. Would you share with our readers some of the life lessons your expeditions have taught you?

In the book, I talk about Tom Sawyer. I feel like he did when he walked in on his own funeral. You see what your life would look like with you no longer in it. And that changes how you view things and value things. A new car or house is less important than the people you love and your dreams. But living your dreams is a hard thing to do. I’m not saying, quit your job and give all your money away, but think about what will mean something to you in the long term, with a focus on family and friends, because that's what really matters when you're facing death. You're going to be thinking about the loves and friendships and dreams you didn't nurture. Thanking everyone, every day, is really important.

This interview was edited for length and clarity.