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At nearly 8,850 meters above sea level,. Mt.

Everest’s summit is unquestionably the highest point on Earth. But from a climber’s perspective, it doesn’t always feel that way. Thanks to the physics of our atmosphere, at times, it can seem lower than its neighbor,.

K2 — the second highest peak in the world. Both Everest and K2 climb over 8,500 meters into the sky. At these heights, climbers often carry supplemental oxygen, because there’s so little air to breathe.

This is because as altitude increases, air pressure decreases. There are a couple reasons for this. For one, because they’re further away from the core of the planet, the air molecules higher up literally feel less pull from gravity.

But also, the air lower down has more air sitting on top of it. So there’s more physically pressing down on it than on higher-altitude air. Now, thanks to the physics of gases, we know that decreases in air pressure are proportional to decreases in air density.

So, the decreasing pressure as you ascend means that, quite literally, there are fewer oxygen molecules in any given volume of air. But, unfortunately for us humans, our lung capacity needs time to catch up to this change. So the higher up a climber goes, the fewer oxygen molecules they take in with each breath.

The thing is, while elevation is a big factor in air density, it’s not the only one. So the air pressure atop Everest doesn’t just depend on the peak’s height. It turns out different weather conditions can cause the air pressure on Everest to vary by up to 34 hectopascals.

That’s like losing 737 meters of height! And, since Everest is only about 250 meters higher than K2, sometimes, K2 feels higher than Everest. Everest’s air pressure changes are due to atmospheric circulation; that’s just a fancy word for the way air moves around our planet.

It’s the same thing that affects our daily weather and climate. So basically, it’s just like how, at sea level, we can experience high pressure fronts and low pressure fronts. But if you’re a climber, particularly one climbing without supplemental oxygen, this means your experience on Everest could vary a lot depending on how high the summit feels on that day.

In fact, researchers found that all climbers who successfully climbed Everest without oxygen did so within a relatively narrow air pressure range. That’s not a huge surprise, because air pressure tends to be higher when weather is good, and climbers tend to wait for parts of the year when there is better weather — like between May and October. But this also means that climbers usually summit Everest when it feels like it’s at a lower altitude.

Or to put it another way, climbers haven’t really experienced the full height that Everest has to offer. And they probably won’t going forward. See, air pressure tends to increase when temperature increases, because when air heats up, the molecules in it start to move faster and collide with each other more.

Well, research shows that the air pressure on Everest’s summit has increased in the past decade, which is tied to an increase in temperature. But more importantly: a global temperature increase of two degrees — the goal of the Paris Agreement — would make Everest’s summit feel about 120 meters lower. So, ultimately, Everest is probably going to get a bit easier to climb… when it comes to the air, anyway.

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