Scott Stoll logo world traveler. A bicycle wheel and the globe symbolizes Scott's journey around the world on a bicycle.
Underwater bubble ring of oxygen
A bubble ring underwater looking like the "O" in oxygen. Photo courtesy of Joakant.

Introduction to global oxygen depletion

This article is part of a series

Are humans consuming oxygen faster than it can be replaced? 

We are all aware of our reliance on fossil fuels and their byproducts of greenhouse gases and pollutants, like carbon dioxide (CO2) and carbon monoxide (CO). But have you ever wondered about the other half of the equation? As humanity burns more and more fuel, we are also burning more and more oxygen. Simultaneously, we are destroying the plants and microorganisms that make the oxygen. At what point does the Earth reach a tipping point? And, how long before we run out of air to breathe?

In this series of articles, I answer these questions and explore how global oxygen depletion affects climate change. Below I highlight some of my discoveries. But first, you may want to know why I care.


I began actively researching this way back in 2005. I had just returned from riding a bicycle around the world, and I was tired of choking on car exhaust. But my interest started when I was a young teenager. I remember asking my mother, “How do the trees make enough oxygen for all the cars?” I’m not sure how I even thought of this, but I do remember being dissatisfied with the answer, “Don’t worry. People wouldn’t make cars if there wasn’t enough air.” My mom had more faith in humanity than I did. 

When I began my research, I soon learned that there wasn’t an answer. I also learned that it couldn’t be explained by climatology alone. Trying to determine where our oxygen comes from and where it goes spans almost every area of science, from biology and photosynthesis to chemistry and combustion formulas to how the land and sea absorb oxygen, and even astrophysics — our atmosphere is leaking oxygen into space! To be cliché — it’s complicated! 

My curiosity buried me in articles and scientific papers. I began to connect some dots and discovered many holes in the scientific literature. I even learned to do some math and chemistry to test my ideas. Since then, I have gathered a great deal of information and discovered many areas that would benefit from further investigation. That’s why I’m posting this information — in hopes of inspiring in-the-field research. I genuinely believe this is an issue of global importance. For what it’s worth, it’s not just me. I have gathered a small group of people to explore this issue from our different areas of expertise. 

An illustration of oxygen molecules (O2) and fossil fuel (C) going into the engine of a car, and molecules of carbon dioxide (CO2) coming out the exhaust pipe.

How much oxygen does a person breathe?

I’d like to start by putting into perspective how much oxygen is being consumed in average daily life. 

According to NASA, the average person doing an average amount of work needs 0.84 kilograms of oxygen per day (24 hours) to survive. This is the amount of oxygen the astronauts on the International Space Station use each day. To put that into perspective: NASA estimates that humans only need 0.62 kilograms of food. So, by weight, you are actually consuming more oxygen than food.

Now compare that to how much oxygen a car burns. In one hour, traveling at highway speeds of 70 miles per hour (MPH) with a fuel efficiency of 24.9 miles per gallon (MPG), a car consumes as much oxygen as one person breathes in 33.7 days. Wow! 

And, a car burns almost as much when idling. Think of that next time you are stuck in a traffic jam. And, lots of daily activities, like taking a hot shower or cooking a meal, consume almost as much energy as driving a car. 

How much oxygen does a person breathe? Infographic. This illustrates that the huge volume of oxygen used by a car in one hour takes a person 6.2 days to use.

Is climate change twice as bad as we think it is?

As you probably know, there is a lot of evidence that climate change is being driven by greenhouse gas emissions, which warm the atmosphere and cause volatile weather. But what you may not know is that as we put carbon dioxide into the atmosphere, we are also taking out molecular oxygen (O2), the kind we breathe. You could think of oxygen as a global cooling gas. So, the change in our atmosphere is double — we are both subtracting one gas and adding another. So, I think it is reasonable to assume that the weather, and climate change, will be at least twice as bad as predicted by greenhouse gas emissions alone. And, it does seem like everyone agrees the weather is worse than predicted. 

To me, this is prima facie evidence. And like all my ideas, I hope to inspire more research into this area. 

A graph and timeline of the oxygen content of the Earth's atmosphere.
This graph shows that the oxygen content in the Earth’s atmosphere is not constant. In fact, for two billion years there was no oxygen at all. Then the oxygen levels went all the way up to about 39% in the Permian Era then suddenly dropped. Currently, it is assumed to be 20.95% at sea level. It’s hard to measure and there isn’t much data, but the numbers have been dropping. And 19% is an estimate of how much oxygen is practically available when including water vapor.

Is it possible to run out of oxygen?

This is the first question I asked myself. And the answer is yes! The Earth can run out of oxygen, and it has happened before. There have been several oxygen-related mass extinction events, like the Huronian glaciation and Snowball Earth, which you can see as the big drop in the graph. You can also see that oxygen is not a constant factor in Earth’s history. In fact, for billions of years, there was no breathable oxygen at all. I present this as circumstantial evidence that we may be in for a surprise. 

Another reason it is possible to run out of breathable oxygen is that both oxygen and fossil fuels are the byproduct of photosynthesis, so if we recombine them by burning them, there will be nothing left. I know that’s an over-simplistic explanation, but you get the idea. 

Photosynthesis is very inefficient

It’s hard to believe, but photosynthesis produces hardly any extra oxygen. It took billions of years for the atmosphere to fill up. This is because a plant also breathes oxygen. In fact, all plants, animals, and, even machines do basically the same thing — they burn sugar to create energy. The excess oxygen in the atmosphere is an accidental leftover. You can see the full explanation in my article: How much oxygen do plants (the Earth) produce?

This all means that the breathable form of oxygen isn’t easily replaced. And, according to my calculations, we are burning oxygen at a rate 35 times faster than it is being replaced. 

The double-edged sword

Increased consumption and decreased production of oxygen

The first dots that I connected in the scientific literature was that not only is humanity burning oxygen to create electricity and power our vehicles, but we are also destroying Earth’s ecosystem and ability to replace the oxygen. Soon, I learned even more frightening facts, like enormous methane deposits trapped in the permafrost, which, if released all at once, would burn out the oxygen in our atmosphere. (It’s happened before. It’s called the Siberian Traps Permian Extinction Event.) 

I discovered that practically speaking, oxygen is not a renewable resource; it’s not something that gets recycled by trees. Plants do release oxygen in a process called photosynthesis by breaking the bond of water. But once oxygen is locked into a chemical bond with carbon, practically speaking, it is permanent. Limestone is an example.  

To make matters worse, the plants and phytoplankton that produce the oxygen are dying due to rising sea temperatures, pollution, and urbanization. Even now, massive dead zones exist in the ocean and on land. 

Are we running out of air to breathe?

To answer this question, I needed to know how much oxygen we have, how much is being produced, and how much is being consumed.

I started by demonstrating how to calculate the mass of oxygen is in the atmosphere. Then I showed how the accepted value is a generic estimate and explain 10 reasons why global oxygen measurements are wrong. Then I calculated how much oxygen the Earth is producing via photosynthesis (not much) versus how much oxygen humanity is burning via the combustion of fossil fuels (more and more every day). Finally, I was able to crunch the numbers to find out how long it will take to run out of oxygen

I think if you read the articles, you will find the explanations very convincing, but if you just want to know the bottom line, here it is: The Earth will run out of breathable air in about 420 – 2702 years. If humanity continues to grow, consume resources, and destroy the ecosystem, that number drops fast. But life will get uncomfortable much sooner, maybe even in our lifetime. For the record, oxygen levels don’t have to drop to zero. Just a small drop of 1-2% can cause a loss of concentration and coordination. And, living under these conditions for the long term can cause many health issues. 

What happens if the world runs out of oxygen?

The article you are reading is based on years of research. The facts and science are real. However, in my new debut sci-fi novel, I extrapolate these ideas into the worst-case scenario: A firestorm devastates the Earth’s atmosphere, and a handful of survivors question whether it is worth saving themselves.

Will humanity survive the oxygen apocalypse? Find out now

Does science agree?

Science agrees that we are using more oxygen than is being produced. And a lot of research is now being done. Still, global oxygen depletion is not a mainstream idea. As far as most people think, there is a tremendous amount of oxygen in the atmosphere, and we consume very little in comparison. My research indicates the measurements are off. 

Even after two years of humanity being locked down, the Earth’s oxygen reserve is still being tapped into at unprecedented rates due to global fossil fuel use. However, this is not apparent because, at the same time, the ocean temperatures are rising and releasing oxygen into the atmosphere. Likewise, the glaciers are melting and releasing trapped air bubbles and dissolved oxygen gas. This offsets current readings. And when the oceans and glaciers stop outgassing, what happens?

It bears repeating: is the Earth at an unforeseen tipping point? 

Global oxygen depletion logo. An illustration of the Earth  as a big O2 molecule.

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Stay tuned

There is a lot more to be said, but for now, I hope these few highlights have given you a basic understanding of global oxygen depletion — it’s the opposite side of the coin from carbon emissions. 


It is my theory, and science is beginning to support this, that the oxygen in our atmosphere is being measurably and quickly reduced due to humans both burning fossil fuels and destroying the ecosystem that produces the oxygen. Oxygen depletion, in my opinion, will soon be recognized as the greatest crisis humanity has ever faced. And it will probably happen in our lifetime. Even now, it could take millions of years to replace the oxygen we have used. It is critical to start changing our habits and infrastructure while we still can. Because as we all know, we can’t simply stop driving our cars tomorrow. 

I break down all these topics. For more information, please see my articles on Global Oxygen Depletion.

Call to action

Join me — and many others working behind the scenes — as we explore global oxygen depletion. You can start by joining our Facebook group or forwarding this article to someone you think might be able to advance the research. It will take all of us to solve the challenges of climate change. In the meantime, may I recommend riding a bicycle and planting a garden? 


See the links above, plus my other articles. 

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