I found this study interesting. I thought it might be good to think about how human activity changes the planet. Yes, there is a measurable degree of uncertainty to the time frame, but it is a measurable certainty that atmospheric O2 is currently decreasing. We don’t seem to think of O2 as a consumable resource and take the air we breathe as an unchanging constant.
Below is the abstract. To add some context to the time frame in the abstract of 3,600 years the pyramids are roughly 4,500 years old, and this is about the same time or a bit earlier that writing systems were developed. I realize these are long time frames when compared to the human life span. What do you say we just keep kicking the can done the road.
There are a number of other studies on the causes such as deforestation, ocean dead zones, forest fires, and burning fossil fuels. If you care to look for them. I saw a report that the oceans have lost about 2% of their O2. For every carbon atom to become CO2 it takes two oxygen atoms. The reason we currently have about 21% of the atmosphere made up of oxygen is because life came up with photosynthesis.
Abstract
There has been a clear decline in the volume of oxygen in Earth’s atmosphere over the past 20 years. Although the magnitude of this decrease appears small compared to the amount of oxygen in the atmosphere, it is difficult to predict how this process may evolve, due to the brevity of the collected records. A recently proposed model predicts a non-linear decay, which would result in an increasingly rapid fall-off in atmospheric oxygen concentration, with potentially devastating consequences for human health. We discuss the impact that global deoxygenation, over hundreds of generations, might have on human physiology. Exploring the changes between different native high-altitude populations provides a paradigm of how humans might tolerate worsening hypoxia over time. Using this model of atmospheric change, we predict that humans may continue to survive in an unprotected atmosphere for ~3600 years. Accordingly, without dramatic changes to the way in which we interact with our planet, humans may lose their dominance on Earth during the next few millennia.
The solution may just be as simple as fewer humans. Everybody should endeavor to stop air conditioning homes. I never had one in my home and never will.
So if matter can neither be created of destroyed at atomic levels how can there be “less” oxygen? Breaking of the Oxygen molecules into atoms? How’d that happen?
A “study” that shows movement of oxygen might be of value.
But showing “less” means it had to disappear or be broken down into atomic particles.
So…where’d it go? Into the dirt? Into the water?
Off planet?
(just watch…the "answer’ will be to convince some people give up some additions rights and liberties. What-cha-wanna-bet)
It is being attached to carbon atoms when all life metabolizes nutrients and you breath out CO2. When your steel knife rust it is oxidized by O2 or when combustion takes place O2 attaches to free carbon. This is simple chemistry. This O2 comes from the atmosphere and is produced only by green plants and algae. They strip it off of CO2. On a molecular level it doesn’t disappear. O2 is highly reactive and doesn’t exist long as such. Before bluegreen algae developed photosynthesis the atmosphere didn’t have a free O2 component. When it was being strip from CO2 by the first organisms that could do photosynthesis it caused the great oxidation of planetary iron. Think how much it took to make red rocks and red clay. It is called by science the “Great Oxidation Event” and happened between 2.5 and 2.2 billion years ago. So, until the majority of exposed iron was oxidized the atmosphere and water held little free O2. Once it could accumulate in the environment It caused a mass extinction as it was toxic to most of the existing microorganisms. Most of life now requires O2 for their metabolism.
What we have that allows for O2 in the atmosphere is caused by a balance of natural phenomena. The balance of nature and the web of life is being changed by our activities which among other consequences is changing the atmospheric equilibrium. It can also be changed by natural means such as desertification or extreme vulcanism. Algae in the Oceans produce about half of the atmospheric O2. Nutrient runoff is creating dead zones in the Ocean. The BP oil spill has created a large benthic dead zone in the Gulf. These things add up over time.
Basically, you reduce the amount of plant life you reduce O2, or if you increase the uptake of O2 you reduce what is available. At the moment it is decreasing annually by a small amount. 3,600 years gives us some “breathing room” (Pun intended) so don’t get too bent out of shape. I had wondered about the O2 levels and came across this paper. It is something to think about. It always amazes me how little science is of interest to some. As a trained biologist and wildlife ecologist it is a passion for me. All fields of science, I find interesting. Knowlege is a true treasure.
Thankfully oxygen and hydrogen are also strongly attractive, or we wouldn’t be able to paddle. The point I am trying to make is O2 doesn’t stick around because it wants to stick to other elements. Only because plants can unstick it from CO2 is it part of the atmosphere.
Incidentally demographic studies suggest the world population is on track to be declining by the end of this century. This may present a problem for the growth economy concept. Of course, we don’t really know where the AI revolution will lead us. We live in interesting times to say the least.
In the famous words of ScupperFrank… Paddle On!
When you burn something it takes O2 out of the air and combines it with carbon. We are producing 35 billion tons of CO2 a year. O2 is most of that weight.
Half the CO2 is being absorbed by the ocean, turning it into carbonic acid. Although it is slowly making the ocean acidic now, It will eventually eat thru the entire carbonate / bicarbonate buffer and acidity will skyrocket. At that point coral will go extinct. I’m more concerned with that than lack of oxygen.
I considered bring ocean acidification into the discussion as it also applies to the algae and other ocean life forms. here are a couple of informative links.