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The oxygen crisis

Most mainstream media have abandoned almost all quality control in their science reporting that is now arguably slightly below the image of science as presented in the leading pornographic magazines.

The latest extreme example of this observation comes from a Gentleman called Peter Tatchell, a political campaigner from the left wing of the Green party (a description that probably makes Karl Marx a staunch conservative in comparison; he's been also denounced by the British Parliament as a "homosexual terrorist" in 1994):

The Guardian, China Daily
He argues that there exists a more serious crisis than the "CO2 crisis": the oxygen levels are dropping and the human activity has decreased them by 1/3 or 1/2, he says. Wow. ;-)

The reality is, of course, that the oxygen percentage in the atmosphere has been 20.94 or 20.95 percent for thousands of years and probably much longer than that (see the historical graph on page 2 of Dudley 1998 that covers 600 million years). The amount of oxygen in the atmosphere is so huge that the biosphere (and fossil fuels which used to belong to the biosphere as well) is completely unable to change this amount significantly.

It may be useful to mention that the oxygen is only 1/5 of the atmosphere and the atmosphere is just 1/1,200,000 of the mass of the Earth. However, the Earth is damn heavy, 6 x 10^{24} kilograms, so the mass of the oxygen in the atmosphere is something like 10^{18} kilograms - about 150,000 tons per capita. Be sure that we can't burn that much oxygen even if everyone in the world were using a private jet on a daily basis. ;-) There is a simpler way to see that man-made changes to the oxygen levels are trivial and we will look at it now.

Estimating the oxygen change

For a schoolboy who is not skipping his science classes at the elementary school, it shouldn't be difficult to see why we can't significantly influence the amount of oxygen in the atmosphere.

How can he do it? Well, he must realize that virtually all processes related to life and human activity - breathing (by animals and plants) and burning (combustion) - exchange the atmospheric O2 molecules by CO2 molecules or vice versa. Sometimes, one needs two O2 molecules and only produces one CO2 molecule but this subtlety won't change our final result significantly.

Virtually all other compounds participating in the relevant chemical reactions are either liquids or solids which is why they don't influence the composition of the atmosphere and we will ignore them.

When you realize what the words above mean, you will see that the man-made decrease of oxygen (O2) is controlled by the increase of carbon dioxide: they're inseparably linked to one another. The human activity has increased the CO2 concentration from 280 ppm two centuries ago to 385 ppm today (the schoolboy should have seen these elementary numbers during his "CO2 crisis" classes). Because many people don't know what the acronym ppm (parts per million) really means, even if they like to use it, let me tell you that it is the same thing as 0.0001%.

So the carbon dioxide went from 0.028% to 0.038%: the difference is 0.01% of the volume of the atmosphere. Because O2 and CO2 molecules occupy the same volume at a given pressure and a given temperature (since pV = NkT), the decrease of O2 should be equal to the increase of CO2 if the molecules were exchanged for one another: the oxygen should drop by 0.01% of the volume of the atmosphere.

As we have already mentioned, two oxygen molecules are replaced in typical "combustion" chemical reactions for one carbon dioxide molecule, so the oxygen drop might be 0.02% instead of 0.01%. However, in the long run, there exist other processes besides the combustion-like processes involving CO2 that we have considered - for example processes involving deep ocean sediments - and these processes tend to restore the oxygen levels (as well as the CO2 levels).

At any rate, you see that the oxygen level couldn't have decreased by more than 0.01% or so, from 20.95% to 20.94%, which is pretty much exactly what was observed. We needed centuries or millenia to achieve this modest "goal". It is very clear that even if we burned all forests, plants, animals, and fossil fuels in the world, we couldn't get the oxygen levels below 20% (and maybe not even 20.9%).

Evaluating the impact

Does the tiny decrease of oxygen levels change some important things? It doesn't. The most "spectacular" change is that the wildfire risk decreases by something like 0.01%, too (and maybe slightly more), as the oxygen levels drop. Because wildfires are somewhat unpopular and their decrease would be good news, you won't read about it. ;-)

At any rate, all these changes are negligible given the tiny change of the O2 levels.

Tatchell writes "I am not a scientist, but this seems a reasonable concern." It seems reasonable to whom? To me, worries about the "oxygen crisis" seems to be a ticket for someone to be stored in a mental asylum. The point here is not whether Tatchell is a scientist: he's clearly not. The question is whether he is dangerous enough a weirdo to be isolated from the society.

We won't be able to change the oxygen level in any significant way. Incidentally, while the overall amount of oxygen in the atmosphere is essentially constant, the amount of oxygen in various parts of organisms varies dramatically. For example, the human body must keep the concentration of this harmful-if-abundant gas around 5% in most organs. Oxygen is not only a corrosive gas but also a metabolic poison under most cellular reactions. Its optimal percentage depends on the life forms which is why the varying percentage of oxygen in amber - a point mentioned by Tatchell - says absolutely nothing about the overall O2 volume.

Men have been able to change the overall carbon dioxide (CO2) concentrations measurably because it is a trace gas: there was almost none to start with, so it is easy to change its volume by relatively large amounts, proportionally speaking. But oxygen is one of the gases that the Earth's atmosphere has been made out of for 0.5 or even 2.5 billion years. You can't change that.

Incidentally, if you care how the oxygen became so important, probably 500 million years ago, the Earth needed an intense period of upheavals in its crust and it still took about 2 million years for all the change to materialize: see Science Daily. This rate is very fast from a geologist's viewpoint but surely not fast enough to be considered an urgent problem for policymakers. ;-)

Other errors

Tatchell writes a lot of other incredible nonsense, for example that the oxygen in cities is much (by 15%?) lower than it is in the countryside. He probably believes that the pressure drops from 1000 to 900 millibars in the cities. ;-) He also tries to pretend that some scientists support his idiotic propositions. Gimpy, who respects Tatchell's courage, explains that Tatchell has all the symptoms that define a crank. He satisfies most of my defining criteria of crackpots, too.

Is someone at the Guardian who has some common sense left? Could you please stop printing insane people like Peter Tatchell who help to transform your daily into an expensive and dirty piece of toilet paper?

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snail feedback (7) :

reader John Lovaas said...

In regard to your conclusions about atmospheric 02 levels in the recent past-

Figure #1 of the Dudley paper quoted above shows that atmospheric O2 levels have ranged from around 13% up to around 35%. It would appear to be extraordinarily difficult to determine atmospheric O2 levels for the previous "thousands of years and probably much longer than that" from a chart with a time axis of 600 million years presented within a span of 2 inches or so.

I would suggest it is better to analyze and critique the data Mr. Tatchell used to form his opinion, rather than by contrasting his point of view with an inaccurate assessment of a scientific paper.

reader Luboš Motl said...

Dear John, I don't exactly know what data Mr Tatchell used to form his opinion.

The only thing I know is that he has either used wrong data or he has interpreted correct data incorrectly.

Incidentally, the Dudley chart I linked to *is* enough to support the statement I wrote.

Notice that the changes are smooth and it takes hundreds of millions of years to achieve the changes indicated in the graphs (a few percent, up to 10 or so as a maximum). In a few millenia, you won't simply change it by more than a tiny fraction of a percent.

I insist on what I wrote and I insist that Mr Tatchell's writing is complete insanity of a person with rudimentary misunderstanding of science and the real world.

reader GVJim said...

Atmospheric oxygen is also eliminated from the mix by fresh lava flows, landslides, clay and soil formation, farm tilling, ditch digging, calcination of cement; oxidation of freshly exposed faces of road cuts and open pit mines, and oxidation of foundry metals, etc.

It might be that CO2 levels have not not risen, but that 02 levels have fallen due to processes other than respiration/combustion.

Please critique. Thanks! GVJim

reader Dirk said...

C02 may have changed because the ocean has warmed- outgassing C02. As the planet cools, it's possible that C02 could decrease- wouldn't that be a major embarassment for some folks.

But a large asteroid could burn up some oxygen, I suppose.

reader jbryant said...

There actually is a real oxygen crisis happening now: Oxygen levels have dropped roughly 20 percent off the Southern Californian coast over the past 25 years. Scientists estimate that oxygen levels overall may have declined by one-third over 50 years. NASA reports that in the north Pacific Ocean oxygen-producing phytoplankton concentrations are 30 percent lower today, compared to even the 1980s. The UN Environment Program said in 2004 that there were nearly 150 "dead zones" in the world's oceans.

Lloyd V. Berkner was one of the world's top scientists with NASA. He pointed out that diatoms, which are microscopic plants in the oceans provide more than half of the world's oxygen for us to breathe and are being destroyed in oil spills. He wrote that it would only take a relatively small number of such disasters, in the wrong places, at the wrong times, to trigger a sudden and irreversible drop in the world's oxygen levels. Such an event could occur very rapidly.

Half of the world's oxygen is produced via phytoplankton photosynthesis. The probable effects of increased UV radiation as the primary result of ozone depletion includes the destruction of phytoplankton at the base of the food chain and this may become a grave matter within a few decades.

reader jbryant said...

Professor Ian Plimer of Adelaide University and Professor Jon Harrison of the University of Arizona accept that oxygen levels in the atmosphere in prehistoric times averaged 35 percent compared to only 21 percent today.

Levels are lower in densely populated, polluted city centers and industrial complexes. OSHA rules on atmospheres in closed environments state, "if the oxygen level in such an environment falls below 19.5% it is oxygen deficient, putting occupants of the confined space at risk of losing consciousness and death."

Scientists from CSIRO have measured the decline in oxygen that has occurred during the past 20 years, the longest period over which such an assessment has been made. The team analyzed air dating back to 1978 from CSIRO's unique archive of pristine air collected at the remote Cape Grim Baseline Air Pollution Station operated by the CSIRO and Bureau of Meteorology in northwestern Tasmania. The oxygen reduction is just 0.03 percent in the past 20 years. Langenfelds stated.

So, we can all breath easy. On the other hand, we can also be mindful of the pitfalls of hubris.

In forty years, the population has doubled to over 6 billion people and is predicted to double again within the next twenty years or less. 150,000 tons of available oxygen per capita as mentioned will be very soon a somewhat less respectable 75,000 tons per capita. One human may breathe 100 tons of oxygen in one lifetime and this should be no cause of alarm. But, where merely adding a single additional fact may so easily deprive a single person of 75,000 tons of oxygen, it may still be well worth weighing carefully the possibility of the unforeseen.

In the overall context, it is my view that the margins of safety are slight enough to warrant at least a prudent caveat: Any manner of analysis of such a matter that does not take into account the possibility of catastrophic change, where such appears possible, may readily engender unintentionally flawed conclusions.

reader Nualgi said...

The problem is not of oxygen levels of atmosphere but of dissolved oxygen levels of water.

Please read about Dead Zones and Fish Kills.

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