17
Aug
08

Global Warming? How about Global Oxygen Depletion!

The Guardian (surprise!) has an author who’s pulling the panic switch, this time on the reduction of oxygen in the atmosphere.

The author’s premise– increased CO2 in the atmosphere and decreased forests = a fatal decline in oxygen concentrations.

The problem is interesting, and blaming internal combustion is almost silly.  The global concentration of CO2 on the planet is 345 ppm (or, 0.0345%).  Let’s assume for arguments sake that all 345 ppm is from petroleum burning (which we know it’s not).  Now, the molar ratio of carbon to oxygen is 1:2, so it takes two moles of oxygen to bind to one mole of carbon.  So, if all 345 ppm of carbon come from burning, then it would remove a similar amount of oxygen from the atmosphere.  In fact, to cause a percentage decrease in oxygen concentration on a global scale, there would have to be about 10000 ppm of CO2 in the atmosphere, or 1%.

Now, I’m being a little liberal with math here, and there are other variables.  Depending on the hydrocarbon burned, the amount of oxygen varies, and there’s also generation of water, which consumes oxygen as well.  But the amount of oxygen consumed per carbon is still minimal.

The panic sets in when the uniformed look at a molar equation.  Octane is C8H18.  To burn it in a balanced form you’d get the following equation.  2 C8H18 + 25 O2 –> 16 CO2 + 18 H2O.  That is, to generate 34 moles of gas (CO2 and H2O), you need 25 moles of O2.  The uniformed eye would look at the amount of oxygen consumed by the octane and start to panic– and it is quite a ratio!  But the atmospheric concentrations is what you want to look at, and the amounts of CO2 in the atmosphere give away just how much oxygen is being consumed.

I think this statement in the article says it all:

I am not a scientist, but this seems a reasonable concern.

Well, I’m not a journalist, but I do believe you’re a moron.

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4 Responses to “Global Warming? How about Global Oxygen Depletion!”


  1. August 28, 2008 at 5:38 pm

    One of my favorite questions to ask the non-chemistry types when they bring up these points, is this:

    If you took a bottle of wine (750mL) and dumped it in an ocean, let it disperse evenly throughout all the oceans in the world, and came back one year later and filled the bottle back up with sea water, what are the statistical chances that one of the original molecules will re-enter the bottle?

    The answer is greater than 100%, as there are more molecules in a single bottle of wine than there are volumes of wine bottle in all the oceans of the world.

    Some people just don’t understand the relative sizes of the systems they’re dealing with, let alone the complexity of the relationships. I suppose I’m preaching to the choir here, though.

  2. 2 Mr Silly
    January 21, 2010 at 11:09 pm

    I don’t get the above statement “…there would have to be about 10000 ppm of CO2 in the atmosphere, or 1%”.

    All we need to understand is coal is practically just carbon. Burn it and it takes (robs) 2 oxygen atoms from the air. If taken up by plants, the oxygen circulates. But if sequestered, the O2 stays robbed = atmospheric depletion.

    I once heard we each share about a million tonnes of atmosphere. Population growth since must have reduced it.

    The World will, or must, be governed 95% of the time by the rules of crisis management. Add greed, short sightedness and rampant ignorance in the face of complex existentially threatening planet wide problems = pessimism = reality.

  3. 3 Mick Russom
    February 12, 2010 at 8:04 pm

    Why focusing on CO2 and AGW is silly.

    – The greatest contributors of warming/cooling are ocean surface flux, heat flux, humidity and clouds. Also one must consider light input and planet wide albedo as well as magnetosphere strength. CO2 has a very low overall impact. Insulators (such as CO2) have a non-linear diminishing return in terms of efficacy. The more CO2 that is put up, the less insulating effect it will have per unit.

    – Modern CO2 level is as at 400ppm.

    – Precambrian CO2 was 4500 ppm, Oxygen @ 12.5%, temp +7C modern.
    – Ordovician CO2 was 4200 ppm, Oxygen @ 12.5%, temp +2C modern level.
    – Carboniferous CO2 was 800ppm (over double today), yet it has a nice Oxygen level at 32.5%. Also, temperatures were the same or slightly lower than today’s temp.
    – Jurassic CO2 1950ppm, 26% O2 and ~ 3C above modern. (That’s about 5x today’s CO2, more oxygen, similar temps).
    – Cretaceous CO2, 1700ppm, O2 @ 30%, temps about 4C higher. This is the realm of the greatest biodiversity the world has ever seen. Lots of oxygen, lots of CO2 but no man-made AGW. Imagine living in an atmosphere with this much oxygen. Lots of CO2 around to feed plants and create biodiversity.
    – Neogene to modern. Where we are today. Most of the atmospheric oxygen loss (about 8% of the total) occurs before industrialization.
    – At no point, even with many times the current CO2, did the greenhouse effect run away like it has on Venus.

    It seems to me that people should consider planting trees that produce a lot of O2 out of normal CO2 respiration. That would help albedo and do more for the world than any attempt to prevent CO2 changes. Build nuclear power plants (lots of them) and try to get to fusion as soon as possible. Then pollution (everything BUT CO2, which is plant food) can finally slow down. Things like MTBE, metals (mercury, cadmium, arsenic, etc), PDBE, BPA, etc, etc. CO2 is the last thing to worry about – really.

    PLANT TREES. Global taxes and communist regimes are not going to help.


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My name is Doc. Welcome to my blog. If you're visiting from another blog, add me to your blogroll (and I'll happily reciprocate). I have a Ph.D. in Chemistry and live in Wisconsin. If you have any questions, feel free to email me. My email is docattheautopsy at gmail. (No linking to deflate the incredible spam monsters).

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