A Simple Calculation

I think this deserves its own post before it gets buried in the comments. doorman asserted that

A. CO2 levels have increased from 280-380ppm
B. Human industrial activity only accounts for a very small percentage of total worldwide CO2 emissions.

Point A is true, of course. A very simple calculation and a little googling though shows that the human contribution to the CO2 in the atmosphere is everything but small. What we need:

Carbon CycleFirst we calculate the total mass of the atmosphere. This is just the surface area multiplied with the weight of the atmosphere: 5.100656e+14 m² * 1.02e+4 kg/m² = 5.202669e+18 kg. To get the mass of the carbon dioxide we multiply this with the fraction that is the carbon dioxide: 5.202669e+18 kg * 0.000582 = 3.027953e+15 kg, or about 3000 gigatons.The excess of CO2 since 1850 is (1 – (280/380)) * 3000 gigatons = 789 gigatons.

We can now compare this with the world carbon dioxide emission rate, which was according to this source 25,028 million tons = 25.028 gigatons in 2003 (compare this with the emission of the volcanoes). So if the rate stayed constant (it does not, it’s increasing), we can accumulate the excess in about 32 years. Of course the emission rate wasn’t as high as it is now beginning in 1850, but you get the idea. It gets also more complicated because a large fraction gets dissolved in the oceans.

The image is from here. Note that the values there are the mass of the pure carbon. To compare with carbon dioxide values, you need to multiply them by about 3.67 – carbon dioxide has one carbon atom with atomic weight 12 and two oxygen atoms with atomic weight 16, and (2*16+12)/12 = 3.67.



Filed under global warming, science

7 responses to “A Simple Calculation

  1. Pingback: 59th Skeptic Circle « Fermi Paradox

  2. Nice bit of calculation.

    From your previous article (“It’s not the Volcanoes”) the higher estimate for the typical annual emissions from Volcanoes is 230 million tonnes.

    32,000 million tonnes vs. 230 million tonnes. Is a few orders of magnitude enough to reinforce the “It’s not the Volcanoes” message?

    Any idea how high emissions would have to get to noticeably alter atmospheric pressure?

  3. Is a few orders of magnitude enough to reinforce the “It’s not the Volcanoes” message?

    I would think so. Maybe I should have stressed that more.

    Any idea how high emissions would have to get to noticeably alter atmospheric pressure?

    The pressure does not change much. Compared with the total mass of the atmosphere, the CO2 level is much too low. Moreover, the combustion of carbon consumes oxygen, so the total number of molecules in the atmosphere does not change at all. Though you could argue that CO2 is heavier and therefore the pressure increases, but that’s neglibible.

    Interesting in that context: the decrease in concentration of O2 in the atmosphere has been measured, see here and here.

    This is yet another indication that the CO2 is indeed coming from the combustion of carbon and is not coming from the volcanoes or the oceans.

    • You say CO2 doesn’t come from the ocean ????? then why did the drillng ship sink while drilling for oil in th south east . also why did the lake in the moountains in South America belch up CO@ from the lake and kill s many people ? and you tell me that it doesn’t come from the ocean also BUll

  4. If co2 is heavier than air how can co2 rise to form a layer around the earth acting as a reflection mechanism. If, in fact, it does reflect heat back to the earth, why wouldn’t it also reflect some of the sun’ s heat back to space thus present a cooling effect?

    • CO2 is heavier than air, but that does not mean that it does not get mixed up and carried into the upper layers of the atmosphere. Did you ever wonder if plants on mountains get less carbon dioxide? There is no significant difference. Also, CFCs, responsible for the destruction of the ozone layer are heavier still and are nevertheless carried to the stratosphere.

      But, it’s actually irrelevant. It does not ‘form a layer around the earth’. The greenhouse effect actually takes place close to the ground as well as in upper layers. CO2 absorbs long wave radiation which comes from the ground (because it is warm), but *not* the short wave radiation that comes from the sun. You do not understand the greenhouse effect correctly.

      I have written a post here: https://fermiparadox.wordpress.com/2007/05/13/understanding-the-greenhouse-effect-part-1/ , but you can also look it up at the wikipedia.

  5. Snit

    Don’t waste your time quibbling over details of this “theory”. (global warming) The so called evidence is riddled with contradictions, confusion, partisan politics, and just plain BS!

    There’s a much better way to approach the “cap and trade” promoters – Who stands to make the most money? Follow the cash. Forget the carbon dioxide.