This weekend’s open thread here on AB produced an awesome post by reader, statistician and obvious genius Jan Galkowski on the significance of last week’s report on the level of CO2 now in the atmosphere. Here’s part of the thread, including Mr. Galkowski’s post:
Rjs / May 11, 2013 4:54 am
in case you missed it, yesterday we breached 400 parts per million of atmospheric carbon dioxide…
all you need to know in just one chart…
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Sammy / May 11, 2013 3:54 pm
rjs,
Don’t fall for the scare tactics. The y axis scale on your graph is “parts per million.” So we’ve gone from 300 max parts per million, to 400 parts per million. Or .0003 to .0004 percentage CO2. This is statistically insignificant. Plus, as Jack pointed out, there “little correlation with global temperature.”
This graph backs up Jack’s point over a longer time frame; and also shows that we are historically at a low in atmospheric CO2:
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Sammy / May 11, 2013 3:54 pm
rjs,
Don’t fall for the scare tactics. The y axis scale on your graph is “parts per million.” So we’ve gone from 300 max parts per million, to 400 parts per million. Or .0003 to .0004 percentage CO2. This is statistically insignificant. Plus, as Jack pointed out, there “little correlation with global temperature.”
This graph backs up Jack’s point over a longer time frame; and also shows that we are historically at a low in atmospheric CO2:
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Jan Galkowski / May 12, 2013 2:52 pm
@Sammy,
Surely you’ll agree the argument that materials in systems are safe as long as their concentrations are small is erroneous. There are many examples where tiny amounts will derail proper operation.
But, to your specific point, the fact that CO2 concentration is, as Richard Alley calls it, The Biggest Control Knob of Earth’s climate is due to a simple confluence of [t]hree physical facts.
First, blackbody radiation from a body at Earth’s temperature happens to have the bulk of its outgoing radiation in the region of the infrared spectrum between 400 per cm and 1000 per cm.
Second, CO2 happens to have a broad absorption between 550 per cm and 750 per cm.
Third, CO2 happens to resonate strongly at 667 per cm and, when it goes to ground state, reemits photons with frequencies very close to that. CO2′s cross-section for 667 per cm photons is very high. Thus, a stray photon at 667 per cm will in all likelihood be reabsorbed by another CO2 molecule.
This means about 2/3 of the radiation in the 550-750 per cm band gets captured by CO2, and the stronger the concentration, the more thorought the lasing effect of emission and reabsorption.
The net of this is that about 1.8 Watts per square meter are re-radiated from CO2 in the lowest 100 meters of atmosphere all around the planet. 1.8 Watts per square meter times the area of the Earth is about 690 Terawatts. That energy has to go somewhere, and does, boosting convection in atmosphere and oceans, as well as being conveyed in the water evaporation and condensation cycle, which essentially serves as a heat pump. Some goes into deep ocean, raising its temperature and weakening its ability to absorb CO2.
The greater differences in energy density, as always, demand equalization, so the poles warm more, percentagewise, than the tropics and intermediate lattitudes. This 690 Terawatts increases to 2000 Terawatts at 700 ppm CO2.
There is no trending or paleoclimate evidence needed to establish this. This is simple physics. It would be truly remarkable if 690 Terawatts of additional forcing had no effects upon Earth weather.
They who might be interested in more details regarding this should monitor my blog,
http://hypergeometric.wordpress.com
where a 4-part lecture describing these mechanisms and the reason we know atmospheric CO2 increases are due to people’s actions, namely fossil fuels, will be described in detail, probably some time this summer.
Thanks.
Those among us who can do such things as add and subtract will have an easier time understanding the specifics of Mr. Galkowski’s post than those among us (okay, the one among us) who cannot. But even those of us in the latter category can understand the gist of this. And its importance. (Trust me on that.)