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I have been having some difficulty with this, so perhaps someone could please sort out any mistakes, and let me know.

Consider a vertical column of the Earth’s atmosphere based on a square of area 1 m^2.

This air column has a mass of 1.01×10^4 Kg.m^-2.

The mass of the neutron (& proton) is approximately 1.67×10^-27 Kg.

So the mass of the nitrogen molecule is 4.68×10^-26 Kg.

Therefore, the number of N2 molecules in the column is approximately 2.15×10^29.

Now, carbon dioxide is currently present at the level of about 380 ppm by volume, and so the number of CO2 molecules in our 1 m^2 column is about 8×10^25.

The absorption cross section of a molecule of CO2 for an infrared photon of 14 micrometres wavelength (the optimum) is about 5×10^-22 m^2.

Therefore, the number of CO2 molecules required to ensure 100% probability of absorption of a photon emitted from anywhere within the 1 m^2 base area is 2×10^21 molecules.

The energy of a 14 micron infrared photon is 1.34×10^-20 Joules, and so the 2×10^21 molecules providing the absorption cover can absorb 26.8 Joules.

But, there are 8×10^25 molecules of CO2 in the column, and so the 100% cover can be provided

8×10^25 / 2×10^21 times over, ie. 4×10^4 times. So the energy which can be dealt with by the CO2 is 26.8×4×10^4 Joules, in the base area of 1 m^2. ie about 10^6 Joules.

Given a relaxation time of 10 microseconds for the CO2 molecule to decay from its excited state, it follows that the process just described can be repeated 10^5 times within 1 second. And so the possible power which the carbon dioxide could cope with for 100% absorption is 10^11 Watts per square metre.

However, the limit is set by the Earth’s energy balance to about 235 W.m^-2.

So the carbon dioxide is grossly oversubscribed by a factor of 4×10^8.

This means that although the original GHG effect works very well, the idea of anthropogenic “enhanced” greenhouse effect is totally non-viable as far as carbon dioxide is concerned, because there has long been far, far more carbon dioxide in the atmosphere than required, and so another 30% ( or several orders ) extra will have absolutely no effect.

Aubrey E Banner, Sale, Cheshire, UK

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# Greenhouse Gas Effect and Carbon Dioxide

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