If it seems hard to believe that 400 ppm of CO2 can have an influence on climate, it is well to remember that that very same CO2 is responsible for all life on earth. Remove it, and the planet loses all life.
That much said, the question remains as to how much change in climate would be caused by how much change in CO2.
In the two attached PDFs, I use two different sets of numbers. I am certain that Will Happer's numbers are better than the IPCC's, but when quarreling with IPCC enthusiasts, it is best to use their own numbers against them. The first attachment is the article below. See second attachment posted here.
To make a long story short, the greenhouse effect --- the net reduction of IR from the surface value (ca. 398 W/m^2) to the amount radiated to space (ca. 239 W/m^2) --- is 159 W/m^2. Allow for a little disagreement here, as it will have no effect on the outcome.
Presently, the amount of greenhouse effect due to CO2 alone is 30 W/m^2. (Known both from IR spectra and from measurements from satellites).
The increase in greenhouse effect that would be caused by doubling CO2 (say from 400 to 800 ppm) is 3.7 W/m^2 (IPCC) or 3 W/m^2 (Happer). So, doubling of CO2 would increase the GH effect from CO2 by 12% (IPCC) or 10% (Happer), and it would increase the total greenhouse effect by about 3 to 3.7 parts out of 150 or 159 (Happer & IPCC, respectively), a whopping 2%-to-2.3%. The entire greenhouse effect makes our planet about 33ºC warmer than it would be if (per impossible) it had the same albedo but no greenhouse effect.
Another important thing to consider is that if the concentration of a greenhouse gas increases, there are two effects: An increase in its ability to absorb IR in the atmosphere, AND an increase in the ability to send more IR to space from high altitude.
Howard "Cork" Hayden
A Must-Read: Energy: A Textbook, $25 at
Chromoergic psychosis: The delusion that energy has a color, usually green.
It is clear that the IPCC has some serious misunderstandings about basic physics. The lesson in this short essay is that the radiation from the surface of the planet (for that matter any planet) is determined by the Stefan-Boltzmann radiation law.
Another common misconception is that the atmospheric pressure heats the lower atmosphere, and that is why the surface is warm. At the grade-school science level, work is defined as force multiplied by the distance through which it is applied. The three-dimensional version is that work is done on a gas when outside pressure moves the surface inward, decreasing the volume. The work done—pressure times the change in volume—becomes heat. That is, when you pump up your bicycle tires, you push air into a smaller volume, and the air warms up a bit. As soon as you quit, the air begins to cool down to ambient temperature. The pressure inside an oxygen tank is typically about 20 times sea-level atmospheric pressure. That high pressure does not make the tank hot