Grendel wrote on Nov 28
th, 2008 at 8:57am:
Now how about proving that CO2 increases... increase temperature. How about proving that all the other "Greenhouse" gases don't have the same effect or more of an effect on temperature.
So far all you've managed to do is point out that green house gases.. sorry CO2... increases marginally within the overall atmospheric makeup as a reaction to increased temperature.
Your question is - how does increasing atmospheric CO2 result in an increase in mean global temperatures?
I should note that CO2 accounts for approximately 93-95% of the radiative forcings at this point in time. Other greenhouse gases such as methane, N2O and CFC's have a relatively low contribution, even though methane has approximately 8 times the Greenhouse Warming potential of CO2 taken over a 50 year period. (That's off the top of my head - feel free to look it up)
The heating effect is a very well understood relationship, although the CO2 forcing part of the equation has a few feedbacks attached to it. The greatest effect on global temperature is due to the water vapour feedback, which hopefully as you can appreciate is a function of temperature. Arrhenius understood this relationship way back when, and the forcing equation is based on a derivative of the Stefan Boltzmann equation - some very basic physics.
Increase temperature by increasing CO2 and you increase atmospheric water vapour concentration, which in turn drives the temperature up further.
Imagine the infrared radiation coming from space (ie from the sun). It hits the earth, and a proportion of the radiation escapes into space - it is reflected. Some surfaces reflect somewhat better than others.
For example, pine forest has a very low albedo, and this absorbs IR radiation very effectively whereas ice tends to reflect to a much greater extent.
On the balance, the earth reflects about 51% of the total incident radiation it receives. OK?
When IR radiation of specific frequencies come in contact with CO2 in the atmosphere, they are absorbed and re-emitted at different (lower) angles. The overall effect is that 1. The layer of atmosphere closer to the earth (the troposphere) heats up more and 2. the layer above that (the stratosphere) experiences a net cooling effect. Do you understand that part? Both effects have been observed.
One question - What happens to air density as the mole fraction of water vapour increases? (In other words as air gets more humid, does it get denser or less dense?)
That's not a trick. I'm just trying to get you to follow the logic.