ResponseFreedomClause is correct on several points. But, he is incorrect on others and, most importantly, he is incomplete.
What he says about absorption is correct. When sunlight enters the atmosphere it is eventually either reflected back to space or absorbed by something. Once it is absorbed, it is reradiated back out as IR light. Infrared radiation falls under the classification of 'long wave' electromagnetic radiation (Note: 'electromagnetic radiation' is the precise term for light, including the visible light we see with our eyes, but also including things such as gamma rays, x-rays, uv, IR, and radio). These long waves are too big to be absorbed by O2 and N2 molecules, so they pass right by them. If our atmosphere was nothing but nitrogen and oxygen then we would be like the Moon - blazing hot in the daylight and freezing cold at night. This is because there would be nothing to retain the heat and it would all go straight back out into space. But, we do have other gases in our atmosphere and these gases can absorb IR. These are the gases we refer to as 'greenhouse gases.' The term is a misnomer, but we're stuck with it.
The two principle gases we have in our atmosphere that act this way are CO2 and water vapor. Water vapor is much more efficient than CO2 at absorbing IR than CO2, but it is temperature dependent. Cold air loses its water vapor. That means something must work to warm the atmosphere independently of the amount of water vapor. CO2 fits the job very nicely. It would take a very cold atmosphere in order to lose the CO2 so we have the greenhouse effect present even when the temperature drops.
A good demonstration of the efficiency of these gases can be seen in a dry desert. The temperatures may get very high during the day (depending on the desert - not all deserts are hot), and then experience a very large drop in temperature at night. This is because the air is dry and the heat is not being retained as well.
So far, Mr. FreedomClause is correct. He is also correct when he states gases that absorb IR radiation then reemit it at the same frequency. So, once again, O2 and N2 don't have a chance to absorb any of that heat.
But, we know there is a way to heat the atmosphere because we know it doesn't drop to sub-zero temperatures every time the Sun sets. Somehow, the atmosphere is retaining heat at night and we all know this for a fact. It gets cooler at night, but it doesn't drop 270 degrees C (500 F) as it does on the Moon when the Sun sets. But, if O2 and N2 don't absorb IR, what is that method?
It is actually pretty simple - collisions. Mr. FreedomClause is incorrect when he says CO2 does not convert the IR energy into kinetic energy. In the dense part of the atmosphere where we live, molecules in the air collide with great frequency - typically between 1 and 10 billion times per second. This comes out to an average of about .13 nanoseconds between collisions (a nanosecond is one-billionth of a second). At these high rates, the molecule frequently doesn't have time to reemit the energy as IR and will instead lose the energy to the other molecule via collision. Since the vast majority of molecules in the air (about 99%) are N2 and O2, it is highly likely a molecule of CO2 excited by the absorption of a photon of IR energy will transfer that energy to a molecule of O2 or N2 before it gets a chance to reemit it (many will still have time to reemit before they collide - thank goodness or else we would all have incinerated long ago). This is the process in which IR energy heats up the atmosphere.
A couple of final notes. Remember, when CO2 reemits the photon of energy, half will go generally upward, but half will go generally downward. Meaning, basically half of the reemitted IR radiation is sent back to the surface where it originated and the surface (water, ground, or ice) is very efficient at absorbing IR.
Also, he discusses an experiment consisting of two bottles with thermometers in them. One bottle has a CO2 atmosphere and one has an N2/O2 atmosphere. He critiques that it is the glass bottles that affect the experiment, not the difference in the atmosphere. I would debate that point, but I don't need to. I developed a lab experiment years ago that I used in my astronomy labs. This experiment was pretty similar to what Mr. FreedomClause describes except I used 2-liter, plastic soda bottles. The plastic does not absorb IR well, so this complaint is invalid. The result of having hundreds of students repeat this experiment showed the CO2 bottles consistently warmed up much faster than the N2/O2 bottles.
So, while this was a well-thought out submission, the conclusion is wrong. The fatal flaw is the omission of collisions of greenhouse gas molecules with other molecules once they have absorbed IR radiation. Once that factor is included it is easy to see how the atmosphere is heated.
One final note: None of this is controversial and nowhere did I make reference to manmade greenhouse gases. Everything here is equally valid for the naturally occurring greenhouse effect which makes our planet habitable. But, what happens when you increase the amount of greenhouse gases?