What is the Greenhouse effect?
I have heard so many different explanations I am wanting some clarification. I am a little confused about the thermodynamics.
1. I have read it works like a blanket, or insulation. Piping Insulation does not transfer heat back to the pipe. Insulation calculations also do not use radiation, and the insulating factor is the air in the foam not the air. It appears to me if this explanation was used we are talking about convection, not radiation. Insulation on a pipe does have a temperature gradient linear like the earth.
2. I have seen the word re-radiate used. I alwaysed used the Q=A F12 S(T^4-Te^4) Sorry I can not get an epsilon or sigma on my post. Every time I try it I get a negative heat transfer from the earth to the CO2. I have read something about an Open system, but have never seen it defined, derived or calculated.
3. I from my own background believe what is really happening and makes thermo since is, most of the effect is at the ground level. The air above a hotspot, (an unshaded area) gets warmer than the shade, and it can re-radiate to the shade. In the upper atmoshere Greenhouse gasses will warm and convect and radiate to the gasses around them, then they will to the gasses around them, ultimately warming the ground.
Rock,
Are you saying that it just absorbs the reflcted poriton, and not the radiated portion of the earth? A greenhouse does not work that way. It is do to a loss of convection.
I understand what the theory is, I was just wanting to know what deffinition would be used. I have already seen reflected and absorbed. Wikki says absorbed. I agree reflected makes more since.
What is the re-radiation calculation of one molecule of CO2@ 0degF to the earth at 70 def F.
I figured no-one on yahoo could answer this. I took 12 hours of thermo/heattransfer in college. I am by no means an expert, but know enough that most people butcher the second law, and butcher the difference between heat and energy.
"Greenhouse" is a poor analogy, IMO. A greenhouse loses heat by convection, the earth loses heat by radiation. They use this analogy because people think they understand it.
That said, CO2 absorbs certain wavelengths of light that would normally be radiated out into space. The more CO2 there is, the more these wavelengths get absorbed. The global warming proponents state that this slight (in absolute, but high in relative) increase of CO2 is causing slightly more heat to be re-radiated back to earth.
Computer models (depending on the assumptions, of course) predict a further warming of the earth. Stand by for real-world confirmation or refutation….