Why The Radiative Capabilities Of Gases Do Not Contribute To The Greenhouse Effect - Printable Version
+- Global Warming Skeptics (http://www.globalwarmingskeptics.info)
+-- Forum: Our Blue Marble (http://www.globalwarmingskeptics.info/forum-9.html)
+--- Forum: Stephen Wilde's Science Presentations (http://www.globalwarmingskeptics.info/forum-74.html)
+--- Thread: Why The Radiative Capabilities Of Gases Do Not Contribute To The Greenhouse Effect (/thread-2016.html)
Why The Radiative Capabilities Of Gases Do Not Contribute To The Greenhouse Effect - Stephen Wilde - 10-26-2013
A link to my latest article:
RE: Why The Radiative Capabilities Of Gases Do Not Contribute To The Greenhouse Eff - Richard111 - 10-28-2013
Stephen, many thanks for this article. Something this layman can follow and understand. Here are some of my thoughts on CO2 performance as a 'greenhouse gas'.
I posted a graph from Perry's HERE that shows the full spectral emissivity of CO2. Note that the temperature is 1,500K!!! CO2 is a very lively emitter at that temperature, especially in the 15 micron band!!! At temperatures found in the atmosphere, most certainly under 300K, the 2.7 micron emission will not be seen and the 4.3 micron band will be severely limited and seems to be ignored. It is generally accepted that CO2 is quite active from 13 to 17 microns over the temperature range found in the atmosphere. I suspect the edges of the band will be less than the central peak at 15 microns but cannot find any graphs that display this.
Collisions, conduction, effect the 'translational energy' of the CO2 molecule which can push up the vibrational energy level and cause the CO2 molecule to emit a photon within its emission bands. This results in a slight loss of vibrational energy but no loss of kinetic energy. If that CO2 molecule immediately absorbed another photon this results in NO ENERGY EXCHANGE.
In trying to understand what is happening I think of the atmosphere in layers with an average temperature for each layer and using M&B and net energy transfer see a small steady UPWARDS movement of energy. Nothing going back to the surface. At the top of the atmosphere the radiation escapes to space.
I created a trace showing IR emission over the 13 to 17 micron band with the help of this Planck Curve utility. (beware, unsigned application but it seems safe) This confirms there is no backward (downward) transfere of energy because the 13 to 15 micron radiation band does not exceed the peak radiation temperature. It's all on the back slope so to speak.
So, for what it's worth, this is my reasoning as to why there can't be 'backradiation' from CO2 in the atmosphere and why it does not qualify as a 'greenhouse gas'.
(Oops... had to shorten the heading! My Eff! )