UPDATE: Arthur Smith has the answer, just look at the first comment. Having put this baby to bed Eli will wrap it up tomorrow but now anytime someone raises the dread climate change is just N Rays flag, constant readers of Rabett Run can tell them, uh uh. Got that Marky?
R. W. Wood was probably the greatest American experimental physicist of the last century. He was renowned for his design of simple and penetrating experiments (mostly optical). Although it is rumored that he had a first name, Eli only has heard him referred to as R. W. Wood, even by those who knew him (Eli is old enough that only one generation separates him from an older Wood). Wood was the successor to Henry Rowland at Johns Hopkins and outdid the old master (Rowland perfected the diffraction grating). Wood was an immensely practical scientist, as anyone who has ever heard the N Ray story could tell, perhaps rivaled only by Fermi, who had the huge advantage of being a wonderful theoretician (physicists worship theory and tolerate experiment, everything in physics starts with theoretical models).
So, what brings us here? Among other things that Wood did, was to try and devise a test of whether thermal radiation could be trapped in the atmosphere
From this Wood concluded that
To test the matter I constructed two enclosures of dead black cardboard, one covered with a glass plate, the other with a plate of rock-salt of equal thickness. The bulb of a thermometer was inserted in each enclosure and the whole packed in cotton, with the exception of the transparent plates which were exposed. When exposed to sunlight the temperature rose gradually to 65 oC, the enclosure covered with the salt plate keeping a little ahead of the other, owing to the fact that it transmitted the longer waves from the sun, which were stopped by the glass. In order to eliminate this action the sunlight was first passed through a glass plate.
There was now scarcely a difference of one degree between the temperatures of the two enclosures. The maximum temperature reached was about 55 oC. From what we know about the distribution of energy in the spectrum of the radiation emitted by a body at 55 o, it is clear that the rock-salt plate is capable of transmitting practically all of it, while the glass plate stops it entirely. This shows us that the loss of temperature of the ground by radiation is very small in comparison to the loss by convection, in other words that we gain very little from the circumstance that the radiation is trapped.
Is it therefore necessary to pay attention to trapped radiation in deducing the temperature of a planet as affected by its atmosphere? The solar rays penetrate the atmosphere, warm the ground which in turn warms the atmosphere by contact and by convection currents. The heat received is thus stored up in the atmosphere, remaining there on account of the very low radiating power of a gas. It seems to me very doubtful if the atmosphere is warmed to any great extent by absorbing the radiation from the ground, even under the most favourable conditions.Eli and others, including the dread Stoat, have thought about this demonstration for a long time and certainly it is a favorite of the denialati, including some of our home grown ones, as an at this time ongoing interchange shows.
Eli had a flash of understanding this afternoon about what RW was measuring and why it is not relevant to the Greenhouse Effect. The hint is that the absorptivity of the glass in the IR is roughly unity as is that of the black cardboard, and therefore their IR emissivity is also unity in the IR by Kirchoff's law. Another hint, if you can understand what is wrong in the bunnies discussion of the Greenhouse Effect, you should have a good idea of what Wood measured and why it did not prove what he thought it did.
Now that the Bunny has ruined your Saturday night, Ms. Rabett is calling:)