Guys, take it from a physicist. This experiment is a scam. The counter to false information from the GCC crowd is not our own false information, but scientific truth, and reproducing this kind of nonsense just makes FR out to be a bunch of no-nothing kooks.
Trapping of infrared radiation by the sky, clouds, etc. is important to the heat balance of the earth. That has never been questioned except by this imbecile of an "infrared" expert who is no expert on anything.
Infrared light within the biosphere does not come, principally, from the sun, and so "filtering" it out with glass will do nothing. Finding a meaningful representation of the spectrum is somewhat hard, but here is the best I could find:
Please ignore the stuff about indium nitride bandgaps which as to do with solar cell development and is irrelevant to this discussion. This graph plots photons per unit area, per time. The energy in any color band is obtained my multiplying the flux in this graph by the energy of the photons (shown at the top in electron volts), and when the multiplication is done will be seen to peak in the blue. The amount of energy from below the red (infrared) is very small.
Most infrared in the biosphere is the result not of infrared from the sun, but of the reradiation from the earth of visible and ultraviolet light that is absorbed. Once reradiated, the longer infrared which represent heat energy is reflected by the glass in a green house, hence the green house effect. Because the reflection away from the glass above a greenhouse in this experiment does not affect the visible light incident on the green house, the extra sheet of glass has no effect. Indeed, this idiot does not even understand that the greenhouse itself would already reflect incident infrared from the sun before it entered the greenhouse, and so the extra sheet of glass is superfluous.
CO2 doesn't reflect IR.
This idiot does not even understand the concept of "opacity." Diffuse CO2 does not act as a mirror to IR. It acts as an impenitrable fog. It is like looking at a cloud backlit by the sun. The cloud is plenty bright enough reflecting sunlight back to the observer, even though the reflection is not specular, like a mirror.
The "greenhouse" effect is a real effect and CO2, and other greenhouse gases (including methane and clouds), are very important in keeping the earth warm. No one, besides this idiot, has ever questioned that.
The question is whether human generated CO2 will have a significant impact on climate, given all the other sources of variability of climate. It is this hypothesis that skeptics doubt. That CO2 is a "greenhouse" gas has never been questioned by any knowledgeable scientist.