You Shall Not Pass!
Chad addresses the issue of the greenhouse effect in your car, and whether putting a sunshade inside or outside matters: Greenhouse Physics and Car Shades
In the first comment we find the following question
Does car window glass block IR?
to which Chad answers
I like the idea of testing this with a piece of glass and a heater. You could probably do it with a toaster or an electric stove and a Pyrex baking dish (don’t put the dish directly on the burner, though, because they can explode that way)
Here you go. I had a beaker rather than a baking dish, and I used the IR thermometer I demoed a few months ago
You can see that the filaments are heating up, but when the beaker is put in place, the temperature drops to ambient. So it blocks basically all of the IR in the region of sensitivity of the device.
SFN RSS
The classic Greenhouse BS bomb is to make a little greenhouse of transparent NaCl crystal slabs plus shaded thermocouple inside and outside, and put it in the sun. IR has near nothing to do with it. A greenhouse is about containing convection.
Talk to folks in Arizona. Atmospheric greenhousing there is all about humidity, water vapor being the overwhelmingly preponderant Greenhouse Effect gas. A 100 F day in 5% humidity wll plunge into the 60s overnight. A humid day will stay hot at night. That requires parts-per-hundred water in air, and lots of them, not parts-per-million. The air’s CO2 content does not change – or drops with water loading.
Adding CO2 to an already optically dense atmosphere is not Beer’s law, absorption proportional to concentration. It is absorption proportional to log(concentration),
http://3.bp.blogspot.com/_Y1xTrEn3pwg/S6P0S6Hy4wI/AAAAAAAACG8/3YVixy57XQ4/s400/LineBroadening.gif
http://www.mazepath.com/uncleal/green3.jpg
Enviro-whinerism: Expensive, Shoddy, Deadly
containing convection does help keep temperatures high, but trapping emitted IR radiation also plays a significant role,
Here is a video using an IR camera showing how glass is opaque to IR:
http://www.youtube.com/watch?v=Uckr-j95jaM
Brighter is warmer (actually emissivity times temperature).
The camera is sensitive to wavelengths from 8 to 14.5 microns and uses a germanium lens (since glass doesn’t work). The car window is raised and lowered clearly demonstrating the effect. Also note the reflections of IR in the windows. Smooth glass is a very efficient reflector of IR at these wavelengths.