Wikipedia: Greenhouse effect/Talk

Are there materials which are equally transparent at visible and infrared wavelengths? If so would a greenhouse made of those materials still work?

I think it would still work, because a big effect of a greenhouse (as opposed to the atmospheric greenhouse effect) is the suppression of convection, not just radiation.

I maybe wrong. Anybody know?

See the end of [[1]] for an argument supporting the above.

I would say greenhouse built with different materials will accumulate heat at a different rate if the convection in both cases are kept the same.

I disagree with the conclusion made by the Woods' experiment in your link above. I think his experiment has a flaw that his two boxes are made of black cardboards. So as the walls of the box are heated by the sun from the outside, the heat transfer and radiated as infrared from the inside surface of the walls into the interior. Basically, the heat transfer by the cardboards overwhelmed the greenhouse effect. I couldn't believe such a flawed paper could be written by a professor!

To improve his experiment, his boxes should be made purely of the materials in question. i.e. one built of regular glass and the other with rock salt plates to show the unbalanced energy flow. I'll bet the measurement would be different. He will also get different results if he built the boxes with several layer of heat insultion bricks.

The convection plays a major role of letting out the heat from the greenhouse, but it does not play a role in the accumulation of the heat. It is meaningless to introduce this variable in the experiment to confuse the result.

I think a greenhouse made of rock salt plates (if that's the material I was looking for above) should heat up faster, but its terminal temperature will be slightly lower.

I think the point of Woods' experiment is this: both boxes heat up at exactly the same rate, mostly because of the hot sides but partly also because of the transparent tops. But shouldn't the rock salt box lose its heat through the infrared transparent top? Apparently it doesn't. But I agree, a greenhouse made completely of rock salt would be a lot more convincing.

I don't understand your comment about this variable being meaningless. The claim is that greenhouses heat up because radiation can enter but cannot leave. I claim greenhouses heat up because radiation enters, and the hot air cannot leave. The truth is probably in between, but the question is which effect is larger.

His argument is analogous to saying the jobs in Silicon valley are not high paying because the cost of living here is too expensive. His experiment measured the saving, not the income.

The result of his experiment should depends on the relative surface area of the window in relation to the walls. My point is the window is too small to be of any significance.

When he opens the windows, the experiment is on an open system unless he measures the temperature changes in the laboratory also. The valid experiments would be a greenhouse made of glass compared to a greenhouse made of another material with other variables kept constant. e.g. 1. a glass house compare to a clear plastic film house. 2. a brick house with closed windows compared to a greenhouse with closed windows. 3. a brick house with open windows compared to a greenhouse effect with open windows. etc. When greenhouse effect is extended to the global scale, the convection is insignificant unless the hot air can circulate outside of our atmosphere.

I don't disagree the convection can affect the result of the experiment greatly. It is also my reason for keeping this variable constant. When we argue that greenhouse effect is all about trapping heat, it is meaningless to open the trap. Yes, keeping the air in the system help trap the heat, but convection is not making a difference. Even when all the windows are closed, convection can still spread the heat by circulation the air within the greenhouse.

I guess the keypoint is the transformation from light energy to heat. If the only object inside the green house is a mirror, the air may not heat up at all. Another experiment can be measuring the temperature of an object inside a vacuum jar when the energy source is the light and convection is eliminated.

Use a passenger car under the hot sun as an example. The passenger compartment heats up hotter than the truck (both with no convection). If a sun shade is put on the windshield, the car is cooler. Both observations suggest that Greenhouse effect is much more than just convection as suggested in this talk page.