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Politics : The Environmentalist Thread -- Ignore unavailable to you. Want to Upgrade?

To: Thomas A Watson who wrote (18986)	12/26/2007 11:42:17 PM
From: neolib	Respond to of 36921

They magnified what they see as differences as failed to point out the magnitude of the similarities. Even a sheet of 4 mil clear plastic makes a good greenhouse BECAUSE it does an OK job of shutting down convection (and conduction is relatively low as well) while allowing radiation transfers between systems. The whole point of a greenhouse model for the earth is that the vacuum of space shuts down convection and conduction, but not radiation. If you take a greenhouse of plastic and one of glass, and DON't allow ANY internal to external convection, then the glass one will achieve a higher equilibrium temperature BECAUSE of the different radiation effects it has during the day, while during the night (assuming condensation) they will preform about the same. The point is that convection should be discussed in terms of transport from inside to outside the greenhouse. The fact that the air inside the greenhouse heats up to the same temp as the surface inside the greenhouse, is simply a fact that the total heat capacity of the air inside the greenhouse is very small. Nobody is expecting the air temp of the atmosphere to heat up to the earth's surface temp for the entire volume of the atmosphere, and especially not so in the sunlight portion of one day. Any idiot who has gone up a mountain should realise that. Nobody gives a shit that it heats top to bottom or bottom to top or that convection is involved inside a greenhouse. Its going to heat easily in the course of a day because its heat capacity of a small volume is small. Who gives a rats ass? Heck, pull a vacuum in the freaking greenhouse and ignore the air temp! That gets rid of your convection idiocy totally. It is largely irrelevant. The greenhouse metaphor is asking what the equilibrium temp is for a system with ONLY radiation transfer across the system boundaries WHEN incoming and outgoing radiation have different spectrums, AND there is a blanketing medium which behaves differently to these two spectrums. That is precisely what a glass greenhouse and the earths atmosphere have in common. A plastic greenhouse will on average have a lower equilibrium temp (especially if the greenhouse has a vacuum given that will destroy the nighttime condensation)