[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Greenhouse

To Kelly

>>>How could it keep Earth heat in without keeping some solar heat out?
>>My error, it keeps MORE in than it keeps out:
>That would be a neat trick.  In the daytime the bulk of energy would be
>coming from the sun, so it should reflect/reemmit/whatever more of that then
>from the earth sources.  At night of course it would work the other way
>around.  So you'ld expect a cooling effect in the day and warming at night.

I think the problem is that we cannot compare radiation temperature with
ambient temperature so easely. If you lay a black piece of paper on the
ground at a calm hot summer day, it will become very hot, my guess is that
it will be about as hot as a similar paper on the moon.

>> I think I made a mistake, by using the word reflection, 
>> it seems that the heat is absorbed by the atmosphere. 
>> This means both solar-heat and soil-heat. Other radiation 
>> is going through the atmosphere without much interaction.
>Reflection is a bit simplistic, but the general effect is similar.

No, absorbtion means the atmosphere can get warmer, while in the case of
reflection it gets no chance to do that.

>Oh, and most of the spectrum is effected by its passage through the
>atmosphere.  visible light is the least effected.

Yes, I should have said has less interaction than IR.

>> Let me quote the following:
>> "The surface of the earth is warmer than it would be in 
>> the absence of an atmosphere because it receives energy
>>  from two sources: the sun and the atmosphere."
>Obviously simplistic given the diffences between Earth and moon.  Lunar temps
>snap between 200F degrees above zero to 200f degrees below durring the day
>night cycle, and change rapidly at sunset/sunrise.  Its more corect to say
>the atmosphere (and water) moderates the temperature changes dramatically.
> Since they act as heat sinks.

See also above about comparing radiation temps with abient temps. Besides
that I assume that the mean temperature of the Earth is about 30 degrees
higher than the temps on the Moon.

>> To end this discussion properly, I would strongly 
>> recommend that you read
>> the "bad greenhouse" page. (I think you didn't do that yet) 
>> I (http://www.ems.psu.edu/~fraser/Bad/BadGreenhouse.html)
>Ok, I'll read and comment.  I'ld recomend some books, but I've no idea whats
>avalible in North Europe.

You can check what is available in my library :)


At least I think it is a non-local connection. Just type "PCEL" or some of
the other passwords that are given. Don't reserve books in my name! :)