http://www.grist.org/article/environmentalists-need-a-new-president/N10#c526563

@baxissimo 

I try to always remember to grab a copy of what I write before hitting the posting button on any site . Too many ways to screw up . Here's your post from my email with my comments interspersed :

@Bob Armstrong 

baxissimo said :
"It's far too poorly understood that the temperature computed without a parameter for absorptivity/emissivity applies to any gray body , ie : body with a flat spectrum , no matter how dark or light ."

I could perhaps believe that when it comes to how much energy is emitted by a body at a given temperature (I'm not an expert on black body radiation), but to say albedo doesn't affect absorptivity is just silly talk.

My reply :
This observation that for gray bodies , absorptivity = emissivity and therefore how light or dark the body does not change its temperature is essentially Kirchhoff's insight 151 years ago . The temperature of a radiantly heated body is determined by the correlation of its spectrum with the spectra of its heat sources and sinks . For an object with a flat spectrum , the correlation is the same for both and so the absorptivity/emissivity parameter drops out . If this were not true , you could make a cryogenic cooler simply by coating the inner chamber of a vacuum bottle with MgO which has an albedo of about .9 . 

You've motivated me find a reference in a 1938 text to an elegant classic experiment demonstrating this basic fact : http://cosy.com/Science/Ritchie%27sKirchhoffExperiment.html .

baxissimo said :
Do you understand that when electromagnetic radiation is absorbed by a body that it can (and often will be) re-radiated at different wavelengths? Clearest example: visible light gets absorbed by something painted black, which gets hot, and re-radiates the energy in the infra-red spectrum. You must get this, because it is basically just the black-body radiation law.

Something painted white, on the other hand, reflects most of the incoming energy in the visible part of the spectrum without changing the spectrum of the radiation. That energy is not absorbed (in the black-body sense of absorption), it just bounces off the surface. So I see nothing strange about considering the earth as a black-body with respect to how it radiates the heat it has, while not treating it as a black-body sink of energy. By your logic it seems even if the earth were a
giant mirror ball reflecting all energy beamed at it back unchanged, you'd still say it's temperature should be 278K because of the energy incident upon it from the sun. As far as I can tell, on your web page you are assuming that all incident radiation from the sun is absorbed, which is
clearly wrong. If that were the case, the earth would appear as a big black ball when viewed from space, not the lovely blue-green marble with whispy white clouds that we all know.

My reply :
Try walking on a white sand beach in the sun . It gets hot as hell too . I get tired repeating physics I essentially learned reading boy's science books as a child in the 1950s . That's why I have implemented these century old relationships at http://cosy.com/Science/Basics.html and in more detail at http://cosy.com/Science/TemperatureOfGrayBalls.htm . Your paragraph above clearly shows I have a ways to go in making them clear enough . The 278K temperature , as I said applies to any flat spectrum sphere , however light or dark . Look up Marty Hertzberg's work for a different path to the same fact . Or ask any physicist to work thru the equations . Or , try that forgotten method , do some experiments .

baxissimo said :
The greenhouse effect is essentially due to the earth's atmosphere being transparent to visible light but opaque to infra-red. So energy comes in spread over the whole spectrum
(http://en.wikipedia.org/wiki/File:Solar_Spectrum.png), much of that zips straight through the atmosphere, hits the ground and gets absorbed. At that point it is re-emitted black-body-style, mostly in the infra-red portion of the spectrum. But the energy can't get out of the atmosphere as easily as it got in, now that it's infrared. It's like shining a light into a fog. A lot of it gets bounced right back at the surface instead of escaping.

My reply :
A central reason from an analytical perspective why the "null hypothesis" must be a gray ball is that that removes the average brightness or darkness from the equation leaving just the pure correlations of the spectra as described above .  Starting from the assumption that the spectrum of the naked earth is as "anti-greenhouse" , as it could possibly be ( actually even more than it could possibly be ) confounds spectrum with albedo - which is best defined as average reflectivity . Thus I strongly predict you have never seen a coherent quantitative explanation of the effect of spectrum on temperature , one from which , given a set of spectra , you can calculate a temperature .. 
 
baxissimo said :
And then you start talking about tipping points above. I'm afraid I don't see what that has to do with anything we've been discussing.

My reply :
It doesn't . It's just that the very idea that such phenomena are possible reveals just how pathetic the general understanding of the physics has been .