CO2 and stratospheric cooling

I really don’t understand the “CO2 causing stratospheric cooling” thing.

I mean I get the basic idea that CO2 mostly heats up the troposphere, and as a result there is less IR to go into the stratosphere and above, causing those layers to cool. But some of the details don’t make sense. From this website (the only source that RC gives to explain it):

Can someone explain how the bolded part doesn't violate the laws of physics?

And this claim does agree with another, equally confusing claim I’ve heard a few times, that is (if I understood it right) something to the effect of: “CO2 in the upper atmosphere acts as a radiator for heat, accelerating the heat loss to space and thus causing cooling.”

Wouldn’t the fact that the direction of emission is random (360 degrees) mean that CO2 is just as effective at warming the stratosphere as it is the troposphere? (The fact that concentrations are lower and there is less IR aside...how does what is left not do the same thing as what happens in the troposphere?)

Can anyone tell me where I'm confusing myself on this one?

Quote:

Originally Posted by dana1981 

Until the stratosphere reaches a new equilibrium where it's not radiating as much energy to the higher levels of the atmosphere, it will cool.

I still don't see how it can be releasing more than it is getting. Where are these extra photons coming from?

I mean I get the basic shift of equilibrium argument. The way I understand it is, if we're trapping more IR than is being released, then the surface will warm in order to force more IR out and so maintain equilibrium once again--the analogy I read was like a sink with a drain and a faucet. If you have water coming in and out at a constant rate, then you partially block the drain, the water will rise until the pressure forces the rate of water out to again equal water in, and the water level can again remain constant, albeit at a higher level than before.

I guess I just don't get why the explanation isn't more along the lines of "stratospheric GHG's are getting less IR, since the lower troposphere isn't in equilibrium yet." In the stratosphere the energy out still equals energy in, there's just less coming in (and thus cooler temps.) 

I mean that's how I always intuitively imagined it anyway...

Quote:

Originally Posted by gcnp58 

The stratosphere cools because it is easier for it to radiate (more greenhouse gases to radiate) but there aren't more photons getting to it from below (because of the GHGs in the troposphere).  It gets fewer, gives off more, which means it is radiating energy.

Okay, I think I get it better now. I was under the impression that a GHG molecule itself doesn't have any means of emitting IR, unless it is receiving a wavelength at the same time. But I guess they have some heat associated with them all the time, and it is the energy from this heat that is being emitted. So they can emit even without receiving, just by the heat energy contained in the molecule itself--is that kind of sort of right?

It's still not clear why it shouldn't already be in equilibrium though. It seems that once the incoming IR from the troposphere weakens, the stratospheric GHG's should cool in just--well, a few hours at most. IR into the stratosphere would still equal IR out, but the flux is now smaller and so temperatures are lower, explaining the relatively lower temps. Why does equilibrium in the stratosphere take such a long time to be reached?

And once the troposphere reaches equilibrium, wouldn't the stratosphere go back to the same temperature? I mean total energy leaving the Earth into space can't change right?