You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
I omitted the technical details, but it's this: the temperature should be set by: incoming energy flux = epsilon sigma T^4, where epsilon is the emissivity, sigma is the Stefan-Boltzmann constant, and T is the temperature.
Since anything absorbed by the GHGs has already been absorbed by the Earth, the absorptivity (and thus the emissivity) shouldn't be changed by the GHGs, and so I don't see how T can be changed by the GHGs.
I should have said earlier in the thread, but the key thing I'm worried about: why is epsilon in the Stefan-Boltzmann relation changed, since net absorptivity apparently isn't? Or is S-B the wrong way to be thinking?
Update: I believe @PESimeon has isolated the source of my confusion. A summary (more or less) can be found here:https://twitter.com/michael_nielsen/status/1096990267259809793 …
Thankyou for all the comments and the links. It's very much appreciated, and has clarified matters greatly for me, especially (though certainly not just) in the part of the thread linked in the last tweet.
The temperature of the earth at the ground is not the same as the temperature of the upper atmosphere, where the IR has its last chance to radiate from Earth. Analogy: your clothes radiate at a lower temperature than your skin. Your clothes make the air above your skin warmer.
Good point. So you're saying the temp of the Earth+atmosphere system is determined by the Stefan-Boltzmann relation, but the Earth may be quite a bit warmer.
Basically, the GHGs "slow down" the radiation that the earth emits back to space ("It's like a blanket!")https://scienceofdoom.com/2014/06/26/the-greenhouse-effect-explained-in-simple-terms/ …
Yes I understand that - I used the blanket analogy in the thread. But it doesn't address the question of why the emissivity in the SB relation changes.
I watched a video lecture series that explained this, but can’t find it right now. I think this information here: http://people.atmos.ucla.edu/liou/Lecture/Lecture_3.pdf … should help, would be most efficient to probably start with last slide and work up.
That doesn't seem to address my main concern, which is why the emissivity in the Stefan-Boltzmann relation is changed by the greenhouse gases. But perhaps I missed that?
Just thinking here, but as the IR radiation travels away from the earth, every time it gets absorbed by a bit of GHG it would heat up that GHG, and cause that GHG to re-radiate. That re-radiation could go in any direction. 50% chance of that direction being right back at earth.
So the more GHG in the atmosphere, the more opportunities that re-radiating IR has a chance to get bounced back at earth. Thus reducing the net flux of IR out of the atmosphere.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.
