Intuitively, the GHGs makes the atmosphere a little like a one-way "blanket", allowing some energy through (at optical and UV frequencies), but making it harder for the infrared radiation to get back out again.
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The net effect is for the Earth to have to heat up a little extra, thus producing a little more infrared so that at equilibrium the total amount of energy escaping is the same as the total amount of energy incident.
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What I don't understand: the IR that's being blocked by the GHGs is energy which has already been absorbed by the Earth. So this shouldn't change the Earth's overall absorbivity, and I don't see how it could change the Earth's temperature.
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Twitter may not be the best medium for this(??) But if someone who understands this well can point me to a good explanation, I'd appreciate it. Thanks!
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@AndrewDohertyQu@dabacon@worrydream@patrickc Do you know?2 replies 0 retweets 1 likeShow this thread -
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.
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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.
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Replying to @michael_nielsen
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/ …
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Replying to @ThomasMiconi
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.
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Replying to @ThomasMiconi
Did a quick skim - looks like a nice article, and I will do a detailed read. Thanks!
8:47 PM - 16 Feb 2019
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