Greenhouse effect - not what I thought..

[confused2]

It seems most of the infrared from the surface of the earth is absorbed a few tens of metres above the surface and this hasn't changed significantly since pre-industrial levels of CO2. So what is going on?

Gleaned from Sabine.. [Hossenfelder]

As carbon dioxide concentration increases more and more of the infrared radiation is emitted from higher levels [in the stratosphere] where the temperature is lower - which makes the cooling increasingly less efficient. So the surface of the planet gets warmer (ultimately warming the entire atmosphere) until the energy balance is re-established.

In a nutshell: increased solar radiation predicts stratospheric warming and increased CO2 predicts stratospheric cooling - and what we see is (apparently) stratospheric cooling.

https://www.youtube.com/watch?v=oqu5DjzOBF8

I'd suggest starting at 10:33 - her PhD version

Obviously she has simplified bits..
Many papers and much research (and balloons?).

[C C]

[...] https://www.youtube.com/watch?v=oqu5DjzOBF8

I'd suggest starting at 10:33 - her PhD version

Obviously she has simplified bits..
Many papers and much research (and balloons?).

Sabine (Twitter image of graphic): I had an infographic made to explain how the greenhouse effect really works.
https://twitter.com/skdh/status/1622099529553018881
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VIDEO TRANSCRIPT EXCERPT: . . . So I guess we’re back to “it’s all a hoax”. Okay, to understand what’s really going on, we have to add one more subtlety.

It’s that all  those greenhouse gases don’t absorb infrared light  equally well at all wavelengths, they absorb light  only in certain parts of the infrared spectrum. The best absorber is water vapor.

That’s because  the water molecule has a lot of resonances. It’s a really really good infrared wiggler. If we  look at earth from above in the infrared and add the absorption from water, then the spectrum changes roughly like this. You can think about this as change as an increase of the effective altitude of emission again, but a slightly different altitude for different wavelengths.

For example at shorter wavelengths the light comes on average from an altitude of about 4km. At longer altitude it’s more like 5km. And each of those altitudes have their own effective  temperature, which you see on those two sides.

Carbon dioxide now has a much stronger  absorption but it’s only in a specific part of the spectrum. This is around a wavelength of about 15 micrometres.

The relevance of carbon dioxide for our climate comes from this emission band being pretty much near the peak of the  infrared emission. At preindustrial levels, carbon dioxide takes out a big chunk of  radiation coming from the surface of earth.This lower part of the absorption line.

That’s the emission curve that belongs to the temperature at the average altitude of  emission, about 220 Kelvin or minus 60 degrees Celsius. But here’s the thing. If you increase  the carbon dioxide even more, then this ditch can’t get deeper, because the temperature  at that altitude doesn’t drop any further.

If you’ve ever had the pleasure of interacting  with a climate change denier, this is exhibit A. Look, they’ll say, nothing we do will  make any difference. And it’s indeed correct that the bottom of the ditch basically won’t change much.

But this isn’t the relevant part. The relevant part is that carbon dioxide doesn’t just absorb light in this very narrow range. It also absorbs it to both of those sides, and in  fact in some other part of the spectrum which I haven’t drawn.

If the concentration of carbon dioxide increases further, then the emission of more and more wavelengths  in the spectrum moves up to higher altitudes, so they move to lower temperatures. Which in  this figure means that the ditch gets wider.

So, increasing carbon dioxide levels filters  out an increasingly bigger chunk of the wavelength window that we use to cool the planet. Another way to put it is that when carbon dioxide levels increase, more and more of the infrared radiation is emitted from higher altitudes, where the temperature is lower, which makes  the cooling increasingly less efficient.

And then the surface of the planet will warm  until the energy balance is re-established. This carbon dioxide ditch doesn’t get  wider by a lot. It’s just a tiny bit.  But this is the major reason for the enhanced  greenhouse effect that we’re seeing right now.

Can such a small difference really have so  big consequences. Well, if you think about it...