Friday 9 October 2020

Skeptical Science shoots itself in the foot yet again.

From Skeptical Science:

The greenhouse effect occurs because greenhouse gases let sunlight (shortwave radiation) pass through the atmosphere. The earth absorbs sunlight, warms then reradiates heat (infrared or longwave radiation). The outgoing longwave radiation is absorbed by greenhouse gases in the atmosphere. This heats the atmosphere which in turn re-radiates longwave radiation in all directions.

Some of it makes its way back to the surface of the earth. So with more carbon dioxide in the atmosphere, we expect to see less longwave radiation escaping to space at the wavelengths that carbon dioxide absorb. We also expect to see more infrared radiation returning back to Earth at these same wavelengths.

This is promptly shot down by Concerned Citizen/Matt Sykes at comments 6 and 8:

[Re] the picture showing solar light penetrating the atmosphere but terrestrial IR being trapped, what happens to the solar IR? The sun produces [more] IR at the frequency absorbed by CO2 [than] the earth. The atmosphere must therefore absorbs and re-radiate half of this back into space...

Point #3. Energy balance. So an increase in CO2 will absorb, and re-emit to space more IR from the sun as well as absorb and re-emit to earth more IR from the earth. Since the sun produces more IR than the earth how does the extra CO2 cause warming and not cooling? I am genuinely interested in the science behind GH gases, it is just that logically there seem to be problems with the theory.
That seems very plausible to me, and if true, this single observation would completely demolish the whole MMGW theory in one fell swoop. It appears to be undisputed that solar radiation is 55% infrared. This is at shorter wavelengths than terrestrial infrared emissions, but a large chunk of them are absorbed by 'greenhouse gases' on the way in.

It stands to reason that the earth's surface receives the same amount of infrared whether:
a) the solar infrared punches straight through a GHG-free atmosphere, or
b) the solar infrared and terrestrial infrared 'mix' in a GHG-laden atmosphere and half is re-radiated back down.

Similarly, the amount of infrared radiation going back to space is the same whether:
a) the terrestrial infrared punches straight through a GHG-free atmosphere, or
b) the solar infrared and terrestrial infrared 'mix' in a GHG-laden atmosphere and half is re-radiated back to space.

I have re-created the picture to illustrate this (a) without and (b) with 'greenhouse gases':


DaveM said...

True greenhouse effect is a convection thing and not a wavelength thing. It's a misnomer

A K Haart said...

Interesting and if true they shot their foot clean off. Strange though - I've never seen this particular argument before, I just assumed the radiation folk knew what they were talking about and took it from there. Hmm...

Mark Wadsworth said...

DM, yes of course, but we now use the term to mean whatever the MMGW people want it to mean. It's about beating them at their own game.

AKH, it had never occurred to me either. The precise maths of this are tortuous, but it stands to reason that earth's atmosphere gets approx the same amount of IR from the Sun as it does from the ground (averaged over 24 hours etc), it's got to do with the shape of the emission curve at 6,000 K vs at 288 K.

Bayard said...

I thought that the reasoning was that the incoming IR had a different wavelength from the outgoing IR and the outgoing is scattered whereas the incoming isn't.

Mark Wadsworth said...

B, it is far more complicated than that.

1. "infrared" is a non-scientific term. It just means "that portion of the electro-magnetic spectrum which has longer wavelengths than that portion of the e-m spectrum which we humans can register as visible light". It's anything longer than "visible" and shorter than "microwave", which again are human-defined categories with no clear boundaries. Some animals can see the shorter IR wavelengths; others can see the longer UV wavelengths. Most animals are colour blind.

2. Visible light *is* scattered. The longer the wavelength, the more it is scattered, hence why the clear sky looks blue (shorter wavelength). Red is scattered more than green which is scattered more than blue; IR is scattered more than red etc etc.

3. Remember R-M-I-V-U-X-Y (going from long to short wavelength).

Whereby "V" can be split into R-O-Y-G-B-I-V, and so on.

Bayard said...

I know it's far more complicated than that, I was just putting the Alarmist's riposte to your killer argument: CO2 only reflects the outgoing radiation back becasue the incoming radiation is a different wavelength and is unaffected by CO2. Yes it's bollocks, but that's the NuGospel.

Mark Wadsworth said...

Re 2 above, blue is scattered more than green or red. I got that the wrong way round.

Mark Wadsworth said...

B, in NewSpeak, the sun emits "near infrared" and the earth emits "thermal infrared".

The Alarmists use using sneaky terms to suggest that the longer wavelength, lower energy radiation is hotter than the shorter wavelength, higher energy radiation by referring to the former as "thermal" and the latter as "near".

Mark Wadsworth said...

... and CO2 and H2O absorb a similar amount of the near-IR as they absorb of the thermal IR.

Mark Wadsworth said...

I have now stumbled across the classic Alarmist counter-counter argument.

It boils down to "CO2 absorbs some solar IR (in mesosphere and thermosphere). Therefore this warms the atmosphere even more"

These people don't understand plus and minus. If solar IR is being absorbed higher up, then it is not warming the surface and the troposphere. So this ought to cancel out at worst.

ontheotherhand said...

The website moderator responds to comment 81 'Clouds keep the surface warm at night because they prevent some infrared radiation from escaping to space. During the day they do the same thing but also prevent some of the Sun's radiation from reaching the surface, and the energy prevented from coming in can exceed the energy prevented from getting out to space'

Isn't the same argument true fur CO2 and IR?

Mark Wadsworth said...

OTOH, yes.

I like his use of "can exceed" when it quite clearly does by a huge amount.

Robin Smith said...

Not fully got head around this yet, but seems science is starting to suggest the 'observer IS the observed'.

And those banging on about objective reality might be mistaken, not through lack of intellect, but ignorance. See Rupert Sheldrake and J Krishnamurti

It's a red pill moment.