[alancalverd]

Quote from: alancalverd on Today at 10:24:42
Quote from LNER
"Travelling by train produces up to 513% less carbon emissions than flying".
So, your argument is something like "Because someone wrote bad advertising copy, physics is wrong".

If I doubt anything written by a Believer, I'm castigated as a Denier, so I have to accept whatever garbage appears in print.

[Bored chemist]

So the question is at what height the 14 micron absorption band is effectively saturated. 

The figure you gave for this was 1 metre...

Sadly, they imply that 99.5% of the 15μm radiation is absorbed in the first meter of the atmosphere

is that close enough?

Do you realise that photons don't really know if they are going up, along, or down?

[alancalverd]

So if we accept the physics, increasing the concentration of CO2 in an entirely static atmosphere is only going to affect the temperature of the lowest few centimeters. That's pretty trivial compared with the geostrophic and convectional mixing of the remaining 12,000 meters of the real troposphere, and all the interesting effects of water. 

Photons may not know which way they are travelling, but the greenhouse effect depends on the outgoing photons being strongly absorbed because they are predominantly IR, and the incoming photons being less strongly absorbed because they are mostly visible.

[Bored chemist]

So if we accept the physics

What physics are you saying you accept?

but the greenhouse effect depends on the outgoing photons being strongly absorbed because they are predominantly IR

Yes.
Do you realise that the CO2 in the atmosphere also emits IR?
Do you realise how that makes a difference?

[alancalverd]

Do you realise that the CO2 in the atmosphere also emits IR?
Do you realise how that makes a difference?

Presumably, increasing [CO2] either increases (due to absorption) or decreases (due to emission) mean temperature, or has no effect (due to saturation).

What is absolutely clear is that the atmosphere has been > 99% opaque in the CO2 infrared spectrum for as long as it has been measured.

[Bored chemist]

What is absolutely clear is that the atmosphere has been > 99% opaque in the CO2 infrared spectrum for as long as it has been measured.

Yes... So what?

[Bored chemist]

What physics are you saying you accept?

[alancalverd]

I think it is a good idea to accept all the known laws of physics until they have been disproved.

So we have this blackish spherical body of 60% liquid water, 10% ice, and 30% rock covered with water in various forms,  being heated on one side by visible radiation and simultaneously reflecting some of the visible, and radiating in the infrared. The body is covered with a blanket of gas, one of whose constituents is opaque at 15 microns and has negligible absorbance at other IR wavelengths. What happens to the radiation balance if we increase the concentration of that constituent?   

I think of CO2 as a notch filter with a very sharp spectral characteristic. If one stage of the filter rejects > 99% of that frequency but has no effect on the rest of the spectrum, how is the total energy of the received (or transmitted) spectrum affected by adding a second stage?

[Bored chemist]

I think it is a good idea to accept all the known laws of physics until they have been disproved.

Yes.
But which ones did you think you were referring to here?

So if we accept the physics, increasing the concentration of CO2 in an entirely static atmosphere is only going to affect the temperature of the lowest few centimeters.

[Bored chemist]

What happens to the radiation balance if we increase the concentration of that constituent?   

There are 3 possibilities:
The surface gets warmer.
The surface stays at the same temperature
The surface gets cooler.

Is there a mechanism by which the additional CO2 can directly cause cooling?

[Bored chemist]

If one stage of the filter rejects > 99% of that frequency

What does it do with the energy it rejects?

[alancalverd]

So if we accept the physics, increasing the concentration of CO2 in an entirely static atmosphere is only going to affect the temperature of the lowest few centimeters. That's pretty trivial compared with the geostrophic and convectional mixing of the remaining 12,000 meters of the real troposphere, and all the interesting effects of water. 

OK, the lowest few centimeters heat up a bit quicker, so the next meter doesn't get as hot as it used to, then convection and wind mix it all up and the mean atmospheric temperature doesn't change. Something to do with conservation of energy.

[Bored chemist]

here's a useful simplification.
Compared to radiative heat transfer (at the speed of light) the atmospheric mixing which is over a millionfold slower, is too slow to make a difference (on average).

[alancalverd]

Precisely my point. The lower few centimeters heat up quickly but the total energy emitted from the surface in the 15 micron region remains the same, so atmospheric mixing ensures that the mean temperature of the atmosphere doesn't change - at least not because of increasing CO2 level above saturation.

You can heat water from the bottom in a kettle, or from the sides in a microwave, but a kilowatt is a kilowatt and a bit of stirring will give you the same average temperature after the same length of time.

[Bored chemist]

Alan; you fly.
You know that it's cold "up there"
And since you claim to know how science works you should know that the earth can only lose heat to space from the cold stuff up there. The IR radiated into space is not the IR radiated from the ground.
The better the "lagging" between the surface of the earth and the outer reaches of the atmosphere, the warmer the bit of the earth where we live gets.

Adding more CO2 is, as I have pointed out at length, adding more lagging.

In the meantime, you missed this

What happens to the radiation balance if we increase the concentration of that constituent?   

There are 3 possibilities:
The surface gets warmer.
The surface stays at the same temperature
The surface gets cooler.

Is there a mechanism by which the additional CO2 can directly cause cooling?

[alancalverd]

Not according to Believers, who think that adding more blankets reduces your heat loss  linearly with thickness or density of the blanket.

[Bored chemist]

reduces your heat loss  linearly

Show me where anyone said it was linear.
Or stop straw-manning.

[alancalverd]

Perhaps you can lead me to a better or more widely accepted prediction (not retrospective model)  of the effect of adding CO2 to an atmosphere containing 300 ppm. The Mauna Loa graph is, if anything, slightly supralinear.

[Bored chemist]

Perhaps you can

Perhaps I could, but lets see you demonstrate your claim first.

reduces your heat loss  linearly

Show me where anyone said it was linear.
Or stop straw-manning.

[alancalverd]

The claim is that adding more CO2 from the present level will increase global temperature.

The observation is that the correlation is supralinear.

The fact that the principal CO2 absorption band is saturated within a few feet of the surface, suggests that if CO2 is the culprit, the curve should be no more than linear at low concentrations, and tend to an asymptote at high concentrations. Exactly the opposite of what we observe.

Science says that if the hypothesis doesn't match the facts, the fault is in the hypothesis.