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Discussion > How Simple Physics Demolishes the "Greenhouse Effect".

Ross Lea - not sure how what Rhoda says relates to the paper you pointed to.

In it the author says:

"...Under this unphysical scenario, the surface would emit thermal radiation which would be absorbed by the atmosphere, which would emit again towards the surface, which would emit more thermal radiation towards the atmosphere, which would absorb more energy and would radiate even more energy towards the surface, etcetera, etcetera, until toasting the Earth."
"In conclusion, backradiation from a cooler atmosphere warming up a warmer surface is a myth that is 100% discredited by correct unbiased experimentation"
Nobody who understands the GHE asserts that backradiation warms the surface. Only "climate scientists" who don't understand simple physics and who are essentially bullshitters, giving bullshit explanations of the GHE to other people who don't understand simple physics.

As I said (3:31) It's standard Dragon Slayer stuff: (1) Give an incorrect explanation of the GHE (2) Point out that it's nonsense (3) declare that therefore the GHE does not exist.

Dec 1, 2015 at 6:17 PM | Registered CommenterMartin A

Where is Entropic Man when he's needed?

Dec 1, 2015 at 6:46 PM | Unregistered CommenterMartin A

Martin: If you look at all the earth energy flow diagrams, like that of K-T, you will see that the back-radiation is absorbed by the surface (in fact the back-radiation is twice that received from the sun). This energy absorption is needed to raise the temperature of the surface to match that needed to explain the 'greenhouse effect'. Which is contrary to what you assert: "Nobody who understands the GHE asserts that backradiation warms the surface."

Dec 1, 2015 at 7:16 PM | Registered CommenterPhillip Bratby

I'm with SandyS, Rhoda and Ross Lea.

I think it is a pity when the tone of some responses on a discussion thread move a regular poster (Mike Jackson) to write:

"TBYJ / MartinA
Sorry to have ruined your afternoon. ☺
I must be very stupid so I shall refrain from troubling you further."

But thanks to all who replied. I need to read the paper again.

Dec 1, 2015 at 7:36 PM | Unregistered Commenterjolly farmer

As this is a discussion thread I will put forward my view for discussion.

When it comes to the effects of CO2 on climate I am not a “Luke Warmer” I subscribe to the view held by Prof. Lindzen “ he responded during the interview with calm, collected answers. His funding comes from the US government. The reason he won't change his mind is that years of scientific research have lead him to the conclusion that the human impact on climate change is negligible.”
Let us take am empirical example. Presumably the CO2 concentrations in the atmosphere are the same over tropical deserts and rain forests on the same latitude. (I have personal experience of both). You will notice that at night the temperature plummets in the desert where as in the rain forest the temperature range is much smaller. This is undoubtedly due to the presence of water vapour because it is assumed that the CO2 concentrations in the atmosphere are about the same. (in fact as the trees absorb CO2 during the day the concentration of CO2 is probably lower). So the impact of water vapour is orders of magnitude greater than that of CO2.

The current IPCC theory depends on the so called positive feedback which has never been demonstrated to exist. Prof. Roy Spencer did a study on water vapour feedback and concluded that if there was any feedback it was slightly negative. ( This makes sense from our/my experience. When you fly over clouds they are predominantly white reflecting sunlight back to space. If you lay in the sun and a cloud passes over head you instantly sense a drop in temperature. If the cloud was absorbing the heat it would disperse so it must be reflected back out to space. So I believe as Dr. Spencer doses, that the effect of increase water vapour is neutral or slightly negative.

When it comes to sensitivity to doubling of CO2 it is completely meaningless. The assumption is that all the observed warming is due to the increased concentration of CO2 in the atmosphere but there is no justification for that; many other factors may be involved that are not taken into account. The concentration of sunspots and global temperature has a much better co-relation although a linking mechanism has not been confirmed. There is some very interesting work by Henrik Svensmark ( and Jasper Kirkby. (the lite version) The scientist version ( The telling graph is 45min onward. He was cautioned by the director of CERN to only report his results and NOT to draw any conclusions. This very important graph was relegated to the appendix in the final paper. Real science at work.
Enjoy the Holocene.

Dec 1, 2015 at 7:57 PM | Unregistered CommenterRoss Lea

Phillip - after what you said earlier :

Precisely. I had never heard of back-radiation and never considered back-radiation in all my work, because it didn't do anything - it is cancelled by exactly the same forward-radiation. So it should never be considered and anybody who considers it is being deceptive.
Dec 1, 2015 at 4:48 PM | Registered CommenterPhillip Bratby

There is no need to define a greenhouse effect - it is just a bit of propaganda to fool people into thinking that here is a unique phenomenon that humans are interfering with. What happens is just bog-standard heat transfer and fluid flow.
Dec 1, 2015 at 11:58 AM Phillip Bratby

I thought you had no truck with back radiation warming things nor with the idea of the GHE.

But now you are now saying something that seems to accept both back radiation and the GHE:

Martin: If you look at all the earth energy flow diagrams, like that of K-T, you will see that the back-radiation is absorbed by the surface (in fact the back-radiation is twice that received from the sun). This energy absorption is needed to raise the temperature of the surface to match that needed to explain the 'greenhouse effect'. Which is contrary to what you assert: "Nobody who understands the GHE asserts that backradiation warms the surface."
Dec 1, 2015 at 7:16 PM Phillip Bratby

Phillip - I assume you are referring to something like this diagram: this diagram

All I see in the diagram are arrows going up and down. Nothing about temperature nor about GHE.

(A) I am not sure why you say "This energy absorption is needed to raise the temperature of the surface to match that needed to explain the 'greenhouse effect'." Where did you get that? Is that from a calculation or what? Do you believe it (in view of what you said earlier)?

(B) I am not sure why you say 'Which is contrary to what you assert: "Nobody who understands the GHE asserts that backradiation warms the surface." '

To me, if somebody is maintaining that back radiation warms the surface, then that's pretty convincing that they don't understand the GHE. What convinces you that they (whoever they are) *do* understand it?

Dec 1, 2015 at 8:17 PM | Registered CommenterMartin A

Spare me your hurt feelings.

I explained my annoyance at this topic rearing its head again, and my small review of the paper abstract was directed at the author, not Mike, whom I have a lot of time for, after many years of interaction on this board. He did not ruin my day, and I am not annoyed by him. As I expected and predicted, this 'demolition' of greenhouse physics was nothing of the kind. I hate being right.

As I said earlier, when confronted with a logical rebuttal, the 'denier' response is NEVER to admit they were wrong, but to change direction. As far as I can see, this is happening here, running from the inexorable logic and feigning hurt because of the tone of the discussion. This is pathetic. It is cowardly. If you are big and tough enough to challenge the body of physics from a position of limited knowledge, at least stand your ground and argue the case. Running away and saying it's because the discussion is not civil enough is rubbish, and a cop out.


TBYJ, you may need to clarify your terms. RADIANT energy does what you say. Heat energy used in that context isn't really right. The exchange of radiant energy results in a change of heat energy always from hot to cold.

I agree this is a terminology problem, but what you say in the above quote is nonsense. Radiant energy simply describes a direction of travel, not a type of energy. Heat energy can be radiant energy, or it can be random. Where the terminology breaks down is where people use "heat" and "heat energy" to mean the same thing. 'Heat energy' is a vector of energy, 'heat' is an arithmetic addition of those energies.

If a hot and cold body are close, heat energy is travelling from both bodies. The amount is proportional to the temperature of the bodies, given by the SB law. Any body above absolute zero is emitting heat energy. This means a small amount of heat energy from the cold object falls on the hot object. And a larger amount of heat energy from the hot object falls on the cool object.

The word which the lay person knows as 'heat' (and not heat energy) is the arithmetic subtraction of these. Because the amount of heat energy from the hot object is much larger then the cool object's heat energy, the net (arithmetic sum) energy is a flow of heat energy from the hot to cool proportional to the difference in the temperatures. To the lay person, this looks like the hot is sending to the cool, but the cool is not sending to the hot. This is the usual mis-statement of the law which leads to all the confusion. They are both sending out energy, but what lay people know as 'heat' hides that reality in a neat bit of arithmetic.

So is it just a daft semantic word-play, who cares what is actually happening if the net effect in the 'real world' is heat only flows from hot to cold? Am I just being picky? No. There is another effect that effect bodies cooling down.

The small bit of heat energy that falls on the hot object has to go somewhere. The hot body is emitting an amount of energy, and as it does so, it is cooling down. If we left the hot object on its own, eventually it would emit all its heat energy away.

Lets imagine the hot body at 100 degrees C is emitting a million photons a second (it's much more than this in reality) and this lets it cool by 1 degrees per second (the actual temperature decay is exponential, but lets keep it simple) Since 'number' of photons is proportional to temperature, as it cools it emits proportionately fewer photons.

Time 0 - temperature = 100, photons emitted = 1000000
Time 1 - temperature = 99, photons emitted 990000
Time 2 - temperature = 98.1, photons emitted 981000
Time 3 - temperature = 97.2, photons emitted 972000

Now we place a cooler object beside it, and it is at 0 degrees and emits 10,000 photons, 1000 of which fall on the hot sphere:

So now the hot sphere has to take into account the net emitted photons (outgoing minus incoming)

Time 0 - temperature = 100, photons emitted = 1000000, absorbed = 1000, total = 990000
Time 1 - temperature = 99.1, photons emitted = 991000, absorbed = 999, total = 990001
Time 2 - temperature = 98.2, photons emitted 982000, absorbed = 998, total = 981002
Time 3 - temperature = 97.3, photons emitted 973000, absorbed = 997, total = 972003

So you can see over time by comparing the two temperature decays that although the presence of the cooler sphere cannot HEAT the hotter one, it can PREVENT it cooling as fast because it is providing a few photons which make it cool a little bit more slowly.

Stopping something cooling as fast is the same thing as saying it is making it hotter than it would be if the sphere wasn't there.

Cool objects cannot HEAT hot objects, there is no heat exchange in that direction, but by the exchange of heat energy, a cool object can make a hotter object hotter than it would be if the cold object wasn't there by preventing cooling.

Just remember that when you pull your scarf on.

Dec 1, 2015 at 8:26 PM | Unregistered CommenterTheBigYinJames

Martin: I do have no truck with back radiation warming things and with the idea of the GHE.

No, I do not mean a diagram like you show, but one with figures and text on it. Like these

Dec 1, 2015 at 8:27 PM | Registered CommenterPhillip Bratby

My understanding of the "greenhouse effect"

The Sun’s temperature is approx. 6000 K, so it radiates mostly in the visible spectrum. The Earth’s temperature is approx. 300 K, so it radiates mostly in the infra red (both objects are approximately black body radiators).
If the Earth’s atmosphere contains “greenhouse” gases, i.e. ones that interact significantly with infra-red radiation (e.g. H2O, CO2) much of the outgoing infra-red radiation is intercepted, and re-radiated in all directions by the gas molecules.
This would prevent much of the infra-red from escaping into space, as much of it is reradiated back to Earth.
However the radiation energy received by the Earth must equal the radiation energy outgoing, otherwise the Earth would warm or cool until equilibrium is reached.
According to the Stefan-Boltzmann law, radiative output is proportional to the fourth power of the radiating body’s temperature.
Thus the Earth’s surface needs to be warmer than in the absence of IR-active gases to output sufficient radiative energy to maintain the equilibrium between the Sun’s radiative energy arriving and the Earth’s leaving into Space. In effect it needs to work harder according to Stefan-Boltzmann to output sufficient radiative energy into space.


Dec 1, 2015 at 8:30 PM | Unregistered Commenterrotationalfinestructure

TBYJ: But when we consider the earth it is not just radiant energy we have to consider because conduction, convection and evaporation will increase if radiant energy is reduced. So it becomes just a more complex heat transfer problem that we have to solve.

Dec 1, 2015 at 8:33 PM | Registered CommenterPhillip Bratby

Phillip - those diagrams look to me the same as the one I pointed to.

rotationalfinestructure - that's more or less as I see it. I'd talk about lapse rate, to take in what Phillip said about conduction, convection and evaporation also being involved in transporting heat from the surface. ie the lapse rate tells you what temperature the surface has to be to get the right temperature* at the altitude where most of the finally departing radiation leaves from.

*ie so the outgoing radiation matches the absorbed incoming solar radiation.

Dec 1, 2015 at 8:59 PM | Registered CommenterMartin A

This business about the direction of heat flow seems to cause problems. The heat flowing from one body to another by radiation cannot tell in advance whether it is flowing towards a higher or lower temperature, however, since the amount of heat radiated by a body is a function of its temperature, it is obvious that by equilibrium, everything will have reached the same temperature and the hotter bodies will have lost the most heat.

The great leveller is not how much heat is gained, but how much is lost by the end of the process.The hotter bodies will lose the most.

Dec 1, 2015 at 10:43 PM | Unregistered CommenterSchrodinger's Cat


My feelings are not hurt.

I note your proclamation of your "inexorable logic", and that you "hate being right". I note your use of the words "pathetic" and "cowardly". Your playground language: "running away", "if you are big and tough enough".

I conclude that you are ill-mannered and boorish.

Dec 2, 2015 at 12:01 AM | Unregistered Commenterjolly farmer
Dec 2, 2015 at 7:35 AM | Unregistered Commentersplipin

As usual in these discussions TheBigYinJames is right. I don't know how he has the patience to carry on. I certainly don't.

Dec 2, 2015 at 8:45 AM | Registered CommenterJonathan Jones

It's wearing thin, believe me.

Dec 2, 2015 at 9:23 AM | Unregistered CommenterTheBigYinJames


TBYJ: But when we consider the earth it is not just radiant energy we have to consider because conduction, convection and evaporation will increase if radiant energy is reduced. So it becomes just a more complex heat transfer problem that we have to solve.

You can think of the earth system in two parts. The upper atmosphere, where the air is so thin that convection has essentially stopped (where the kinetic energy of the sparse molecules can no longer hold the air up against gravity) and it's all about radiation, and the lower atmosphere and the land (where because the mean time to kinetic collision is much smaller than the relaxation time of IR emission) it's all about kinetic collision and convection.

Looking at the planet from space, what you are seeing are photons which come out of the top of the atmosphere. In the visible spectrum, these photons passed through the atmosphere unmolested, so you 'see' the land and sea. If you could switch your eyes or camera to the IR spectrum, what you would 'see' instead would be photons not unmolested from the ground, but photons which were emitted from the very top layers of the atmosphere.

In IR, the earth looks the same way Venus does to us in visible - you can no longer see the surface, just a top of the atmosphere. here is a nice photo of what it would 'look' like if we could 'see' IR (note this photo uses 4.92 µm, 2.25 µm and 1.20 µm instead of the usual RGB, so you can see some 'depth')

So we have the weird situation where the sun heats the earth's surface (because the sun's photons can pass through the atmosphere mostly unmolested) but the earth's surface cannot radiate the heat back out, because the IR photons it would use to do this cannot penetrate the CO2 and H2O (and others) in the atmosphere. If radiation was the only way the land could lose heat, then the earth would fry.

Luckily, when CO2 and H2O absorb these photons, they become more energetic. The exact mode of absorption, which is an accident of when and how the photon interacts with the atoms in the molecules as is essentially random) can make the molecules either vibrate more, or move faster. This is what 'heat' is. The temperature of the CO2 and H2O molecules goes up. They bump into the far more numerous O2 and N2 molecules and they heat up too. The air heats up. The lower atmosphere heats up.

Note that at air densities near the surface, the molecules are so packed together that the mean time to collision is shorter than the mean relaxation time of the molecule. What this means is that before the air molecule can emit its energy in IR, it will have bumped into another molecule an released its energy that way instead. What this means is IR plays little part in the heat transfer at lower altitudes.

The more energetic the air, the higher the temperature, it rises up over the cooler air by convection. The cooler air falls, and it too absorbs heat from the ground, the hot air rises, expands, loses temperature, and eventually you get a situation where you have a gradient of temperature, with the hotter air on the bottom where the air is dense, right up the cooler air at the top where it is sparse. This is known as the adiabatic lapse rate. At this point IR has played very little part in establishing this temperature gradient.

Now at the top of the atmosphere where the air is sparse, the collisions are fewer and at longer intervals. It is more likely that a CO2 or H2O molecule would be able to release an IR photon before colliding. So the higher you go, the less dense the air, the more of the energy is released as IR. The radiated photons come out in random directions, so by geometry, about half of them go towards space, and half back towards the ground.

The ones which go out to space are the ones you can see in the photograph. These are the IR photons which allow the earth to cool off all the heat provided by the sun.

The ones which go back towards the earth (the back radiation, yucky as that term is) heat the air just below the top of the atmosphere, which in turn, heats the air under it.. etc. So if the lapse rate tells us how many degrees the temperature changes per kilometre, and we changed the temperature of the top layer, then the bottom layer must get hotter as well, because it's no longer just being heated by the land, but also by the air above it.

This is how 'greenhouse' gases make the surface of the earth hotter than they would be if they weren't there.

So what happens if we increase the concentration of greenhouse gases? Obviously the IR absorption effect is already completely saturated at ground level. Adding more CO2 at ground level makes practically no difference to the mechanism. If CO2 was like fog, the fog would be a little thicker but you still couldn't see the stars, it makes no difference if you add some more fog, you still can't see the stars.

What happens when you add more CO2 happens at the top of the atmosphere, this is where the action is.

Imagine a bowl of clean water 30cm deep where you have placed a ruler vertically. You can see right down to the bottom of the ruler, the 0cm mark..

Add a bit of food colouring until the water becomes murky. You now can't see the bottom of the ruler, perhaps you can only make out the 10cm mark, everything below that is obscured.

Add some more. the water is very murky now. You can now only see the 20cm mark, and nothing below it.

What you have done by adding absorptive material (in this case the colouring) is raised the 'window' where light can escape. In the slightly murky water, light photons can escape from any point above 10cm, but none from below. In the very murky water, light photons can escape from any point above 20cm, but none from below.

So by adding absorptive material, you raise the level from which the light can escape, and effectively trap photons from below it.

Exactly the same thing happens with the absorptive material of greenhouse gases. If you could hold a giant ruler on the earth, and add more CO2, what you are doing is effectively making the atmosphere a bit more murky. The level at which the IR photons can escape starts to rise, and you 'trap' more IR photons below it.

So if the level from which your IR photons escape rises, this means the lapse rate has farther to go. If your extra CO2 makes the atmosphere more murky and effectively makes the IR 'window' rise 10km, then by the application of the lapse rate (remember which is driven purely by convection) the temperature of the endpoint at the surface has to go up 1 degree.

So by adding some CO2, you've made the atmosphere more murky to IR, raising the point at which photons can escape to space, meaning the lapse rate has farther to go, meaning the surface is hotter.

Now 'back radiation' has played a part in this (as described earlier), but it's not the main show.

Please let this be the final time I have to explain this.

Imagine the top of the atmosphere starts at

Dec 2, 2015 at 10:14 AM | Unregistered CommenterTheBigYinJames

Before the buns in this bun fight go stale and start hurting ;) can we just step back and look at the hard facts and not the theory.

Regardless of whether there is a viable GHE theory or not the simple fact is going by the graph of Dr Jones of Climategate infany as posted in Bookers Tele article yesterday,

the planet is not reacting to the increased CO2 concentration in the atmosphere as the way the Warmist scientists suggest and want.

'The world has in fact been heating up for 200 years, ever since it emerged from what climatologists call the “Little Ice Age’ when, between 1350 and 1800, it markedly cooled. The temperature rise of 0.5 degrees C between 1975 and 1998, hailed as “the hottest year in history” was no greater than that recorded between 1910 and 1940, before “global warming” was thought of.'

Of course to get the Theory of GHE is good to have but in reality either it does not exist or its effect has been greatly exaggerated, at most its turned a cooling phase after 1998 into a flatline. It would be nice to know which but does it matter compared to the complete waste of money that is COP21 and the prospect of a first world developed country having powercuts due to following the cult.

Dec 2, 2015 at 10:48 AM | Registered CommenterBreath of Fresh Air


Knowing the truth is always better than not.
The GHE is real even if its effects are mitigated by other earth processes.

The whole point of my argument is that we don't waste our time arguing against pretty well established physics, because not only does it make us look stupid, it is not necessary to disprove the GHE to disprove CAGW.

CAGW is a speculative theory, GHE is a well-understood.

Dec 2, 2015 at 10:52 AM | Unregistered CommenterTheBigYinJames

What TheBigYinJames said.

Dec 2, 2015 at 10:57 AM | Registered CommenterJonathan Jones

Ok, wrong end of sticks syndrome.

I will put my view in a different manner.

The real concern must be the mad theory that we are wasting billions of £'s on vs the one that currently no one is wasting any money but lots of key presses on.

So given the choice between mad theory 1 AGW and mad theory 2 Sky dragon theories where should sceptical resources be applied ?

You seem to be suggesting that because Theory 2 is odd and wacky it should be stamped on at all opportunity as it may dilute the fight against theory 1.

My view is Theory 1 is the real enemy and Theory 2 is best just ignored, it does not matter if Theory 2 is right or wrong the effect is the same an 18 year pause as no-one yet is using it to waste Billions of £ on it.

So I ignore theory 2 and let the posts wither with the tumbleweed.

And even if GHE is accepted no theory is ever 100% correct, so yes there will always be new mad versions of it as all theories no matter how good need testing from time to time, just live with them as they are never going away so why waste the time.

Dec 2, 2015 at 11:54 AM | Registered CommenterBreath of Fresh Air


The trouble is that wacky-type theories don't just sit around being benignly ignored by the sceptical side. They get paraded around as if they were legitimate scientific theories, when every single one I've looked at is riddled with errors and misconceptions.

it's not just a matter of resources. Yes, we shouldn't waste our time on GHE-busting theories, not simply because they waste our time, which could be better spent on attacking the real weak-points of the CAGW argument. The real damage they do is that of scientific legitimacy.

If you attack a CAGWist about the lack of clouds in the modelling, or the decreasing estimates of climate sensitivity, or CO2 residence times, or the divergence between models and reality, or temporal resolution of historical proxies, or natural sinks, or cherry-picking in data collection, and any one of a dozen more areas, then they have a very shaky leg to stand on. Other scientists sit up and take notice, if you can take one of them down on scientific ground.

If instead you attack them with a crackpot theory which is obviously wrong, then no matter how long and hard you go at them, you've lost all credibility. We always ask why don't scientists speak up against the obvious frauds and misrepresentations within climate science. It's because the alternative is worse. Climate science has its problems, some of them of problems of personality, some of them problems of immaturity, some of them problems of scale. All disciplines of science have problems, and other scientists can recognise and dismiss them.

If the only alternative is a rag-bag of loonies, crackpots and ill-informed morons, then they will stick with science, warts and all, thanks you very much. This is what other scientists 'see' when they see these wrong theories. They don't see the many respected and sensible scientists doing good work in the field. They see the foaming at the mouth ones, parading the latest crapola nonsense as if it was real science.

No scientist wants to throw science under that bus.

Dec 2, 2015 at 12:59 PM | Unregistered CommenterTheBigYinJames

One of the strangest aspects of the Great Delusion is how it has inspired so many attempts by non-CAGW believers to show that the physics of the twentieth century is erroneous or, at very least, has been misunderstood.

Dec 2, 2015 at 1:02 PM | Registered CommenterMartin A


The Great Delusion will have eventually faded away. In ten years? In a century? In a thousand years? Who can say.

But whatever causes it to fade away, it will not be that somebody has pointed out some errors in its 'science'.

On the other hand, it is very convincing to the uncommitted when CAGW believers say to them "There, you see? Deniers talk scientific nonsense".

Dec 2, 2015 at 1:07 PM | Registered CommenterMartin A

Skydragons are like trolls, as you may have noticed they feed off attention, then if you do knock one out another appears as if on cue. And does anyone on the warmist side take any notice of skydragon knockdowns, no they don't. They don't need skydragons to believe sceptics are mad, Lew's studies have confirmed it anyway ;).

Dec 2, 2015 at 3:29 PM | Registered CommenterBreath of Fresh Air