Model CO2 as Greenhouse Gas: Tips & Results

[sylas]

I don't believe this is correct. See the following chart: (chart removed... see above... sylas)

That's not thermal infrared. Look at the wavelengths. The wavelength for thermal infrared radiation is more like 10 microns, way off to the right of the diagram where reflectance drops off sharply. The AVHRR channel 1 band in your chart is pretty much centered on visible light, I think.

I may not get back to this for a bit; but a quick look at my references confirms my opinion that the warmth of a cloudy night is a very strong greenhouse effect from cloud; meaning it is due to thermal emissions, not reflection. A detailed cloud model does consider infrared reflectance; but it is not a major factor, and not the main factor for why cloudy nights are warmer.

I'm not totally confident on this; but for the time being I still think my original statement is correct as given.

Cheers -- sylas

 

[Andre]

I may not get back to this for a bit; but a quick look at my references confirms my opinion that the warmth of a cloudy night is a very strong greenhouse effect from cloud; meaning it is due to thermal emissions, not reflection.

But who is paying the energy bill? If clouds emit IR sponaneously, then they would cool rather strongly, which would facilitate the condensation process, hence generating more clouds.

However most clouds tend to dissipate in the night.

 

[sylas]

But who is paying the energy bill? If clouds emit IR sponaneously, then they would cool rather strongly, which would facilitate the condensation process, hence generating more clouds.

EVERYTHING radiates infrared spontaneously. It's a basic property of matter. What I am describing is not any different to what you are used to; I'm describing the thermodynamics of the world you and I experience right now. This includes cooling at night, and condensation on the washing I forget to bring in this afternoon.

The Sun pays all the energy bills that matter.

It may help to bear in mind that the backradiation from the sky is real. It's measured. It's significant; night time included. Hence as you try to work on the physics of what happens to clouds and temperatures, you know for a fact you are going wrong somewhere if you think the atmosphere doesn't provide radiation to the surface at night, all night. That follows anyway from the physics; but it's still a handy sanity check to keep us on track.

With that in mind as an empirical fact about the world, let's see how the physics works.

The atmosphere does cool down at night; but the heat capacity of air is sufficiently high (about 1 kJ/kg/K) that it easily remains warm all night. There is about 10⁴ kg of air per m², so the heat capacity of the atmosphere is roughly 10⁷ Joules/m²/K.

This radiates to space about 240 W/m²; which is offset by a net energy flow up from the surface. Don't be confused by physically naive descriptions which suggest that greenhouse warming means that there's a net flow of energy from atmosphere to the surface. Its the other way around. The atmosphere is heated from the surface, at night as well as in the day. The effect is analogous to a blanket, which keeps you warmer even though it is colder than you are, and the net flow of energy is still from you into the blanket. The atmosphere is warmed by the surface, or a blanket is warmed by a body; and that means you are warmer than if you were radiating direct to space without impediment.

I don't know the rate at which heat energy is lost from the atmosphere at night, but will be less than 240 W/m². Over 11 hours we have about 40000 seconds; so the energy lost at night should be, ball park, 10⁷ J/m², or less; which is enough of itself to lower temperatures about a degree.

This is not an attempt to actually calculate the temperature change; just give a bit of basic thermodynamics to show that there's plenty of heat in the atmosphere to keep things mild over the span of a night. In more detail, we would find that night time usually brings an "inversion" in the lower part of the atmosphere close to the surface, so much of the temperature drop occurs low in the atmosphere, which makes good sense thermodynamically. And this means, by the way, that the clouds don't actually drop in temperature as much; most of the changes to cloud will probably be related to the inversion and currents.

And given that the cooling is pretty limited, effects on cloud are going to depend on a lot more than the simple measured facts of backradiation and associated cooling. The physics of cloud is actually pretty complex.

Cheers -- sylas

 

[chriscolose]

Guys, much of this is basic physics or atmospheric stuff, and shouldn't really feature much disagreement. Reflection is not the same thing as absoprtion and re-radiation. The physics is different. Clouds tend to have a cooling effect in daytime (depends on the cloud type, altitude, etc) and warm during the night time. Clouds especially have a warming effect in the polar night. Clouds or greenhouse gases also do not reflect IR light to any significant degree at Earth-like conditions. When an absorbing surface is present, the average emission temperature is less than the surface value, and the loss of energy to space is much less efficient than the infrared emission from the surface. Thus you can define the greenhouse effect as $$\sigma T^{4}_{s} - \sigma T^{4}_{eff} \approx 150 W m^{-2}$$

One significant difference between an absorbing greenhouse effect and a scattering greenhouse effect (the latter requires considerations in many alien planets) is that one's magnitude is essentially dependent on the temperature profile vertically, wheras in a scattering case you have near independence of the cloud altitude.

 

[Andre]

.

With that in mind as an empirical fact about the world, let's see how the physics works.

It appears that the problem is more terminology and definitions. So we agree that the noctural cooling of the atmosphere due to radiation amounts to an order of magnitude of one degree. However there is a distinct difference between Earth surface cooling with or without cloud cover, at least an order of magnitude higher in no wind conditions. Why?

Before it was called greenhouse effect, it was explained that the clouds reflected the surface heat radiation, and the clear dark night did not. Hence, what's in a name?

.more detail, we would find that night time usually brings an "inversion" in the lower part of the atmosphere close to the surface, so much of the temperature drop occurs low in the atmosphere, which makes good sense thermodynamically.

We won't find so much of an inversion under a cloud cover, it's more a clear air property like shown http://www.myoops.org/twocw/usu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/Unit_7__Atmospheric_Stability_and_Instability_2.html :

http://www.myoops.org/twocw/usu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/inversion2.jpg

See also this post:

But the first thing in greenhouse effect is understanding how it works.

The global warming hypothesis assumes that the difference between basic Earth black body temperature and actual atmospheric temperature is caused by radiative properties of the greenhouse gases, of which water vapor is the most important, basically nullifying all other mechanisms. In reality it is convection and latent heat transport, which heats the atmosphere from the surface at daylight, while there is no comparable mechanism at night to cool it again. So this mechanism is one way only. This can be demonstrated when comparing day and night lapse rates in the atmosphere, where the difference between day and night is greatest at the Earth surface

http://mtp.jpl.nasa.gov/missions/texaqs/austin_poster/Image11.gif

http://mtp.jpl.nasa.gov/missions/texaqs/austin_poster/MTP_Austin_Paper.htm

Hence the upper levels hardly cool at night as the only cooling mechanism is ... greenhouse effect, radiation out. And at those levels, with strongly reduced water vapor, radiation escapes to outer space much easier. This effect appears to be neglected in the IPCC endorsed literature and if you don't account for it in the models, you're basically stuck to the GIGO principle.

It is all in this thread, discussing the Chilingar et al 2008 study.

https://www.physicsforums.com/showthread.php?t=252066

In this mechanism the concentration of greenhouse gasses for temperature is strongly reduced. More greenhouse warming simply increases the convection rate, removing the excess heat again from the surface.

 

[sylas]

It appears that the problem is more terminology and definitions. So we agree that the noctural cooling of the atmosphere due to radiation amounts to an order of magnitude of one degree. However there is a distinct difference between Earth surface cooling with or without cloud cover, at least an order of magnitude higher in no wind conditions. Why?

Before it was called greenhouse effect, it was explained that the clouds reflected the surface heat radiation, and the clear dark night did not. Hence, what's in a name?

The answer to "Why?" has been given. It's an atmospheric greenhouse effect; arising from the capacity of cloud to absorb and emit thermal radiation.

Cloud is much more complex than a gas like carbon dioxide, because it also reflects, absorbs and scatters shortwave radiation. Hence the net effect of cloud in the atmosphere is very complex; and still far from well understood. But at night, the effect is much simplified; since there's really only the longwave to worry about.

This is not just terminology. This was a real physical error in the description by someone. If a technically incorrect term is used in a physics forum, it is picked up. When negitron proposed reflection was more important, he was making a genuine substantive physical comment, which I appreciate. As it turns out, he was incorrect, but it was still a useful substantive contribution. Next time it might be me who gets the details wrong. I was not completely sure, and so I went back to check on the physics of it. I am sure now, having checked, that the effect of cloud is due to thermal emission; not infrared reflection. Had it been the other way around, I'd have acknowledged and fixed it. That's how we all make substantive progress in real physical understanding.

I do not think this process was ever called "reflection", except (even now) in descriptions that are physically inaccurate. It's one of my pet peeves with simplistic accounts of the atmospheric greenhouse effect that speak of infrared being reflected. The real cause -- thermal absorption and emission -- has been known for about 150 years. It turns out that the impact of cloud on longwave radiation is also by absorption and emission, rather than by scattering and reflection as applies to shortwave.

Indulge me... I loved the description of what we now call the atmospheric greenhouse effect given by Victorian scientist John Tyndall in a public lecture in 1863, after his discovery of the strong thermal emission and absorption of "greenhouse gases". I mentioned it also back in msg #10. A DjVu reader will be required, and with this you can read Contributions to Molecular Physics in the Domain of Radiant Heat (Tyndall, 1872) [17 Mbyte djvu file, 446 pages]. The public lecture is recorded on pages 421-424. It focuses on water vapour, which is the strongest contributor to Earth's atmospheric greenhouse. Cloud is not mentioned, but it works in the same way. Here's an extract:

Looking at the single atoms, for every 200 of oxygen and nitrogen there is about 1 molecule of aqueous vapour. This 1, then, is 80 times more powerful than the 200; and hence, comparing a single atom of oxygen or nitrogen with a single molecule of aqueous vapour, we may infer that the action of the latter is 16,000 times that of the former. This is a very astonishing result, and it naturally excited opposition, based on the philosophic reluctance to accent a fact of such import before testing it to the uttermost. From such opposition a discovery, if it be worth the name, emerges with its fibre strengthened; as the human character gathers force from the healthy antagonisms of daily life. It was urged that the result was on the face of it improbable [...]

(snip here about a page describing experimental tests for other possible causes)​

No doubt, therefore, can exist of the extraordinary opacity of this substance to the rays of obscure heat; and particularly such rays as are emitted by the Earth after it has been warmed by the sun. It is perfectly certain that more than 10 per cent. of the terrestrial radiation from the soil of England is stopped within 10 feet of the soil. This one fact is sufficient to show the immense influence which this newly-discovered property of aqueous vapour must exert on the phenomena of meteorology.

This aqueous vapour is a blanket more necessary to the vegetable life of England than clothing is to man. Remove for a single summer-night the aqueous vapour from the air which overspreads this country, and you would assuredly destroy every plant capable of being destroyed by the freezing temperature. The warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost. The aqueous vapour constitutes a local dam, by which the temperature at the Earth's surface is deepened; the dam, however, finally overflows, and we give to space all that we receive from the sun.​

The analogy of the dam is apt. The Earth still radiates the energy to space which it receives. It just needs to be warmer than it would be without this barrier to thermal radiation. This lecture remains an accurate intuitive account of the relevant physics. Elsewhere in this lecture he also notes the equality of emissivity and absortivity.

We won't find so much of an inversion under a cloud cover, it's more a clear air property like shown

I think you've missed the point here. I gave inversion only as an easy example of how the atmosphere does not simply drop uniformly in temperature. I calculated a uniform temperature difference just to address your claim that cooling is "strong". In fact, the total cooling at night over the atmosphere is small, because of the substantial heat capacity.

The inversion is only a simple example to show that the temperature change is not uniform. Whether there is an inversion or not, it remains the case that the fall in temperature at night is mostly at low altitudes.

Be that as it may, inversions tend to be quite common at night, and they quickly break up in the morning. What your photograph shows is a case where the nighttime inversion persists into the day. You are quite right that inversions are stronger when the there is no cloud, of course; this is because of the increased low level cooling when there is not so much of the atmospheric greenhouse effect at work.

A friendly caution: beware of relying on Chilingar. He's not an atmospheric physicist at all, and it shows. He's a petroleum geologist (a good one, by all accounts) who for some reason has taken up denial of conventional climatology, with some dreadful error ridden papers that show his lack of familiarity with the field and which conflict with pretty basic physics. The papers have had no impact on real climate science and have been something of an embarrassment to other critics of conventional climatology; though of course they are uncritically lapped up in low quality blogs and the like with no background to tell sense from nonsense in atmospheric physics.

Perhaps it might be best for me to add a more specific reply to that thread you have quoted. It's about a year old, but I think it may be useful anyway, if it is going to be cited now in other discussions.

Cheers -- sylas

 

[BrianG]

Mainly, we all agree CO2's greenhouse effect is too weak to measure experimentally. Bummer, pseudo science strikes again.

 

[chriscolose]

Mainly, we all agree CO2's greenhouse effect is too weak to measure experimentally. Bummer, pseudo science strikes again.

Perhaps if you actually bother to listen to anything sylas writes or read a standard textbook on the subject you would not make such outrageous statements. There is a long history of experiments and developments on the subject of the greenhouse effect, with the 33 K greenhouse influence being a very well-defined number and not disputed in science, and yet you're so confident you know the answer.

 

[BrianG]

Perhaps you could post a SINGLE experiment showing a temperature increase with two samples, one at 200ppm CO2, or more and the other at 500ppm CO2 or less, something in the range our contemporary atmosphere. Even a field experiment would be satisfactory; we’ve done controlled releases of manmade aerosols and verified their cooling effect. I'm not questioning the spectral qualities of CO2, any more than I question the sky is blue, but I've never seen an experiment where a few hundred, or even thousand parts per million of CO2 causes any kind of temperature change in a sample exposed to light.

You go on ad infinitium about spectra, but you have no evidence of temperature change from human emission of CO2.

 

[sylas]

Perhaps you could post a SINGLE experiment showing a temperature increase with two samples, one at 200ppm CO2, or more and the other at 500ppm CO2 or less, something in the range our contemporary atmosphere.

As I explained to you previously, this won't work. The atmosphere is ten kilometers and more thick. What you are doing is proposing to test whether a wool blanket can warm you more than cotton by experiments on two threads.

You can do that, if you study the properties of the material in the thread... just as you can study directly the interactions of radiation and different gases. But you don't drape a thread over a thermometer, or put jars with 200ppm and 500ppm of CO2 over a thermometer, and expect to learn anything useful.

Even a field experiment would be satisfactory; we’ve done controlled releases of manmade aerosols and verified their cooling effect. I'm not questioning the spectral qualities of CO2, any more than I question the sky is blue, but I've never seen an experiment where a few hundred, or even thousand parts per million of CO2 causes any kind of temperature change in a sample exposed to light.

As I explained previously, it is the total amount that is more relevant for how much radiation is absorbed and emitted in total, and hence for the temperature impact, not the density.

The energy consequences for an atmosphere follow by elementary thermodynamics from the known spectral properties; and temperature effects are indeed measured in a lab, with quantities of CO2 comparable to the quantities in an atmosphere.

Field experiments do measure directly the thermal radiation from the sky, at day, and in the night, and look at the spectrum and the energy, and get results which are... of course... consistent with the fact that carbon dioxide and water mainly lead to one heck of a lot of energy coming down to the surface from out of the sky... energy that is the driver of a surface greenhouse effect.

You go on ad infinitium about spectra, but you have no evidence of temperature change from human emission of CO2.

CO2 is the same no matter how it is emitted. And I HAVE given a number of experiments which show temperature change from the interactions of radiation with carbon dioxide.

You appear to want to focus on the proportion of carbon dioxide, as if so many ppm tells you the temperature, no matter how much of it you are using... even if in a small lab based experiment. What you SHOULD be looking at is the temperature effect of roughly 60 kilograms of CO2 per square meter... which is a column of about 3 meters or so of pure carbon dioxide.

Nor will that give you the same temperature effects, as these things don't scale so simply. But using the right total amounts would certainly be closer than trying to compare 200ppm and 500ppm in a flask by measuring temperatures. We have indeed given the experiments here which give strong temperature effects from this quantity of carbon dioxide; if you read the link to John Tyndall's book from the nineteenth century, you get a wealth of detail of about the early experiments in which they worked to rule out every other possible cause of their observations, and ended up with this new and surprising discovery (as it was then) that carbon dioxide, and water, are both hundreds of thousands of times more effective than the other major constituents of the atmosphere for its capacity to trap heat at the surface and maintain a livable climate.

------

I can't tell you any different from what I have told you already. You can't do a lab experiment on an entire atmosphere. You CAN do lab experiments with comparable quantities of carbon dixoxide or water vapour and obtain clear and strong temperature changes. These experiments are not longer particularly significant for real science, though they can be useful for teaching in schools. The idea that a small flask with 200ppm or 500ppm is going to give any great effect is simply an error of understanding of basic thermodynamics.

The experiments you want have been described already. The experiments you are proposing are invalid, because they use far too little gas for useful temperature results... though you can study the basic thermodynamics properties with small quantities.

Finally, let me assure you that I don't have any real animosity over this. I'm not much of a social campaigner: I just like to help with science education in general, in this and in other topics.

Cheers -- sylas

 

[chriscolose]

By the way, the whole atmospheric greenhouse effect requires a declining vertical temperature profile (i.e., the lapse rate). So even testing the infrared abilities of CO2 in a confined setting, you're not going to get a good picture of how the actual atmosphere works.

 

[sylas]

By the way, the whole atmospheric greenhouse effect requires a declining vertical temperature profile (i.e., the lapse rate). So even testing the infrared abilities of CO2 in a confined setting, you're not going to get a good picture of how the actual atmosphere works.

Precisely.

 

[BrianG]

What your saying is pure speculation and theory, that changing a small amount of CO2 will have an effect on temperature.

It takes a container 40 meters in diameter to detect neutrinos, are you telling me neutrino/matter interactions are stronger than the greenhouse warming effect? What about increasing the pressure in both containers, if the containers are ten meters high and the atmosphere is held at 1,000 bar, that can represent a significant amount of gas. As long as the gasses are swapped from container to container, you can eliminate extraneous variables.

I'm not worried about spectral properties; I don't lose sleep over blue sky. Its climate change mitigation that's got me going and you cited no experimental proof at all.

 

[cleanwater]

Brian G: The greenhouse gas effect does not exist no mater what BS Sylas says- he has acknowledged that he does not have any education in physics- and it is obvious to anyone that has taken at least college physics that Sylas makes up his answers as he goes along. If you want to get correct information go to one of the following web-sites or read the paper "Greenhouse Gas hypothesis Violates Fundamentals of Physics" by Heinz Thieme
the web-site to see is www.strata-sphere.com
As I have said repeatedly water and its many forms are responsible for all of the warming above Black body theoretical temperature. Water has none of the properties of a supposed ghg. CO2 or Methane cannot and will not cause an increase in global temperature.
Your proposed test will show nothing because the ghg effect is a fairy-tale.
Skyhunter complains that I repeat the same info -well the truth is worth repeating when people show that they don't want to understand.

 

[sylas]

What your saying is pure speculation and theory, that changing a small amount of CO2 will have an effect on temperature.

On the contrary. I have described experiments several times, which you either ignore, or don't understand. This is very much experimental science, and has been for over a century. Just as in any other area of the science, what you learn from experiment can be applied to the real world; but it is flatly false to say my remarks are pure speculation and theory. What I am explaining here is really very elementary thermodynamics, discovered by good old experimental physics.

You should be aware that that skepticism about global warming is not at all the same thing as denial of a greenhouse effect altogether. Skepticism comes in many forms, from legitimate caution about open research questions, to a naïve failure to follow high school physics.

I'm not meaning this as an insult; because we all start out this way... but your objections are the latter. The good news is that it is comparatively easy to fix, and if you are able to learn then it opens the way for you to either understand climate science a lot better, or -- if you remain a skeptic -- to let your skepticism become at least consistent with thermodynamics.

I've described the experiments several times, and most relevant to direct measurement of temperature are the experiments of John Tyndall in the 1860s, which directly measured substantial temperature changes with small amounts of carbon dioxide in a lab. Similar experiments can be and are performed now at high school level.

What is a "small amount"?

It is quite true, of course, that a jar with 200ppm and another with 500ppm CO2 is a tiny amount of carbon dioxide, and this has a negligible effect on temperature.

Do you agree that this amount is many orders of magnitude less that the amount of carbon dioxide found in a column of atmosphere the same width as a jar?

For example. How much CO2 is involved in the greenhouse effect on Earth? Well, the density of air at sea level is about 1.25 kg/m³. There's about 10 tons of air per square meter in the atmosphere (air pressure is just the weight of this air) and if it was all at sea level conditions, you'd have about 8000 cubic meters of air, or a column 8 kilometers high.

Now 1ppm is one part per million by volume. So 385ppm is the same amount of carbon dioxide as in a blanket of pure carbon dioxide about 3 meters thick. That is the amount of CO2 involved in the greenhouse effect.

The experiments I have described for you measure significant temperature impact with substantially less CO2 than this.

It takes a container 40 meters in diameter to detect neutrinos, are you telling me neutrino/matter interactions are stronger than the greenhouse warming effect? What about increasing the pressure in both containers, if the containers are ten meters high and the atmosphere is held at 1,000 bar, that can represent a significant amount of gas. As long as the gasses are swapped from container to container, you can eliminate extraneous variables.

Ten meters high is a fraction of a percent of the atmosphere. There's just no comparison. What you need to do is increase the density of the carbon dioxide in your container, or else you cannot possibly get anywhere near the amounts involved in the greenhouse effect.
----

By the way; I don't ask you to take anything from me on faith. You should check further for yourself, and learn more about the relevant physics without just relying on one person.

However, for the record, cleanwater's remarks about me personally are false. I DO have university level education in physics. What I actually said is that I did not pursue that as a career -- I am not a physicist; though I have of course studied physics at Uni. When I went into postgraduate studies, I went the direction of maths and computer science. But my first degree was a BSc, and physics was one of my areas of study.

You are best to check the claims of anyone, no matter how qualified, by further study on your own behalf. That's what I have done for myself also. It's also a good idea to step back from hot topics and brush up on underlying basics.

Cheers -- sylas

 

[sylas]

"Greenhouse Gas hypothesis Violates Fundamentals of Physics" by Heinz Thieme the web-site to see is ...

This is not an acceptable reference for this forum. Check the rules.

Furthermore Thieme is a nut, and couldn't do basic thermodynamics to save his life. Seriously. He's way WAY off in the extreme of the lunatic fringe when it comes to climate. One of his favourite arguments, in the private website you have listed, is that atmospheric backradiation is impossible.

Atmospheric backradiation is directly measured, and has been for over 50 years. An early direct measurement of this is described in Stern, S.C., and F. Schwartzmann, 1954: An Infrared Detector For Measurement Of The Back Radiation From The Sky. J. Atmos. Sci., 11, 121–129. (online) Thieme's "refutations" are pseudoscience at the same level as young Earth creationism. In a field full of confusion and poor argument, Thieme stands out as a far extreme of willful ignorance of physics.

 

[cleanwater]

Sylas -The minute you tell me that you put the CO2 in a jar tells me that you do not understand that you have a faulty experiment. CO 2 or dry air do not heat up when they absorb IR radiation. ( Check the work of Niels Bohr) The glass jar can and does absorb IR and does heat up. This heating of the glass is what heats the gas inside the jar- this is one of the things that is wrong with the University of Bremen experiment. If you want proof of this I can supply you with the paper that was peer reviewed that shows just how much heating is caused by IR radiation absorbsion by glass.
AS I have described earlier and you have not understood is that I have done the experimental work that shows that the ghg effect is a Fairly -tale that Thieme and Gerlich &Tscheuschner know a hell of a lot more than you. The fact that you try to put them down is because you do not understand what they have proven.

 

[chriscolose]

Actually he does understand what they're doing. In fact, sylas, myself, and several others have a paper in the works detailing their errors, as does Smith (2008). You continue to repeat "check Niels Bohr" when gases heating up isn't even what the greenhouse effect is about. Just like G&T, you've only introduced a lot of strawmans, just like G&T made a whole essay about how the greenhouse effect is unlike real greenhouses, and how pots of boiling water falsify a greenhouse effect because the pot is cooler with water in it.

There is a 33 K gap (and a 150 W/m^2 gap) between the surface temperature (emission) and the effective temperature (emission). This is the greenhouse effect and it's been understood for well over a century. It also serves to have remarkable predictive and explanatory power over a broad range of planetary applications (faint young sun, early Mars, Venus, etc). Repeating the same stuff won't change that.

 

[Andre]

There is a 33 K gap (and a 150 W/m^2 gap) between the surface temperature (emission) and the effective temperature (emission). This is the greenhouse effect and it's been understood for well over a century.

Really? Isn't just an explanation, disregarding/downplaying the effect of other heating processes like latent heat, convection and advection as discussed in the other thread? Yes I know, the radiation numbers seem far more bigger, but the other effects are one way only while radiation is two ways, in and out, and tending to balance and cancel out.

If the atmosphere was unable to radiate, it would still be heated by those three until a certain equilibrium, which definitely bigger than zero; especially since there is no way that the atmosphere could loose the heat without radiation, since it can't convect or advect downwards. So not all, if any of those 33 degrees can be greenhouse effect.

It also serves to have remarkable predictive and explanatory power over a broad range of planetary applications (faint young sun, early Mars, Venus, etc). Repeating the same stuff won't change that.

Could you please indicate in the Fourth assessment report of wg1of the IPCC where it substantiates a remarkable predictive and explanatory power over a broad range of planetary applications?

 

[sylas]

Sylas -The minute you tell me that you put the CO2 in a jar tells me that you do not understand that you have a faulty experiment. CO 2 or dry air do not heat up when they absorb IR radiation. ( Check the work of Niels Bohr)

You've mentioned Bohr several times now.

What Bohr actually did was pioneer physics of how electrons interact with light by changing energy levels in an atom. This does not heat up materials much; since temperature depends on the motions or kinetic energy of atoms; not the potential energy of electrons in different orbitals.

However, Bohr never suggested anything so silly as to think this disproved the measured fact that that gas does heat up when it absorbs IR radiation. The excitation of electrons to different energy levels is not the only way light and matter interacts!

The main process by which IR radiation is absorbed in a gas is interaction with vibration modes of the whole molecule. These involve lower energy levels than excitation of electrons, and so interact well with low energy IR radiation. Molecules like O2 or N2, which are the major components of air, do not have suitable vibration modes. But CO2 and H2O (the major contributors to the greenhouse effect) are dipolar, and have a shape that admits a range of vibration modes and give them the capacity to absorb IR radiation.

Vibration energy of a molecule is a form of kinetic energy, unlike the energy of an electron raised to a higher orbital, which is a form of potential energy. Hence the IR absorption does indeed correspond to higher temperatures, whereas absorption by raised electron levels... not so much.

There are some diagrams of the relevant vibrational modes here: http://chemistry.boisestate.edu/people/richardbanks/inorganic/electromagnetic%20spectrum/vibrational_modes.htm . (Supplied as part of online chemistry tutorials by Prof. Richard Banks, Boise State University.)

Slightly more technical, including spectra and energy levels here: Water Absorption Spectrum. (Supplied by Prof. Martin Chaplin, London South Bank University).

From Professor Banks' http://chemistry.boisestate.edu/people/richardbanks/inorganic/electromagnetic%20spectrum/spectrum.htm :

Infrared Radiation

Infrared radiation has an intermediate energy and extends from about 1 millimeter in wavelength to the visible region. Infrared radiation has the same energy as molecular vibrations. Chemical bonds are analogous to springs and can either be bent or stretched. The stretching and bending vibrations of bonds between different atoms all have different energies. When infrared radiation matches the specific stretching or bending energy of a particular bond, it will be absorbed if there is a dipole associated with the bond.

When a molecule absorbs infrared radiation, the amplitude of vibration is increased and the molecule heats up. This heat can be lost in either of two ways. The molecule can come into direct contact with another body and directly transfer the heat or the molecule can re-emit infrared radiation.​

Τhe is really basic stuff. The heating of certain gases by absorption of infrared radiation is a simple and straightforward measurement.

I suspect you are getting distorted information from unreliable sources. For example, there is absolutely nothing by Bohr to deny that you can heat a gas by absorption of IR radiation. Bohr studied a different process, involving higher energies and electron levels, which was foundational to understanding the quantum nature of the atom. I would love to know who started the idea that this could be interpreted as a disproof of all other lower energy IR interactions! It is either completely clueless, or worse, deliberately dishonest. It is definitely not from Bohr himself.

Cheers -- sylas

 

[chriscolose]

Really? Isn't just an explanation, disregarding/downplaying the effect of other heating processes like latent heat, convection and advection as discussed in the other thread? Yes I know, the radiation numbers seem far more bigger, but the other effects are one way only while radiation is two ways, in and out, and tending to balance and cancel out.

If the atmosphere was unable to radiate, it would still be heated by those three until a certain equilibrium, which definitely bigger than zero; especially since there is no way that the atmosphere could loose the heat without radiation, since it can't convect or advect downwards. So not all, if any of those 33 degrees can be greenhouse effect.



Could you please indicate in the Fourth assessment report of wg1of the IPCC where it substantiates a remarkable predictive and explanatory power over a broad range of planetary applications?

No one downplays the importance of other processes, and they're all included in basic discussions in textbooks and in climate models. It's just a matter of understanding the difference between the surface and top-of-atmosphere energy balances, or the fact that the surface temperature cannot exceed a certain value (determined by the incoming absorbed solar radiation) without a greenhouse effect. The 33 K greenhouse effect *is* purely from greenhouse gases and clouds.

The IPCC is not a textbook on atmospheric physics or comparative planetology. Your request is rather strange. I suspect it's a distraction, but my opinions on certain commenters here are in violation of forum conduct policy.

 

[sylas]

Really? Isn't just an explanation, disregarding/downplaying the effect of other heating processes like latent heat, convection and advection as discussed in the other thread? Yes I know, the radiation numbers seem far more bigger, but the other effects are one way only while radiation is two ways, in and out, and tending to balance and cancel out.

If the atmosphere was unable to radiate, it would still be heated by those three until a certain equilibrium, which definitely bigger than zero; especially since there is no way that the atmosphere could loose the heat without radiation, since it can't convect or advect downwards. So not all, if any of those 33 degrees can be greenhouse effect.

That can't work, Andre. Imagine you have an atmosphere that is heated by convection and latent heat, but does not absorb radiation except possibly to a much smaller extent.

The atmosphere will heat up, to be sure, and you'll get a lapse rate in the atmosphere as usual.

The surface of the planet will radiate energy governed by its temperature, and that radiation will stream out into space unimpeded. That energy will have to balance the energy received from the Sun. Now, Earth receives about 240 W/m² from the Sun. To radiate that amount of energy, the surface will have a temperature of (240/σ)^0.25, which is 255 Kelvin... about 33 degrees less than what we have at present.

This is really basic first year level thermodynamics, Andre. You cannot have a higher mean temperature than this, or else the radiation from the surface, which by hypothesis is going straight out to space, exceeds what you receive from the Sun.

If you have an atmosphere which does not absorb infrared radiation to any appreciable degree, it would come to a convective equilibrium temperature, where there is no net flow of energy. There's no energy loss out from the top of the atmosphere; by the first law you know that there's no net gain of energy coming up from the bottom either.

We are about 33 degrees warmer than that... and that is a consequence of our atmosphere's capacity to absorb and radiate infrared radiation.

Now don't take this the wrong way... but I want to take the bull by the horns here. It's not meant to be personal at all; I have no problem disagreeing strongly with someone on a matter of physics or maths, and still being friends. With that understanding, I'll not mince words; but I want to assure you I'm only speaking of the substantive physics issues.

We have not been discussing global warming theories here, or the matter of changes to atmospheric composition; this is about the existence of a greenhouse effect AT ALL. It is about the thermodynamics of a convective-radiative equilibrium in an atmosphere that absorbs infrared radiation. When an atmosphere absorbs IR radiation, it also emits IR radiation, and the net effect of that by basic thermodynamics is a higher temperature than you would have otherwise.

It's one thing to be skeptical of various matters in modern climatology. I have a frankly low opinion of most of the skeptical arguments in popular use; but in amongst all that noise there are real open questions and unsolved problems and uncertainties. There are also some splendid opportunities for learning more about the relevant physics in learning to identify bad arguments.

The denial of greenhouse effect altogether, or the claim that IR absorption would work to actually have a cooler atmosphere than otherwise, is pseudoscience. This includes the model of lapse rates proposed by Chilingar. This is not the only field or the only instance where a well qualified scientist in some other field goes off the rails into nonsense in some other area. If Chilingar's model is right, every basic textbook on atmospheric physics is wrong. But his account of the adiabat is physically nonsense.

Could you please indicate in the Fourth assessment report of wg1of the IPCC where it substantiates a remarkable predictive and explanatory power over a broad range of planetary applications?

The IPCC reports are not a textbook to introduce basic planetary physics. For that, you want an undergraduate level textbook. I suppose it is remarkable; but no more and no less than any other area of science where we have been able to learn more about how the natural world operates.

I have been learning a lot about atmospheric physics over the last year or so by studying Principles of Planetary Climate, by Professor Pierrehumbert, of the University of Chicago. The book is not yet published; but is under contract to be published by Cambridge Uni Press. A draft, complete in the first eight chapters, is available online, and it is geared towards his teaching of the unit "Geosciences 232: Climate Dynamics of the Earth and Other Planets".

I like the book because it is pretty comprehensive, and quite mathematical, which suits my learning style. It is technical and I am a long way from understanding it all, but the first few chapters are fine, and already take you through a range of diverse examples in different planets. The download is available at the above link, but it is pretty large. You might like to have a look.

There's nothing there that is particularly controversial... or at least there shouldn't be. Plenty of other undergraduate level texts do the same kind of thing, including consideration of physics sufficiently generally to apply to a range of planets.

Cheers -- sylas

PS. Wrote this offline independently, before I saw Chris' reply.

 

[BrianG]

It's the lack of an experimental test that shows a 300ppm difference in an atmosphere's CO2 causing the smallest measurable degree of warming. CO2 doesn't absorb heat from IR; it merely scatters it all around. Heat still flows from hot to cold. The greenhouse effect of a large amount of CO2 is untested in the lab or in the field.

The effects of aerosols have been tested in the field and the lab. The effect of neutrino/matter reactions have been tested and measured. The effects of climate change mitigation is purely theoretical and even the pseudo science says that doubling CO2 creates one unit of warming, though the size of that unit of warming is way too small to measure.

 

[chriscolose]

One can only hope that some day you'll read enough to create one full sentence of correct information.

 

[Andre]

You cannot have a higher mean temperature than this, or else the radiation from the surface, which by hypothesis is going straight out to space, exceeds what you receive from the Sun.

Now let's concentrate on that. How about running a null hypothesis on Earth instead of using a -perhaps too simple- model that leads to the 33 degrees?

Assume that the atmosphere of our model is completely inert, no radiative properties and that the Model- Earth acts as a radiative transmitter, but not completely like a black body, since it does not meet its qualifications (like an ideal conductor, while the Earth is a near ideal insulator).

Furthermore, we have diurnal rotation effect and a point emitter, also known as the sun, instead of a universally emitting sphere around the Earth as the 33 degree model assumes.
So at any moment in time there is a point on earth, perpendicular to the sun that receives the full ~1365 W/m2, which translates, with an albedo of 0.3, via Stefan-Boltzman, to a temperature of 360K (87C or 189F). Of course this is only a moment in time but we can also we can imagine for instance a cone of +/- 60 degrees which takes the sun 8 hrs for the sun to travel) at the border of this cone this point receives half of the total radiation in, (682.5 W/m2) which is still good for a Stefan Boltzman temperature of 303K (30C or 86F). So there is a good deal of time that any point under the zenith of the sun heats up well above the theoretical “black body” temperature every day.

Note that this heat energy is assumed to be in radiation equilibrium, as dissipation via radiation into space is already accounted for. Other ways of energy dissipation are both conduction to deeper layers under the surface and conduction to the boundary layer of the atmosphere. Conduction is a very ineffective way of losing heat. However, while heating, the atmosphere boundary layer decreases in density and gets buoyant. Via convection the heat is dissipated higher into the atmosphere. So, even without radiation absorption, there is a way to bring surface heat into the atmosphere during daytime, convection.

How about night time? There is no radiation in and the Earth surface starts to cool down due to radiation out. The cooling rate can be any value, and the minimum temperature reached is mostly time dependent. It’s however not very relevant for our model of the rotating earth. Remember that in our model the atmosphere is inert and does not radiate. Therefore, there is only conduction to the lower boundary layer in which heat energy can travel back to the surface, where it can be radiated. But as the cooling air boundary layer is getting denser, it will not mix well with higher layers (inversion) and the dissipation of heat from the atmosphere decreases rapidly. Only the lowermost layer is cooled effectively. Therefore the heating of the Atmosphere via convection is mostly one way. It goes up but it hardly comes down. Hence –lacking radiation- the thermal energy must accumulate day after day just as well as after million years until equilibrium with the ineffective conduction at the surface is obtained.

Now this was based on one point perpendicular under the sun. How about the poles for instance? With only very little in-radiation, the surface temperature is way, way down. For instance at a latitude of 80 degrees, the solar influx is only 17% at maximum at noon and hence the maximum value at day time is 237 W/m2 which translates to a maximum Stefan Boltzman temperature of 232K (-40C and F) So there won’t be a lot of convection going on there. However the convecting energy in the equatorial plane is the engine of a conveyer belt in the atmosphere, which is know on Earth as the Hadley cell which effectively divides the convected heat energy of the tropical regions while more complex processes bring the energy to the polar regions eventually. Obviously the same one way principles apply here, the much colder surface still cannot get a lot of energy out of the inert not radiation atmosphere via conduction of the boundary layer only, as the same physics apply.

So concluding, on a model planet with a hypothetically inert atmosphere, the atmosphere will be heated one way only. At day time, thermal energy of the surface enters the atmosphere via conduction and convection. At night time and in the Polar Regions the atmosphere only cools via conduction in the boundary layer. Obviously there is no cooling due to radiation in an inert atmosphere and thermal equilibrium is only reached when the ineffective boundary layer cooling equals the convective heating. Obviously, that will be substantially more than zero, which is assumed in the 33 degrees black body radiation model. Note that this latter model is based on linear processes, which is not valid when one way valves (convection) are added in the reality.

So, if we make the inert atmosphere in our null hypothesis radiative again with the addition of radiative gasses (mistakenly known as greenhouse gasses) more processes can take place. Now the heating of the lower atmosphere during daytime is also enhanced by the absorption of the surface out-radiation, which stimulates more convection. But also the atmosphere can radiate energy to outer space, and help cooling the atmosphere that way. Now obviously these processes act in opposite directions And then we did not add the water cycle with latent heat and clouds, adding to the complexity.

Conclusion: the 33-degrees black body radiation model is meaningless considering the more complex processes on Earth

This is basically the idea of the much quoted Chilingar et al 2008 and I would appreciate it to see what exactly is wrong with the physics of that.

 

[sylas]

Now let's concentrate on that. How about running a null hypothesis on Earth instead of using a -perhaps too simple- model that leads to the 33 degrees?

Assume that the atmosphere of our model is completely inert, no radiative properties and that the Model- Earth acts as a radiative transmitter, but not completely like a black body, since it does not meet its qualifications (like an ideal conductor, while the Earth is a near ideal insulator).

There's a very simple mathematical theorem here that applies in this case, for all possible permutations of your proposed model.

The total energy received from the Earth is the solar constant of ~1365 W/m², and 30% of that is reflected, using your numbers, with which I concur. The cross section of the Earth is one quarter of the surface area, which is why we divide by four when taking average energy inputs per unit area. But in any case, the total energy is

$$\pi R^2 \times 1365 \times 0.3 \approx 5.3\times10^{16} \; \text{Watts}$$​

Now, by the first law of thermodynamics, all that has to be radiated back to space. Because Earth distributes heat around the globe fairly well -- much better than the Moon, for example -- it is usual to give an "effective" temperature for the planet, which is the temperature that would radiate that amount of energy if uniform over the whole sphere.

You are proposing we take into account the obvious fact that temperature is NOT uniformly distributed. Here's the thing, however. The power radiated goes as the fourth power of temperature. So if you increase the temperature in some places and reduce it in others, the increase has a proportionally larger impact on the energy output. That is, you have to make the colder regions take a LARGER fall than the increase in the warmer regions. This applies for any redistribution of temperature, by any means.

This is a necessary consequence of Hölder's inequality, which means:

$$\frac{1}{S} \int_S T dS \leq \left( \frac{1}{S} \int_S T^4 dS \right)^{0.25}$$​

Added in edit. The above formula was originally incorrect; I had omitted the normalization with area S. See [post=2296963]msg #99[/post] by vanesch for the original incorrect version, and why it needed fixing. I've updated this post with the corrected formula he provided.​

The above represents a surface integral. One is the integral of temperature; the other is an integral of power emission. The power integral is constrained to balance the solar input by the first law.

What that means is that the value 255K (-18C) as an effective surface temperature is a strong upper bound on the average temperature, given any redistribution of temperature around the globe at all which maintains the energy output.

The only way you can actually get higher temperatures than a 255K average; the ONLY way, is if the energy radiated from the surface can't actually get directly out into space. In other words, the 33 degrees is a strong [strike]UPPER[/strike] LOWER BOUND on the consequence of absorption of radiant energy in our atmosphere.

That's a theorem; as strong as any result you can get in physics. Given your stated assumptions, of a radiatively inert atmosphere, and the unstated assumption of a surface emissivity of close to unity (which it certainly is, at the relevant wavelengths; I include this for completeness) the 33 degrees falls out from the laws of thermodynamics. It's that fundamental.

Note that this heat energy is assumed to be in radiation equilibrium, as dissipation via radiation into space is already accounted for. Other ways of energy dissipation are both conduction to deeper layers under the surface and conduction to the boundary layer of the atmosphere. Conduction is a very ineffective way of losing heat. However, while heating, the atmosphere boundary layer decreases in density and gets buoyant. Via convection the heat is dissipated higher into the atmosphere. So, even without radiation absorption, there is a way to bring surface heat into the atmosphere during daytime, convection.

But not out into space. Convection can heat up the atmosphere, but if the atmosphere cannot absorb infrared radiation then it cannot emit it either. There's nowhere for the heat to go. By the first law of thermodynamics, such a planet has an atmosphere which reaches a pure convective equilibrium. The atmosphere may heat up and cool down with the diurnal day night cycle or seasons, in various complex ways, but only through an exchange of energy to the surface. There's no way the atmosphere can actually be a net sink for heat from the surface; so ALL the radiation from the surface goes to space; and that means the surface is at a temperature to balance solar input. By Holder's inequality, this is necessarily an average temperature of -18 degrees, or less.

That is, the greenhouse effect -- absorption of IR radiation -- accounts for AT LEAST 33 degrees of extra surface warmth.

This is not advanced physics. This is very elementary thermodynamics.

I sympathize with people who get confused on these points, because there is a lot of outright pseudoscience expressed on this topic, which can easily lead the unwary astray. It's not always easy to pick the pseudoscience at first sight, for a non-professional. There are even a couple of cases where scientists have managed to express such ideas in the actual scientific literature. This is really unusual, and represents a startling failure of the journal to manage basic quality control; but it happens, in this and other fields. The cases I know of are in low impact journals, with authors who are not active in the relevant fields of physics. Even that is not enough to explain how this happens... I am honestly at a loss to account for how anyone could possibly write papers like Gerlich and Tscheusner, or Chilingar et al.

But second guessing how that happens is beside the point. The actual argument expressed is on a par with young Earth creationism -- another field of pseudoscience with its own credential scientists also writing rock bottom crank science.

So, if we make the inert atmosphere in our null hypothesis radiative again with the addition of radiative gasses (mistakenly known as greenhouse gasses) more processes can take place. Now the heating of the lower atmosphere during daytime is also enhanced by the absorption of the surface out-radiation, which stimulates more convection. But also the atmosphere can radiate energy to outer space, and help cooling the atmosphere that way. Now obviously these processes act in opposite directions And then we did not add the water cycle with latent heat and clouds, adding to the complexity.

The "complexity" here is smoke and mirrors. There is certainly plenty of complexity and a whole pile of open research questions here that can be legitimately a focus for more rational skepticism of various conclusions.

But not the question of "cooling". That is not an open question at all. As you give the atmosphere a capacity to interact with thermal radiation, you inevitably find that the atmosphere heats up; it gets more energy from the surface than when radiatively inert. What complexity means is that you can't easily derive how much it will heat up, nor whether you'll get local reductions offset by larger increases elsewhere, in complex ways. But the net effect of additional heating is a necessary consequence of basic thermodynamics, entirely independent of any concerns about the acknowledged complexity.

In a convective equilibrium, you will find temperatures fall with altitude. That is because pressure falls with altitude; as packets of air move up or down, they expand or contract, giving lower temperatures at altitude. There's a well developed theory for the "dry adiabat" that derives this relation, using basic thermodynamics. Note that this result is independent of the thermal emissivity. It depends simply on the "potential temperature", which is the temperature that air at a certain pressure would have if compressed in a return to surface levels. Allowing the atmosphere to absorb and emit radiation will drive stronger convection, certainly; but the adiabat is unaffected because the potential temperature is unaffected.

Now... since the main part of the atmosphere is necessarily cooler than the surface, the effect of adding a capacity to absorb and emit radiation will result in a net flow of energy from the surface into the cooler atmosphere. That follows from the second law. The additional energy going into the atmosphere will help drive additional convection, which also increases the net flow of energy into the atmosphere. This is now balanced by the loss of radiant energy out from the top of the atmosphere. What we have now is called "radiative-convective equilibrium". And that involves a higher temperature than the pure convective equilibrium.

I repeat, this is basic first year level physics. It's not in any doubt whatsoever. It is also completely irrelevant to most expressions of skepticism about conventional climatology; it's part of the rock bottom lunatic fringe of denial, in conflict with fundamentals of physics that are a basis for even to starting to look at the real complexities and uncertainties that exist in the field.

Conclusion: the 33-degrees black body radiation model is meaningless considering the more complex processes on Earth.

This is on a par with claiming that the conservation of momentum model is meaningless given the complexities of interactions of orbits in a multi-body gravitationally bound system.

On an exam, your comment could only be marked wrong. The 33 degrees is a necessary lower bound on the impact of the atmosphere's capacity to absorb infrared radiation, that holds by basic physics no matter how complex the processes you invoke. Complexity can't overrule the basic laws like conservation of energy; and that's the level of fundamentals from which the 33 degree bound follows.

This is basically the idea of the much quoted Chilingar et al 2008 and I would appreciate it to see what exactly is wrong with the physics of that.

The idea that adding a capacity to interact with thermal radiation has a net cooling effect.

(And by the way: you say "much quoted"... but by whom? You know the citation count on that paper? Zero. There's a handful of citations in an earlier error ridden paper he wrote in 2006; most importantly a devastating rebuttal response. In my opinion, finding the people who quote Chilingar is a good way to identify people whose skepticism is grounded in a profound lack of comprehension of the relevant physics... mainly amongst bloggers or the like. But scientists? Not so much...)​

Chilingar ignores the standard and completely uncontroversial thermodynamics of lapse rate, and comes up with his own definitions, without any experimental or observation support, without any refutations of the conventional thermodynamics of potential temperature and lapse rate, and in complete conflict with what should be learned in first year uni by anyone studying atmospheric physics.

I don't expect you to believe me on my own authority here. I'm making strong criticisms of Chilingar's competence in basic physics, despite the acknowledged fact he is a prominent and successful scientist in his own field. That may give you pause before accepting my analysis above. Good! That's skepticism, and skepticism is good. The thing is, you should on the same basis be skeptical of Chilingar's claims.

It is possible to be a "climate skeptic", but many people who identify themselves that way are better described as credulous naifs. My suggestion is... don't take my word for anything, and don't presume Chilingar's word either. After all, if Chilingar's lapse rate ideas have any merit then we'll have to rewrite all the physics of the dry adiabat! That's possible in principle, but a genuine skeptic should be cautious of jumping on that bandwagon too quickly!

Instead, take a bit of time to check the background. I cited for you an online text above. Try reading through chapter 2, of Principles of Planetary Climate, by Professor Ray Pierrehumbert. This chapter is "Thermodynamics in a Nutshell", and it includes derivations of the dry and the moist adiabat. Pretty much any other text on atmospheric physics should deal with this topic as well. I appreciate that this will take time; and I am not demanding you simply accept my claims at once. I anticipate we'll eventually wind up this discussion without reaching a mutual recognition the implications of thermodynamics for the hard bounds on properties of a complex climate system, and that's fine with me. But I hope I might have shaken your confidence enough to look into the physics more thoroughly over coming months, offline.

Cheers -- sylas

 

[mheslep]

... I'm making strong criticisms of Chilingar's competence in basic physics, despite the acknowledged fact he is a prominent and successful scientist in his own field. ...

In the case of peer reviewed publications by reputable scientists, isn't the place for that kind of criticism in the literature itself and not here?

 

[sylas]

In the case of peer reviewed publications by reputable scientists, isn't the place for that kind of criticism in the literature itself and not here?

That's an important question of policy. I am strongly opposed to any such notion. I think both venues are legitimate for strong criticism of peer reviewed papers.

I've taken time to set out some of my thoughts in more detail... its a bit long, sorry!

1. Responses in physicsforums

Criticism of peer reviewed papers in this forum should be held to the highest possible standard. It should not be prohibited as a general rule; but it had better be well founded. I will gratefully accept any substantive comment on the actual physics I explained in my post. It has long been a deliberate policy of mine to seek out and welcome corrections to any of my posts, and to publicly retract my errors as fast as possible, with thanks and recognition to anyone who helps me find them.

In all honesty, I am not in the slightest doubt of the physics I explained previously. But I'll never take offense at a genuine and substantive critique, whether valid or not. I aim to learn from mistakes, and hence anyone willing to help me find them is my friend. I've put a bit of work over the last year or so into learning more about atmospheric physics and thermodynamics, and I now feel pretty comfortable with it at the level I am using here. But it would be great to have a well informed second opinion especially from a colleague with a strong background specifically in atmospheres and thermodynamics.

As context for your question, there are two points I'd like to make.

1. Peer review isn't perfect. Sometimes it can fail quite spectacularly. Bad papers do get published occasionally, and we cannot simply presume that a paper published in a scientific journal is above criticism. So if we insist such criticism is not permitted here, it must be for some other general policy reason. If you recognize that it does happen occasionally that a physically invalid paper gets past peer review; such a policy would risk a window for physically invalid ideas to be introduced without fear of correction.
2. On this discussion in particular; the main substance of my post was not, in fact, criticism of the paper. It was on a very specific example and question proposed by Andre. I explained the whole thing, without mention of the paper at all, using only very straightforward physical thermodynamics. The paper came up because it was the basis for Andre's claim that interaction with thermal radiation leads to a cooler atmosphere than otherwise.

Andre cannot be faulted on policy. We disagree on some physics, which is not a problem so much as an opportunity for a useful substantive exchange. I think an exchange like this is really useful in this kind of forum, and I appreciate Andre's willingness to be part of it, and the way he engages the topic. Andre's claim, for all that it is IMO physically incorrect, is properly based on a published paper, and so permitted in the forum.

In my own reponse, I first explained why 33 degrees is entirely proper as an expression of the magnitude of Earth's greenhouse effect. This number is widely used in introductory material on atmospheric physics. That first part is self-contained. After that, I also went on to answer his question of why Chilingar gets a physically incorrect result... which he certainly does.

It is mainly because Chilingar (who is a petroleum geologist; not an atmospheric physicist) invents a completely invalid theory of lapse rate. That's not the end of the problems, but it's a start and easily checked by comparison with any simple introduction to thermodynamics of the adiabat.

2. Published responses

Now in fact, there IS published criticism of Chilingar's work, though not of the 2008 paper specifically. My own post is not based on that; I wrote my post independently and from my own working knowledge of atmospheric physics, and after reading Chilingar for myself. But you can find quite blistering refutations of Chilingar in the literature... in reference to a slightly older paper with many of the same errors repeated.

References:

• Khilyuk, L.F., and Chilingar, G.V. (2006) On global forces of nature driving the Earth’s climate. Are humans involved? in Environmental Geology Vol 50, No 6, Aug 2006.
• Aeschbach-Hertig, W. (2007) Rebuttal of “On global forces of nature driving the Earth's climate. Are humans involved?” by L. F. Khilyuk and G. V. Chilingar in Environmental Geology Vol 52, No 5, May 2007.

It would be tempting, and easy, to go into a cheap attack looking at secondary matters of the journal and citations and so on. But in brief, the paper has no impact on climate science. The formally published rebuttal gives the reason as a closing paragraph:

It is astonishing that the paper of Khilyuk and Chilingar (2006) (as well as Khilyuk and Chilingar 2004, for that matter) could pass the review process of a seemingly serious journal such as Environmental Geology. Such failures of this process, which is supposed to guarantee the quality of published literature, are likely to damage the reputation of this journal.

-- (Aeschbach-Hertig 2007)​

There's also a second aspect to your question about the proper place for criticism.

There's a problem with trying to refute work that is this bad within the scientific literature; it's not automatically a useful thing to do.

This paper has no prospect of any impact whatever on atmospheric physics in practice... so why would you bother? The one possible reason is to put out an explanation for people who aren't familiar with the field. But that can backfire. If anyone was actually serious about understanding these issues, they'd be reading basic texts on the subject. If someone feels all at sea with the subject matter, they'll just come away with the misleading impression that this is a scientific debate on a par with other disagreements between working scientists. But it isn't.

Professor Aeschbach-Hertig, who actually IS an environmental physicist specifically involved in climate research and paleoclimate in particular, also has his own blog; which is not a legitimate reference in the forum. Those who care can find it; and see what he thinks of the new paper. The criticisms go well beyond being merely incompetent at physics.

In all honesty, there's nothing in Chilingar's paper that deserves to be taken seriously in the scientific literature. That it got published at all, even in a low impact journal like Environmental Geology, is an indication of problems at the journal itself; and there's actually more to the story than just a bad publication. However, I can't just presume that here in physicsforums.

Cards on the table; that's my view of the whole debacle. But for discussion here at physicsforums, I will aim to be scrupulous in focusing on the merits of the physics itself.

I am not particularly interested in contributing to a situation where people work out who to cheer for on the basis of secondary ideas like "consensus" or "impact" or credentials or publication venue or the presumed allegiances of the author. My main interest is physics and physics education. I'm interested mainly in contributing to a situation where people know a bit more about the actual physics... in climate, in cosmology, in relativity, in any area of science where there's public interest and/or confusion.

Cheers -- sylas

 

[vanesch]

Ok, if you allow me to nitpick, although I agree with what you write concerning the black (or grey body) body temperature of the Earth without greenhouse effect: non-uniform irradiation can only result in a still lower surface-averaged temperature. This is because the "penalty" is a stronger-than-linearly rising function of T, so for constant "penalty", the maximum overall T you can achieve is when T is uniform. When it varies, you "pay" more. That's like tax: for a given amount of tax over 10 years to pay, best is to have as uniform an income a year. If you have all your income in 1 year, and nothing else in the 9 others, your overall 10-year income for the same tax will be lower than if you had a uniform income.
That's why it is a bookkeeping advantage of being able to spread extra income over as many accountancy years as possible.

This is a necessary consequence of Hölder's inequality, which means:

$$\int_S T dS \leq \left( \int_S T^4 dS \right)^{0.25}$$​

The above represents a surface integral. One is the integral of temperature; the other is an integral of power emission. The power integral is constrained to balance the solar input by the first law.

However there must be a typo in the formula you gave, because set T = 1 and S = 10 and you see the problem:

10 < (10)^(0.25) ??

The Hoelder inequality requires you to have 1/p + 1/q = 1.

We can fix this, by taking q = 4, p = 4/3, f = 1 and g = T.

We then have:
$$\int_S T dS \leq \left( \int_S 1^{1.33} dS\right)^{0.75} \left( \int_S T^4 dS \right)^{0.25}$$
or:

$$\int_S T dS \leq \left(S\right)^{0.75} \left( \int_S T^4 dS \right)^{0.25}$$

or:

$$\frac{1}{S} \int_S T dS \leq \left(\frac{1}{S} \int_S T^4 dS \right)^{0.25}$$

So there was a normalization missing.

It doesn't change your argument.

I was hesitating to report this nitpicking, but since you asked for it...

 

[sylas]

I was hesitating to report this nitpicking, but since you asked for it...

I did indeed, and you are quite correct. The integral as I gave it was not an average temperature at all, or an "effective" temperature (which can be considered as a kind of weighted average). I had left out the normalization. Urk. I've made a brief addendum to my post pointing to your correction.

Thanks -- Sylas

 

[vanesch]

Now... since the main part of the atmosphere is necessarily cooler than the surface, the effect of adding a capacity to absorb and emit radiation will result in a net flow of energy from the surface into the cooler atmosphere. That follows from the second law. The additional energy going into the atmosphere will help drive additional convection, which also increases the net flow of energy into the atmosphere. This is now balanced by the loss of radiant energy out from the top of the atmosphere. What we have now is called "radiative-convective equilibrium". And that involves a higher temperature than the pure convective equilibrium.

I have to say that I'm intuitively puzzled here. I think I'm going to follow your advice and go through the book. Intuitively, I would have thought that you get BETTER heat transport (lower thermal resistance) if you have both radiation and convection, rather than convection or radiation alone. You would think that you have "resistors in parallel", no ?

 

[chriscolose]

I have to say that I'm intuitively puzzled here. I think I'm going to follow your advice and go through the book. Intuitively, I would have thought that you get BETTER heat transport (lower thermal resistance) if you have both radiation and convection, rather than convection or radiation alone. You would think that you have "resistors in parallel", no ?

I'm not quite sure I understand. This diagram (from Trenberth, Fasulo, and Kiehl) shows global energy flows. If you're referring to the surface, it loses heat both through radiation and convection.

 

[lisab]

But second guessing how that happens is beside the point. The actual argument expressed is on a par with young Earth creationism -- another field of pseudoscience with its own credential scientists also writing rock bottom crank science.

Sylas, I appreciate how much time and effort you put into your posts. They're very informative.

But for those of us who are trying (in our precious spare time) to understand this stuff, it's really distracting to get editorializing like this...I believe Evo made a post recently (in another thread, I believe) about using terms like "denier" and "warmer." I totally agree with her; it brings something akin to partisanship to the discussion, which kills the discourse.

This isn't meant as a personal attack and I hope you don't take it as such.

 

[sylas]

Sylas, I appreciate how much time and effort you put into your posts. They're very informative.

But for those of us who are trying (in our precious spare time) to understand this stuff, it's really distracting to get editorializing like this...I believe Evo made a post recently (in another thread, I believe) about using terms like "denier" and "warmer." I totally agree with her; it brings something akin to partisanship to the discussion, which kills the discourse.

This isn't meant as a personal attack and I hope you don't take it as such.

No problem; I appreciate the point and understand what you mean. I also agree -- but with some qualifications.

I'll try to explain my own policy a bit -- ironically more distraction from the business of physics. I'll make sure my next post is exclusively on the physics; and I propose to look the useful questions from vanesch.

There's a dilemma discussing the many different arguments that turn around climate science, because they are not all of the same quality. There are genuinely open questions and unsolved issues. There are also basics that are not in any credible doubt, and make up a foundation for consideration of open questions. And there is not a hard and sharp dividing line between these extremes.

1. When peer view fails

We run into a problem -- and it is not unique to climate science -- when scientists who ought to be trustworthy to tell good argument from bad are actively pushing ideas that are physically nonsense. I'm not meaning all disagreement with conventional ideas.

The situation we have in this instance is revolved using fairly easy thermodynamics. The counter view so far has been based on ideas expressed in a paper published in a science journal by a first rate scientist.

One could point out a few secondary points. It's a low impact journal. The scientist is first rate all right, but not in atmospheric physics; he's in a different field. The citation trail before and since this paper shows that the ideas have been roundly rebutted in the literature, and have not excited any apparent further interest or debate in the field of atmospheric physics itself.

My own preference is to focus on the merits of the physics itself. But the inference of that is that either my own explanations are missing something, or else the published paper has somehow made outright errors that should be apparent to a decent undergraduate student.

I think it should be okay to say so, when the situation is that stark, alongside the details of physics. Otherwise one has the impression that it is just part of the "scientific debate". And it really isn't.

2. Different levels of disagreement

I've suggested previously a crude distinction between different levels of conflict in climate science.

1. There's denial of the greenhouse effect altogether. This sidesteps any question of changes to climate; it is not about warming in response to small changes. It's about the underlying thermodynamics of temperature at all. That is, people argue that the capacity of an atmosphere to interact with thermal radiation is not, in fact, the reason for Earth having a livable climate at the surface that is well above the "effective radiating temperature" of the planet as would be observed from deep space, which is about -18C.
2. There's dispute over the effects of changing atmospheric compositions on the magnitude of Earth's energy balance. That is, given a change to the concentrations of greenhouse gases (gases that interact with thermal radiation), how much additional energy is delivered at the surface? This is called the "forcing".
3. There's dispute over the response of the whole climate system to a forcing; the climate sensitivity. That is, given a change to the flux in radiant energy, how much does the surface warm or cool in response to restore the mean energy balance? This is called the "sensitivity".

Roughly speaking, the first is comparable to creationism, and in my opinion is it best to say so, frankly. It's just not a rational scientific debate at all; it's rather a case of explaining some relevant thermodynamics, much like we explain how relativity resolves the so-called twin paradox.

The second is somewhat in between, in my view. The forcing from greenhouse gases, especially carbon dioxide, is one of the least difficult issues in the whole field of climate science. But it is quite technical, and nailing it down gets into pretty complex ideas, ultimately based on quantum physics and requiring a lot of computer power to calculate. The end result (3.7 W/m² of forcing for a doubling of CO2 concentration for conditions as on Earth) is known to within 10% accuracy or so. The guts of this dispute are whether or not carbon dioxide is a significant player in the whole game. The details are sufficiently subtle that I am sympathetic to the difficulty of sorting it out.

The third is a definite wide open research question. Theoretical and empirical evidence indicates that climate sensitivity is between 0.5 and 1.2 degrees per unit forcing, and it is possible in principle to look at arguments for values outside these bounds. A credible scientific case, however, will certainly have to deal with the evidence that has already been applied to infer these bounds.

There are other genuine open questions as well. Evaluating and refining models. Sorting out regional effects and sources of short term variation. Sorting out the carbon cycle. Looking at vertical heat transport in the ocean. Sorting out all the consequences of increasing temperature. Figuring out the details of more complex forcings, like aerosol and cloud, which are far more complex than thermal emissivity as given by something like CO2.

3. Skepticism of an onlooker

Finally, there's always legitimate skepticism for anyone not well up on the physics and wanting to learn more. There are competing voices in the public sphere especially, with extraordinary claims of incompetence and worse flying in all directions.

If anyone does feel competent to pick sides and attempt to argue specifically for certain propositions in the whole discussion, then they take a level of responsibility and their actual competence is on the line for evaluation. I'm doing that; and in all seriousness I welcome substantive challenges or criticisms that address the specifics of my posts. I don't claim special authority. I have studied this as an amateur, but as far as credentials go I have no special standing. My posts stand or fall on their own intrinsic merits; and as we've seen I do make technical errors that can be identified by other readers.

But I appreciate there are many readers who are not claiming to have any special brief to argue for one perspective or the other; they are genuinely unsure who to believe or how the details of the arguments work. It is way out of line to dismiss them with pejorative labels.

It can be very frustrating for such readers to have a debate which merely has both sides calling the other idiots. What they want is exposition of the actual arguments.

Conclusion

You make a good point. For all that, I will continue, sometimes, to suggest some of the voices in this debate are outright pseudoscience, and that some of what passes for skepticism is credulous naivety and ignorance -- but only when it takes the form of actually making judgments on the worth of different arguments.

I will not be insulting to people who are asking questions or who are simply remaining uncertain about details. I am also sympathetic to those who read material which is nonsense but who find it persuasive. This does indicate a lack of basic physical knowledge; but we've all been there, and the great majority of us remain there for great swathes of physics.

There's no sin in needing to learn more about physics, and my aim above all else is to learn more and to contribute to greater understanding of physics in others. I've managed both so far (special nod here to contributors in the cosmology forum, who have helped me significantly in recent months).

Cheers -- sylas

 

[chriscolose]

Great post by sylas.

I am not quite sure how many third-party readers we have who are not posting, but just digesting the back-and-forths going on here. It may be worthwhile for any of those readers to ask specific questions they may have; I'm sure someone will be able to either explain it in detail, or if not at least provide a starting reference.

I agree that it is necessary for those familiar with the science to make sure third-party readers can at least differentiate between legitimate skeptical arguments and that stuff which does not belong in a science forum. Admittedly, I don't have the patience (which I find admirable in sylas) for people who yell "hoax" and "fraud" and continue to insist that the greenhouse effect is not real. I'm quite happy that sylas has chosen to respond substantively to those people, as he is probably best placed (knowledge-wise) to do so.

For those third-party readers who are interested, I'd like to briefly summarize much of the discussion going on and the current status of understanding in the climate community, by way of expansion on the "three levels of skepticism" discussed by sylas.

• 
  
  The energy coming in and out of the planet (determined essentially by the output of a planet's star, the distance to that star, the reflectivity of the planet, and the composition of the planet's atmosphere) serve to define the basic boundary conditions which constrain the global climate. A starting point for those interested in the physics of climate change is to understand the energy budgets of the top of the atmosphere and the surface, and the radiative forcing ability of various agents which can potentially change Earth's temperature.

• 
  The 33K greenhouse effect is real and undisputed in legitimate scientific arenas. It is the difference between the emission temperature of the Earth (which would be the surface temperature without an atmosphere, keeping the planetary albedo at 30%), and the emission from a blackbody with the temperature of the surface of Earth.

• An observer looking at the surface from space would see an upward radiation flux of roughly 390 Watts per square meter (a form of heat loss by the planet) in the absence of an atmosphere. In reality, an observer looking down would see roughly 240 Watts per square meter being emitted at the top of the atmosphere, which means that roughly 150 Watts per square meter is absorbed by the atmosphere. The greenhouse effect does not work to warm the surface unless the atmospheric temperature decreases with altitude. The greenhouse effect thus requires convection to move the heat upward to where it can be radiated to space at a lower temperature. By Stefan-Boltzmann, this emitting temperature is much weaker than the surface value, and so basically the greenhouse effect acts to make the planet much less efficient at getting rid of its heat. Accordingly, the net radiation into the planet (by the sun) is balanced at the top of the atmosphere (not the surface) by outgoing infrared energy, and one can extrapolate down to the surface by (emission height)*(lapse rate) to achieve the surface value, which is greater with an atmosphere that is opaque to infrared radiation. It is impossible for a planetary temperature to exceed that of the net incoming solar radiation (neglecting heat fluxes from the interior, which is negligible for the terrestrial planets, but important for gaseous planets in the outer solar system) in the absence of such an atmosphere

.

• 
  Carbon Dioxide absorbs strongly at Earth-like temperatures, particularly in the 15 micron band where significant absorption occurs from about 12.5 microns to 16.7 microns. See
  
  
  
  
  
  The standard equation used today to determine the radiative forcing (essentially the change in net irradiance at the tropopause after allowing stratospheric temperatures to re-adjust to equilibrium) for carbon dioxide is given in Myhre et al 1998, and is
  
  $$F = \alpha * ln(C/ C_{0})$$
  
  Where C is the final concentration of CO2 and Co is the initial concentration (e.g., the pre-industrial value in this context) and alpha today is taken to be 5.35. This suggests that a doubling of Carbon dioxide will lead to a 3.7 W/m^2 forcing

• The actual temperature change that will result per unit forcing is essentially the sensitivity of the climate system, i.e.,
  
  $$\Delta T = \lambda F$$
  
  where lambda is the climate sensitivity paramater (in K per Watt per squar meter) and constraining this value is currently a very active topic of research. Meshed into lambda is the change in water vapor, change in ice cover, change in lapse rate, change in cloud cover, etc and other feedbacks which may influence the radiative balance of the planet. These can be further decomposed into their longwave and shortwave components. Clouds represent the largest source of uncertainty, although several decades of research has not led to a considerably different pciture of sensitivity, where lamba is taken to be between 0.5 and 1.2 K per watt per square meter, which leads to a 2 to 4.5 K increase in global mean temperature per doubling of CO2.

• CO2 is also not the only thing going on for the "forcing" part of the equation, although it must be a significant part. The relevant physics and constraints of radiative imbalance allow no other possibility. Mostly because of aerosols however, the total forcing from pre-industrial to current times is somewhat uncertain, and so there's still wiggle room for other ideas (like cosmic rays or Martian death beams or whatever else) to play a role (although probably not very big, probably much smaller than the methane forcing or aerosol influence). Detecting other influences does not make AGW invalid, it simply means other things affect climate and multiple causes are present, but anthropogenic activities continue to remain a dominant mechanism in present climate change, and will be in the near future should emissions go unabated

• 
  Lots of other interesting things are happening (or could happen) and should be discussed like the competing effects of higher SST's and wind shear on hurricane intensity anomalies, ecological impacts, the sensitivity of the Greenland ice sheet to collapse, the possibility of various "tipping points" which may occur, the best way to project sea level rises, the understanding of short-term variability and decadal scale prediction. There's a lot of open questions about this stuff, and it's a lot more interesting than whether a greenhouse effect exists or whether man is influencing climate. I don't say that because it's my opinion, just because it's the stuff that is being discussed in the literature and in academic conferences...not whether basic thermodynamics is being represented correctly in undergraduate textbooks.