Tuesday, October 30, 2012

Astrophysicist explains why conventional greenhouse theory is incorrect

Astrophysicist Joe Postma has a new paper showing from both a theoretical and observational basis why the assumptions of conventional greenhouse theory are incorrect. Postma debunks the popular myth that greenhouse gases act as a "heat trapping" "blanket" to allegedly increase global temperature by 33C. 

Related: Prior papers by Joseph Postma


A Discussion on the Absence of a Measurable Greenhouse Effect

Joseph E Postma, M.Sc. Astronomy

Abstract: A contextual flaw underlying the interpretation of a back-radiative greenhouse effect is identified.  Real-time empirical data from a climate measurement station is used to observe the influence of the “greenhouse effect” on the temperature profiles.  The conservation of heat energy ordinary differential equation with the inclusion of the “greenhouse effect” is developed, which informs us of the temperature profile we expect to see when a “greenhouse effect” is present.   No “greenhouse effect” is observed in the measured data. The latent heats of H2O are identified as the only real heat-trapping phenomenon and are modelled. A discussion on the existence of universal principles is used to explain why simplistic arguments cannot be used as justification for the greenhouse effect.

Excerpts:


1.1. The problem, and truth, of the albedo

A well-known attempt at a theoretical  disproof of the postulate of an  “atmospheric greenhouse effect” (GHE) was found in  Gerlich &  Tscheuschner’s [1] “Falsification of the Atmospheric CO2 Greenhouse Effects Within the Frame of Physics”.  One of the rebuttals to this paper was Smith’s [2] “Proof of the Atmospheric Greenhouse Effect”.  A fault can be levelled at both of those papers in that no true empirical tests were made of either’s claims, no matter how well-established the physical principles might have seemed to be in either’s assessments.  Generally, the inference of an atmospheric GHE is made by comparing the Earth’s near-surface-air average temperature to  its global effective blackbody radiative temperature  calculated from the  absorbed energy from the Sun – there is a difference of 33K.

There exists a simple contextual flaw in this inference because the average terrestrial albedo is  much higher than the true surface albedo due to the presence of clouds in the atmosphere, resulting in a terrestrial albedo of approximately 0.3, while the true surface albedo is actually much less at only 0.04 [3].  That is, without greenhouse gases, the albedo would not still be 0.3, but 0.04.  The physical surface is not where the average terrestrial albedo of 0.3 is found, and so the direct comparison of related temperatures using the same albedo is  unfounded, because one system is being compared to a qualitatively different system with different absorptive (and presumably emissive) properties. But for a common example, in this [4] online textbook, we read: 
“The temperature of the surface of the Earth without these greenhouse gases would be 255 K. With these greenhouse gases the average temperature of the surface of the earth is 288 K. Our total of greenhouse warming is 33 K.”
However, without greenhouse gases, the albedo would not be 0.3, which thus leads to the 255K value.  The albedo would actually be 0.04.  Therefore a valid comparison is actually found in the theoretical temperature of the Earth-ensemble without  greenhouse gases (GHG’s) and with a correctly corresponding albedo, to that with  greenhouse gases with their corresponding albedo.  In this physically meaningful comparison, the difference in temperature between the theoretical ground surface, and the observed surface with an atmosphere and GHG’s on top, is only 12K, reducing the inferred strength of the GHE by almost two-thirds.  That is, the average global surface temperature without GHG’s, calculated using the usual method of the Stefan-Boltzmann Law with conservation of energy given the known solar input and the surface-specific albedo, results in a value of 276K.  

The observed average surface temperature with GHG’s present is actually 288K (15C), and so the “greenhouse  effect”  should  actually be thought to only provide 12K worth of additional temperature, not the 33K which is always incorrectly cited.

It should be noted that  the much higher albedo, with GHG’s present, is caused by the presence of clouds from droplet-condensation of the GHG water vapour.  This reduces the amount of sunlight absorbed by the system and thereby  must  reduce the temperature, in spite of the warming effect of the GHE from water vapour’s own presence.  In light of that one may ask: What would be the theoretical temperature of the surface of the Earth, with GHG’s including water vapour present, but when no clouds form?  Without knowing (as yet in this paper) the mechanism of the GHE and how to account for it, we can’t directly answer the question, but it should be at least 276K, as above, given that the albedo isn’t reduced from clouds. However, the answer can simply and easily be tested empirically on days where there are no clouds.  This will be done later in this report.  Without the albedo-increasing cooling effect of clouds (they prevent heating from solar insolation) above the surface, the GHE should manifest much  more clearly.    We must also acknowledge the fact that since the bulk portion of the terrestrial albedo is caused by cloud-tops, at altitude, we still cannot directly infer that the resulting 255K  terrestrial temperature  with clouds present should be found at the physical ground surface, whether or not there is a GHE, because the radiative surface with albedo equal to 0.3 does not reside with the ground surface.  There is a vertical dimension which affects the interpretation and must be taken into consideration.  Martin Hertzberg adds additional detail [5], with the point being that treating the emissivity as unity such as to arrive at the “Cold Earth Fallacy” is also unjustified:
“Since most of the albedo is caused by cloud cover, it is impossible for Earth to radiate out into Space with unit emissivity if 37% of that radiation is reflected back to Earth, or absorbed by the bottom of those same clouds. Even for those portions of Earth that are not covered with clouds, the assumption that the ocean surface, land surfaces, or ice and snow cover would all have blackbody emissivities of unity, is unreasonable. This unrealistic set of assumptions - leading to sub-zero average temperatures for Earth - is shown in Fig.1; and it is referred to  there as the “Cold Earth Fallacy”.”
A second and related ambiguity is that the 33K “GHE” value is a comparison of a calculated effective blackbody radiative temperature as should only be observed from outside the system (from space), via an integrated emission spectrum, to a specific kinetic temperature measured at only a single  depth-position inside the thermodynamic and  radiative ensemble.    That is, the average radiating emission altitude of outgoing energy from the terrestrial ensemble is actually between 5 and 6 km [6], and this is where the kinetic temperature of 255K is found.  In terms of radiation, the ground surface of the Earth is not the radiating surface, and therefore we shouldn’t expect the ground surface to have that temperature. In terms of the radiating surface, the temperature of the Earth as an integrated thermal ensemble inherently including the atmosphere, as seen from space, is exactly the same value as the theoretically-calculated effective blackbody temperature.  The Earth, in terms of its only means of exchanging energy – radiation – is exactly the temperature it is supposed to be.  But for most natural radiating gaseous systems with central gravity, such as stars, there will be a generally fixed effective blackbody temperature, while the kinetic temperature of the gas typically follows a distribution, in the main radiating layers, which increases in temperature with depth; see Gray [7], Table 9.2, for example.  This is true for stars because the source of energy is below the radiating layers; however, the same is true for the terrestrial atmosphere because the bulk source of  heat  energy, similarly, comes from solar radiation generating heat at the bottom-most layer of the atmosphere, at the surface-atmosphere boundary.  (Some solar radiation is absorbed directly into the atmosphere via absorptive extinction; see [8] and [9] for example.)   And so, because the ground surface is where the solar heat is (mainly) initially deposited, which then works its way through the atmosphere conductively and radiatively, the surface and lower layers should be expected to be warmer than the integrated average layer and upper layers.  

This fact is particularly relevant when we consider the actual maximum heating potential of sunlight under the solar zenith: considering a surface albedo of, say, 15%, and no clouds in the way, the real-time insolation temperature works out to ~378K or 105C, via the Stefan-Boltzmann Law.   As a matter of fact, the instantaneous average heating potential of sunlight over the sun-facing hemisphere, assuming an integrated albedo of 0.3, has a  hemispherically integrated average value of  322K or  +49C.    Note that the bihemispherical average temperature at the surface is actually only  +15C.    Because this energy is initially deposited by sunlight within the first few millimeters of land surface  (for the ocean most sunlight is absorbed within 200m depth), and this is therefore the only (main) place where the insolation is converted to heat, we find much justification for finding said surface to be warmer than the integrated average of the entire atmospheric thermodynamic ensemble above the surface conducting heat  away from  it, similar to the classical problem of a bar heated at one end.   The effective blackbody radiating temperature, being an integrated sum of the emission from all wavelengths and points along the optical (i.e. physical) depth of the atmosphere, necessarily requires that higher kinetic temperatures than said radiative average will be found below the depth of average radiative emission, essentially by the mathematical definition of what an integrated  average is, and 
independent of any “GHE”.
...



5.3. Summary Statements

1) The surface of albedo is not the ground surface, and so it never was correct to associate 
the  radiative temperature of -18C with the ground surface in the first place, since the albedo is what determines the equilibrium temperature and the albedo is not found with the physical surface.

2) Even as the climate models show, an increase in cloud height causes an increase in temperature at the surface. This is not due to a backradiation GHE but due to the lapse rate of the atmosphere combined with the average surface of equilibrium being risen further off of the surface.

3) A real greenhouse doesn't become heated by internal backradiation in any case, but from trapped warm air which is heated by contact with the internal surfaces heated by sunlight, and then physically prevented by a rigid barrier from convecting and cooling. The open  atmosphere doesn't do what a greenhouse doesn't do in the first place, and the open atmosphere does not function as a rigid barrier either.

4) The heat flow ordinary differential  equation of energy conservation is a fundamental equation of physics. It combines the fundamental mechanics of heat flow together with the most venerated law of science, conservation of energy. This equation predicts what should be observable if backradiation or heat-trapping is introduced to the equation, in accordance with the main idea of the atmospheric GHE, that a higher temperature than the insolation will be achieved.  A higher-than-insolation temperature is not achieved in experimental data, and we make it clear how one could test the postulate with even more surety by using the "Bristol Board Experiment".

5) An important factor for why the introduction of backradiation into the equation fails to match the real world is because radiation cannot actually increase its own Wien-peak frequency and its own spectral temperature signature; radiation cannot heat up its own source.  The Laws of Thermodynamics are real and universal.


6) The rate of cooling at the surface is enhanced, rather than retarded, relative to the entire atmospheric column, by a factor of 10.  Therefore, backradiation doesn’t seem to slow down the rate of cooling at the surface at all.  Backradiation neither causes active heating, nor slowed cooling, at the surface.  (Given Claes Johnson’s description of radiative heat transfer, radiation from a colder ambient radiative environment should slow down the rate of cooling, and we agree with that.  What we didn’t agree with was that “slowed cooling” equated to “higher temperature” because that is obviously sophistic logic.  And now in any case, it is apparent that sensible heat transfer from atmospheric contact at the surface dominates the radiative component process anyway, leading to ten times the rate of cooling at the surface relative to the rest of the column.)

7) Given the amount of latent heat energy actually stored (i.e. trapped) within the system, and that this energy comes from the Sun, and  considering  the Zero-Energy-Balance(ZEB) plot, it is quite apparent that this energy gets deposited in the equatorial regions and then shed in the polar regions.  This trapped latent heat prevents the system from cooling much below 0C, which keeps the global average temperature  higher than it would otherwise be and thus leads to an “interpreted appearance” of a GHE caused by “GHG trapping”, when the only trapping of energy is actually only in H2O latent heat.

8) Subsoil readings prove that a large amount of energy is held at a significant temperature (warmer than the surface) overnight, and because this soil is warmer than the surface, and the surface is warmer than the atmosphere, then the direction of heat flow is from the subsoil to the atmosphere.  And as  discussed, the atmosphere seems to enhance surface cooling rather than impede it.

9) The heat flow equation can be modeled to show that the Sun is capable of maintaining large amounts of water under the solar zenith at about 14 degrees C. This is very close to the surface average of +15C. The Sun can maintain a liquid ocean at +14C because it takes  a long time for heated water to lose its thermal energy.    This is also in combination with the surface of albedo being raised off the surface where the lapse rate will maintain a near-surface average of +15C in any case.


10) The issue has never been about whether radiation moves freely about in the atmosphere (it does), the question is whether once it has arrived at the surface, does it get more than one go at generating heat (i.e. “back radiation” heating)?  We say “no” because a) no such phenomenon as “back radiation heating” is cited in any thermodynamics textbooks and b) nor has any such effect been measured empirically.  GHE believers are left not knowing whether to support the “back radiation” heating or the “delayed cooling” (i.e. “blanket effect”) argument for the GHE; this is because each is a contradiction in terms and may separately be shown to not have any empirically proven basis.  The Laws of Thermodynamics probably play a part in this.

11) As Alan Siddon’s has explained [41], it isn’t actually clear, and there seems to be a plain logical contradiction, when we consider the role of non-GHG’s under the atmospheric GHE paradigm.  If non-GHG’s such as nitrogen and oxygen don’t radiate, then, aren’t they the ones trapping the thermal energy which they sensibly pick up from the sunlightheated surface and from GHG’s?  If on the other hand they do radiate, then aren’t they also GHG’s?  If a GHG radiates, and the others gasses don’t, then doesn’t that mean that GHG’s  cause  cooling because they provide a means for the atmosphere to shed thermal energy?   If the GHE is caused by trapping heat, then aren’t all non-GHG’s contributing to the effect since they can’t radiatively shed the thermal energy they pick up?   Isn’t how we think of the GHE therefore completely backwards?   In any case, everything with a temperature is holding heat; the only place trapping can be thought to be occurring is in latent heat.



2 comments:

  1. http://www.principia-scientific.org/supportnews/latest-news/75-absence-of-any-greenhouse-gas-warming-dulls-doha-climate-conference.html

    ReplyDelete
  2. Mark,
    Many thanks for posting Postma's paper and the link to our latest article. FYI WUWT is still being gatekeeper-in-chief on all matters GHE.Right in the middle of a perfectly good conversation, with good science being discussed:

    wattsupwiththat.com/2012/12/01/weekend-open-thread-4#comment-1164308

    “Mr. Postma and everybody else involved in this idiotic discussion over “magic gas”

    The greenhouse effect exists, get over it. The only questions are magnitude, sensitives, and feedbacks.

    This thread is closed, along with a warning to any other “Slayers” out there posing under other names (Doug Cotton this means you).

    Your GHG science is pointless, wrong, and unwelcome here. Take it somehwere else, and please, be as upset as you wish. – Anthony Watts”

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