In connection to a recent post by Roy Spencer: Skeptical arguments that don't hold water, I thought I might take the opportunity to clarify and summarize certain key points that I have argued for on this blog. Roy Spencer is an incredibly valuable source for understanding the reasoning and conceptual twists needed to support the castle of sand upon which modern atmospheric physics is founded. He is also very kind to deliver the standard climatology explanation for the atmospheric lapse rate:
“Without the destabilization provided by the greenhouse effect, convective overturning would slow and quite possible cease altogether. The atmosphere would eventually become isothermal, as the full depth of the atmosphere would achieve the same temperature as the surface through thermal conduction; without IR emission, the middle and upper troposphere would have no way to cool itself in the face of this heating.”
The same thing can not be said about some other people in Spencer's entourage. For example, in a 2003 issue of Energy & Environment a certain Mr Hans Erren threw a "Cotton-argument" when hypothesizing about the situation in the atmosphere in the absence of so called greenhouse gases:
"...Upper layers would be cooler because the vertical component of the thermal molecular speed
However, maybe the time log for this statement of his is sufficiently old for him not to get caught in the "Cotton-sock" of Spencer's commentators field.
Another view inconsistent with that of Spencer and the IPCC was put forward by Robert G Brown:
"In nature, the dry adiabatic lapse rate of air in the atmosphere is maintained because the system is differentially heated from below causing parcels of air to constantly move up and down."
This makes no reference to any greenhouse gases. Is it the case that the system is heated from below only when there are greenhouse gases present?
At this point the observant reader should have noticed that the "debate" going on here is not about opposing scientific views but rather some kind of tribal fight for petty prestige. So what is the tactic of Spencer & Co? I think it is to simply ignore good arguments put forward against the GGH and instead focus on rebutting bad ones, because these indeed exist. By this method they hope to impart on the public an illusion that they, enlightened scientists, are winning the battle against the deluded barbarians and, in the fly, save their beloved trademark the Greenhouse Effect for future generations.
An example of a good argument is to point to the non-zero lapse rate in Jupiter's atmosphere in the pressure range from 1000 to 100 mB. This observation refutes the theory of Spencer that GHGs are necessary for the lapse rate and this is probably the reason why he never comments on it. Instead he makes a list of 10 other arguments of mixed quality. I will try to comment on these.
1. THERE IS NO GREENHOUSE EFFECT
Here it seems as if Spencer equates the existence of downwelling IR-radiation (back-radiation) with a physical effect with the name of the "Greenhouse Effect". However, this does not qualify as a thermodynamic effect at this stage, since nothing has been said quantitatively about warming or cooling of any part of the atmosphere. Furthermore, no assumption is made on the function of this downwelling radiation, will it act as radiation pressure or be part of some ordinary diffusive process. Moreover, why this obsessive focus on radiation, why not talk a little more about other quasi-particles such as phonons and direct molecular collisions. Most important perhaps, no effect of this kind has been attributed solely to so called greenhouse gases. If, however, people insist on denying the existence of downwelling IR-radiation, yes, please stop that.
2. THE GREENHOUSE EFFECT VIOLATES THE 2ND LAW OF THERMODYNAMICS
There are ways to argue why Spencer's and IPCC's version of the GE violates the 2nd law, but it must be stated in very precise way. I have done that in an older post. It is not sufficient, however, to simply say that
"The GE cannot work since the 2nd law prohibits heat transfer from the cold atmosphere to the warmer surface."
Although there might be some sound reasoning behind this, it can easily be obscured and disarmed by pointing to the fact that the walls in your house passively increases the inside temperature under constant radiator-forcing. The statement is problematic since its relevance to the GGH is unclear. Where does the GGH state (explicitly or implicitly) that the cold atmosphere actively (rather than passively) heats the surface. Answer: Nowhere. Finally, the statement expresses a certain ignorance of the basic problem at hand since it doesn't address the fundamental question: Why is the upper atmosphere colder than the surface in the first place?
3. CO2 CAN'T CAUSE WARMING BECAUSE CO2 EMITS IR AS FAST AS IT ABSORBS.
I think Spencer is right here. Dead herring.
4. CO2 COOLS, NOT WARMS, THE ATMOSPHERE.
You should never make any definitive statements about the warming or cooling effect of CO2 at its present concentrations. Tentative speculations, ok. It could be that CO2 cools slighty by absorbing IR radiation from the sun and warms slighly through the Neanderthal effect. Who knows?
However, here Spencer is kind enough to deliver the following:
"the net effect of greenhouse gases is to cool the upper atmosphere"
Some people simply don't get the meaning of this. They immediately confuse themselves by altering the statement to
"the greenhouse gases in the upper atmosphere has a cooling effect"
A cooling effect on what?? The surface? The upper atmosphere?
Moreover, if a theory predicts a cooling of the upper atmosphere and a warming of the lower, then by default, this implies an increased lapse rate in some part of the atmosphere.
5. ADDING CO2 TO THE ATMOSPHERE HAS NO EFFECT BECAUSE THE CO2 ABSORPTION BANDS ARE ALREADY 100% OPAQUE.
Dead herring. I would also consider this as a kind of lukewarmist argument since it assumes that the absorption bands of CO2 have some particular importance.
6. LOWER ATMOSPHERIC WARMTH IS DUE TO THE LAPSE RATE/ADIABATIC COMPRESSION.
I guess that Spencer makes some valid points here. At least, the "adiabatic theory" lacks a coherent physical model to support it. We should, however, be open to arguments of this kind since they might be needed to explain certain parts of the planetary atmospheres. As an extreme example: The interior of the sun. No pressure effect there?
Spencer asks: "If adiabatic compression explains temperature, why is the atmospheric temperature at 100 mb is nearly the same as the temperature at 1 mb, despite 100x as much atmospheric pressure?"
Yes Spencer, if greenhouse gases are needed to support the lapse rate between 1000 and 100 mB, then why does it exist on Jupiter?
7. WARMING CAUSES CO2 TO RISE, NOT THE OTHER WAY AROUND
I have no opinion on this.
8. THE IPCC MODELS ARE FOR A FLAT EARTH
I havn't inspected the IPCC models in that detail, which are not that easy to get access to I presume. However, this seems to be a rather inefficient argument.
9. THERE IS NO SUCH THING AS A GLOBAL AVERAGE TEMPERATURE
This is somewhat similar in nature to the previous one. For now, inefficient. Perhaps it has some relevance when evaluating the statistical trends for small temperature variations, but it seems to be a distraction from more important issues.
10. THE EARTH ISN’T A BLACK BODY
Dead herring. Just as you can write down a heat diffusion equation linear in temperature you can write down a diffusion equation using the temperature to the power of four. Which is the best? Who knows? In any case you would need to adjust the tranport coefficients to match the empirical results.