söndag 29 januari 2012

The Greenhouse Effect according to Liou

Below are some excerpts from Liou's "An Introduction to Atmospheric Radiation" relevant to the ongoing debate.

onsdag 18 januari 2012

Roy explains the Greenhouse Effect

I would like to congratulate Roy Spencer for yet another excellent and accurate account of the greenhouse effect. A good read for all those greenhouse effect deniers out there who more or less deliberately obscure matters so that ordinary people cannot think clearly. Spencer writes

"One of the first things you discover when putting numbers to the problem is the overriding importance of infrared radiative absorption and emission to explaining the atmospheric temperature profile. These IR flows would not occur without the presence of “greenhouse gases”, which simply means gases which absorb and emit IR radiation. Without those gases, there would be no way for the atmosphere to cool to outer space in the presence of continuous convective heat transport from the surface.

Indeed, it is the “greenhouse effect” which destabilizes the atmosphere, leading to convective overturning. Without it, there would not be weather as we know it. The net effect of greenhouse gases is to warm the lowest layers, and to cool the upper layers. The greenhouse effect thus continuously “tries” to produce a lapse rate much steeper than the adiabatic lapse rate, but convective overturning occurs before that can happen, cooling the lower troposphere and warming the upper troposphere through a net convective transport of heat from lower layers to upper layers."

Now for some comments. The convective overturning results in a bouyant layer of air characterized by a constant potential temperature, which, as far as I know, is not identical to the "adiabatic lapse rate". This could be a source of confusion, and it is of utmost importance for everyone to clearly understand how the convective "lapse rate" of Roy Spencer differs from for example that of H. Jelbring and others. For Roy Spencer it is the MAXIMUM lapse rate that a convective layer can TOLERATE. Greenhouse gases would like to steepen it further though. For H. Jelbring the dry adiabatic lapse rate is the lapse rate that an air parcel MOST HAPPILY installs itself into, because that is its most relaxed state. 
Put in more technical terms, they differ through their interpretation of the thermodynamic system as either beeing very far from equilibrium, or rather close to equilibrium. In previous post though, I have tried to expose how the greenhouse hypothesis is very ambiguous indeed on whether it is in equilibrium or out of equilibrium. But that is another story that I will leave for now. I would though like to propose some intermediate solution:

Could it be that it is the sunlight, and not the greenhouse gases that destabilizes the atmosphere. It is so simple that it sounds almost silly.

Moreover, could Spencer or someone else come up with BOTTOM-UP description of how the greenhouse gases actually destabilize the atmosphere. I tried to construct my own radiative transfer model in the posts "A simple radiation model", "The heat equation revisited", which were initially critisized for not taking into account a variable thickness of the atmosphere, which I did in, "It's the density, stupid". The latter did not alter my previous conclusions, but as far as I can see strengthened them.

But finally, I think we should accept Spencers challenge and try to put numbers into our models. I will be busy with other things for a while, but maybe there is some young talent out there who can perform it, who knows.

söndag 15 januari 2012

Tallbloke's buzzing Talkshop

Some week ago I discovered Tallbloke's Talkshop which has feautured several posts and discussions on for example Hans Jelbring's 2003 paper "Greenhouse Effect as a function of Atmospheric Mass" and a more recent paper of Nikolov and Zeller. These authors are courageous in the sense that they propose new theories raising important questions about apparent correlations between atmospheric pressure and temperature open for anyone to discuss and critizise. Proponents of the "official" greenhouse theory seldom offer us the same curtesy, since they almost never mention any sources of the often quoted 1C "no feedback sensitivity" from a doubling of CO2 for us to check and scrutinize. Moreover, many of them shamelessly support inconsistent statements on the reason why the temperature decreases with height in the first place. Since it is the IPCC and not Hans Jelbring who dictates climate policies, sometime I would like the table turned, and we could all contribute to this happening.
Nevertheless, I would like to air some of my own thought about the Jelbring hypothesis and those similar to it.

1. As far as I can see it is incomplete as regards to the boundary conditions. It doesn't predict any specific surface temperature as a function of atmospheric mass. One could argue that for certain physical reasons the surface temperature should have a certain value, and then temperatures at other altitudes will be recovered by following the adiabat. Or, you could argue that the temperature at 10km height should have a specific value, and then the surface temperature is recovered accordingly. This is not specified.

A correction: Nikolov and Zeller do indeed provide a formula for the surface temperature, but I still think it would be desirable to justify the fitted parameters with boundary conditions.

2. As far as I can see there are no conclusive arguments from either statistical mechanics nor Navier-Stokes equations supporting the conjecture that the equilibrium configuration of the atmosphere should be adiabatic rather than isothermal. But this does of course not exclude the possibility that our thermometers measure the wrong temperature almost everywhere, or that any of the physical models referred to are invalid.

3. It does not predict the existence of a stratosphere. One reason that could be raised is that the lapse rate is reversed at a certain altitude because of the absoption of UV-light by ozone. But if this explanation is proposed then you could equally well argue that the surface maintains a higher temperature because of the absorption of sunlight at lower frequencies. 

Which leads to my last point. What would happen to the temperature in your house during winter if you were to double the thickness of your walls. It would probably increase because a thicker wall slows down the cooling. Now think about it, a thicker wall means a more massive wall, and there you have it: Greenhouse Effect as a function of Atmospheric Mass. This is of course just a conjecture that needs the same scrutiny as any other theory. But I believe that this is an approach that has until now been largely neglected.

söndag 8 januari 2012

Some questions to Gerhard Kramm et al.

Professor Gerhard Kramm at the University of Alaska stands out as one of few meteorologists who publicly express doubts about the validity of the so called greenhouse effect, most recently done in a paper coauthored with Ralph Dlugi, where in the abstract they state that

"..it is time to acknowledge that the atmospheric greenhouse effect and especially its climatic impact are based on meritless conjectures."

 The main argument of the paper appears to be that the temperature difference of 33 degrees C between the measured surface temperature and that of a hypothetical earth without an atmosphere modelled as a blackbody in equilibrium with the incoming solar radiation, lacks rationale and that therefore any explanation of this temperature difference, for example as a result of greenhouse gases, also lacks rationale. 

The very definition of the greenhouse effect seems to be elusive. There can be no doubt that the canonical version not only attempts to explain why the surface temperature is higher than the hypothetical equilibrium temperature but also why the temperature at higher altitudes, for example at the tropopause, is lower.

On Wikipedia you can find the following information on Prof. Kramm

"Since 2003 Kramm has served as an associate faculty at the College of Natural Science and Mathematics, UAF, where he has taught atmospheric dynamics, atmospheric radiation, physics of the atmospheric boundary layer, and turbulence."

Given this I thought it would be interesting to ask the following questions to Prof. Kramm:

1. Where is the TOA ("Top of the Atmosphere") and why is it situated where it is?

2. Is the difference in average temperature between the surface and the tropopause fictitious, and if not, what is the reason for its existence?

3. To your knowledge, does there exist any "sophisticated radiative transfer model" moving beyond the simple formulas that you can find in for example Goody and Yung chapter 9, and in that case where can I find it?