Discussion > An experimental demo of GHE.
RKS,
Re. your experiment - what colour would you piant the walls? Or would mirrors be better?
Roger Longstaff
The logarithmic effect of CO2 seems to be taken as read in many articles - e.g
http://wattsupwiththat.com/2010/03/08/the-logarithmic-effect-of-carbon-dioxide/
http://joannenova.com.au/2010/02/4-carbon-dioxide-is-already-absorbing-almost-all-it-can/
seems to based on a 2009 paper by Lindzen & Choi
As I have said before I am often surprised that many who are in the Slayers camp (or at least in disagreement with the settled science) are either practical engineers - and/or from the field of spectroscopy like Mike Hammer -
http://jennifermarohasy.com/2009/03/radical-new-hypothesis-on-the-effect-of-greenhouse-gases/?cp=11
An interesting read
Retired Dave
Dung et al,
the logarithmic (log 2 at least) effect of CO2 is already taken into account by expressing the sensitivity in terms of 'as doubling of'
So e.g. if the sensitivity is 2C per doubling.....
To get 2C warming effect we have to double the CO2, e.g. from 300ppm to 600ppm
To get a further 2C warming, we have to double again, from 600ppm to 1200ppm
To get a further 2C warming, we have to double again, from 1200ppm to 2400ppm
This is exactly the same as saying that you get less temp increase for the same amount of CO2 the farther you go on - which is the logarithmic effect I think you are referring to.
TheBigYinJames
TBYJ: I think we all know that's how sensitivity is expressed and defined. The question Dung asked, surely, and that Martin A answered, on behalf of the mainstream view, in a rather surprising way (I thought), is how we know that the relationship really is logarithmic. I'd like to understand more too. On which, the end of Where's my best evidence? last July may help us identify the SoD thread Martin was referring to.
Richard Drake
RKS,
Re. your experiment - what colour would you piant the walls? Or would mirrors be better?
Jan 6, 2013 at 11:22 AM | Roger Longstaff>>>>
A tricky one!
I think black walls would absorb any CO2 generated sideways radiation with any heat generated being removed by convection - seems the least worst option. There is of coarse the problem that any heat generated at floor level would be rapidly removed by convection but that, of course, simply mimics the real world and it is paramount that the source lamp simulates realistic levels of insolation as closely as possible. We are simply trying to simulate the EFFECT and perhaps cannot expect to achieve results accurate enough to fully describe the real world, though who knows what a bit of tweaking might achieve.
RKS
lso with a spinning globe with heating to one side - the mean temperature would be the same at whatever rate of rotation. Slow it down, the hot side gets hotter - the dark side gets colder, speed it up, the hot side gets less hot - the dark side gets less cold - the mean temperature remains the same. again, why would it not?Interesting discussion!
Jan 6, 2013 at 9:33 AM | Registered RKS
...why would it not?
Here's my take on why it would not.
If the rotation is slower, the temperature rises to higher values (as you point out). Since radiation is proportional to T^4, the energy re-radiated to space is more than proportional to the increase in temperature. So, with higher peak temperatuures, the total energy radiated to space will be greater.
So, since more energy is being discarded, the mean heat in the surface will be less and the mean temperature will be lower.
Does that make sense?
Martin A
Here's something interesting. I was intrigued by the N&Z approach of computing the average temperature by carrying out a double integration over a spherical surface and wanted to examine their results. First I took the standard approach and calculated the incoming solar power to Earth (W) as pi * R^2 * (1-alpha) x 1366. I don't think there is anything controversial in this. I then used the S-B relationship to estimate the total radiated power as 4 * pi * R^2 * sigma * T^4 . Equating these two equations I find the grey body temperature to be 254K. This isn't far from the temperature quoted in many texts. I'm not surprised by this as the method I've used is the same as that used by others.
As pointed out by N&Z, Roger Longstaff, SKS and others here one shouldn't use the standard form of the S-B equation. Doing so implies that the surface temperature is equal everywhere on the planetary body. It isn't and so it's necessary to account for the variation in surface temperature and radiated power by considering the variation in incoming and outgoing power dependent on latitude. This can be done analytically as suggested by N&Z.
I took a somewhat ad-hoc numerical approach and calculated the average incoming power over a daily cycle and subsequent surface temperature for each 1 degree of latitude. I multiplied this temperature by the area associated with each 1 degree of latitude to give a temperature x area for each 1 degree latitudinal band between 0 and 90 degrees. Finally I divided this by the total area of the hemisphere.
Doing this I find the average temperature to be 252K. i.e it is remarkably close to the temperature calculated using the standard approach.
I haven't got time to check my estimate or to check the integration carried out by N&Z so don't know where the discrepancy lies. I'm not surprised that my two estimates are close. The very low S-B temperatures are only recorded for high latitude areas (>65 degrees). These account for only a relatively small fraction of the total spherical area, say some 6 to 7%.
I'd be very happy for someone else to cross check this observation either by repeating my numerical approach, or by carrying out the analytical integration.
Paul Dennis
I had a good sleep last night (thanks to some sherry!) and I'm feeling much more genial about the N&Z paper today, and I've had a few more thoughts on it.
Firstly the spherical integration mistake they found in the IPCC, while interesting and important in its own right, isn't really connected with the rest of their argument, as far as I can see... except in the general logical fallacy that if they can get that wrong, what's to say the rest of it is right? The IPCC isn't science, it's a politicised snapshot of the science, and I think the common ground amongst most skeptics is that it's junk to a greater or lesser extent, and I'm not at all surprised it's riddled with mistakes such as this. But you can't extrapolate from that to the real science going on underneath, as tempting as it is to do so.
Now onto the N&Z ideas:
1. GHE posits that a 'delay' in outgoing energy due to the emission and absorption or IR in LW bands - GHE posits this is the dominant delaying mechanism, and therefore depends on the composition of the atmosphere, since only GHGs can make this happen.
2. N&Z's ATE posits that the delay in outgoing energy is dominated by thermal kinetic collisions, and that increased pressure (and the resultant geometric closeness) caused by gravity makes kinetic collision the dominant delaying mechanism, and therefore does not depend on the composition of the atmosphere, just the pressure.
So I need to go back to one of rhoda's questions from away back in this thread..... when a solid sphere with a gaseous atmosphere is deciding how to get rid of the heat... in what ratio does it use IR emission against kinetic convection to move heat from the surface into the air? It seems this question (which I brushed over at the time) might be very important in answering this question.
Imagine a molecule in a rock on the surface vibrating at a rate in line with its temperature. How do we work out if it simply bashes a nearby air molecule and transfers kinetic energy to that, or decides to emit a photon? Bear in mind that it can be any air molecule, including all the more numerous N2 and O2 molecules.
My take on this is that it's likely to be a ratio, not one or the other. GH theory already allows for some of the energy to be done this way, N&Z seems to posit that ALL of it does.
Rather than trying to prove GHE, which requires large atmospheres, surely there's a small experiment we could do to prove or disprove the N&Z offering?
TheBigYinJames
is how we know that the relationship really is logarithmic. I'd like to understand more too. On which, the end of Where's my best evidence? last July may help us identify the SoD thread Martin was referring to.
Jan 6, 2013 at 12:00 PM Richard Drake
I'll try to track it down when I'm back home next week.
Martin A
If the rotation is slower, the temperature rises to higher values (as you point out). Since radiation is proportional to T^4, the energy re-radiated to space is more than proportional to the increase in temperature. So, with higher peak temperatuures, the total energy radiated to space will be greater.
So, since more energy is being discarded, the mean heat in the surface will be less and the mean temperature will be lower.
Does that make sense?
Jan 6, 2013 at 12:11 PM | Martin A>>>>
That does seem to make sense although I'm sure I've seen an explanation somewhere that explains things differently.
Interesting!
RKS
If the rotation is slower, the temperature rises to higher values (as you point out). Since radiation is proportional to T^4, the energy re-radiated to space is more than proportional to the increase in temperature. So, with higher peak temperatuures, the total energy radiated to space will be greater.
So, since more energy is being discarded, the mean heat in the surface will be less and the mean temperature will be lower.
Does that make sense?
Jan 6, 2013 at 12:11 PM | Martin A>>>>
That does seem to make sense although I'm sure I've seen an explanation somewhere that explains things differently.
Interesting!
Jan 6, 2013 at 12:52 PM | RKS >>>>>
I've found where I saw that alternative explanation, it was on the N&Z Q&A part 1, and don't forget Ned Nikolov is a PhD physicist. It goes as follows:-
"Adding axial rotation to a stationary planet residing in a vacuum, where there is no friction with the external environment does not provide any additional heat energy to the planet surface. Faster rotation and/or higher thermal inertia of the ground would only facilitate a more efficient spatial distribution of the absorbed solar energy, thus increasing the uniformity of the resulting temperature field across the planet surface, but could not affect the average surface temperature."
I've emailed him to make your point, as it's got me thinking as well, but I know he's busy at the moment.
RKS
Jan 6, 2013 at 12:29 PM | Paul Dennis:
Paul,
I checked the N&Z analytical integration about a year ago, with the help of a mathematician. We concluded that their maths was correct. There was also a big row on WUWT that also led to the same conclusion, if I recall correctly.
However, as you say, your numerical integtration should match their resuslt, and the discrepency you note is interesting. I agree that someone should make an independent calculation, but please inform us if you discover the cause of the discrepency.
Roger Longstaff
2. N&Z's ATE posits that the delay in outgoing energy is dominated by thermal kinetic collisions, and that increased pressure (and the resultant geometric closeness) caused by gravity makes kinetic collision the dominant delaying mechanism, and therefore does not depend on the composition of the atmosphere, just the pressure....
Jan 6, 2013 at 12:32 PM | TheBigYinJames>>>
I'm afraid I saw nothing in their theory where N&Z's ATE posits that the delay in outgoing energy is dominated by thermal kinetic collisions, and that increased pressure (and the resultant geometric closeness) caused by gravity makes kinetic collision the dominant delaying mechanism, and therefore does not depend on the composition of the atmosphere, just the pressure. Have you perhaps misquoted or misunderstood?
In fact they do not, from what I have read, mention that ATE causes a delay in outgoing energy at all.
ATE behaves as following:-
The atmosphere does NOT produce warming from static pressure.
It will only produce warming when irradiated by an energy source. No energy source and the atmospheric molecules will freeze to the surface.
Gravity places most molecules and maximum density at the surface. Incoming solar energy gets more molecules to interact with for each unit of volume at the surface where that density is higher.
The more molecules per unit volume the higher the temperature and the less molecules per unit volume the lower the temperature.
Thus there is a temperature gradient from surface upward which is entirely a result of the density gradient but only for so long as energy is being supplied.
That is what the Ideal Gas Law defines and quantifies and it provides a specific rate of temperature decline with height that is dependent on pressure and insolation alone for any planet with a given strength of gravitational field.
The Greenhouse Effect according to the Gas Laws is a consequence of pressure and insolation alone. The maximum temperature occurs at the surface with no need for downward IR from GHGs up in the atmosphere. There is an energy exchange between the surface and the molecules at or just above the surface and that includes some downward IR from air to surface. That is backradiation in a limited sense but it is not what AGW proponents mean by it.
The Ideal Gas Law provides the relevant equations via PV=nRT without any need to include a term for radiation at all. If radiation were relevant then the absence of a term for it would render the Ideal Gas Law invalid.
The upshot is that surface temperature for a planet with a gravitational field is derived from insolation and atmospheric mass alone.It is the mass of the entire atmosphere, not just GHGs, which gives the pressure and molecular density at the surface to fix the surface temperature at a given level of solar input.
GHGs can affect the amount of energy whizzing about in the air but not the surface temperature.The expansion of the atmosphere from more GHGs reduces molecular density at the surface without changing surface pressure so there are less molecules per unit of volume at the surface to interact with insolation hence a cooling of the surface exactly proportionate to the warming of the air.
Furthermore the system response is instant. More energy in the atmosphere causes immediate expansion.
The effect of more energy in the air from GHGs (when there is no change in pressure or insolation) is simply an increase in the volume of the atmosphere with no change in surface temperature but instead an air circulation change. That circulation change alters the rate at which energy is transferred to space so that the slowing down effect of energy transfer by GHGs is negated by a faster rate of energy transfer from the expanded atmosphere.
That's how I've read the Ideal Gas Law, including quotations from Stephen Wilde, Fellow of the Meteorological Society, with regard to planetary atmospheres - not just from N&Z as their work, though well advanced, is not unique among those not indoctrinated in radiative physics.
RKS
Logarithmic formulas...
.... The question Dung asked, surely, and that Martin A answered, on behalf of the mainstream view, in a rather surprising way (I thought), is how we know that the relationship really is logarithmic. I'd like to understand more too. On which, the end of Where's my best evidence? last July may help us identify the SoD thread Martin was referring to.
Jan 6, 2013 at 12:00 PM Richard Drake
OK, I found it. I posted the following on SOD:
http://scienceofdoom.com/2011/09/02/radiative-forcing-and-the-surface-energy-balance/
I posted:
___________________________________________________________________________________
on April 22, 2012 at 5:23 pm | Reply Martin A
(...)
Please excuse my asking a question whose answer may will already be available on your site.
Wikipaedia gives a formula that I have often seen referred to for the forcing due to CO2 (said to be a 1st order approximation):
Delta F = 5.53 ln ( C / C0 ) W m^-2
It gives a reference [Myhre et al., New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters, Vol 25, No. 14, pp 2715–2718, 1998] which is inaccessible to me – I have no library access and no budget to access paywalled papers.
I remember that this formula is quoted by IPCC, who give the same reference.
My question: Is the derivation of this formula available on Science of Doom, or elsewhere online? I am interesting to know the method used to derive it and what assumptions and approximations were used in its derivation.
Thank you for any help.
________________________________________________________________________________
Science of Doom replied:
_______________________________________________________________________________
scienceofdoom
Martin A,
The most important point about this formula is it is calculated as a curve fit to a number of points on a graph. So don’t think of it as a derivation, more a “handy ready reckoner”.
More discussion about it in CO2 – An Insignificant Trace Gas? Part Seven – The Boring Numbers.
Each point on the graph was calculated from solving the radiative transfer equations through the atmosphere. These equations can only be solved via numerical methods – no analytical solution can be derived.
You can see the radiative transfer equations and their derivation from first principles in Understanding Atmospheric Radiation and the “Greenhouse” Effect – Part Six – The Equations.
These two posts should get you started. Feel free to ask further questions if these still leave unanswered questions.
_________________________________________________________________________________
A bit later, someone posted a link to the relevant paper:
http://folk.uio.no/gunnarmy/paper/myhre_grl98.pdf
Martin A
A bit later, someone posted a link to the relevant paper:
http://folk.uio.no/gunnarmy/paper/myhre_grl98.pdf
Jan 6, 2013 at 3:00 PM | Martin A>>>>
It's a bit difficult to read on my screen but the axes for CO2 on page 2717 don't seem logarithmic to me.
A delta from 400 to 800 ppmv seem to give approx a range of 2 to 5 Wm^2.
RKS
I like the RKS experiment (but I think that the walls should be mirrors, bearing in mind that they are heavily insulated). Apart from the chamber being heavily instrumented, we would need to monitor the power consumption of the refrigeration unit.
As the UK has spent billions on CAGW mitigation, and plans to spend hundreds of billions more, I'm sure that a reputable university (not UEA!) would be willing to spend £100k to £200k to set this up. Rhoda - this is the original point of your thread - what do you think?
And then we could all place our bets.
Roger Longstaff
Jan 6, 2013 at 3:15 PM RKS
I was just giving the reference that, by IPCC and elsswhere, has been quoted as the source of the "logarithmic" relation. I don't hold any brief for the content of the paper.
I must say I was disappointed. I had assumed there was some kind of model whose analytic solution took the logarithmic form, rather than it coming from a fitting to the results from numerical solutions.
I'd wondered if you looked at the assumptions used in making such a model, you could work out the limits on the applicability of the formula. But if you fit a curve to some numerically generated points, it normally makes no sense to extrapolate outside the range of the points,
Martin A
Jan 6, 2013 at 3:15 PM RKS
I was just giving the reference that, by IPCC and elsswhere, has been quoted as the source of the "logarithmic" relation. I don't hold any brief for the content of the paper.
I must say I was disappointed. I had assumed there was some kind of model whose analytic solution took the logarithmic form, rather than it coming from a fitting to the results from numerical solutions.
I'd wondered if you looked at the assumptions used in making such a model, you could work out the limits on the applicability of the formula. But if you fit a curve to some numerically generated points, it normally makes no sense to extrapolate outside the range of the points,
Jan 6, 2013 at 3:53 PM | Martin A>>>>>
I wasn't criticising, merely making an observation.
It looks as if we've been misinformed regarding the logarithmic forcing attributed to CO2. As with the untraceable source of folklore that a doubling of CO2 causes a 2K rise in atmospheric temperature, we seem to have another 'well known' property that came from an unknown source.
RKS
RKS
Thanks for trying to explain N&Z, but I think I have a better handle on it that you think:
Gravity places most molecules and maximum density at the surface. Incoming solar energy gets more molecules to interact with for each unit of volume at the surface where that density is higher.
Incoming solar energy cannot interact with the majority of air molecules, no matter how dense (up to a point), because diatomics do not absorb those wavelengths. If you are discounting radiative warming, then it has to be convection/kinetic exchange from the ground providing that increased interaction, and increased pressure near the surface would enhance this effect.
So how I stated the ATE effect follows in terms if enhanced convection is absolutely correct, since enhanced convection due to increased pressure is the ONLY mechanism allowing the better-than-adiabatic lapse rate described by ATE. How you try to refute it here is confusing (and wrong) Go and ask N&Z yourself.
Alternatively points 4 and 5 on the section "Can Earth warmth be due to atmospheric pressure? "Facepalm" moment of truth" on this page may convince you.
http://climatewiki.org.uk/Nexus:Unified_Theory_of_Climate_(Primer)
TheBigYinJames
It looks as if we've been misinformed regarding the logarithmic forcing attributed to CO2. As with the untraceable source of folklore that a doubling of CO2 causes a 2K rise in atmospheric temperature, we seem to have another 'well known' property that came from an unknown source.
Jan 6, 2013 at 4:07 PM RKS
Yes.
In science generally, but particularly with "climate science", it can be enlightening to try to track things back to their origin.
Martin A
RKS
The expansion of the atmosphere from more GHGs reduces molecular density at the surface without changing surface pressure so there are less molecules
Unfortunately the 'expansion' of the atmosphere (unproven) by addition of 100 parts per million CO2 (remember, we've removed O2 from the atmosphere during combustion, so it's not all 'extra') is nowhere near enough of an effect at ground level to counter the absorption effects of CO2.
I have a little more respect for N&Z because I now understand their argument, both in terms of increased convection dominating photon exchange at the surface, and also as asymmetric heat path length (or flux delay, the term which confused you). RKS, I would recommend that before you try to talk down to someone who actually does have a grasp of mathematics and physics, you would get your muddled ducks in a row.
TheBigYinJames
BigYin,
Please, no insults here. RKS understood the message of N&Z before you did, when it was heresy. We are all struggling to find the truth!
Let's not turn this into a battle of egos, as happened on WUWT, lest the truth be obscured.
Roger Longstaff
Yes apologies for the tone. My excuse is that it gets tiresome when I was trying to be generous to N&Z by trying to consider its merits as a competing theory with GHE, to be contradicted by an explanation which neither describes physical reality NOR the actual N&Z paper itself.
N&Z might be onto something, as I said after my first reading of it, some of it is beyond me and I'm happy to put it on the 'maybe' pile until it's either refuted or not. Incorrect explanations like those given above do nothing but obscure whatever merit it may have. With the greatest respect, when RKS explains it in those terms, it makes me doubt both his understanding of it, and the fervour with which is is being touted as a new reality.
TheBigYinJames
So how I stated the ATE effect follows in terms if enhanced convection is absolutely correct, since enhanced convection due to increased pressure is the ONLY mechanism allowing the better-than-adiabatic lapse rate described by ATE. How you try to refute it here is confusing (and wrong) Go and ask N&Z yourself.
Alternatively points 4 and 5 on the section "Can Earth warmth be due to atmospheric pressure? "Facepalm" moment of truth" on this page may convince you.
http://climatewiki.org.uk/Nexus:Unified_Theory_of_Climate_(Primer)
Jan 6, 2013 at 4:24 PM | TheBigYinJames>>>
I'm sorry but N&Z most definitely state that lower tropospheric temperature is a product of atmospheric pressure and SOLAR IRRADIANCE modified by Near-surface Atmospheric Thermal Enhancement (ATE) defined as a non-dimensional ratio (NTE) of the planet actual mean surface air temperature (Ts, K) to the average temperature of a Standard Planetary Gray Body (SPGB) with no atmosphere (Tgb , K) receiving the same solar irradiance, i.e. NTE = Ts /Tgb [Para 3 of the UTC document]
You say insolation cannot interact with the majority of the air molecules - N&Z, after years of refining their theory, say that it does.
I have not misread - you have ascribed words to the theory that were not there.
You may disagree with these two PhD,s after a short look at their work and that's fine, but I'm just the messenger here and have so far found no fault with their logic.
Again from their paper:-
"Equations (5) and (6) imply that pressure directly controls the kinetic energy and temperature of the
atmosphere. Under equal solar INSOLATION [my caps], a higher surface pressure (due to a larger atmospheric mass) would produce a warmer troposphere, while a lower pressure would result in a cooler troposphere. At the limit, a zero pressure (due to the complete absence of an atmosphere) would yield the planet’s graybody temperature."
Again - temperature is a product of pressure and insolation - it can't be clearer than what is written on the page.
I really shouldn't need to quote from a paper you claim to have read and comprehended so often so I'll cease further discussion at this point.
No animosity, I just don't see us meeting on common ground on this subject.
Regards,
RKS
An interesting and informative comment about the Ideal Gas Law by Stephen Wilde:-
"The role of the IGL in fixing surface temperature for a planet with an atmosphere is settled science predating your radiative theory.
The S-B Law is neither contradicted nor denied. The IGL simply deals with a situation that the S-B Law was never designed to deal with. It is supplementary to the S-B Law for application only where there is an atmosphere."