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The Greenhouse Effect - A Few Cracked Panes
#1
Although the cornerstone of the "greenhouse effect" is so-called "back-radiation" from "greenhouse gases" in the atmosphere, the foundation stone is the Stefan-Boltzmann law. The reason for all the quotation marks in the sentence is because without a correct application of the law, all those principles are without basis, and so are worthless.

From: Earth’s Annual Global Mean Energy Budget, J. T. Kiehl and Kevin E. Trenberth, February 1997, Bulletin of the American Meteorological Society 78, 197-208 (http://www.geo.utexas.edu/courses/387h/PAPERS/kiehl.pdf)

"For the outgoing fluxes, the surface infrared radiation of 390 W sq.m corresponds to a blackbody emission at 15°C"

At face value, this looks fine, except it assumes an ideal radiator, and radiation into surroundings at absolute zero (-273°C). The Stefan-Boltzmann law defines the radiation of a body as proportional to the 4th. power of the absolute temperature, multiplied by the emissivity (1 for an ideal radiator) for radiation into a vacuum. (see http://hyperphysics.phy-astr.gsu.edu/hba...tefan.html) However, the earth's surface is not radiating into a vacuum, but into the atmosphere. For radiation into surroundings above absolute zero, the radiation is proportional to the absolute difference between the fourth powers of the two temperatures. This implies that if the temperature difference is zero or negative, there is no outgoing radiation. This is not surprising; a cooler body cannot heat a hotter body, neither can two bodies at the same temperature exchange heat or infrared radiation. These effects would violate the Second Law of Thermodynamics. The linked page has a calculator; emitter and surroundings temperatures and emissivity can be input to calculate radiation in Watts per sq.metre if the area of the emitter is set to 1. Given a surface temperature of 15°C with emissivity .9 and an atmosphere at 10°C, the surface would emit 23.79 W sq.m. This is far from the figures quoted on the "energy balance" diagrams of 390 or 396 W sq.m. In any case, the cooler atmosphere can't possibly heat the hotter surface.The Stefan-Boltzmann law doesn't allow radiative flux in the "negative" direction. A straight calculation using the emitter/surroundings temperatures gives a negative result!

Kiehl and Trenberth (and others) back-calculate the temperature of the top-of-atmosphere (TOA) from the measured (by satellite) outgoing infrared radiation of 235 W sq.m as -19°C, assuming an ideal emissivity of 1. They then conclude that the surface would emit the same without an atmosphere despite the surface having a smaller area, and neither surface nor atmosphere having the ideal emissivity (likely to be more like 0.9 for land/water), and even then, not identical emissivities. The TOA isn't even a surface, but a layer. I can find no quoted figure for the emissivity at TOA, so I have no idea what the correctly calculated temperature at TOA might be. The assumed surface temperature of -19°C "without greenhouse effect" has to be wrong in any case. The Ideal Gas Law can be used to calculate the air temperature at the surface, assuming a nitrogen/oxygen/water-vapour atmosphere at a pressure of 1 bar. This gives about 15°C with no requirement for any input from the sun. A calculation for the atmosphere of Venus (surface pressure 93 bar) gives a result close to the observed surface temperature. The difference can be explained by the unique atmospheric conditions on the planet; there is no need for any "greenhouse" effect calculations. Indeed, with an atmosphere similar to that on Earth, the calculated temperature is around 200°C hotter.

The "greenhouse effect" is a failed hypothesis; if its proponents employed real physics instead of misapplied laws and bad assumptions it would fall apart. The panes of the greenhouse are cracked; those that aren't cracked are missing.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
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#2
Were is the top-of-atmosphere (TOA) located?

Is it the Stratosphere or Mesosphere or ?????

The chart here shows the layers of the atmosphere

[Image: atmslayers.gif]

From PhysicalGeography.net
It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952
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#3
From My NASA Data Glossary (Other good defs there):

top of atmosphere:
a given altitude where air becomes so thin that atmospheric pressure or mass becomes negligible. TOA is mainly used to help mathematically quantify Earth science parameters because it serves as an upper limit on where physical and chemical interactions may occur with molecules in the atmosphere. The actual altitude used for calculations varies depending on what parameter or specification is being analyzed. For example, in radiation budget, TOA is considered 20 km because above that altitude the optical mass of the atmosphere is negligible. For spacecraft re-entry, TOA is rather arbitrarily defined as 400,000 ft (about 120 km). This is where the drag of the atmosphere starts to become really noticeable. In meteorology, a pressure of 0.1 mb is used to define this location. The actual altitude where this pressure occurs varies depending on solar activity and other factors
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
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#4
Quote:Kiehl and Trenberth (and others) back-calculate the temperature of the top-of-atmosphere (TOA) from the measured (by satellite) outgoing infrared radiation of 235 W sq.m as -19°C, assuming an ideal emissivity of 1. They then conclude that the surface would emit the same without an atmosphere despite the surface having a smaller area, and neither surface nor atmosphere having the ideal emissivity (likely to be more like 0.9 for land/water), and even then, not identical emissivities.

Where is THEIR TOA?
It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952
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#5
(06-25-2010, 04:40 PM)MostlyHarmless Wrote: The "greenhouse effect" is a failed hypothesis;
if its proponents employed real physics instead of misapplied laws and bad assumptions it would fall apart.

The panes of the greenhouse are cracked;
those that aren't cracked are missing.

Here, here, the hypothesis has failed, it has already fallen apart,
"greenhouse proponents" merely ignore or dismiss the facts.
Alan Siddons et al "Moon" paper is the final nail in the coffin for the greenhouse effect "theory".

I wholeheartedly agree the panes are cracked (shattered really), or missing,
but the IPCC et al have attempted again and again (never convincingly) to glue or sticky tape them back together.
Their "greenhouse gases effect" is now obviously snake oil salesmen territory.
ie, it is plainly a scam, it is not what we observe, IT IS NOT SCIENCE.

More importantly and relevantly to our everyday lives, it is NOT a basis or information, or projections, but more realistically a dogma,
to base good political policies upon.
There is no doubt at all that we will all be harmed by the continuing blind adherence to
the so called "greenhouse gas effect" failed hypothesis that has now (undeniably) become a dogma.
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
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#6
(06-25-2010, 06:58 PM)Sunsettommy Wrote:
Quote:Kiehl and Trenberth (and others) back-calculate the temperature of the top-of-atmosphere (TOA) from the measured (by satellite) outgoing infrared radiation of 235 W sq.m as -19°C, assuming an ideal emissivity of 1. They then conclude that the surface would emit the same without an atmosphere despite the surface having a smaller area, and neither surface nor atmosphere having the ideal emissivity (likely to be more like 0.9 for land/water), and even then, not identical emissivities.

Where is THEIR TOA?

The definition I gave is all I have - the climatologists use the term so frequently none seems to take the trouble to define it. This would tend to confirm they are writing for the "club" - outsiders need not apply.
(06-26-2010, 12:18 AM)Derek Wrote: Here, here, the hypothesis has failed, it has already fallen apart,
"greenhouse proponents" merely ignore or dismiss the facts.
Alan Siddons et al "Moon" paper is the final nail in the coffin for the greenhouse effect "theory".

I wholeheartedly agree the panes are cracked (shattered really), or missing, but the IPCC et al have attempted again and again (never convincingly) to glue or sticky tape them back together.
Their "greenhouse gases effect" is now obviously snake oil salesmen territory.
ie, it is plainly a scam, it is not what we observe, IT IS NOT SCIENCE.

I've just put the latest "energy "budget" figure through the correct version of the Stefan-Boltzmann law. An outgoing radiation of 396 W sq.m from the surface into an atmosphere at 10°C gives a surface temperature of a tad under 72°C. The "greenhouse effect" should be renamed the "pressure cooker" effect.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
Reply
#7
(06-26-2010, 01:04 AM)MostlyHarmless Wrote: I've just put the latest "energy "budget" figure through the correct version of the Stefan-Boltzmann law.
An outgoing radiation of 396 W sq.m from the surface into an atmosphere at 10°C gives a surface temperature of a tad under 72°C.
The "greenhouse effect" should be renamed the "pressure cooker" effect.

Big Grin Thank you MostlyHarmless. I remember listening to Dr. Miskolczi some time ago now,
stating that AGW relies upon a surface / air temperature discontinuity.
But, I did not think it was that BIG, from memory I think Dr Miskolczi suggested it was 7 degrees (my memory now says he suggested 6 to 7C).
Which I find strangely "coincidental"..."Spinach" springs to mind...
Don't rock the boat too much perhaps - especially when trying to put forward a new version of the "same old"...

My apologies to you, in that my maths and computing skills are not upto standard,
but I think we are still at the basics / brain storming stages anyways in all things greenhouse / climate related.
Idea - Is there any way a It's the "regolith" wot does it (Land and Oceans) budget could be put together. ?
Surely any "regolith" effects should be accounted for first, and what is left, is then maybe an atmospheric greenhouse effect,
if indeed such a thing exists in the first place.

I've never got past, nor has anyone ever really attempted to answer the question of the "speed" of the greenhouse effect,
given that photons move at the speed of light in an atmosphere that is a few tens of miles thick at most...No time at all really.
Specifically I am thinking along the lines of the "Moon" paper mentioned above, and my plot from a few years ago now,
land and sea are both powerful, and slow enough for a "regolith effect", photons simply are too damned fast.
Remembering as well that O2 and N2 are the real insulators in the atmosphere.
ie,
[Image: Dailywaterjacketsized.jpg]
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
Reply
#8
Quote:The definition I gave is all I have - the climatologists use the term so frequently none seems to take the trouble to define it. This would tend to confirm they are writing for the "club" - outsiders need not apply.

Maybe they did define it in their paper,but I doubt it.

If this is correct then they are sloppy about it,because that means the math conclusions are too variable given that they are not clear on the actual altitude they are supposed to measure against.

The chart I posted seems to show that gaining altitude,it cools rapidly to reach the -60c level.That alone suggest that CO2 is doing little or none to keep the Troposphere warm.The WEIGHT of the atmosphere would be a better cause for the surface to be warm than a smattering of a trace CO2 molecule lurking around.
It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952
Reply
#9
The chart you posted SST is of some interest, and not a little concern.
1) I would of expected more upper troposphere warming (but it is not shown) due to cloud absorbtion of incoming sunlight, and
the relase of latent heat by condensing water vapour.
2) There may be an upper warming shell above this layer as well due to dust, and / or (so called) GHGs absorbing OLR,
but this appears to be "swamped" or not shown by the below given explanation". ?
3) Then I would of thought temperatures would of dropped sharply, but this again appears to be not the case the way the plots are plotted. ?
"Space" is surely not 2000 degrees celcius......as the below seems to imply.

As I see the chart there are two phases of warming in a cooling with hieght atmosphere.
(I agree there may well be two warming "shells", but to me their location seems wrong.
The amounts seem intuitively wrong as well, the lower one reduced, and the upper one over emphasized (and extended).)
The upper one in particular is "peculiar"..
http://www.theozonehole.com/atmosphere.htm
Excerpt,
Thermosphere
The Thermosphere extends from the mesopause to 430 miles (690 km) above the earth.
This layer is known as the upper atmosphere.

The gases of the thermosphere are increasingly thinner than in the mesosphere.
As such, only the higher energy ultraviolet and x-ray radiation from the sun is absorbed.
But because of this absorption, the temperature increases with height and
can reach as high as 3,600°F (2000°C) near the top of this layer.

However, despite the high temperature, this layer of the atmosphere would
still feel very cold to our skin because of the extremely thin air.
The total amount of energy from the very few molecules in this layer is not sufficient enough to heat our skin.


I am beginning to wonder what these atmospheric temperature profiles actually show. ???
It seems a contrived or distorted picture. The phrase "normalised" appears to be applied to the plots,
would "real" be better......But maybe that's a different picture.
ie,
the temperature increases with height and can reach as high as 3,600°F (2000°C) near the top of this layer.
As civil a response as I can muster to the above is,
"pull the other one, it's got bells on"........
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
Reply
#10
(06-26-2010, 05:03 AM)Sunsettommy Wrote:
Quote:The definition I gave is all I have - the climatologists use the term so frequently none seems to take the trouble to define it. This would tend to confirm they are writing for the "club" - outsiders need not apply.

Maybe they did define it in their paper,but I doubt it.
They didn't, and I was referring to the extensive Googling I've done to
try to establish the precise definition of TOA.

Quote:If this is correct then they are sloppy about it,because that means the math conclusions are too variable given that they are not clear on the actual altitude they are supposed to measure against.
Not really, they're calculating the effective temperature from outgiong (OLR) radiation. The error they make is in assuming that the effective temperature is the actual temperature. the few graphs I've seen of the spectrum of the OLR suggest that their calculation is flawed. Stefan-Boltzmann assumes that the radiation is "full-spectrum" (in LW infrared of course). If it isn't, and it appears it isn't, then it would take a pretty good radiation physicist to make adjustments and recalculate the effective temp. These climatologists aren't physicists. I'm pretty sure they don't consult physicists - they certainly don't consult mathematicians and statisticians.

Quote:The chart I posted seems to show that gaining altitude,it cools rapidly to reach the -60c level.That alone suggest that CO2 is doing little or none to keep the Troposphere warm.The WEIGHT of the atmosphere would be a better cause for the surface to be warm than a smattering of a trace CO2 molecule lurking around.

The reason for the rapid cooling with altitude is mainly due to the Ideal Gas Law effect. Pressure reduces, and temperature goes down with it. Your "weight of the atmosphere" argument is exactly what I was talking about at the end of my original post. The fact that the temperature profile isn't a smooth curve beginning on the troposphere line and accelerating rapidly up to the top left hand corner shows there's a lot going on on up there. Incidentally,the profile of your graph has been used to confirm that the cooling of the surface is almost entirely by conduction/convection and not radiation, giving the lie to the radiation/greenhouse effect theory. A largely radiative transport system gives a dramatically different profile.
(06-26-2010, 01:37 AM)Derek Wrote:
(06-26-2010, 01:04 AM)MostlyHarmless Wrote: I've just put the latest "energy "budget" figure through the correct version of the Stefan-Boltzmann law.
An outgoing radiation of 396 W sq.m from the surface into an atmosphere at 10°C gives a surface temperature of a tad under 72°C.
The "greenhouse effect" should be renamed the "pressure cooker" effect.

Big Grin Thank you MostlyHarmless. I remember listening to Dr. Miskolczi some time ago now,
stating that AGW relies upon a surface / air temperature discontinuity.
But, I did not think it was that BIG, from memory I think Dr Miskolczi suggested it was 7 degrees (my memory now says he suggested 6 to 7C).
Which I find strangely "coincidental"..."Spinach" springs to mind...
Don't rock the boat too much perhaps - especially when trying to put forward a new version of the "same old"...

My apologies to you, in that my maths and computing skills are not upto standard,
but I think we are still at the basics / brain storming stages anyways in all things greenhouse / climate related.
Idea - Is there any way a It's the "regolith" wot does it (Land and Oceans) budget could be put together. ?
Surely any "regolith" effects should be accounted for first, and what is left, is then maybe an atmospheric greenhouse effect,
if indeed such a thing exists in the first place.

I've never got past, nor has anyone ever really attempted to answer the question of the "speed" of the greenhouse effect,
given that photons move at the speed of light in an atmosphere that is a few tens of miles thick at most...No time at all really.
Specifically I am thinking along the lines of the "Moon" paper mentioned above, and my plot from a few years ago now,
land and sea are both powerful, and slow enough for a "regolith effect", photons simply are too damned fast.
Remembering as well that O2 and N2 are the real insulators in the atmosphere.
WRT the temperature calculations, I had to make a few assumptions, for example a surface temp of 15°C and atmospheric temp of 10°C. Changing those assumptions changes the radiation flux, but not by much. For the surface to radiate 396 W/sq.m the surroundings have to be at absolute zero. I recommend having a look at Stefan-Boltzmann Law and playing with the calculator. I've checked the results - they're accurate. For Kiehl and Trenberth to use the "single temperature" form of the law is akin to a "schoolboy howler". It's so fundamental, no physicist would make such an error. If I thought there was any chance of getting it published, I'd write a letter to the Bulletin of the American Meteorological Society to point out the authors' error.

I've noted the arguments in the Re-Radiation thread. Siddons is attempting to illustrate in an empirical rather than purely scientific way what I've been talking about. Stefan-Boltzmann calculates the difference between the fluxes of bodies at different temperatures. The cooler body can't heat the hotter body, it just slows down its rate of cooling. A simple way to look at it is that energy from the hotter body has left that body - it therefore cools down. The smaller amount of energy from the cooler body cannot fully replace that lost energy; it just slows the rate of cooling.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
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#11
(06-26-2010, 02:09 PM)MostlyHarmless Wrote: WRT the temperature calculations, I had to make a few assumptions, for example a surface temp of 15°C and atmospheric temp of 10°C. Changing those assumptions changes the radiation flux, but not by much. For the surface to radiate 396 W/sq.m the surroundings have to be at absolute zero. I recommend having a look at Stefan-Boltzmann Law and playing with the calculator. I've checked the results - they're accurate. For Kiehl and Trenberth to use the "single temperature" form of the law is akin to a "schoolboy howler". It's so fundamental, no physicist would make such an error. If I thought there was any chance of getting it published, I'd write a letter to the Bulletin of the American Meteorological Society to point out the authors' error.

I've noted the arguments in the Re-Radiation thread. Siddons is attempting to illustrate in an empirical rather than purely scientific way what I've been talking about. Stefan-Boltzmann calculates the difference between the fluxes of bodies at different temperatures. The cooler body can't heat the hotter body, it just slows down its rate of cooling. A simple way to look at it is that energy from the hotter body has left that body - it therefore cools down. The smaller amount of energy from the cooler body cannot fully replace that lost energy; it just slows the rate of cooling.

Thanks for that hyperphysics link. Will try it out. I don't have the background to add to this discussion. I've tried to work things out for myself from very basic principles. See my posts here.

Given the importance of this subject and the length of time it has been circulating I am amazed at the lack of any tutorials of the physics of atmospheric radiation for the layman.
Environmentalism is based on lies and the lies reflect an agenda that regards humanity as the enemy of the Earth. - Alan Caruba
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#12
We are told CO2 absorbs at 2.7, 4.3 and 15 micrometers (µm).

If we assume a surface radiating at 15C, is it possible to calculate how much IR energy is absorbed by the CO2 from this link here?

I feel it should be possible to derive a figure for the "percentage" energy absorbed from any radiating surface by CO2. I also feel this should be a constant as long long as the CO2 remains above some minimum, say 100ppmv. (The same argument for H2O would vary with the humidity.)

I only have a vague idea of what I am attempting here so any advice, helpfull or not, is appreciated. Wink
Environmentalism is based on lies and the lies reflect an agenda that regards humanity as the enemy of the Earth. - Alan Caruba
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#13
(06-26-2010, 10:18 PM)Richard111 Wrote: Thanks for that hyperphysics link. Will try it out. I don't have the background to add to this discussion. I've tried to work things out for myself from very basic principles. See my posts here.
You don't need anything other than a sceptical, enquiring mind. Your empirical (first principles) approach is the right one. I'm not an expert - I've just got a basic grasp of the fundamental physics involved, though from what I've seen to date, it's a better grasp than many climate scientists have. Ask questions, comment if you need further explanation - if someone with a proposition can't clarify or explain some of the detail or defend their position from a position of knowledge (even limited) then they perhaps should have kept quiet.

I don't remember who said it, but it might even have been Rutherford (sounds like him, see my sig!) - "If you can't explain your science to a layman, you're working in the wrong field". I have an enormous respect for the great scientists of the past. Maybe Rutherford would have brought some commonsense and scepticism to the field of climate physics were he still with us (I'd have loved to have met him).
Quote:Given the importance of this subject and the length of time it has been circulating I am amazed at the lack of any tutorials of the physics of atmospheric radiation for the layman.
It doesn't surprise me. All the real climate scientists are just too busy working on the real science, and from what I've seen, enjoying doing it. Have you noticed what a dour lot the warmists are? Presumably they believe at least some of the crazy predictions based on their flawed models. Perhaps some of them realise they're working with a crock of whale poo, but just plod on producing the required results. They have to eat and they have to guarantee their grants won't dry up. There must be some basically sound tutorials, or simplified explanations out there, but they're swamped by warmist propaganda.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
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#14
(06-26-2010, 02:09 PM)MostlyHarmless Wrote: I've noted the arguments in the Re-Radiation thread. Siddons is attempting to illustrate in an empirical rather than purely scientific way what I've been talking about. Stefan-Boltzmann calculates the difference between the fluxes of bodies at different temperatures. The cooler body can't heat the hotter body, it just slows down its rate of cooling. A simple way to look at it is that energy from the hotter body has left that body - it therefore cools down. The smaller amount of energy from the cooler body cannot fully replace that lost energy; it just slows the rate of cooling.

Thanks again for your reply. In the above bolded excerpt I am also to the best of my understanding in the school of thought that says that a "cooler body can't heat the hotter body".
I have heard the below explanation on many occasions, and it does make some sense, or at least a way to view it.
" energy from the hotter body has left that body - it therefore cools down.
The smaller amount of energy from the cooler body cannot fully replace that lost energy; it just slows the rate of cooling.
"
Am I correct that this is a "all radiation is positive" view point.
I am definatey somewhat "fuzzy" on this, does it not seem more intuitively correct that
radiation is absorbed by an object relatively, and emitted by an object "positively".

I recall explanations by Nadif (at Jennifer Marohasy's blog I think) that radiation flows can be considered as effectively relative,
because the hotter sources radiation cancels out the lower sources radiation "in transit" between the objects.

I suppose the answer is simple really, does a hotter object cool at a different rate with the presnce of a cooler object as compared to the presence of no other object.
Such a simple experiiment, but I am not aware if it has been done.

Much like another simple set of experiments I have not heard of being undertaken, namely
the concentrating of radiation from a cold object to see if it makes a cold spot, or a hot spot ?
Conversely concentrating sunlight with a magnifying glass, is bound to make a hot spot, yes,
but hotter than the sun, I would of thought not.
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
Reply
#15
(06-27-2010, 02:02 AM)Derek Wrote: Thanks again for your reply. In the above bolded excerpt I am also to the best of my understanding in the school of thought that says that a "cooler body can't heat the hotter body".
I have heard the below explanation on many occasions, and it does make some sense, or at least a way to view it.
" energy from the hotter body has left that body - it therefore cools down.
The smaller amount of energy from the cooler body cannot fully replace that lost energy; it just slows the rate of cooling.
"
Am I correct that this is a "all radiation is positive" view point.
I am definatey somewhat "fuzzy" on this, does it not seem more intuitively correct that
radiation is absorbed by an object relatively, and emitted by an object "positively".

I recall explanations by Nadif (at Jennifer Marohasy's blog I think) that radiation flows can be considered as effectively relative,
because the hotter sources radiation cancels out the lower sources radiation "in transit" between the objects.
There's no "cancelling out" in the sense that two radiation flows partly destroy one another, it's just a mathematical concept. we're not talking about conduction here, but radiation flux, which is a vector, and thus has direction. Put simply, if there's a flux of 100 W/sq.m in one direction
towards a cooler body, and a flux from that body of 90 W/sq.m in the reverse direction, then there's a net flux of 10 (100-90) W/sq.m heating the cooler body. The flux to the hotter body simply slows down its rate of cooling. Both flows exist, but cannot be considered in isolation, as is done in the radiation budget diagrams. In those diagrams, you can see that the surface receives 161 W/sq.m from the sun, and loses 17 (thermals), 80 from evaporation, and therefore a net 63 to the atmosphere (1 absorbed). How then does the atmosphere, which absorbs 76 incoming solar, 80 from latent heat, 17 from thermals and 63 from the surface manage to re-radiate 333 back down? The outgoing radiation to space is shown as 238.5, which I accept (for now!)
Quote:I suppose the answer is simple really, does a hotter object cool at a different rate with the presence of a cooler object as compared to the presence of no other object.
Such a simple experiment, but I am not aware if it has been done.
Of course those experiments have been done, they were the basis for the Stefan-Boltzmann law among others.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
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#16
(06-27-2010, 02:02 AM)Derek Wrote: I suppose the answer is simple really, does a hotter object cool at a different rate with the presence of a cooler object as compared to the presence of no other object.
Such a simple experiment, but I am not aware if it has been done.
(06-27-2010, 03:40 AM)MostlyHarmless Wrote: Of course those experiments have been done, they were the basis for the Stefan-Boltzmann law among others.

Excellant, I have had this (or very similar) said / stated to me on many occasions, but without examples actually being given.

Please excuse my "persistence" but this is a major "sticking point" for me,
and I think it might help if I try to explain why.
Two objects, one hotter than the other. You use 100 and 90 so I will stick with these figures.
IF radiation is all positive, then if your previous description holds, in that,
energy from the hotter body (100) has left that body - it therefore cools down.
The smaller amount of energy from the cooler body (90) cannot fully replace that lost energy; it just slows the rate of cooling.

ie, -100 +90 = net -10
On it's own the hotter object would cool at a faster rate of -100 = net -100

Or,
IF radiation is relatively absorbed then the cooler recieved radiation by the hotter object will cool the hotter body faster.
ie, The surface of the object is 100 and it absorbs radiation at 90, so cooling it (not replacing lost energy) by a difference of -10.
This must be added to the -100, so the object cools at -100 and -10 = net -110.
On it's own the hotter object would cool relatively slower to the two object example.
ie, net -100

I realise mine is a "heat flow" point of view, as if mixing bodies of water at different temperatures,
or, an "electrical viewpoint", adding wires of the same voltage does not increase the voltage, it increases the amperage,
but in my everyday life these seem a more realistic view point.
Hence I ask (politely) for the experiments that show this view point (heat / water / electricity) is not correct for radiation.
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
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#17
Derek, I've been trying to find that out myself.

Have been using a different argument. Assume greenhouse gases absorb 50% of surface radiation, the argument is half will be radiated back to the surface, that is 25%. To me this means surface radiating efficiency has been reduced to 75%. No warming, just a slower rate of cooling. This is not a forcing in my mind.

To my thinking this means the level of "back radiation" drops off at twice the surface cooling rate.

Ah, well, all will come clear in due course.
Environmentalism is based on lies and the lies reflect an agenda that regards humanity as the enemy of the Earth. - Alan Caruba
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#18
So Richard111 am I to deduce from the above that you are also in the "all radiation is positive" school of thought.
That is not meant to be derogatory, it is simply a question.

However, if your answer is yes, can I also ask you if you know of an experiment that has been conducted (not merely thought through...)
that shows the heat / water / electricity point of view is not correct for radiation.
ie, radiation is actually absorbed relatively.
The whole aim of practical politics is to keep the populace alarmed
(and hence clamorous to be led to safety)
by menacing it with an endless series of hobgoblins, all of them imaginary.

H. L. Mencken.  

The hobgoblins have to be imaginary so that
"they" can offer their solutions, not THE solutions.
Reply
#19
(06-28-2010, 08:05 AM)Derek Wrote: Please excuse my "persistence" but this is a major "sticking point" for me,
and I think it might help if I try to explain why.
Two objects, one hotter than the other. You use 100 and 90 so I will stick with these figures.
IF radiation is all positive, then if your previous description holds, in that,
energy from the hotter body (100) has left that body - it therefore cools down.
The smaller amount of energy from the cooler body (90) cannot fully replace that lost energy; it just slows the rate of cooling.

ie, -100 +90 = net -10
On it's own the hotter object would cool at a faster rate of -100 = net -100
Yes -that's exactly it. SB defines net heatflow simply as the difference between the two heatflows. If the surroundings is a vacuum, then its temperature is 0°K, so heatflow is zero. The sign (it's a vector) has to be used, otherwise the two bodies would heat one another indefinitely, and ultimately vapourise! People can get confused over the concept, but it all makes sense when you realise that energy is being transferred between the two bodies. The atmosphere with GHGs doesn't warm the Earth, but simply slows its rate of cooling.

Showing the large radiation values on the "energy budget" diagrams is misleading and unnecessary. Only the net outward flow need be shown. However, that's not to say that the large values in themselves are correct. Kiehl and Trenberth make assumptions about the emissivity (ideal = 1) of surface and atmosphere that don't bear much scrutiny. They are obviously trying to hype up the values they calculate. They have an argument (albeit weak), so by choosing insupportable emissivity values they weaken it further themselves.

Quote:Or,
IF radiation is relatively absorbed then the cooler recieved radiation by the hotter object will cool the hotter body faster.
ie, The surface of the object is 100 and it absorbs radiation at 90, so cooling it (not replacing lost energy) by a difference of -10.
This must be added to the -100, so the object cools at -100 and -10 = net -110.
On it's own the hotter object would cool relatively slower to the two object example.
ie, net -100
You're losing me - the hotter body is at some unspecified temperature. In a given time, it loses 100 units, and gains 90 units from the cooler body, net loss 100-90 = 10. Conversely the cooler body loses 90 units and gains 100, net gain 10.
Quote:I realise mine is a "heat flow" point of view, as if mixing bodies of water at different temperatures,
or, an "electrical viewpoint", adding wires of the same voltage does not increase the voltage, it increases the amperage,
but in my everyday life these seem a more realistic view point.
Hence I ask (politely) for the experiments that show this view point (heat / water / electricity) is not correct for radiation.
Your analogy is not entirely wrong at all. What you may be confusing is energy flow and energy content. Consider that voltage is analogous to temperature and energy flow to current. The difference between the electrical circuit and bodies emitting radiation is that current is proportional to voltage difference; radiation is proportional to the fourth power of the absolute temperature of the body. Bear in mind that voltage is not an absolute quantity, but is the difference in potential between two points in a circuit. There's no "opposing flow" in circuits or fluids in pipes, but there's opposing potential or pressure. Connecting two batteries in parallel is (crudely) analogous to placing two identical hotter bodies adjacent to a cooler one. The temperature difference is the same, but the heat flow to the cooler body will initially be doubled. The basis for radiation theory is quantum theory, which I understand the finer points of as someone standing on a beach understands the ocean.
Ernest Rutherford: "If your experiment needs statistics, you ought to have done a better experiment."
Reply
#20
I to deduce from the above that you are also in the "all radiation is positive" school of thought.

I'm afraid so. I have read explanations from people with letters after their names who state that a photon does not have a temperature signature. The electromagnetic signature defines the "band" of the photon energy path. If a molecule is capable of absorbing the photon it will do so and gain that energy.

If you look at graphs for two identical objects at different temperatures you will note the hotter object will have a higher line than the cooler even though the shapes of the graphs are similar. The "area under the graph" defines the level of energy for each object. In effect there are many more photons being emitted from the hotter object than the cooler, remember this varies as to the fourth power of the temperature, so just a few degrees makes a big difference. "Net" radiation will defines the energy exchange between the two objects.

This is my understanding of how it works. Be happy to read up other explanations.

BUT, I have never read a peer reviewed paper that explains this in detail, my information is aquired from comments on blogs and I make a value judgement and choose what I think makes most sense given my current level of understanding.

Always happy to learn new. Smile
Environmentalism is based on lies and the lies reflect an agenda that regards humanity as the enemy of the Earth. - Alan Caruba
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