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The Myth of Backradiation
#21
May I add my welcome to you Nasif as well, and
I also look forward to future postings from you.

Myself and Richard111 do love a good blunder...
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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#22
I think you do have back radiation from Infra Red Interacting Gasses (IRIGs) of Infra red at certain wavelengths that finds its way back to the ground but as the ground is already sufficiently hot enough to be emitting IR at those wavelengths then the ground cannot be heated further. It merely momentarily absorbs, then immediately emits the photon again. It is possible for a material to interact with IR radiation without being warmed by it.

All the IRIGs do is scatter IR throughout the lower atmosphere, not heating the ground at all.

As said above by Nasif, convection and evaporation are the major cooling mechanisms of the earths surface and I think that as these are essentially slow mechanisms, this accounts for the earths surface being tolerable for life and for the temperature remaining fairly constant between day and night.

So, I think THERE IS a "greenhouse" analogous effect but it is not due to IRIGs but the slowness of convection and evaporation. I read somewhere else that this is why cloudy nights in winter are warmer than clear nights- not due to IR but due to convection being slowed even further.

We could affect the climate, but only by massive physical changes to the earths surface that would radically alter albedo and convection/ evaporation mechanisms. Hence the urban heat island effect.
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#23
(07-30-2010, 08:22 AM)Climate Realist Wrote: convection and evaporation are the major cooling mechanisms of the earths surface and
I think that as these are essentially slow mechanisms,

Err, I think you'll find conduction / convection heat losses are vastly greater than radiation,
hence they are a lot faster near the surface.
Latent heat is faster / larger again (given the right conditions, ie, wet), probably orders of magnitude larger than radiation losses.

btw - was the first sentence in your post 22 above implying relatively absorbed ?
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
#24
Convection/ evaporation moves heat around by moving hot matter, which moves, at the most, at a few miles per hour, wheras radiation photons travel at ~186,000 miles per second. If IR was the major means of heat transfer, the earth would get very cold very quickly at night. And it does not!

However, I understand that the magnitude of heat moved by convection/ radiation far outweighs that moved from the earths surface by IR radiation. So yes, I agree with your statement.

First sentence in post 22 implys that IR radiation can be moved around without heating anything. IR radiation in itself is not heat. It can only heat material by vibrationally exciting the atoms and molecules in matter. This I think does not happen with back radiation because the ground matter is already excited to that degree so the IR photons from back radiation cannot heat the ground thus the 2nd law is preserved.

You would need radiation of a "hotter" more energetic wavelength to heat the ground further, hence sunlight can heat the ground but not back radiation.
(07-04-2010, 03:34 PM)Sunsettommy Wrote: -snip-

Why do the majority of the skeptics feel the need to be hostile over the possibility that maybe back-radiation does NOT warm up a surface that is hotter than the back-radiation itself is?

-snip-

Sunsettommy summarises why the GHE fails very succinctly in the above sentence.
Heat always flows from hot to cold, much live rivers always flow downhill.
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#25
Seriously folks, do have a look at Roy Spencer's blog.

Lots of discussion and mad scientist tests in the back yard on radiation from a clear sky. I was a bit discouraged by his first post but now I suspect he is leading us towards some revelation. We will see.
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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#26
(07-30-2010, 09:47 AM)Climate Realist Wrote: ...I agree with your statement.

You would need radiation of a "hotter" more energetic wavelength to heat the ground further,
hence sunlight can heat the ground but not back radiation.

Thanks in the first, and in the second,
what does cooler, less energetic radiation do to a hotter more excited absorber. ?
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
#27
This is giving me the giggles. The "hot" ground doesn't care where the photon came from, the surface of the sun, a molecule of CO2 in the air or from my backside. Hey! - parts of me are radiating at 37C ! - and believe me that is hotter than any ground here in Pembrokeshire!!!

Hot objects emit more energy than cold objects. In all the discussions above we are refering to a solid at a specific temperature covered by a gas at a lesser temperature, possible only a few degrees difference. The gas is acting as an insulator thus REDUCING the rate of cooling of the "hotter" ground. How? By feeding back a few photons of the energy it is radiating away on its own journy towards entropy. All things will stop radiating at zero degrees Kelvin. Meanwhile they will happily absorb any photon that fits to slow down this inevitable process towards thermodynamic nirvana.
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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#28
(07-30-2010, 01:39 PM)Richard111 Wrote: 1) The gas is acting as an insulator thus REDUCING the rate of cooling of the "hotter" ground.
2) How? By feeding back a few photons of the energy it is radiating away on its own journy towards entropy.
Also Big Grin
1) But as the gas/es is/are also conducting, and (in a gravity field) convecting, it is not insulating surely ?
Are you suggesting the presence of the gas "traps" heat in the surface - surely not ?

2) Your comparing to absolute zero again..Of a very few photons compared to the large amounts conducted / convected away.
- Which whilst conducting / convecting won't radiate virtually any photons as O2 / N2 don' radiate much, if at all, at your "nether regions" temperature or below (or quite a bit higher either).
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
#29
(07-30-2010, 10:50 AM)Richard111 Wrote: Seriously folks, do have a look at Roy Spencer's blog.

Thanks I've had a quick skim through, and so have posted.

" Errr, I assume the air temperature sensor is getting some regolith (and vegetation) released heat, particularly at night
(relative cooling by day I would also assume), and the cavity sensor is getting none, or very little (day and night).
Would this be bound to produce a higher air temp than cavity temp at night, and
slightly lower (air temp) during (at least the early part of) the day. ?

If you have allowed for this, and I had missed it on my quick skim through so far, then please accept my apologies.

yours,
Derek.
"
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
#30
Okay, enough frivolity. If I may put a direct question to Nasif Nahle. You write:


(07-29-2010, 11:48 AM)Nasif Nahle Wrote: I have made the calculations and the mean free path for a photon without "touching" a molecule of carbon dioxide is 48.02 m. It means that the photon travels an average of 48.02 m without being absorbed by a molecule of CO2.

Could you please expand on this statement. Did this calculation apply to the 15 micron band or to all bands absorbed by CO2? In either case can you quantify how much, as a percentage, this amount of radiation is with regard to the total surface radiation. I ask for percentage as the surface temperture varies widely but the amount of energy absorbed will remain constant with regard to the available energy.

Does this question indicate I am on the right track or not?

Later you write:

(07-29-2010, 11:48 AM)Nasif Nahle Wrote: Fortunately for living beings on Earth, there are lots of molecules of water vapor (10000 ppmV - 50000 ppmV), nitrogen (780000 ppmV) and oxygen (208000 ppmV), and dust particles (highly variable) and other molecules that intercept photons before they leave the Earth.

I took this to mean that we (living beings) are fortunate that there is enough "polution" in the atmosphere to maintain a viable living surface temperature. But then I looked up your bio and think you may have another meaning entirely.

Many thanks for your time.
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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#31
(07-31-2010, 12:13 AM)Richard111 Wrote: Okay, enough frivolity. If I may put a direct question to Nasif Nahle. You write:


(07-29-2010, 11:48 AM)Nasif Nahle Wrote: I have made the calculations and the mean free path for a photon without "touching" a molecule of carbon dioxide is 48.02 m. It means that the photon travels an average of 48.02 m without being absorbed by a molecule of CO2.

Could you please expand on this statement. Did this calculation apply to the 15 micron band or to all bands absorbed by CO2? In either case can you quantify how much, as a percentage, this amount of radiation is with regard to the total surface radiation. I ask for percentage as the surface temperture varies widely but the amount of energy absorbed will remain constant with regard to the available energy.

Does this question indicate I am on the right track or not?

Later you write:

(07-29-2010, 11:48 AM)Nasif Nahle Wrote: Fortunately for living beings on Earth, there are lots of molecules of water vapor (10000 ppmV - 50000 ppmV), nitrogen (780000 ppmV) and oxygen (208000 ppmV), and dust particles (highly variable) and other molecules that intercept photons before they leave the Earth.

I took this to mean that we (living beings) are fortunate that there is enough "polution" in the atmosphere to maintain a viable living surface temperature. But then I looked up your bio and think you may have another meaning entirely.

Many thanks for your time.

Big Grin Well, Richard. The carbon dioxide is so dispersed in the bulk volume of gases of the atmosphere (0.00069 Kg/m^3) that it is not a good catcher of photons. The mean free path length of a photon traveling on any trajectory in the atmosphere is intercepted almost immediately by any molecule of gas, including water vapor, or any dust particle, except by the carbon dioxide. Any photon travels 48.01 meters without touching a molecule of carbon dioxide.

The second part of that post is the most interesting because the first molecules on catching photons at a few centimeters, millimeters or micrometers from the source of the photon stream are water vapor molecules. The dust particles also do their work more efficiently than the carbon dioxide. Therefore, if not was for the water vapor and the floating dust particles, including those so called "ice nucleators", the Earth would begin to be frozen in about 0.411 seconds after the sunset, even if the fabulous carbon dioxide mass fraction were 600 ppmV.

Concluding, you are right on your appreciation of these phenomena. The "toxic" water vapor, nitrogen, oxygen, and dust particles makes the Earth gets warmer and sustain the life on this planet, although the carbon dioxide is good, very good for life. Smile

By the way, I have the answer to Roy Spencer's conundrum. He put the box on the ground covered on grass. Grass and most plants release an excess of water through the cuticle of their leaves (Guttation). If Roy's box was isolated in his five exposed surfaces, then he avoided currents of air and eddies, which would retard the formation of dew. As he blocked the flow of air (hot air) over the ground below his box, dew was formed more efficiently and rapidly than in the surroundings. Dew cools the surface by absorbing the heat radiated and conducted from the subsurface materials.

Well that's the answer to Roy's puzzle; unfortunately, he doesn't post anything coming from me. I don't know why. So if any of you wish to post the explanation there, go ahead, you have my permission granted. Don't forget to mention my name. Blush
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#32
Quote:Well that's the answer to Roy's puzzle; unfortunately, he doesn't post anything coming from me. I don't know why. So if any of you wish to post the explanation there, go ahead, you have my permission granted. Don't forget to mention my name

Roy has censored a few others besides you at his blog recently.

I am really unhappy about it because I want to see ALL of the counterpoints made against his presentation.

Science works best when parties to a discussion are allowed to speak their mind on what is presented.

He is doing what RealClimate and other AGW believing websites commonly does,and that is bad.

Angry

What is Roy afraid of?
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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#33
Quote:The mean free path length of a photon traveling on any trajectory in the atmosphere is intercepted almost immediately by any molecule of gas, including water vapor, or any dust particle, except by the carbon dioxide. Any photon travels 48.01 meters without touching a molecule of carbon dioxide.

Ach, once more I am misleading myself with my own misinterpretations. Blush

Thank you Nasif Nahle for the clarification.
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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#34
(07-30-2010, 03:21 PM)Derek Wrote:
(07-30-2010, 01:39 PM)Richard111 Wrote: 1) The gas is acting as an insulator thus REDUCING the rate of cooling of the "hotter" ground.
Also Big Grin
1) But as the gas/es is/are also conducting, and (in a gravity field) convecting, it is not insulating surely ?
Are you suggesting the presence of the gas "traps" heat in the surface - surely not ?

My apologies Richard111, my reply could be interpretted as being rather harsh. This is and was completely unintensionally on my part.
I, too, have untill recently described and thought of O2 and N2 as "atmospheric insulators".
Upon reading Alan Siddons learning by candlelight paper I realised that O2 and N2 move
great amounts of heat up, (and cold down) because of convection (and sinking) that MUST occur in a gravity field.

Yes, O2 and N2 do not effectively radiate at atmospheric temperatures, and they also have no latent heat of change of state, unlike H2O,
but that does not make them "insulators".
O2 and N2 are rather boring infact, they "just" conduct, and then convect or sink.
(O2 may also warm from some higher energy incoming solar radiation)
CO2 and H2O are so much more exciting they radiate, in (to be honest) ways we are uncertain of at present,
AND H2O also carries vast amounts of latent heat as vapour, and sensible heat (cold) as liquid,
WATER in it's many and complex forms / relationships, is THE dominant force in the atmosphere.
As (I understand) you have been saying for a long, long time now.

Re post 33 - seconded, I also.
Thank you Nasif.

btw - I think I "ended" Roy's experiment at post 29 on this thread.
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
#35
I have a question that I have not been able of answering satisfactorily. If the mean free path length of photons emitted by the surface, in clear days and nights, is 0.004 seconds for the CO2, 0.024 seconds for the water vapor at 4% in the atmosphere, and 0.975 seconds for the mixture of air with 4% of water vapor, what the factor impeding the photons to escape from the atmosphere could be? I have not done work on dust particles, Nitrogen and Oxygen; however, I have thought seriously on those greatly abundant gases and particles in the atmosphere. Not as causes of any “global warming”, but as causes of scattering of photons before they leave the atmosphere. Any suggestion or clue?
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#36
Big Grin Not a clue.

But since we are dealing with photons I wonder if there would be any parallels with Rayleigh scattering?
(08-01-2010, 01:09 AM)Derek Wrote: My apologies Richard111, ....

Goodness!! Not needed Derek. Just my untutored way of seeing things. If atmosphere in contact with surface is warmed by conduction then the rate of cooling at that point must slow until cooler air moves in. Nothing is trapped. Just the RATE of energy exchange has changed. Think being in a desert on a sunny day with no wind. And then the wind starts blowing.
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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#37
Richard, you have just described convection, which is, i understand the major cooling mechanism in the atmosphere, and it is the relative slowness of convection that causes the Earth to be tolerable to life. Convection dominates, radiation of IR from the surface and consequent back radiation is both much smaller in magnitude and faster. Therefore changing the amounts of CO2 in the atmosphere cannot alter climate, at all!

By back scattering the small amount of IR that CO2 can interact with you get a tiny slowing of the cooling of the atmosphere. This radiation cannot heat the hotter ground as discussed previously.
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#38
(08-02-2010, 01:13 AM)Climate Realist Wrote: Richard, you have just described convection, which is, i understand the major cooling mechanism in the atmosphere, and
it is the relative slowness of convection that causes the Earth to be tolerable to life. Convection dominates,

May I ask you to clarify convection of what please.
I read the reply to Richard111's post as implying sensible heat, in which case,
what about the latent heat of vapourisation of water, surely this is far, far larger.
(Almost everywhere on the earth's surface is (at least) moist, and water vapour makes air lighter - equals convection)
Either of both are both far more massive than IR, so they always move more heat, and are therefore magnitudes more effective than IR,
I know you have said this in this thread, but referring to IR being faster than convection, without adding this is potentially confusing.

I have reposted / updated an old piece of mine that may help to explain,
particularly the second post on,
Eureka....Revisited.


re Roy's experiment - Surely the big mistake in his experiment is not allowing for the effect of surface heat retention and later release
effecting the air temperature thermometre, and not the cavity air temperature.
Wouldn't this alone explain almost all, if not all, the temp. differences the experiment measures.?
That was the point I was trying to raise in post 29.
I doubt there would be much temp difference left to explain by "back radiation",
what was left after taking surface heat retention / release into account could even be (a little) negative.........
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
#39
Richard111... I have completed my calculations on N2 and O2 and didn't find too much difference. Actually, until now, there is no other explanation for the scattering of photons in the Earth's atmosphere, except for parallel Rayleigh's Scattering, although I have not made calculations for dust particles.
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#40
Richard, yes, I agree with you that the evaporation of water and its condensation in the upper atmosphere moves a lot of heat around the atmosphere and globe and convection is also involved in that. The water from plants in wooded areas evaporates, cools the leaves and hence the local temperature is lower than an adjacent car park ("Parking Lot" in American) where the local weather station Stevenson screen is situated.

This water vapour is carried into the upper atmopshere by convection, where it cools and forms clouds. But you need a source of water than can be evaporated for this to occur.

So convection and evaporation are both important to varying degrees. If we take the example of a desert, there is little evaporation, if any, so the major cooling factors of the earths surface in the desert will be convection of heated air and radiation of IR. Thus a desert will be hotter during the day than a jungle at the same lattitude as will a wood be cooler during the day than a parking lot/ space.
(07-04-2010, 03:34 PM)Sunsettommy Wrote: Well well,
-snip-
Here is a chart to excite anybody!

[Image: divine.gif]

I seem to remember reading somewhere that K+T just made this diagram up. It has no references to show how these figures were derived in any scientific journal.

It is pure speculation.

Well not pure, but corrupt speculation.

Can anyone show how this diagram was derived?
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