Visualizing the "Greenhouse Effect" – Emission Spectra

Guest post by Ira Glickstein

The Atmospheric “greenhouse effect” has been analogized to a blanket that insulates the Sun-warmed Earth and slows the rate of heat transmission, thus increasing mean temperatures above what they would be absent “greenhouse gases” (GHGs). Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up. A real greenhouse primarily restricts heat escape by preventing convection while the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth.

Many thanks to Dave Springer and Jim Folkerts who, in comments to my previous posting Atmospheric Windows, provided links to emission graphs and a textbook “A First Course in Atmospheric Radiation” by Grant Petty, Sundog Publishing Company.

Description of graphic (from bottom to top):

Earth Surface: Warmed by shortwave (~1/2μ) radiation from the Sun, the surface emits upward radiation in the ~7μ, ~10μ, and ~15μ regions of the longwave band. This radiation approximates a smooth “blackbody” curve that peaks at the wavelength corresponding to the surface temperature.

Bottom of the Atmosphere: On its way out to Space, the radiation encounters the Atmosphere, in particular the GHGs, which absorb and re-emit radiation in the ~7μ and ~15μ regions in all directions. Most of the ~10μ radiation is allowed to pass through.

The lower violet/purple curve (adapted from figure 8.1 in Petty and based on measurements from the Tropical Pacific looking UP) indicates how the bottom of the Atmosphere re-emits selected portions back down towards the surface of the Earth. The dashed line represents a “blackbody” curve characteristic of 300ºK (equivalent to 27ºC or 80ºF). Note how the ~7μ and ~15μ regions approximate that curve, while much of the ~10μ region is not re-emitted downward.

“Greenhouse Gases”: The reason for the shape of the downwelling radiation curve is clear when we look at the absorption spectra for the most important GHGs: H2O, H2O, H2O, … H2O, and CO2. (I’ve included multiple H2O’s because water vapor, particularly in the tropical latitudes, is many times more prevalent than carbon dioxide.)

Note that H2O absorbs at up to 100% in the ~7μ region. H2O also absorbs strongly in the ~15μ region, particularly above 20μ, where it reaches 100%. CO2 absorbs at up to 100% in the ~15μ region.

Neither H2O nor CO2 absorb strongly in the ~10μ region.

Since gases tend to re-emit most strongly at the same wavelength region where they absorb, the ~7μ and ~15μ are well-represented, while the ~10μ region is weaker.

Top of the Atmosphere: The upper violet/purple curve (adapted from figure 6.6 in Petty and based on satellite measurements from the Tropical Pacific looking DOWN) indicates how the top of the Atmosphere passes certain portions of radiation from the surface of the Earth out to Space and re-emits selected portions up towards Space. The dashed line represents a “blackbody” curve characteristic of 300ºK. Note that much of the ~10μ region approximates a 295ºK curve while the ~7μ region approximates a cooler 260ºK curve. The ~15μ region is more complicated. Part of it, from about 17μ and up approximates a 260ºK or 270ºK curve, but the region from about 14μ to 17μ has had quite a big bite taken out of it. Note how this bite corresponds roughly with the CO2 absorption spectrum.

What Does This All Mean in Plain Language?

Well, if a piece of blueberry pie has gone missing, and little Johnny has blueberry juice dripping from his mouth and chin, and that is pretty good circumstantial evidence of who took it.

Clearly, the GHGs in the Atmosphere are responsible. H2O has taken its toll in the ~7μ and ~15μ regions, while CO2 has taken its bite in its special part of the ~15μ region. Radiation in the ~10μ region has taken a pretty-much free pass through the Atmosphere.

The top of the Atmosphere curve is mostly due to the lapse rate, where higher levels of the Atmosphere tend to be cooler. The ~10μ region is warmer because it is a view of the surface radiation of the Earth through an almost transparent window. The ~7μ and 15μ regions are cooler because they are radiated from closer to the top of the Atmosphere. The CO2 bite portion of the curve is still cooler because CO2 tends to be better represented at higher altitudes than H2O which is more prevalent towards the bottom.

That is a good explanation, as far as it goes. However, it seems there is something else going on. The ~7μ and ~15μ radiation emitted from the bottom of the Atmosphere is absorbed by the Earth, further warming it, and the Earth, approximating a “blackbody”, re-emits them at a variety of wavelengths, including ~10μ. This additional ~10μ radiation gets a nearly free pass through the Atmosphere and heads out towards Space, which explains why it is better represented in the top of the Atmosphere curve. In addition, some of the radiation due to collisions of energized H2O and CO2 molecules with each other and the N2 (nitrogen), O2 (oxygen) and trace gases, may produce radiation in the ~10μ region which similarly makes its way out to Space without being re-absorbed.

There is less ~15μ radiation emitted from the top of the Atmosphere than entered it from the bottom because some of the ~15μ radiation is transformed into ~10μ radiation during the process of absorption and re-emission by GHGs in the atmosphere and longwave radiation absorbed and re-emitted by the surface of the Earth.

Source Material

My graphic is adapted from two curves from Petty. For clearer presentation, I smoothed them and flipped them horizontally, so wavelength would increase from left to right, as in the diagrams in my previous topics in this series. (Physical Analogy and Atmospheric Windows.)

Here they are in their original form, where the inverse of wavelength (called “wavenumber”) increases from left to right.

Source for the upper section of my graphic.

Top of the Atmosphere from Satellite Over Tropical Pacific.

[Caption from Petty: Fig. 6.6: Example of an actual infrared emission spectrum observed by the Nimbus 4 satellite over a point in the tropical Pacific Ocean. Dashed curves represent blackbody radiances at the indicated temperatures in Kelvin. (IRIS data courtesy of the Goddard EOS Distributed Active Archive Center (DAAC) and instrument team leader Dr. Rudolf A. Hanel.)]

Source for the lower section of my graphic.

Bottom of the Atmosphere from Surface of Tropical Pacific (and, lower curve, from Alaska).

[Caption from Petty: Fig. 8.1 Two examples of measured atmospheric emission spectra as seen from ground level looking up. Planck function curves corresponding to the approximate surface temperature in each case are superimposed (dashed lines). (Data courtesy of Robert Knutson, Space Science and Engineering Center, University of Wisconsin-Madison.)]

The figures originally cited by Dave Springer and Tim Folkerts are based on measurements taken in the Arctic, where there is far less water vapor in the Atmosphere.

[Fig. 8.2 from Petty] (a) Top of the Atmosphere from 20km and (b) Bottom of the Atmosphere from surface in the Arctic. Note that this is similar to the Tropical Pacific, at temperatures that are about 30ºK to 40ºK cooler. The CO2 bite is more well-defined. Also, the bite in the 9.5μ to 10μ area is more apparent. That bite is due to O2 and O3 absorption spectra.

Concluding Comments

This and my previous two postings in this series Physical Analogy and Atmospheric Windows address ONLY the radiative exchange of energy. Other aspects that control the temperature range at the surface of the Earth are at least as important and they include convection (winds, storms, etc.) and precipitation (clouds, rain, snow, etc.) that transfer a great deal of energy from the surface to the higher levels of the Atmosphere.

For those who may have missed my previous posting, here is my Sunlight Energy In = Thermal Energy Out animated graphic that depicts the Atmospheric “greenhouse effect” process in a simlified form.

I plan to do a subsequent posting that looks into the violet and blue boxes in the above graphic and provides insight into the process the photons and molecules go through.

I am sure WUWT readers will find issues with my Emissions Spectra description and graphics. I encourage each of you to make comments, all of which I will read, and some to which I will respond, most likely learning a great deal from you in the process. However, please consider that the main point of this posting, like the previous ones in this series, is to give insight to those WUWT readers, who, like Einstein (and me :^) need a graphic visual before they understand and really accept any mathematical abstraction.

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John Marshall

A very complicated and flawed article.
What are we actually measuring when we measure temperature? It is the measure of Kinetic energy of the atom. In the laboratory CO2 will adsorb IR radiation and increase in temperature. In other words the atoms increase their vibrations. In the atmosphere, where there are other gasses, this CO2 will transfer these vibrations to the other gasses by collision. This is heat conduction.
When gas gets warmer it expands, density falls and it rises, convection. In the troposphere heat is lost through convection not radiation. Radiation is not possible because as this air rises its temperature falls due to adiabatic expansion. Its temperature will fall below that of the surface, and the 2nd law of thermodynamics forbids heat flow from cold to hot ( this is heat flow by any means available) so this rising warm air, relative to the surrounding air though colder than the surface, cannot warm the surface.
We can measure what we might think is the LW IR as back radiation but we probably forget that as energy flows through the atmosphere it has an effect on that atmosphere which will reduce that incoming energy which is revealed as a frequency change ( its speed remains constant) so that measured LW IR is altered solar energy not re-radiated IR from CO2.
At least this is how I see it bearing in mind those old Laws of Thermodynamics.
It is also flawed to use the black body formula for the earth since it is not in equilibrium at any time due to changes to cloud cover.

I’m glad you included the original Petty plots, because I think they are the most informative. The Arctic ones are very helpful. It’s a good idea to include lots of black body curves, so you can see where the radiation is coming from.
You said “some of the ~15μ radiation is transformed into ~10μ radiation during the process of absorption and re-emission by GHGs in the atmosphere”. Well, yes, but not much. Kirchhoff’s Law comes into play. Just as 10μ is easily transmitted, very little is emitted. That’s why the 10μ looks like it is coming from the ground, rather than higher up.

Morris Minor

“…. Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up…..”
I am not sure about this ‘radiation down’ or so called ‘back-radiation’.
According to Trenberth et al. this amounts to about 330 W/m2, nearly twice that of the energy reaching the Earths surface from the sun (184 W/m2). If this is true why isn’t this energy collected and used as an energy source (better than solar energy as no need for storage – this can be collected 24 hours /day).
The reason I suspect we can’t use this energy is because it doesn’t exist – heat will not flow from the cold atmosphere to the warm surface of the Earth.
I think the emission spectra shows the scatter of infra-red from the atmospheric gases that wont reach the collimated collector of the sensors due to its direction of travel?
Thoughts please!

richard verney

Ira
I will enjoy reading and considering your post. I have only quickly glanced at the first few paragraphs and my immediate brief observations are:
I consider your better analogy (ie., that of an electric blanket) to be a worse analogy. An electric blanket has a power source and consumes energy in order to provide heat. Where is this seperate power source in your model Earth?
It would also be useful if you would briefly explain how the Earth emits a smooth blackbody curve given that temperatures vary between about 325K (desserts) and 220 to 235K (Artic/Antartic). What are the emission frequencies at these varying temperatures.

rbateman

Morris Minor says:
March 10, 2011 at 2:21 am
Don’t forget that light has 2 behaviors:
As a particle and as a wave.
As a wave it is contructive going down (in sympathy with incoming solar radiation) but in going up it is destructive and helps to add to Earth’s albedo.
Gets complicated in a hurry, doesn’t it?
Take away the water vapor and the C02 in Earth’s atmosphere would probably freeze out at the poles (most notably the Antarctic).
Remind you of another planet?

Joel Heinrich

The graphics have one (unfortunately very common) error. They are plotted as a wavenumber distribution but labeled with wavelength. You CANNOT just transform the wavenumber into wavelength as they have different peaks. Much like the difference between wavelength and frequency: http://commons.wikimedia.org/wiki/File:PlanckDist_ny_lambda_en.png
The peak of a distribution in wavelength for 280K is at 10.5 µm.
“The dashed line represents a “blackbody” curve characteristic of 300ºK (equivalent to 27ºC or 80ºF). Note how the ~7μ and ~15μ regions approximate that curve, while much of the ~10μ region is not re-emitted downward.”

Better …
.

P. van der Meer

Ira Glickstein, why don’t you explain to your readers why the various curves for blackbody radiation in your article peak in the range of 17μm to 19μm when the http://spectralcalc.com/blackbody_calculator/blackbody.php site comes up with a peak wavelength of 9.659μm for 300K and 11.828μm for 245K. This is also confirmed by the Wikipedia graph (http://en.wikipedia.org/wiki/File:Atmospheric_Transmission.png), showing a peak at about 9μm for 310K.
I look forward to your explanation.

peter_ga

If one defines “greenhouse” as the systems capacity to absorb shortwave radiation being different to and greater than its capacity to emit long-wave radiation, such that a net increase in temperature over a pure black-body temperature is needed for thermal equilibrium, then an important aspect is the ability of the oceans to absorb shortwave to a much greater depth than the depth that emits longwave.
This means that the temperature of the oceans would generally be greater than blackbody temperature, that they will tend to heat the atmosphere above them through various mechanisms, and evaporate water into the atmosphere as well. Earth is warmer because of its oceans, through an indirect greenhouse mechanism, that has nothing to do with co2.

Vince Causey

John Marshall,
“Its temperature will fall below that of the surface, and the 2nd law of thermodynamics forbids heat flow from cold to hot ( this is heat flow by any means available) so this rising warm air, relative to the surrounding air though colder than the surface, cannot warm the surface.”
The second law says no such thing. The misconception that the second law says that heat cannot flow from a cooler to a warmer body is the old nineteenth century understanding which dealt with conducting bodies. It was then rewritten in terms of entropy – entropy must always increase in a closed system.
This is what the second law actually says:
“The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system (Wikipedia).”
The key point to note is that over time, differences in temperature will equilibriate. The idea of greenhouse gases radiating energy back to the Earth’s surface does not contradict this description as long as the temperatures will equilibriate over time.
The second law allows energy from a cooler body to radiate to a warmer body (in fact, allow is the wrong word – all bodies above absolute zero must radiate energy) because it knows that the warmer body must be radiating even more energy to the cooler body and that their temperatures would most definately equilibriate over time.

Scarlet Pumpernickel

So what concentration of CO2 saturates these wavelengths?
There is already proof from Venus that the Greenhouse effect is not exponential http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html

James

The reason I suspect we can’t use this energy is because it doesn’t exist – heat will not flow from the cold atmosphere to the warm surface of the Earth.

Yes it will. When the energy is emitted it is in a random direction and has no knowledge of it is heading towards a warmer or colder body.
Heat will flow from a cold to hot body but at the same time more energy is going the other way. The flow energy from the atmosphere to the surface does exist.

Bryan

Ira Glickstein
You seem to think that an ordinary blanket is unlike an electric blanket in effect to radiation, perhaps you think it does not radiate?
For the record an ordinary blanket is a better radiator than for example the atmosphere.
At night the passive atmosphere is only capable of insulating the hotter Earth surface to some extent.
That is it reduces the heat loss compared to no atmosphere.
During daylight the DLR radiation is mainly redirected and degraded radiation of solar origin that has not reached the surface directly.
There will of course be some DLR which has an energy sourced by the warmer Earth surface.
I think you would do well to read some Physics books that deal with thermodynamics and heat transfer before making elementary errors.

richard verney

Ira
Further to my last comment, your article is interesting and I am still pondering upon its implications. Whilst ultimately at the very top of the atmospher all heat is radiated into space, I consider that below that boundary other forms of heat transfer are far more significant that radiation.
As I have commented numerous times, I do not consider the Earth to be a blackbody and the assumption that it behaves in this simplistic way distorts what is truely happening. The Earth is never at equilibrium. There are constant changes in albedo due to changes in cloud cover, ice, snow, vegetation., seasons etc These variations change the emission properties of the Earth. The oceans act as huge heat sinks such that diurnal changes over oceans is very different to changes in diurnal temperatures over land. There are peaks and valleys and all of this means that the Earth does not simplistically behave as a uniform blackbody.
You state: “the surface emits upward radiation in the ~7μ, ~10μ, and ~15μ regions of the longwave band. This radiation approximates a smooth “blackbody” curve that peaks at the wavelength corresponding to the surface temperature.” I accept that the curves set out in the “Bottom of the Atmosphere from Surface of Tropical Pacific (and, lower curve, from Alaska) tend to follow the 300K and 245k blackbody curve save for dips in the 8 to 14μ wavelengths, the effects of which you are seeking to highlight.
However, the “Top of the Atmosphere from Satellite Over Tropical Pacific” data is very different. This does not follow the 300k or 290k curve. Up to 7μ it seems to follow a 210/220k curve Between 7 and 8μ it takes a path crossing the 220 to 250K curve. Between 8 and 9μ it jumps up to about the 300K curve. Between 18 to 25μ it falls through the 270 down to the 250K curve. My view of this plot, ignoring the dips around the 9.5μ and the 13 to 18μ range is that it does not exhibit a smooth blackbody curve at any part through the 6 to 25μ wavelengths.
What is the explanation and how in the light of that explanation can it vbe asserted that the Earth (even in that snapshot in time) is exhibiting a smooth blackbody emission spectra?
I look forward to hearing your commenst so that I may better understand your article.

James

rbateman says:
As a wave it is contructive going down (in sympathy with incoming solar radiation) but in going up it is destructive and helps to add to Earth’s albedo.

The waves need to be in phase to interfere. The radiation from the surface and the atmosphere is at a completely different frequency and wavelength so doesn’t interfere with the solar radiation.

Steve in SC

Other aspects that control the temperature range at the surface of the Earth are at least as important and they include convection (winds, storms, etc.) and precipitation (clouds, rain, snow, etc.) that transfer a great deal of energy from the surface to the higher levels of the Atmosphere.

Your other modes of heat transfer are SIGNIFICANT and can not be dismissed.
At altitude radiation is indeed the mode of heat leaving the planetary system.
As altitude gets lower radiation becomes less important and transports less and less of the total heat.

cal

Thanks Ira. At last a description that I can pretty well totally agree with. My only caveat is the one Nick Stokes mentioned; that very little energy can be converted into “10 micron ” radiation in the atmosphere as I, and others, pointed out before on your previous thread.
As I also commented then, the facts with good explanations beat a good analogy. The graphs are excellent. It won’t stop some trying to deny them or interpret them in bizarre ways ( we have had a couple on this thread already) but the majority of WUWT readers will understand this contribution.
I also welcome the fact that you have taken the time to do this and persevere in trying to come to a “consensus”. I can’t believe I have just used that word!
I think that the AGWs have exploited the poor science displayed by some posters here to argue that the whole of the sceptic position is ill founded. The fact that the greenhouse gas effect exists is irrefuteable, as your graphs clearly show, and arguing to the contrary plays into the hands of those who wish to exploit the implications of increased CO2. While the effect of CO2 is clear the effect of increasing CO2 is far from obvious.
From the graphs it is clear that CO2 radiates from space from the top of the troposphere and re-radiates back to earth from relatively low altitudes. Paradoxically this is due to the fact that CO2 is indeed a VERY powerful greenhouse gas in the 14-18 micron window so that it will trap energy very close to the earth’s surface and will not radiate, unencumbered, into space until the air density is very low. Due to convection in the lower troposphere, high levels of humidity and clouds it is not at all obvious how increased CO2 and the subsequent reduced altitude of first absorption will effect downward radiation. Nor is it clear what will happen to radiation to space given that this is already taking place near the tropopause where the temperature no longer decreases as one goes higher.
These are the issues that need to be debated not the fundamental science. As far as I know there have been no actual measurements that confirm the signature of greenhouse forcing that would explain current warming on the basis of CO2 changes and this is a travesty!

Water vapour is the main so called “greenhouse gas” yet it does not produce a “greenhouse effect” as in a warming effect because it is a fluid gas. Though it may absorb IR, having done so it obviously expands and convects up through the atmosphere taking the IR up to cloud level. It does so because it is a highly mobile fluid gas.
CO2 does exactly the same thing by absorbing heat at the surface and transferring up to cloud level where it is emitted as IR. The cloud level, which begins at around 5000 meters is the beginning if the emission hight of the atmosphere. We know that CO2 begins emit the same level as water vapour because rain water is acidic. The acidity is caused by the dilution of CO2 into the water vapour as it form into clouds on emission, becoming carbonic acid.
Water vapour has a cooling effect on the surface. In exactly the same way so too does CO2.
How is this a “greenhouse effect” ???
The only place that the “greenhouse effect” is actually observed is in the computer models, not in the real world. The only reason that computer models predict a “greenhouse effect” is because they use a parameter known as “convective parameterisation”. In a computer model, if you over estimate convection you will not see a “greenhouse effect”. But if you underestimate this parameter, it will obviously and naturally result in a “greenhouse effect”.
Greenhouses are designed predominantly to inhibit convection as every body knows.
So in the models we have a “greenhouse effect” but in the atmosphere we do not.

Sjoerd

Ira,
Please leave out the “degree” when talking about Kelvin. It’s “degree Fahrenheit” and “degree Celsius”, but it’s “Kelvin” (without the “degree”). Same when abbreviated: It’s 270K, not 270ºK.
In your first article, you also abbreviated Argon as A, while it is Ar.
And it’s μm, not μ. The graphics you copied from other sources use it correctly, the graphics you made yourself are labelled wrongly.
Small mistakes like this distract from the article and undermine your credibility: If one can’t get simple details like proper usage of units correct, …

Gilbert K. Arnold

Bryan says:
March 10, 2011 at 3:32 am
Bryan: Did you even look at Ira’s brief CV at the bottom of his article. Does the phrase: “BS in Electrical Engineering” mean anything to you? Every EE program that I know of, includes Physics, Dynamics, and Thermodynamics as basic course requirements for graduation. Your insinuation that Dr. Gluckstein read some books that deal with heat transfer and Thermo is a bit of snark that is not needed.

RJ

Would a human being cook if he or she was enclosed in a container of CO2
In theory a percentage of the heat given off would return and increase the body temperature if the GHG theory is correct. Something surely is seriously wrong with the GHG theory.

Ira Glickstein
“the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth.”

No, No and a thousand times No.
Re-emitted radiation does not and cannot heat the Earth significantly, because downwelling IR does not and cannot penetrate the surface of the ocean beyond its own wavelength. The amount of energy from back radiation mixed into the ocean by wind and wave action is negligible and extra co2 therefore cannot account for the additional warming of the ocean bulk in the late C20th.
The greenhouse effect works by *SLOWING DOWN THE RATE THE EARTH COOLS AT*, by raising the altitude at which the atmosphere radiates to space . There is more than a semantic difference. Understanding it this way enables you to understand that it was reduced albedo 1979-1998 allowing more Solar energy to enter the oceans that caused the majority of the global warming at the end of the last millenium.
http://tallbloke.wordpress.com/2011/03/03/tallbloke-back-radiation-oceans-and-energy-exchange/

Bryan

Vince Causey
….”The second law says no such thing. The misconception that the second law says that heat cannot flow from a cooler to a warmer body is the old nineteenth century understanding which dealt with conducting bodies. It was then rewritten in terms of entropy – entropy must always”…….
Clausius was well aware of radiation when he formulated his second law.
He also invented the entropy concept.
He conducted tests with mirrors and lenses to confirm that for radiation as for conduction and convection;
…..”Heat flows from from a higher temperature surface to a lower temperature surface never the reverse.” one expression of the famous second law.
Vince Causey perhaps is confusing radiation with heat.
A colder surface will radiate to a warmer surface.
A colder surface cannot heat the warmer surface.
Heat carries the thermodynamic capacity to do work in the given situation.
Thus work can be done hot to cold.
Work cannot be done cold to hot.
Another way to think about it is the cold surface cannot increase the temperature of the hotter surface all it does is reduce somewhat the heat loss from the hotter surface.

Ira Glickstein
Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up.

Yeah? and where is this ‘electric blanket’ getting its power from? Directly plugged into Trenberth’s mysterious reservoir of “missing heat” perhaps? Lol.
http://tallbloke.wordpress.com/2010/12/20/working-out-where-the-energy-goes-part-2-peter-berenyi/

Joe Lalonde

Ira,
As you have seen many people do not agree with your findings. Nor do I.
First, without planetary rotation, there is no convection as the planets own energy is the centrifugal force it generates at 1669.8Km/hr due to the vacuum of space. The atmosphere bends a great deal of light and solar energy with the suspended molecules in the atmosphere with the tilting of the planet to the sun. The hottest point of the sun is it’s equator that our planet drifts through due to proximity and size of the suns equator. Next very little consideration for the absorption and storage of heat that is then released at night.

DocMartyn

can you state how you generated the radiance curves for each temperature? Typically these type of figures have a fudge factor to correct for the black/white body fraction. I have never believed that one is allowed to do this from first principles.

Alberta Slim

Ira,
That is a terrific presentation.
Most interested people lose interest if an article gets too scientific and complicated.
You are fast becoming our new Isaac Asimov. [especially for GHG theory]
Thanks to you and Anthony for this.

jhborn

Dr. Glickstein, I greatly appreciate your efforts, as well as those commenters who have made constructive criticisms.
In what I hope is one of the latter, I, too, will cast my vote against the electric-blanket analogy.

wayne

If someone could just toss up a link to a spectrum at 800 mbar in the tropics pointing sideways so we could just blow everyone’s mind quickly and hopefully be able to rebuild what’s left outside of this insidious AGWphysics this time. ☺
Fourier’s law of heat diffusion reigns when outside the windows frequencies in the bulk of the lower atmosphere, on both sides of the spectrum. You should not have brought in “back radiation” there unless you are only speaking of the lower 100 meters or so. The term back radiation has it’s place but it is only meaningful within the window wavelengths and mainly in relation to clouds, their BB radiation near 10 µm beams down the window to warm the ground on cloudy nights (and days, but not apparent). Within the thick of the atmosphere, all radiation outside the window can be properly viewed a fast, long-range conduction, that simple. Why? The atmosphere is all but totally black to these frequencies and most radiation only travels mere meters before re-absorption. That’s my current take, and still evolving though quickly now.
Ira, E for effort. I had high hopes as you began this whole series that you were going to be more open and all here could move a notch closer in truly understanding radiation’s relations within the atmosphere. You have many points exactly correct, and your animations can be deemed correct too, but only with the correct limitations and factors applied in the surrounding words. But beyond that, the whole story-line gets off of the track, IMO.

1DandyTroll

“Well, if a piece of blueberry pie has gone missing, and little Johnny has blueberry juice dripping from his mouth and chin, and that is pretty good circumstantial evidence of who took it.”
This is why climate scientist ought not dabble in police work I think, for what if Charles was the one who nicked the piece and in passing Johnny smeared him blue with it?
But essentially the dissipation is 360˚ but mostly, naturally, concentrated at the nap of the earth, just like the stove which will burn if ones hand is too close but the farther away the hand gets the colder it gets, to the point of room temperature, the in between GHGs doing absolutely next to nothing to transfer the heat to that further away location due to it’s own dissipation rate even though the GHGs are pre-heated by being inside the house as well. But of course, eventually, the stove’ll raise the temperature in the kitchen, but only when the floor, ceiling, and the walls are more radiant, but only to a certain point (unless the stove doesn’t burst into flames the paint on the farthest wall ain’t gonna start cooking any time soon.) So whom is the construct of the thief that steals that heat? :p

Cementafriend

Ira, read the following http://climategate.nl/wp-content/uploads/2011/02/CO2_and_climate_v7.pdf which is the basis of a presentation by Dr (Ir) Noor Van Andel to KNMI in February and based on real measurements. Then, think again. -Incoming radiation to the sea surface from the sun controlled by cloud cover, evaporation at the sea surface, convection and pressure changes causing air movements, ToA radiation to space.
Dr Van Andel is a chemical engineer who has developed efficient heat exchangers for use with air see here http://www.xs4all.nl/~fiwihex/english/ Look at some of the links if you want some information on heat transfer theory.

tallbloke says:
March 10, 2011 at 4:26 am
“the hot-water bottle effect”
But what does heat the bottle, in the first place?
It is not “green-house effect”.
http://es.scribd.com/doc/28018819/Greenhouse-Niels-Bohr
Joe Lalonde says:
March 10, 2011 at 4:49 am
First, without planetary rotation, there is no convection
But….what does the Earth rotate…..an homopolar motor?
Then….heat by resistance?

william gray

How do we measure re-emittance of IR? I know absorbtion can be measured.

We live in an upside down world.
Water vapor makes up anywhere from 1-4% of the atmosphere. I can’t find the average because the percentage is so variable. CO2 is .04% of atmosphere. So water vapor is about 100x more plentiful than CO2 in atmosphere. Do anyone know the difference between the strength of CO2 vs WV as a greenhouse gas. Also, we know CO2 gets saturated in its’ greenhouse gas ability. Does this happen to WV? Then we know that man only creates 3% of the atmosphere CO2, well we don’t really know that, it’s just another big guess/estimate. How could we know that when we have forests densities completely changing throughout our world. Here in the US our forests are growing at a very fast rate, still recovering from the clearcuts of >100 yrs ago.
Then we have a possible feedback between CO2 and WV. Is it positive or is it negative? IPCC and modern “science” says CO2 always causes a positive increase in WV, causing amplification of greenhouse effect. But measurement of humidity and water vapor apparently doesn’t show this to be reality.
http://www.climate4you.com/GreenhouseGasses.htm, in fact WV is decreasing the last few years.
Then of course we have the oceans and their cylces, the sun and planetary alignment, undersea volcanoes etc etc etc. But THEY know everything. The SCIENCE is settled.
Yet after 11 years of increasing CO2 and amplification models, their data shows we are back where we started from in temperature with no trend whatsoever.
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1999
We don’t know nothing about climate!

commieBob

1 – Ira has presented us with curves showing the measured values of upward and downward radiation.
2 – One of the graphs shows the energy leaving the planet. The only way energy can leave the planet is by radiation.
3 – The other graph shows radiant energy arriving at the surface in the far infra-red region of the spectrum. Most of this energy is radiated by the atmosphere. It is explained by the heating of the atmosphere by the sun and by heating of the atmosphere caused when the atmosphere is heated by radiation, conduction, evaporation, etc. from heat leaving the surface of the planet.
4 – Under some conditions, upward radiation probably explains most of the heat leaving the surface. The graph comparing Barrow with Nauru is pretty dramatic. There isn’t a lot of heat from the atmosphere beaming down on Barrow. 😉 There also isn’t a lot of heat moving up through the atmosphere in the form of thunder storms in Barrow in November (when the graph was created). Most of the heat leaves Barrow as radiation and little of it heats the atmosphere and returns as back radiation in the range between 13 um and 8 um. (It looks like much/most of it comes back around 15 um.)
On the other hand, the effect of thunderstorms in tropical regions is huge. Evaporation takes heat from the surface and deposits it higher in the atmosphere. From there it can be carried elsewhere or be radiated.
5 – For those who doubt that back radiation exists, consider this: Infra-red radiation is electromagnetic radiation. It is the same as radio waves and light. Here are two examples of radiation from a weaker source going toward a stronger one: a) If I stand with my back toward the sun, I will be able to see a flashlight being shone at me. Nothing about the sun’s radiation will prevent the radiation from the flashlight from reaching me. b) If I stand near a strong radio transmitter, I can still tune in weaker transmitters. Nothing about the stronger transmitter’s signal prevents the weaker signal from getting to me. The net energy flux will still be from the stronger source toward the weaker one. It is a net flux though, in other words, the net flux is the difference between the two signals.
6 – The discussion totally ignores heat removed from the tropics by ocean currents and moved toward the poles. The effect of that heat is also huge. Compare, if you will, the climate of Regina Saskatchewan and London England. In the winter, Regina is a lot colder than London in spite of the fact that London is somewhat further north. The average low January temperature in London is 2.4 deg. C. In Regina, the same figure is -21.6 deg. The difference is entirely explained by heat transported by the ocean.
7 – Ira’s article made stark the difference between a tropical humid atmosphere and an arctic dry one.
8 – Many commenters might spend more time carefully reading Ira’s article and less automatically gainsaying it on the basis of any preconceived notions they may have. It is what it is. It explains one aspect of climate science and doesn’t pretend to be encyclopedic. My only quibble is that it leaves the impression that most of the heat in the atmosphere is caused by radiation.

wayne

william gray says:
March 10, 2011 at 5:16 am
How do we measure re-emittance of IR? I know absorbtion can be measured.
——-
You should be able to get pretty close by taking a spectrum at say 800 mbar in the tropics aimed sideways at night. ☺ That’s the only way I can think of doing it. Wouldn’t that be close?

Domenic

Ira
I applaud your efforts, but you should start off with the simplest case first.
The Tropical western Pacific spectrum is not fixed. You have presented a simple snapshot of of it, I believe. Or is it an average? I don’t see any definition here of what that spectrum really means.
The tropics are EXTREMELY dynamic from a radiational heat transfer point of view. The absorption, transmission, and reflections, are constantly shifting due to water vapor. Everything changes from moment to moment, and it can be drastic. Just imagine lying on a beach on a sunny day, and a thick cloud passes overhead. The temperature you feel on your skin immediately plunges. That’s an immediate change in radiational heat transfer. Those curves you present are actually dancing around dramatically.
Even Barrow, Alaska is a rather complex situation.
I suggest trying to model and understand the interior Antarctic Polar region (Amundsen-Scott, Vostok, etc) first from a radiational heat transfer point of view. There is virtually no water in the atmosphere there. It is dominated by radiational heat transfer. And there are reliable surface temperature data, as well as documented of increased CO2 from 1957 to data.
You have to learn how to simply walk before you can dance the tango with its infinite complexities and beauty.

Fred Souder

Ira,
You should stop saying the greenhouse gases in the atmosphere warm the earth to this crowd. Too may engineers running around here. The atmosphere slows the rate at which the earth loses energy to deep space. Thus, the earth in the sun-earth-space system has a higher equilibrium temp. The “old” rules of thermodynamics still apply: a warm object cannot gain net thermal energy from a cold object.
Thank you for posting the good data though, especially of the IR toward and away from earth at the arctic. I am curious what the ground temperature was on the days that this data was collected, since at the arctic you often have an inverted lapse rate and the atmosphere could indeed “heat” the ground. I am curious if the ground temps are cold enough at the poles, and the lapse rate is positive instead of negative, so that the atmosphere could indeed “heat” the Earth, at least in these specific conditions and locations.

Alberta Slim

After reading all the comments I am, again, uncertain.
There are so many contradictory statements about frequency and wavelength, heat transfers, conduction, radiation etc., etc., …….
Has anyone presented a theory based on photons?
I know……… stupid question

Jeremy

Sorry but this article is filled with misinformation.
“Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up.”
no a much better analogy is a blanket. There is no additional heating coming from the atmosphere.
They seem to give out degrees and doctorates in corn flakes boxes these days.

Alan McIntire

I too have been enjoying your articles. From prior posters, I thought of an additional analogy. Consider traffic flow over a section of road. The number of vehicles in the section being monitored represents joules. Joules are constantly entering the section at one end- radiation from the sun, and leaving at the other end-outgoing raiation cooling off the earth. Now, thanks to greenhouse gases, suppose there’s a traffic accident or a road construction crew closing one of the outgoing lanes The amount of traffic coming into the intersection-radiation from the sun, continues at the same rate, but the outflow due to fewer exit lanes results in a buildup of traffic- joules, in the system.
Note the NET effect is not a warming from the sky, which tends to confuse some posters here, but a constriction of outgoing radiation and a buildup of heat from the sun.

Larry Barnes

As in virtually all such articles focusing on longwave emissions/apsorption/etc, no account is given for the effect of the oceans which are the main determinant of global temperatures on this planet. The oceans absorb the vast majority of solar radiation on this planet and they do so to a considerable depth. Water is a relatively slow conductor of heat and therefore tends to hold it for a good length of time. Ocean currents and temperature layering cause the heat to move from the equator to the poles. Atmospheric temperatures in the tropics are nearly what one would expect from a black body analysis. The so called “green house effect” is really only visible at higher latitudes. This is due almost entirely to the redistribution of heat by the oceans. Atmospheric effects are quite small in comparison. This is not a new idea. until a few years ago oceanic scientists such as Doctor Robert Stevenson could have described all of this in considerable detail. Unfortunately, “climate scientists” with a poor understanding of the influence of the oceans have completely ignored it.

Bomber_the_Cat

Ira, there’s a problem here. as P. van der Meer says at 3:15 am. The blackbody curves are showing a peak at about 18 micron when they should be peaking at about 10 micron for a 300K blackbody.
In fact, if you refer to your previous post ‘Visualising the Greenhouse Effect – Atmospheric Windows’, you have the peak correct at 10 microns.
So, the current graphs don’t make sense – unless I am missing something? I have looked at the source material and that appears to be wrong also.
Has anyone got an explanation for this?

richard verney

tallbloke says: March 10, 2011 at 4:26 am
“….The greenhouse effect works by *SLOWING DOWN THE RATE THE EARTH COOLS AT*, by raising the altitude at which the atmosphere radiates to space . There is more than a semantic difference. Understanding it this way enables you to understand that it was reduced albedo 1979-1998 allowing more Solar energy to enter the oceans that caused the majority of the global warming at the end of the last millenium.
http://tallbloke.wordpress.com/2011/03/03/tallbloke-back-radiation-oceans-and-energy-exchange/
////////////////////////////////////////////////////////
Thanks for the link to your article. I was one of those who was arguing similar points with Willis and I have not seen your article before today. It is an interesting read.
I too respect Willis’ views but he was unable to even begin to explain the physics involved in how heat could be entrained by the oceans given the wavelength of DLR and its penatrative depth and thus become well mixed.
The only point he came up with (which did not answer the question) was that but for GHGs, the oceans would freeze and he referred to a link on scienceofdoom which suggested that without GHGs, the oceans would freeze within about 4 years. The underlying data and codes were not attached to the scienceofdoom article so that that assessment could not be verified. However, as I tried to point out to Willis, it is too simplistic looking at average temperatures and average conditions. The oceans are extremely complex and act as both a huge storage reservoir and a huge heat pump. For example, if one looks at the Baltic, in late summer, the sea temp is 16 to 18C and yet within about 4 months, it freezes over notwithsanding GHGs. There are many parts of the oceans (and inland lakes/seas) that freeze within months and this will tend to give the impression that when viewed on an average basis the seas would freeze within years. However, of course, there are great swathes of the Pacific, Indian Ocean, Atlantic etc receiving immense amounts of solar energy which energy is then pumped around by currents etc. It is almost certainly the case that it is this input and distribution that stops the majority of oceans from freezing over within seasons. Further, one may enquire rhetorically as to what causes the ice to melt/recede on these frozen seas/lakes? It is not an increase in GHCs but rather an increase in solar energy either directly and/or indirectly (via currents/circulation patterns).
I consider it probable that the vast majority of recent warming is due to natural variations and one of the key contenders for this being changes in cloud cover and changes in albedo allowing more solar energy to have penatrated the oceans.

I’ve been working with a combination of the reanalysis data and CO2 data to quantify the relative effects of atmospheric water and CO2 on OLR from the top of the atmosphere (click on my name). I think that a better approach would be to consider the average optical thickness of that blanket of atmosphere. First estimate the temperature at the top of the atmosphere using the S-B law. Then using skin surface temperature (SST) and lapse rates to calculate average optical thickness. (wet in the tropics and dry near the poles). Regress the calculated thickness on precipitation rate, precitatable water, and CO2. This method measures the effects of non-radiative processes of energy transfer as well as the “greenhouse effect”. (the formation of clouds, rain, and snow). You will find that any minor effect of CO2 is lost in the variability in the combination of effects of atmospheric water (vapor, clouds, rain, and snow).

wayne

Scarlet Pumpernickel says:
March 10, 2011 at 3:30 am
So what concentration of CO2 saturates these wavelengths?
There is already proof from Venus that the Greenhouse effect is not exponential http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html
——–
Thanks Scarlet, one impressive analysis. Also since NASA lists Venus’s *average* temperature at 464 C and if the surface was as high as 505 C then the natural dry lapse rate matches the graviation acceleration almost exactly, as it should. (778K-339K)/49.5km = ~8.87 °C/km (g=8.87 m/s2). Neat, 96.5% CO2 and no greenhouse effect at all. Now that’s some pure simple logic!

James

Re-emitted radiation does not and cannot heat the Earth significantly, because downwelling IR does not and cannot penetrate the surface of the ocean beyond its own wavelength.

But the radiation from the Sun has an even smaller wavelength. How come solar radiation can heat the Earth but re-emitted radiation?

nighttime

funny all this blanket stuff, we know that without greenhouse gases the surface can get very hot during the daytime – the moon, though at night leads to rapid cooling.
Seems to me that greenhouse gases lead to cooling during the day, and at night leads to a slow cooling , or in the desert, rapid due to less moisture.
After all if the sun didn’t come up next day how quick before the planet froze.
Such a simple elegant explanation.

syphax

The commentary for this article is pure gold. Mr. Watts, please continue a series of posts on basic planetary science processes; I’m very eager to see what your readership can come up with. I’d love some insight on, for example, how the Coriolis effect really works.

ShrNfr

I suggest we rid the atmosphere of o2 also. I mean it has this fat absorption/emission band at 50-70 GHz. One cannot be too careful you know.