From AGU highlights, interesting, but readers should note that this is one point on Earth in Chile, not a summation of the atmospheric absorption, emission, and transmission of infrared radiation for the entire globe.
For first time, entire thermal infrared spectrum observed
The driving mechanism of the greenhouse effect, and the underpinning of modern anthropogenic warming, is the absorption, emission, and transmission of infrared radiation by atmospheric gases. The heat-trapping ability of a gas depends on its chemical composition, and each type of gas absorbs infrared radiation of different energies. The amount of infrared radiation that escapes into space depends on the net effect of the myriad gases in the atmosphere, with water vapor being the primary gaseous absorber of infrared radiation.
Water vapor absorbs a wide range of infrared radiation, masking the effects of other gases. In fact, in many spectral regions (or infrared radiation energy bands), water vapor is so strongly absorbing that it makes testing the accuracy of infrared radiation absorption parameterizations used in general circulation models difficult.
To surmount this obstacle, Turner et al. headed to a 5.3-kilometer (3.3 miles) altitude site in the Atacama Desert in northern Chile, where the air is extremely dry. Using a broad suite of spectroscopic equipment, they produce the first ground-based measurement of the entire atmospheric infrared radiation absorption spectrum—from 3.3 to 1000 micrometers—including spectral regions that are usually obscured by strong water vapor absorption and emission. Though the data collected will likely be valuable for a broad range of uses, the authors use their measurements to verify the water vapor absorption parameterizations used in the current generation of climate models.
Source:
Geophysical Research Letters,doi:10.1029/2012GL051542, 2012
Title:
“Ground-based high spectral resolution observations of the entire terrestrial spectrum under extremely dry conditions”
Abtsract:
A field experiment was conducted in northern Chile at an altitude of 5.3 km to evaluate the accuracy of line-by-line radiative transfer models in regions of the spectrum that are typically opaque at sea level due to strong water vapor absorption. A suite of spectrally resolved radiance instruments collected simultaneous observations that, for the first time ever, spanned the entire terrestrial thermal spectrum (i.e., from 10 to 3000 cm−1, or 1000 to 3.3 μm). These radiance observations, together with collocated water vapor and temperature profiles, are used to provide an initial evaluation of the accuracy of water vapor absorption in the far-infrared of two line-by-line radiative transfer models. These initial results suggest that the more recent of the two models is more accurate in the strongly absorbing water vapor pure rotation band. This result supports the validity of the Turner et al. (2012) study that demonstrated that the use of the more recent water vapor absorption model in climate simulations resulted in significant radiative and dynamical changes in the simulation relative to the older water vapor model.
UPDATE: The full paper is here (thanks to Leif Svalgaard)
“””””…..DirkH says:
June 15, 2012 at 2:02 pm
kencoffman (@kencoffman) says:
June 15, 2012 at 12:25 pm
“I think it’s sad that man’s activities are so powerful that Mother Nature is stymied. She wants the Earth to shed heat energy, but CO2 traps it. Absorbs it. Blocks it. Stores it. Holds it. How long? Well, for a long, long time which increases the Earth’s surface temperature by an average of 33C.”
Is that sarcasm or do you just not know about Local Thermal Equilibrium and Kirchhoff’s Law? In that case, this might help you:
http://wattsupwiththat.com/2010/08/05/co2-heats-the-atmosphere-a-counter-view/…..”””””
Well there’s a fundamental problem with Tom’s thesis.
Kirchoff’s law regarding equality of spectral emittance, and spectral absorptance; requires a closed system where the materials present are in thermal equilibrium, at a single fixed Temperature , with the ambient EM radiation field present in that enclosure. So first off it requires thermal equilibrium; not LTE, and moreover it also relates ONLY to thermal spectra that are a consequence of the Temperature ONLY; so it does not apply to atomic or molecular line or band spectra.
There are many examples of photon absortion leading to an excited state, where the converse transition is prohibited, and therefore cannot occur; many laser systems depend on that simple fact.
Well the common Helium/Neon gas laser is such a system.
People need to stop traipsing out Kirchoff’s law as the explanation for every climate modelling problem; it simply doesn’t apply.
TheOtherJohninCalifornia says
…” There is nothing wrong with using models – as long as the models represent something with some degree of accuracy. Engineers (like me) use models for everything.”
And you’re right John because your models include all appropriate parameters, the values of which have been empically determined. Most unlike “climate science models”.
@ColdinOz,
Yep, and us Engineers are always testing the validity of the models we use.
If the model doesn’t fit the data, we don’t go adjusting the data until the model does fit.
Imagine that, doing a deflection test on a bridge.. ooo look, there is more deflection than the model says there should be.. lets just modify the deflection test !!!
Or.. “we compacted that clay core in the dam according to the consensus, but the test says its not compact enough yet”…… “oh, we better go with the consensus” !!
What I don’t get … is where the energy is supposed to go AFTER it’s been absorbed by an atmospheric molecule. Where’s the heat sink? The gas becomes warmer — then what happens? Surely it’s transferred by convection to other molecules or re-radiated. How is it “trapped”???
If it’s re-radiated, it’s not going to warm the earth (or our oceans) because that would violate the first law of thermodynamics (the earth is warmer — else it wouldn’t be radiating in the first place). Any re-radiated energy is either going to be absorbed by colder gases or go off into space.
Seems to me that only convection applies and then only when warmer air moves over cooler land or water.
But CO2 has a much lower specific heat than water vapor (like by two and half) so it’s not going to hold a lot of energy compared to H2O– and there aren’t a whole lot of CO2 molecules (vs H2O molecules) in the atmosphere anyway (like twenty five times less — .039% vs. 1% on average). And water vapor captures a much broader spectrum of IR than CO2.
So, how is this “global warming” supposed to work? How can CO2 make any difference?
I’m just asking.
What I don’t get … is where the energy is supposed to go AFTER it’s been absorbed by an atmospheric molecule. Where’s the heat sink? The gas becomes warmer — then what happens? Surely it’s transferred by convection [and conduction (collisions)] to other molecules or re-radiated. How is it “trapped”???
—
You’ve pretty much answered your own questions. Through equipartition if there are any other ir active molecules nearby their temperature will also go up momentarily and they will radiate more than before at all lines they could possibly radiate at. There is also the much smaller radiation of the atmosphere itself through collisions with various other molecular species (inter-electron interactions).
You cannot “trap” heat in a real atmosphere to any meaningful degree at a macro level. Heat will pass through the system according to the macro temperature differences any way you look at it, except at very small atomic scales. It all has to do with the scale you are looking at. If absorption in one layer makes it warmer but you are looking at the difference across many levels then that one layers increase is meaningless overall, the same energy will pass through layer one and layer ‘n’ no mater what the temperature of n/2 is (Stefan-Boltzmann). However, if you are looking at only one, two or three layers then you can play some real “tricks” with this limited viewpoint. AGW proponents absolutely *love* to speak in small layer number examples! The smaller the better to eat you up my dear.
Thank you, Wayne.
So why is their “universal” agreement that the nearly meaningless contribution to atmospheric CO2 by mankind’s burning hydrocarbons (compared to natural sources of atmospheric CO2) contributes even slightly to the earth’s ambient temperatures? Surely if the sun went dark we’d quickly freeze, right? How is the earth supposed to retain more heat (by virtue of its having a trace more atmospheric CO2)?? I don’t see a heat sink.
Moreover, no one is creating Carbon. All’s we can do is return to the atmosphere, from which all those lovely green plants will take it. And the more CO2, the faster green plants will grow. And plant growth requires energy — which comes from the sun — which leaves less energy to be radiated from the earth.
I really, really don’t understand how more CO2 is supposed to make any difference in the ambient temperatures.
Anopheles on June 15, 2012 at 12:08 pm said:
So, they have been telling us they knew these numbers for forty years, and nobody measured them before?
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No, it means they are applying additional checks to previous measurements and calculations.
Ill Tempered Klavier on June 15, 2012 at 12:59 pm said:
It should be noted in connection with kencoffman’s rather trollish comment that these observations tend to support the theory that water vapor is so dominant as an infrared absorber that the effect of carbon dioxide is extremely limited if it can be identified at all.
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You missed an important takeaway and that is the importance of water vapour diminishes with altitude.
davidmhoffer says
So…. except for some very dry regions of earth, which are so uncommon that this team had to go to great lengths just to find a suitable test site, water vapour so completely dominates the effects of all other GHG’s, that they are insignificant to the point of being nearly impossible to measure.
————
It’s real easy to find areas of the world which are extremely dry David. Just go outside and look straight up.
At 10km high where the jumbos fly the temperature is -60C. Since water freezes at 0C there is no water vapour to speak if there.
The desert was dry not just because it is in a rain shadow but because of the altitude.
And it’s easier to deploy the spectrometers at ground level than it is from a jumbo.
therealnormanrogers says:
June 15, 2012 at 3:33 pm
What I don’t get … is where the energy is supposed to go AFTER it’s been absorbed by an atmospheric molecule.
…
So, how is this “global warming” supposed to work? How can CO2 make any difference?
I’m just asking.
—–
It works, roughly, like this – and it’s a good job it does, or the earth would be a darn cold place…
GHGs absorb IR emitted from the surface and then re-emit it. They re-emit it in all directions, so some of what they re-emit goes back to the surface and causes it to warm more (or, if you prefer, cool less) than it would have done otherwise. GHGs don’t absorb direct sunlight much because the Sun, being so much hotter than the Earth, emits much more in the visible and UV part of the spectrum that GHGs do not absorb.
The first law is not violated, since it applies only to a closed system (and in the case of the Earth, there is energy input from the Sun). Another way to think of it is that GHGs act like little mirrors, and no one would argue that mirrors are incapable of reflecting because they are cooler than the Sun.
CO2 makes a difference because it is non-condensing. Water vapour OTOH condenses, as rain, so cannot build up the way CO2 can.
(Nothing in the above that can’t be found in standard text books, where it will be explained much better than I can)
HTH, John
Hi JohnB,
My undergraduate education was in Physics (waaay before grade inflation) and I did take a course in Thermodynamics — and it doesn’t work as you suggest.
The first law (of thermodynamics) is that heat always travels in one direction — from hot to cold(er). It’s not like gas pressure or a chemical reaction which can (and does) go in both directions (unless there’s a precipitate). You can’t make a surface warmer by “reflecting” back heat that it’s radiating.
Hence my questions.
On a per molecule basis, the CO2 absorption/emission event lasts for a billionth of a second and the ’emitted’ photon is at a longer wave length and lower energy, which is then INVISIBLE to an additional CO2 absorption. This causes overlap of the OLR bands and the ‘saw-toothed’ graphs. This now excited CO2 molecule then transfers this kinetic energy to surrounding N2O2 molecules, in a several billionth of a second process, and a convective wave is sent into space. Latent heat of condensation and latent heat of solidification of water vapor at altitude also releases convective energy, which has NO IR SIGNATURE. This convective heat is lost to space by Altitude Attenuation. The convective heat wave rises into thinner and thinner atmopshere until there are no adjoining molecules to share energy with. Thus, massive amount of energy are lost to space with no IR involvement. The “Radiative Balance” is another false metric. See “Magic Realm of Umbrellaman”….and for the ‘real’ level of moisture in the ‘driest place on Earth’ see…
http://www.myweather2.com/City-Town/Chile/San-Pedro-De-Atacama/climate-profile.aspx
George E. Smith says
So please don’t insult us by claiming you made a COMPLETE earth infra-red spectrum, that only goes from 3.3 microns to 100,000 microns.
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George, They don’t have to insult you, you insult yourself.
The IR spectral region is broad. So they explicitly narrow it by referring to the thermal IR spectrum. That means the frequency range defined by the black body radiation of the earth. The green house gases are excited by thermal energy so their emissions are restricted to the blackbody radiation band.
The rest of what of what you say George is also a confused mishmash of wrongness.
DirkH says
Resulting in scattering and of course emission to space, not “trapping” as warmist scientists so frequently write in editorials. You can count the “trapping heat” meme as a lie.
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Your description of the physics is correct. But the trapping thing is not a lie its a metaphor, signifying that the atmosphere has some resistance to the outgoing passage of energy.
JohnB :the Sun, being so much hotter than the Earth, emits much more in the visible and UV part of the spectrum that GHGs do not absorb.”
“The energy distribution within the solar spectrum is approximately 2 percent UV light, 47 percent visible light and 51 percent IR light ”
http://www.viracon.com/index.php?Itemid=197&id=96&option=com_content&view=article
George E. Smith says
There are many examples of photon absortion leading to an excited state, where the converse transition is prohibited, and therefore cannot occur; many laser systems depend on that simple fact.
———–
Wrong again. Lasers depend of establishing a population inversion. The excited state population for HeNe lasers is not established by an absorption from the ground state. Your claim that emission and absorption on a particular transition can be one way is totally false.
The rest of what you said is confused nonsense. DirkH is correct.
ColdInOz says
And you’re right John because your models include all appropriate parameters, the values of which have been empically determined. Most unlike “climate science models”.
————
The models referred to in the article are radiative transfer models or radiation absorption models. They are not GCMs aka global climate models.
Faux Science Slayer says
This convective heat is lost to space by Altitude Attenuation. The convective heat wave rises into thinner and thinner atmopshere until there are no adjoining molecules to share energy with.
———–
My Poe detector is beeping softly.
Faux are you taking the micky on these good WUWT folks?
@sunshinehours1
But the IR emitted by the Sun is mainly short wave IR, which is not absorbed by GHGs.
Again, it’s all in the textbooks
JohnB, this paper disagrees.
“In most climate models, the solar spectrum comprises wavelengths less than 4 μm with all incoming solar energy deposited in that range. In reality, however, the solar spectrum extends into the infrared, with about 12 W m−2 in the 4–1000-μm range”
http://journals.ametsoc.org/doi/abs/10.1175/2010JAS3282.1
CO2 is not only weakened by other overlapping GHGs, it is also weakened by its own broadening. The broadening from the Doppler effect has a tendency to create a flow of energy from the highly saturated center of the band toward its edge where the energy will move out of the atmosphere more easily.
LazyTeenager says:
June 15, 2012 at 4:31 pm
At 10km high where the jumbos fly the temperature is -60C. Since water freezes at 0C there is no water vapour to speak if there.
As you know so much, perhaps you could confirm that all jumbos make contrails above 10km in all circumstances. If they don’t, where does the water in their jet efflux go?
JohnB says:
June 15, 2012 at 5:17 pm
But the IR emitted by the Sun is mainly short wave IR, which is not absorbed by GHGs.
Again, it’s all in the textbooks
=======================================================
I was going to say “they are lying to you, John”, but then I took a cold shower and noticed the word “MAINLY”. Yes, they have taken care of an alibi, of course, this is how the things have been done in climate science in recent times.
The Sun does not skip the GHGs absorption bands: http://www.windows2universe.org/sun/spectrum/multispectral_sun_overview.html
LazyTeenager;
It’s real easy to find areas of the world which are extremely dry David. Just go outside and look straight up.
At 10km high where the jumbos fly the temperature is -60C. Since water freezes at 0C there is no water vapour to speak if there.
>>>>>>>>>>>>>>
3/4 of the earth surface is covered by water. The water vapour immediately above is thousands of ppm. By their own admission, for the vast bulk of the earth surface, co2 concentrations are so overwhelmed by water vapour, that they can hardly be measured.
As for up, way up, think it through LazyTeenager-who-works-so-hard-to-misdirect
At 10km up, there is very little water vapour as you suggest. And what happens to any LW that gets absorbed and re-radiated? Why it runs into that wall of water vapour at lower altitudes.
therealnormanrogers says:
June 15, 2012 at 7:22 pm
Hi JohnB,
My undergraduate education was in Physics (waaay before grade inflation) and I did take a course in Thermodynamics — and it doesn’t work as you suggest.
The first law (of thermodynamics) is that heat always travels in one direction — from hot to cold(er). >>>
The NET heat flow is from hot to cold. Take a look at the SB Law formula. There is no term in the formula for the temperature of the surroundings. A body radiates based on itz temperature. Not on the object next to it being hotter or colder.
If the flow of energy between two bodies was strictly one way, then I could shut off the lights of an on coming car by turning mine on bright. But I cannot. Energy flows are always in ALL directions, and the 1st law refers to the NET between two surfaces.
This is real science and I’ve often wondered why we don’t see more of it. There’s an area near my city where most of our coal powered electricity stations are and I reckon when the air is still you might find higher concentrations of CO2 than usual in that region. Imagine if similar spectral readings were taken during a high CO2 period and again when CO2 was at lower levels, then compared. Perhaps the answer would be too revealing.