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)
Has there not been a space-based observation of the entire infrared emission spectrum of at least a portion of the Earth?
Models models models models models models models models models models models models models models models models models models models models. Enough already.
So, they have been telling us they knew these numbers for forty years, and nobody measured them before?
Some higher resolution charts and additional description can be found here (click on the small charts at the right to display the larger versions):
http://www.arm.gov/science/highlights/RNDE2/view
Please explain the difference is between plots A and B. The following is based on figure 1 from the paper.
For A (31 Aug), 0.805 mm precipitable water vapor
For B (19 Sep), 0.283 mm precipitable water vapor
At that altitude, the absorption bands are much narrower than at the surface because of both the temperature and the pressure differences. This is useful for calibrating models, but it means that the plots are of limited value when comparing them to those in other papers.
On the other hand, the differences in the plots clearly show that water vapor is still a big factor at that altitude.
To bad they don’t bother to say in the abstract what direction the radiometers were pointing.
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.
Why are the curves scratchy?
Is this due to the wavelength precision of quantum mechanics?
The water vapour levels here are 1% and 3% of average Earth conditions so these are extremely dry conditions.
Don’t tell Mosher.
Why are the curves scratchy?
Is this due to the wavelength precision of quantum mechanics?
Yes. Although you aren’t saying it quite right. There are absorption lines where there is a molecule in the atmosphere that strongly interacts (in “resonance”) with a given frequency/wavelength. For many of the molecules, there are so many resonances that they form “bands” and absorb over a broad range, not at a sharp line. There are also line broadening dynamics in place, notably thermal/doppler broadening (where the doppler shift of a given molecule “tunes” it to an outgoing photon that wasn’t strictly resonant with it). However the edges of the broadened bands are still quite sharp, so you’re seeing quantum structure.
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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.
“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.”
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.
What a gem! Own goal! Own goal!
OTOH, doing it in the Chilean desert, which is the driest place on earth (that;s why they put IR telescopes up there) eliminates much of the water vapor continuum, which is probably the biggest remaining uncertainty (everything else is nailed down really strongly, there is a bit more uncertainty wrt the water vapor continuum which is intrinsically hard to model.
The post title would better be put as “Earth’s entire thermal infrared spectrum observed under extremely dry conditions”, which is the novelty here. Doing so allowed the authors a very precise test of radiation codes. FWIW, Antarctica is also high and dry, at least in the atmosphere, but it is also cold, so the amount of IR emission from the greenhouse gases is low. The entire spectrum has been measured many places, just not many places so dry.
NOTE: Eli Rabett is actually Joshua Halpern of Howard University
“..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”
Without the pay-walled paper, I’m a bit confused by what the authors mean by that. Are they saying that the science wasn’t as “settled” as we were so often told?
Or that the models were not “settled”?
Or both?
Without wanting to insult the authors, these days I have trouble even taking the word “observed” in the abstract at face value, until I can see the whole paper.
Mike Bromley the Canucklehead says:
June 15, 2012 at 11:55 am
“Models models models models…” 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. However, they have to represent the characteristic we’re studying, or they’re useless at best, and result in devastating lawsuits and deaths at worst. Engineers in the private sector require proven models (at least match history) before we can use them. That is why you see people like Burt Rutan laugh at the noise climate science puts out. They don’t match real world results, which to an engineer means they’re useless. That is why I have a hard time seeing MSM climate researchers (I don’t know how else to describe them) as scientists – they’re willing to accept poorly correlating results. No hard scientist or engineer would do so – at least for something on which his career depends on.
“The water vapour levels here are 1% and 3% of average Earth conditions so these are extremely dry conditions.”
hmmm.. So the modern models treat water vapour somewhere near correctly when there is basically no water vapour.. is that what they are saying ?
OK.. and so ?????? 😉
To paraphrase:
Water vapor absorbs a wide range of infrared radiation, masking the effects of other gases. So we choose to ignore it.
Thanks Robert Brown,
I am not an expert on the sensing and plotting equipment nor am I an expert of the bandwidth of each absorption wavelength…
Here is why I wanted clarification:
With a black body absorber there are no notches or scratchiness…correct? In determining the atmospheres relative relative energy absorption ratio compared with a black body, we would have to know how wide the scratches are and how wide the notches are? right? It is an integral of the absorption spectrum.
Are the scratches effectively smoothed out due to real world allowances like Doppler and natural variability in the absorption quantas.
Ie a molecule of water (H2(16) O) absorbs 3657.1 cm-1 +/- how much?
How close to 3657.1 cm-1 does a photon have to be to be absorbed?
Is it fair to smooth the absorption lines to null the scratches?
Well the last time I checked, the human eye stopped responding to electromagnetic waves, and converting that energy into the mental machinations in the eye and the human brain to produce the sensory effect that we call “LIGHT”; which therefore by definition IS visible, around an upper limit of 800 nm, and a lower limit of 400 nm. The brain response is so poor at the extreme ends, that humans are only aware of its existence at these extremes under highly controlled laboratory condition. so most humans go through life having never “seen” 800 nm light, so for most practicalpurposes, the “visible” is considered eded, at 700 or 750 nm,
So that means that the Infra-red spectrum begins at 700-800 nm; not 3.3 microns. And between 750 nm and 3.3 microns, common GHGs suchas H2O and CO2 have very significant absorption lines and bands between 750 nm and 3.3 microns.
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.
And I would hardly call these spectra THERMAL spectra. A thermal spectrum does not contain discrete spectral lines, which are characterised by atomic, and molecular resonances, related to atomic or molecular structure.
Thermal spectra are a consequence of Temperature only, and are unrelated to any atomic or molecular electron energy transitions; they are continuum spectra; not closely spaced line spectra. There are no gaps anywhere in a thermal spectrum;no matter how high a wavelength or frequency resolution spectrometer you use, you can never resolve a thermal spectrum into discrete line frequency components; there are no frequencies absent from a thermal spectrum.
And notice that they plot their spectra on a wavenumber or ersatz frequency axis, instead of a wavelength axis. This of course has the effect of shifting the spectral peak to a different wavelength, closer to the CO2 molecular LINE/BAND absorption wavelengths, rather than peaking at around 10.1 microns, which is where a 288 Kelvin Thermal spectrum peaks.
This wave number approach, perpetuates the myth, that Thermal spectra contain only discrete spectral lines, and result in photons with only certain energies.
In a Thermal spectrum ; between any two photon energies, no matter how close in energy, there exist an infinite number of intermediate photon energies. This is not true of a line spectrum, such as make up the absorption band spectra of common GHG moleculees.
Water water everywhere and all the boards did shrink,
Water water everywhere nor any drop to drink.
Water water everywhere absorbs the sun galore,
Water water everywhere the climate wonks ignore.
I see I gave them too much credit; their COMPLETE EARTH THERMAL EMISSION SPECTRUM only goes from 3.3 microns, to 1,000 microns; not 750 nm to 100,000 microns; maybe its 100,000 nm I meant to say.
And I should emphasize that it is a common misconception, that a black body radiation spectrum, which is a true Thermal spectrum (albeit theoretical), consists of millions of extremely closely spaced spectral lines, so that only certain values of PHOTON ENERGY can be found.
That isn’t the case. The Planck derivation of the correct Black Body Radiation spectrum, is a product of CLASSICAL PHYSICS; it is not quantum mechanics. Any value of photon energy (and frequency) is present in the black body radiation continuum. NO photon energies or frequencies, are absent from the black body radiation spectrum.
It is certainly true that the photon energies and frequencies are related by the Planck/Einstein relation, E = h (nu); but every value of E and (nu) is allowed, and present in black body radiation, or ANY thermal spectrum. That constraint simply requires that there must always be an INTEGER number of photons, at any grequency; you can’t have k\fractional photons; buty they can have ANY energy value whatsoever.
“Water vapor absorbs a wide range of infrared radiation, masking the effects of other gases.”
Masking the effects of other gasses, or absorbing the infrared that those other gasses (*cough*CO2*cough*) would have otherwise absorbed, making the increase in such secondary gases moot because H2O already absorbed the infrared in that spectrum?
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/
Short form: CO2 absorbs and re-emits IR to equal amounts. 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.
“””””……Eli Rabett says:
June 15, 2012 at 1:00 pm
OTOH, doing it in the Chilean desert, which is the driest place on earth (that;s why they put IR telescopes up there) eliminates much of the water vapor continuum, which is probably the biggest remaining uncertainty (everything else is nailed down really strongly, there is a bit more uncertainty wrt the water vapor continuum which is intrinsically hard to model.
The post title would better be put as “Earth’s entire thermal infrared spectrum observed under extremely dry conditions”, which is the novelty here. Doing so allowed the authors a very precise test of radiation codes. FWIW, Antarctica is also high and dry, at least in the atmosphere, but it is also cold, so the amount of IR emission from the greenhouse gases is low. The entire spectrum has been measured many places, just not many places so dry……”””””
Well The Atacama, and Antarctica vie for the distinction of having the dryest atmospheres; but I’m happy to accept the Atacama; it’s an interesting place too.
But as to it being an “extremely dry” location; just what does that mean in real terms ?
Let me put it this way; what is the molecular abundance of H2O in the Atacama atmosphere; and is it higher or lower, than the Atacama atmospheric CO2 molecular abundance ?
Surely, that would be a metric as to whether Atacama is truly dry; or not.
Hats off to Rabbett for pointing out that this underestimates the masking effect water vapor has on other GHGs.