Nitrogen – Active In The IR, A GHG?

Sometimes it pays to check the most widely accepted assertions.

Just about every discussion of CO2 and “Greenhouse Gasses” includes a harangue about Oxygen and Nitrogen NOT being active in the IR and NOT being a “Greenhouse Gas”. Yet we know that any object with a temperature above nearly nothing emits photons. Some are X-rays, some are visible light, and some are infrared light. (And radio waves and microwaves and…) So how can you have a world wrapped in hot nitrogen and NOT have it radiate something? So I started to search.

I usually present things as a chronological series of “the hunt”, saving the money quote / link for last (as that’s when it was found, since then the search tends to end). I’m not going to do that this time. Right up front is the “wow link”. I went through a LOT of “the same old same old” to get to it, and the ‘supportive matter’ would be a bit tedious. I’ll put a couple of bits below it. Bits that were more useful than most.

Nitrogen Has ‘Back Radiation’ in the Infrared

Harvard Articles: A Strong Infrared Radiation From Molecular Nitrogen In The Night Sky

I was going to just quote a couple of bits, but since they have a PDF_don’t_cut_paste setting, instead I’ll give a screenshot of the first page. ( I really do wish folks would realize that if you can SEE it you can COPY it and that all they are doing is wasting their time with ‘protection’ measures. Fair Use is Fair Use, after all…) You can click on it to get a more readable size, or ‘hit the link’ for the whole doc.

Nitrogen IR from the sky

Nitrogen IR from the sky

The bottom line here is pretty simple. After doing some sky observing, they found a large IR interference from the open sky. This was chased back to a Nitrogen band at 10,300 Angstroms. It varies over the night, dimming as the sky cools, and increases again just before sunrise. It varies with zenith angle too. It is strong and bright.

So my questions are simple and few:

1) Is it not the case that “That which emits, absorbs” at the same band?

2) Does that not mean Nitrogen IS an infrared absorber and emitter?

3) Does that not mean Nitrogen fits the definition of a “greenhouse gas”?
(wrong as the term may be).

4) Doesn’t this kind of screw up the whole “Only CO2 Matters!” mantra?
(That already ignores water vapor…)

That’s really the whole thrust of this posting. IF Nitrogen (not to mention all it’s ions and N3 and atomic forms) has a bunch of IR bands, doesn’t that kind of play Hob with the whole CO2 thesis? And there is ample evidence for Nitrogen having a bunch of IR bands.

Some Backing Matter & Electric Universe Speculation

These bits are also interesting in some ways, but mostly are just additional evidence for a nitrogen IR behaviour, while the above is a direct measurement by experts in measuring photons from the sky.

Some Sniditude toward NASA:

The title implies they know that Nitrogen has an IR band or three…

Infrared electronic emission spectrum of nitrogen
Author and Affiliation: Benesch, W. M.

Saum, K. A.
Abstract: Nitrogen IR emission spectra from atomic and molecular excited electronic states transitions, studying DC discharges at various pressures
Publication Date: Jan 01, 1970
Document ID:
19700043976 (Acquired Dec 04, 1995)
Accession Number: 70A20092
Document Type: Journal Article
Publication Information: 459 (
Publisher Information: United States
Contract/Grant/Task Num: NSG-398
Financial Sponsor: NASA; United States
Description: 6p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
Imprint And Other Notes: APPLIED OPTICS, VOL. 9, P. 195-200.
Availability Source: Other Sources

Perhaps it’s that whole “electric universe” thing and the degree of nitrogen “excitation” is important in modulating our weather? Somehow I’ve not heard anyone mention that possibility, yet here we have THE dominant gas in the atmosphere “back radiating” in ways that are dependent on the Sun, and probably also dependent on the degree of ionizing from electric / particle flows in the atmosphere. Seems stronger than the imagined “greenhouse gas” effect from CO2. At least this has been observed and measured.

A Graph Of Nitrogen Spectral Lines

Nitrogen Spectrum showing IR bands

Nitrogen Spectrum showing IR bands

Click to embiggen…

Note the strong spectral lines down in the IR end off to the right?

That seems, to me, so say that Nitrogen IS active in the IR end of things, and with a lot of various bands of activity. Note, too, that this is JUST for molecular Nitrogen (one presumes N2) and does not include the various OTHER Nitrogen species (presumably not the N3 that sometimes occurs nor the various ionization products nor all the NxO species nor…) so there’s a large potential for a lot of other IR active species running around “up there” especially under solar irradiation, particle flows and storms, and in the hot thermosphere / mesosphere areas.

In short, it looks to me like the “CO2 Magic Gas IR Is EVERYTHING!” crowd have ignored Nitrogen and got things wrong, again.

The Typical View, but Shows Water

This is mostly the regular old run of the mill “CO2 is important not much else is” kind of treatment most often seen. It denegrates any nitrogen role, but does mention how important water is (for a change).

It starts off well:

Any object warmer than absolute zero gives off electromagnetic radiation. Hot objects give off high energy, short wavelength photons; cooler objects emit lower energy, longer wavelength photons. Earth’s surface, heated by the incoming sunlight, emits relatively long-wavelength infrared photons. These IR photons move upward from the surface through the atmosphere. Here’s where the greenhouse effect comes in! The atmosphere, which is mostly transparent in visible light wavelengths, is definitely not transparent at IR wavelengths. A small amount of the upward flowing IR shoots directly out into space, but the majority of it is absorbed by the atmosphere. This influx of IR energy heats the atmosphere, which in turn re-radiates IR photons. Some go up, while others go down. Eventually the IR photons escape into space, but some make several round trips between the ground and the atmosphere before they depart. Along the way, a lot of energy is transferred to the ground and the atmosphere. That energy becomes heat which warms Earth’s surface and its atmosphere.

They “get it” that ANYTHING warm gives off photons. They get it that the air is substantially already IR opaque and not much is going to make it more so. Then they kind of lose the plot with photons running back and forth and magically heat happens… Close, but not quite. At any rate, further down:

Greenhouse Gases

Although Earth’s atmosphere is 90% opaque to long wave IR radiation, the vast majority of the atmosphere is not composed of gases that cause the greenhouse effect. Molecular nitrogen (N2) and oxygen (O2) make up roughly 98% of our atmosphere, and neither is a greenhouse gas. So, although the greenhouse effect is very powerful, a very small fraction of Earth’s atmospheric gases generate the effect.

So they again “get it” that we’re in the 90%+ range of IR opaque already and then miss the point that any more opaque is not going to do much of anything (maybe speed up convection and evaporation a bit, that’s about it). Then we get the usual dismissal of Nitrogen and Oxygen, when BOTH have IR spectral lines… (I’ve not bothered to include the oxygen bits. Search on “Oxygen IR spectrum” or “Oxygen IR spectra” if you want to chase that down.)

What are the main greenhouse gases? Because of all the press coverage it has received in recent years, you may think that carbon dioxide (CO2) is “the big one”. Though CO2’s role is important, water vapor is actually the dominant greenhouse gas in Earth’s atmosphere. Water vapor generates more greenhouse effect on our planet than does any other single gas. Water, in gaseous form (as water vapor) and in liquid form (as tiny droplets in clouds), generates somewhere between 66% and 85% of the greenhouse effect. We’ll get back to the issue of the large range that “66% to 85%” represents in a minute; it turns out that separating the impact of individual greenhouse gases is not a simple matter.

And that bit is just stellar! They “get it” that we are a Water Planet and that water is THE big working fluid. As evaporation / precipitation and as convective driver, and as IR absorber and emitter (largely important at the tops of clouds).

They even ‘get it’ that ozone matters. Again I’d want to ask if perhaps modulating Ozone via UV variation from the sun has been properly assessed, but I’m sure it has not been…

After water vapor, what are the most important greenhouse gases? In rough order of importance and size of effect, the major ones are carbon dioxide (CO2), methane (CH4) and ozone (O3). There are a number of other gases that contribute to the greenhouse effect to a lesser extent; we’ll mention these here in passing for reference, but not consider them further henceforth. These “lesser greenhouse gases” include nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and chlorofluorocarbons (CFCs).

Now look back up at that water vapor set of numbers. 66% to 85%. Range of 19% How “important” is CO2? Well, they have a nice little chart further down.

Major Greenhouse Gas	% of Greenhouse Effect
Water vapor			36% to 66%
Water vapor & Cloud droplets	66% to 85%
Carbon dioxide			9% to 26%
Methane				4% to 9%
Ozone				3% to 7%

Now note that CO2 is 9% to 26% with a 17% error band. It is lost in the error band on water.

Since we have little to no clue how much water changes over time, and what impact it has overall on climate (other than that when things get very cold and it freezes out of the air we tend to stay in those ice age conditions for 100,000 years… the risk is to the downside in cold); the ‘bottom line’ for me is pretty simple. It’s the water that matters. CO2 not so much.

Now, too, remember that human activity has changed CO2 (maybe…) by about 100 ppm out of 400. And since the IR absorption is logarithmic, it is way less than 1/4 of the effect. Just for simple comparisons, lets call it 1/8 of the total IR absorption of CO2 ( it ought to be significantly less than that). That would make the “human part” about 1% to 3%. That’s IT. The whole magilla. The entirely of ALL human contribution is way more than lost in the error bands of everything else. In short, it is irrelevant.

Trivial variations in water vapor level will entirely swamp ANYTHING people have done. Natural variations in ozone will swamp it. I’d even assert that it is likely simple variation in Nitrogen excitation will swamp it.

All of those larger things are ignored, just so that CO2 can be vilified. Golly.

In Conclusion

This article was inspired by reading: but I’ve lost the link back to what pointed me at it, so can’t properly h/t that source.

The role of other species in the IR “budget” of the planet have been grossly ignored, despite it being very clear that they are larger than any human induced change in the CO2 IR “budget”.

In particular, the role of UV modulation of ozone and the role of Nitrogen and any impacts of solar and cosmic radiation induced changes in ionization levels have been ignored. Nitrogen is roundly dismissed as not active in the IR bands, despite it being enough of a pain in the telescope that as far back as the 1940s folks noticed and measured it with a galvanometer.

There IS “back radiation” in the IR band from nitrogen. It DOES modulate with solar activity / sunrise and set. It is also ignored. That, alone, makes most of the dreck served up as “climate science” rather useless.

Water variation (and error bands) swamps any CO2 effect, and the human component of the total CO2 effect is vanishingly small, less even than the total CO2 error band and way less than the water vapor error bands / variation.

UV / Ozone and ionizing of Nitrogen are likely to be far larger than the 1%-3% of human contributed CO2. This provides a direct mechanism for the “electric universe” folks to explore and it provides a direct mechanism for the Sun to drive climate despite low TSI variations. Solar driven variation in water vapor, Ozone, and Nitrogen ionization totally swamp any human CO2 contribution to the climate.

In short, we are irrelevant, “carbon” is irrelevant, and it’s the sun along with other gasses that matter.

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in AGW Science and Background, Science Bits. Bookmark the permalink.

20 Responses to Nitrogen – Active In The IR, A GHG?

  1. gareth says:

    Hi EM, interesting article. The significance of N2 must depend on the adsorption of N2 (units? – dB/Dobson Unit ??) compared with CO2. Maybe a physicist will happen by…

    Once upon a time I used to work with IR gas detectors. IIRC, these work by thermal expansion of a gas column on the sample side, compared with thermal expansion on the reference side (alternating/chopped IR beam through both sides, diaphragm capacitor microphone as detector). The detectors only work for IR absorptive gasses (we were interested in CO2) and the carrier gas was air, which implies that CO2 has significantly different absorption to air at IR.

    PS: Copying text from PDFs – yes, there is a security “broken by design” feature in some pdf text (that can be got round). This one however appears to just be a pdf created from page images (not text), encoded as JBIG. Open the file with a text editor and you’ll see.

  2. Ron Clutz says:

    Thanks for this investigation and links. If N2 and O2 get their temperatures through collisions among molecules in the same parcel of air, then they must radiate as they can. The issue is the delay from surface to tropopause, resulting in a lapse rate and warmer temps at the surface. What does this say about tripolar molecules doing all the radiating at the tropopause, effective radiating level, etc?

  3. Pingback: N2 is IR-Active: This Changes Everything! | Science Matters

  4. Andrew says:

    N2 only absorbs when it is well above ordinary temperatures. The line being observed in the paper is in the middle of the hot object IR region and well away from the emissions produced by low temperature objects. The writers of the paper are in any case considering that it is being created by recombination of atomic nitrogen after photo dissociation during the day. Tyndall in 1860 considered N2 to be like a vacuum for IR absorption.

  5. omanuel says:

    Thanks, E.M. Smith, for going back to the 1945 study on IR radiation from molecular nitrogen in air.

    Stalin’s lock-step science in the old USSR seems to have been duplicated in the West after WWII ended.

    Click to access STALINS_SCIENCE.pdf

  6. Pingback: Nitrogen – Active In The IR, A GHG? | Climate Collections

  7. cdquarles says:

    By the way, oxygen is active in the IR as well, though primarily in the red to ‘near’ IR. That’s why liquid and solid oxygen are blue tinted.

  8. cdquarles says:

    Hammer hits nail on the head! I’m sorry about the oxygen comment, for you covered it; but still, a FYI for readers who don’t know any chemistry.

    They forget chemistry, at their peril. Phosphorescence, fluorescence, lasing (Is our ionosphere a natural maser, given the necessary conditions?), sono-luminescence, direct chemi-luminescence, solution chemistry (water clouds are the number one aerosol!), surface chemistry (water droplets, ice droplets, soot (not just from human burning!), surface photochemistry (UV, cosmic ‘ray’ particles), gas phase photochemistry, and much, much more.

  9. cdquarles says:

    @Gareth, I’ve done some IR spectroscopy, though many years ago and not at high resolution. If your detectors were tuned to the main carbon dioxide band, ‘air’ would be essentially transparent to those bands, especially with the usual small samples tested in analytical chemistry labs. If you needed to do high accuracy and resolution work, you had to do some more research to get the data needed to correct for contaminants.

  10. gareth says:

    @cdquarles,The IR source wasn’t very “tuned”, being an incandescent lamp. I found a link to the very thing here :

    As you say, N2 is pretty much transparent to IR (see e.g. Wikipedia) – so it won’t contribute much to “Greenhouse Effect”. That it has some emission bands in IR when dis-associated/ionized is not the same thing as IR absorption/emission by diatomic nitrogen.

    @E.M. Smith: “we know that any object with a temperature above nearly nothing emits photons … how can you have a world wrapped in hot nitrogen and NOT have it radiate something?”

    Attempted explanation:

    Temperature of a gas molecule is a function of it’s total kienetic energy. That includes both translational (speed) and vibration.

    Heat transfer is by conduction, convection or radiation. A “hot” gas molecule can transfer heat by banging into something else (conduction), moving somewhere else (convection) or giving out a photon (radiation). The energy in a photon is a function of the frequency (wavelength). Higher frequency (shorter wavelength) equals more energy. A gas molecule cannot emit a photon if the photon energy is more than the energy available, and the energy transferred will be from vibration modes, not translation. Thus a molecule cannot radiate if its vibration energy is less than the photon energy corresponding to the frequency of vibration of its lowest frequency vibration mode.

    Assuming diatomic gasses in the atmosphere, CO2 can give out a photon because its vibration energy (temperature) is at a frequency that corresponds to photon energies in the IR. Nitrogen, however, does not support vibration modes below about 100nm (short UV) so can’t radiate unless it is much more energetic – and it won’t be anything like that hot. To lose heat it would have to transfer energy by conduction – e.g. by banging into a CO2 or water molecule, and that molecule could then loose the energy transferred to it by radiating am IR photon at it’s characteristic vibration frequency

    (I think this is correct, in a hand waving engineery sense – maybe that physicist will happen along and give chapter and verse)

  11. gareth says:

    Doh “Assuming diatomic gasses in the atmosphere, CO2 ”
    Wot I dun ment was just gasses at “normal” (for the mid to upper atmosphere) temperatures – not plasma. CO2 not being, of course, a “diatomic gas”

  12. cdquarles says:

    @ Gareth, an incandescent light emits over half of its power in the ‘near’ IR, but still even in the ‘far’ IR, the emitted power isn’t zero (nor is that true for the Sun). If you look at that emission line spectrum closely, both nitrogen and oxygen are active in that band, for some wavelengths. Your gas detector is functionally subtracting out those lines. The actual gas is translucent, not transparent.

  13. cdquarles says:

    Ugh, I chopped off part of what I wanted to say. Thus, both Tyndall and Arrhenius were wrong, but not completely wrong. They just drew too vast of a set of conclusions from their half-vast available data.

  14. p.g.sharrow says:

    @cd; half baked conclusions based on the results of half assed experiments.
    Arrhenius spent over 20 years teaching his concept that CO2 caused Global Warming would save the world from the cooling of the coming IceAge. IIRC in 1906 Max Planck proved and got Arrhenius to admit to the fact that his experiment was poorly done and his conclusions not warranted. That did not stop him from Educating a generation of weak minds to spread his message. It would seem that politics trumps facts…pg
    “Those that can, will learn. Those that can’t, must be taught”….pg

  15. R. Shearer says:

    Transmission for N2 in IR is as close to 100% as you can get, i.e. no absorption. That does not mean it can’t emit IR, from heating by a hotter molecule or some other excitation or from dissociated atoms recombining.

  16. cdquarles says:

    @pg, Exactly :) When I studied chemistry, Arrhenius was a bit of a laughing-stock. Oh how fashions change and what has happened in the past will happen again (particularly for those who dismiss history).

    @R. Shearer, what you say is contingently true, but I’d say molecular nitrogen is very highly translucent, especially if I needed to do very precise work accurately and at high resolution. Molecular nitrogen does have absorption lines (and conversely emission lines) in the IR. IR is a very wide band.

  17. Svend Ferdinandsen says:

    An interesting summation that makes you think a bit.
    It would help to relate the power in these bands from other gases to the power of water and CO2.
    By the way, it seems that water vapor and water is mentioned more and more as greenhouse gasses, so some realisme is slowly creeping in to the debate about Global Warming.
    Now we still need to get rid of the coupling between climate change and CO2 and revert to the only effect CO2 can ever have is a bit of warming.

  18. gallopingcamel says:

    Carbon Dioxide and Nitrogen are used in TEA (Transversely Excited Atmospheric) lasers. CO2 lasers operate in the IR with exceptionally high efficiency at 10.6 microns. Nitrogen being diatomic emits at shorter wavelengths such as 337nm (0.337 microns). The gain of Nitrogen lasers is so high that reflective output couplers (mirrors) are not needed.

    The Duke University Free Electron Laser uses a UV laser to eject electrons from a photo-cathode (Einstein Nobel prize, 1921). These electrons are accelerated to ~1 GeV prior to storage in s synchrotron. UV lasers tend to be expensive. For example we could have used a quadrupled YAG laser but the price would have been ten times what our Nitrogen laser cost.

    The DFELL bought its Nitrogen laser over twenty years ago from a company located in what used to be East Germany. It is so elegantly simple that I only had to rebuild it every few years.

    The above has some relevance to “Radiative-Convective Climate Models”. I like the Robinson & Catling model that has two radiative channels in the IR and one in the UV/visible:

    Click to access Robinson2014_0.1bar_Tropopause.pdf

    Please take time to look at the supplement to the above letter which shows the R&C model in enough detail to allow amateurs like me to replicate their work:

    In sharp contrast, Mann, Briffa and Hughes can’t produce calculations to back up their 1998 paper (the dog ate my homework):

  19. gareth says:

    @gallopingcamel: “Nitrogen being diatomic emits at shorter wavelengths such as 337nm”

    So that would be in the near UV. Not IR.

    And the photon energy would imply a much higher temperature than would be found in atmospheric N2. So N2 would not be a “greenhouse gas”.

  20. gallopingcamel says:

    As you say 337 nm is in the near UV.

    Diatomic gases (e.g. Nitrogen and Oxygen) and monatomic gases (e.g. Helium and Argon) are “Greenhouse gases” in the sense that adding them to a planet’s atmosphere raises the average surface temperature.

    Please read the supplement to Robinson and Catling’s NatGeo letter if you want to understand the mechanism. If you are not comfortable wading through the mathematics here is a qualitative explanation.

    In the stratosphere heat transfer is primarily radiative and varies linearly with pressure. This explains why temperature rises with altitude in the stratosphere.

    In the troposphere radiative transfer varies proportionally to the square of the pressure which renders the lower atmosphere increasingly opaque to IR radiation once the pressure exceeds 0.1 bar. This explains why temperature falls with altitude in the troposphere.

    The tropopause is the transition layer between these two regions.

    In the troposphere what matters most is the Cp of the gas or gases involved. On most planets the temperature gradient in the troposphere is equal to -g/Cp. There are two exceptions to this rule in our solar system, namely Earth and Titan. The R&C letter uses an arbitrary constant (alpha) to compensate for the liquids on the surface of these two bodies.

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