Methane: The Irrelevant Greenhouse Gas

The mega methane mania finds its roots in the Greenland ice cores where it was observed that large fluctuations of methane coincided with fluctuation in stable hydrogen and Oxygen isotopes (erroneously considered a paleothermometer). Especially around the erroneously considered cold Younger Dryas. To the cherry pickers it looked like the methane spikes had caused sudden large temperature swings, like the ‘more-than-ten-degree-within-a-decade’stuff of Richard Alley and friends.
However this could have been challeneged immediately comparing the Greenland ice core records with Antartica, nothing adds up considering global temperatures. The Antarctic CO2 record has no corrolation with the Greenland isotope ‘temperatures’ while the Greenland CH4 records don’t compare with the Antarctic isotope ‘temperatures’. So something had to be wrong there. But that methane would have nothing to do with global temperature is obviously a too unconvenient truth to alarmists.

Amazing really when the end game is considered. Kill off all the big time f*rters – meat and milk disappears. Eat cats, dogs, birds…ok for China/Europe? So we get veggie with leaves and stuff that needs CO2 for growth…oh no, thats gone as well.
Good article…thanks

Great article, the key to the whole CAGW scam I believe.
CO2 and possibly methane could have a played a major role in getting Earth out of ice ages and snowball Earth conditions, i.e. when there was much less water vapour in the atmosphere. But once the Earth is warm and humid (as it is now) water vapour dominates.
Water vapour even dominates the “consensus” CAGW scare, supposedly doubling CO2 causes a small rise in temperature, which then causes more water vapour, which is the thing that dominates the eventual rise (allegedly).

The tiny increases in methane associated with cows may elicit a few giggles, but it absolutely cannot be the basis for sane regulations or national policy.

And if sane people ran the governments, it would not be an issue. However, given past actions, the sanity of government officials is always in question.

Excellent post! I’ve been blogging about AGW for 10 years, but haven’t really had a grasp on the mechanism until reading this article.

Tom, this is one of those posts where I receive a quantum addition to my education on this subject. Also, the presentation of it is understandable to every reader, regardless of background education and experience. Thanks. I was wondering if your graph above could be made more effective (or probably better make a second graph) by changing the ordinates from simple unit absorption to quantitative units that take the abundance of the gases in the atmosphere into consideration? This would be a more powerful illustration of your very thorough explanation. I hope some of the CO2 worriers join this discussion – Mosher for example, to argue their case. I have no doubt they understand the details of this subject.

TRG says:
April 11, 2014 at 4:40 am

Why have I not heard about this before?

Because it’s wrong.
Indeed, it would be truly amazing if everyone in the world hadn’t realised this except Tom Sheahen.
First it would be helpful to describe the graph as ‘transmission’ instead of ‘absorption’, since that is what is shown. It should also state the path length over which these transmission figures have been assessed. ‘A per molecule basis’ is very dubious ( it looks more like total transmission from ground to space). What is the provenance of this graph?
The failure here is that although CO2 is a very small proportion of the atmosphere, there is no sightline through the full thickness of the atmosphere which will not intersect a CO2 molecule in a very short distance. For example, 95% of radiation at 15 micron will be absorbed within a distance of 1 metre. The atmosphere is therefore opaque to radiation at 15 microns, due to the small amount of CO2 present. Water vapour (if present) also absorbs at 15 microns but not at the 100% level of CO2.
Similarly for methane. In addition, the only reason that methane is considered to be more potent than CO2 is because there is so little of it. Its absorption bands are not saturated and its affects are therefore linear and not logarithmic.

“The main thing to worry about is over-reacting politicians and another layer of unnecessary government regulations. ”
Might soon come to a point where it becomes necessary to leave the West as it strangulates itself under unnecessary self-imposed shackles; and wait it out til the parasites have died off.

My understanding is that its residence in the atmosphere is relatively short and the methane clathrates found in Arctic that alarmists claim will melt are more stable and less likely to melt/be affected by warming than previously believed. There were a few papers that came out in the last year or so on this topic. I hadn’t known about the comparative absorption spectra so unless there is a mechanism that will increase methane by 10,000% no reason to worry about CH4

And the other side of the coin is that all green house gases also emits energy in the same wavelength bands.

kramer says:
April 11, 2014 at 4:45 am
Wouldn’t methane be a factor in dry climates?
Furthermore, does any amount of water in the atmosphere negate the effect of any amount of methane in the atmosphere?

Perhaps I’m blind or simply not seeing things correctly, but at 7.5 microns water only seems to absorb about 40% leaving plenty of room for CH4 to absorb at that wavelength.

Leonard Weinstein says:
April 11, 2014 at 5:58 am
“However, as the atmosphere cools with increasing altitude (from the lapse rate), almost all of the water vapor condenses out, first as clouds at moderate altitudes, and most of the remainder as ice crystals at higher altitudes. The CO2 and methane are not condensed out at the temperatures encountered. ”
Well, and what does water vapor do when it condenses? It forms tiny little blackbodies in the sky…
…which absorb what they don’t reflect with a Planck spectrum at their frigid temperatures… Icehouse effect not greenhouse effect… warm yourself up with the cosy IR blackbody radiation from a bunch of mineral water bottles right out of your fridge. Much warmer than absolute zero!

swood100 says:
April 11, 2014 at 5:54 am
“Furthermore, does any amount of water in the atmosphere negate the effect of any amount of methane in the atmosphere?”
The right word is “cannibalization”. When two gases compete for the same photon only one of them can get it. It doesn’t “negate” the effect, it neutralizes it, obviously.

ferd berple says:
April 11, 2014 at 6:13 am
“if CO2 is already absorbing at the 100% level, adding more Co2 cannot have any effect whatsoever. Or are we to believe that doubling CO2 will result in 200% absorption?”
Enhanced GHE comes about through pressure broadening; only the frequencies at the edges of the band which are NOT saturated can become more saturated.

DirkH says:
April 11, 2014 at 6:15 am
The right word is “cannibalization”. When two gases compete for the same photon only one of them can get it. It doesn’t “negate” the effect, it neutralizes it, obviously.
ne·gate
to nullify or cause to be ineffective: Progress on the study has been negated by the lack of funds.
But the real question is whether any amount of water in the atmosphere will negate the effect of any amount of methane in the atmosphere. Some have suggested that this is happening at an altitude which contains little H2O. Is the absorption at a lower level not important?

swood100 says:
April 11, 2014 at 6:58 am
“Some have suggested that this is happening at an altitude which contains little H2O. Is the absorption at a lower level not important?”
The level is not important, the mean free path length for a given frequency is. Whether a photon is intercepted 1 time or a thousand times on its absorption-reemission-voyage through the atmosphere does not matter. One absorption-re-emission changes its direction arbitrarily and suffices. If the mean free path length is on the order of the thickness of the atmosphere it escapes directly to space; otherwise it becomes part of the “greenhouse effect”.
(Ignoring the tiny blackbodies in the sky here)

The last I heard was that methane is broken down in the atmosphere within 10 years

blackadderthe4th says:
April 11, 2014 at 5:11 am
“…70 years ago the view that co2 could affect the global climate was held by only a tiny minority of climate scientists, many assumed there would be a self regulating mechanism that would put things back into balance.”
There IS such a mechanism. Rainwater removes CO2 from the atmosphere and puts it in the crust, and volcanic action releases CO2 from the crust and puts it back in the atmosphere. When there’s more CO2 in the atmosphere, it’s a little warmer, we get more evaporation of water and more rain to remove CO2 from the atmosphere at a greater rate.

Well expect a small nuclear explosion from Phil pretty soon.
While I tend to discount the threat of CH4, as overblown (it’s another nice fuel we can use) the picture is not as simple as Tom depicts.
But for starters, look at that CH4 band at 3.3 microns; also the CO2 band at 4.xx microns.
Those we can discard completely, as no threat; in fact they are beneficial from a MMGWCCC point of view, because the only source of any 4 micron or less radiation, is the sun itself, and any atmospheric absorption of sunlight is a global cooling effect.
But back to that 7.7 or so micron CH4 band overlaid by H2O.
Well Tom’s graphs are very low resolution transmission spectra, and those “bands” are actually groups of very many much narrower spectral “lines” and there is no assurance that some water line overlaps some methane line, so the fact that the bands overlap, is no assurance that the individual lines do.
The single molecule lines are in fact quite narrow, being resonances of a very precise structure. Those are then broadened as a result of inter-molecular collisions, giving Temperature broadening due to the Doppler effect, and the motion of the absorbing molecule; and also pressure broadening (actually density) due to the numbers of collisions.
Even so, the broadened lines at the modest atmospheric T&P are still quite narrow, and line overlaps are not going to be as Tom’s band transmissions assert.
But Phil, can do the honors. That ozone band at 9.6 microns is actually right in the middle of the so-called atmospheric window, so I’m not sure Tom’s water bands are correctly depicted.
Water is a great LWIR absorber though.

The oxygen that methane combines with to form CO2 and H2O is ozone. The concern with methane is not it’s GHG properties but the ozone depletion aspect. This goes back to the scare before Global Warming of “We’re all going to die of skin cancer”.

george e. smith : April 11, 2014 at 7:48 am , sums it up nicely.
In fact all this transmission stuff is based MODTRAN / HITRAN which is military atmospheric transmission software. I’d guess that this is probably the most though and accurate part of the whole modelling storey.

arthur4563 says:
April 11, 2014 at 6:54 am
I’ve decided that global wa[r]mists are climate chauvinists and a bunch of Dr Panglosses, all believing that this climate is the best of all possible climates, despite having only experienced
this one.
Isn’t that a bit too Candide for the warmists?
I’ll get my coat.

The ratio of the percentages of water to methane is such that the effects of CH4 are completely masked by H2O. … Because of that, methane is irrelevant as a greenhouse gas. The high per-molecule absorption cross section of CH4 makes no difference at all in our real atmosphere.

Sorry folks, but this is very incorrect. Changes in methane concentration do have a significant effect on climate. The figure of longwave radiative absorption by greenhouse gases shows the total absorption of the total atmosphere. In the real atmosphere, heat is transported upward by thermals and evapo-transpiration to above much of the water vapor. The water vapor concentration is low in the upper atmosphere, so this is where much of the heat energy is radiated out to space. (Several other commenters have also made this point.) The forcing effect of methane must be determined by line-by-line radiative code computer programs which take into account the declining water vapor with altitude.
The direct radiative forcing due to the methane concentration increase in the industrial era after 1750 AD is 0.48 W/m2 (Forster et al., 2007). The IPCC WGI SPM page 13 correctly shows the direct concentration-based estimate of methane radiative forcing from 1750 is 0.48 [0.38 to 0.58] W m−2. (CO2 forcing was 1.68 W/m2)
The methane concentrations increased from 722 ppb around 1750 AD to 1800 ppb. Most of the increase occurred prior to 1990 and has since leveled off. The actual CH4 concentration increased at 0.2%/year from 2005 to 2010. CH4 concentrations are forecast by the IPCC to increases at 1.34%/year by 2050 in the RCP8.5 scenario. The RCP8.5 methane growth rate by 2050 is 6.7 times the recent historical growth rate. The IPCC describes the RCP8.5 scenario as a “high emissions” scenario, but numerous reports incorrectly describe it as a “business-as-usual” scenario. The RCP8.5 is actually an extreme and unrealistic scenario as both CO2 and CH4 increases much faster than the historical changes. (CO2 concentrations increase at 0.54%/year from 2005 to 2013. The RCP8.5 CO2 concentrations increase at 1.00%/year by 2050, and at 1.16%/year by 2070, which is more than double the historical growth rate.)
Methane is not likely to cause a significant temperature rise because the methane concentration is not increasing, not because the methane radiative absorption is “completely masked by H2O.”

dumb question: if co absorbs less heat than co2, why not eliminate catalytic converters from cars and take that part of co2 emissions out of the atmosphere?

stevefitzpatrick says:
April 11, 2014 at 9:20 am
If you don’t want to spend money, there is: http://people.su.se/~rcaba/teaching/PhysMetLectNotes.pdf
Ok, skimmed the paper by Rodrigo Caballero. He seems to know several metric tons about the atmosphere and the various interactions. What does HE think about methane? This is the problem with the blogosphere, where we cannot seem to drive the stake of truth anywhere and convey what that actually means. Information gets published like this article, there seems to be some very good comments on why this is a simplistic analysis and not quite right, but again, what is right? Are spectral absorption lines so narrow as to preclude what looks like overlap? I guess I just need to be spoon fed the proof. After reading this thread I still have little idea if methane is the Mothra to the Godzilla of C02, and before I engage with the CAGW crowd, even though their arguments are every bit as vague, I (and it looks like we all) need more info.

lgp says:
April 11, 2014 at 11:24 am
“Your graph shows molecular “bands” not individual molecular “lines” Unless H2O “lines” fall exactly coincident with CH4 “lines”, then H2O does not absorb the same photons as CH4.”
Oho! But did you consider the effect of gravity on the photon? It is redshifted when leaving Earth’s gravity well! So: Are you talking about the photons that go up or the ones that go down?

Steven Mosher says:
April 11, 2014 at 9:03 am
“1) You still get an increase in warming even if the atmosphere is saturated because its absorption in the thin upper atmosphere that counts.”
I thought even warmists knew about Kirchhoff’s Law? so why do you talk about absorption only and not about re-emission? Is it ignorance or manipulative use of language?

Steve Fitzpatrick says:
April 11, 2014 at 8:24 am
“Isn’t it the non-IR active gases, O2 and N2 that delay the cooling by capturing heat from the IR-active gases and then cannot radiate, but only rise and cool according to the lapse rate?”
No; under local thermodynamic equilibrium thermalization and dethermalization must happen to equal amounts (Kirchhoff’s Law); meaning – CO2 aborbs IR photons and gives energy to N2 and O2, but the reverse must happen equally often – N2 or O2 giving energy to CO2, making it re-radiate an IR photon.
That’s why the term “heat-trapping gases” is a propaganda lie by the warmists.

If this is true:

The vertical scale is upside-down: 100% absorption is low, and 0% absorption (i.e., transparency) is high.

Then this is wrong:

H2O absorbs strongly in the 3-micron region, and again between 5 and 7 microns;

. The cannot both be right.

No problem! Strap an inflatable bladder to the backs of cows and attach a hose with a
check valve. Now, shove the other end of the hose up the cows ass. When the bladders
are full, they can be taken to a power plant to generate electricity.
Are these people INFREAKINGSANE? CH4 .0001745%
1.745 parts per million, are you kidding me?

Kirchoff’s Law, and the common argument for it, are restricted to the case of thermodynamic equilibrium, presumably between the “EM radiation field” and the physical medium , which presumably has some defined Temperature.
Solar thermal collection efficiency often depends on the use of spectrally selective surfaces, or coatings, that rely on the fact that the “absorption” of solar energy, is taking place at solar spectrum wavelengths; which correspond roughly to a 6,000 K black body spectrum; while the LWIR thermal emission from the collection surface, which might be at 100-200 deg. C will be spectrally at a totally different wavelength range, for which the emissivity is quite different from the solar spectrum emissivity.
I think people trundle out Kirchoff’s law too often, and for no good reason; or good result either.
I get spooked by Phil’s wavenumber based spectra, since I am not a chemist. So I don’t expect to find the CO2 absorption band right at the peak of the surface LWIR, instead of on the falling tail end.
Readers need to appraised of an important distinction.
The usual wavelength based spectra, a la the solar spectrum, have units of Watts per meter squared PER MICRON OF WAVELENGTH INCREMENT.
The Chemist’s wave number based spectra, like the ones Phil linked to, have units of Watts per square meter PER WAVE NUMBER INCREMENT.
So what ??
Well on a wavelength based scale, the CO2 band is somewhat lower than the peak at 10.1 microns, for the 288 K LWIR spectrum, BUT there are a lot of MICRONS of band width, typically from around 13 microns up to around 17 microns..
On Phil’s wave number based spectrum, the CO2 band is sitting on the spectrum peak, but there are fewer wave numbers down at the low end of the spectrum, whereas the much higher frequency solar spectrum, is up where there are plenty of wave numbers to spare, so even if the Y scale value is lower the PER WAVE NUMBER INCREMENT can add up to a lot of energy.
So you have to pay attention to the scale units of these absorption spectra, so you are comparing apples to apples.

A lot of what is being said in this comment section is beyond me, with people picking holes in other peoples explanation..interpretations…guess work.
What does seem amazing clear though is that the earths climate system is massively complex and it has variables upon variables.
I just can’t see how any computer model even has the scope to account for all of the factors involved, and the biggest limiting factor is that people are inputing the data/variables of system’s that are not fully understood. (we can’t even find a plane that was designed and built by people and probably has some of the best experts in the world looking for it)
So does anybody really know what the hell is going on with the climate?.. the 97% of IPCC scientist? the people on here? (who seem to be in the minority, but do seem to come out with the most facts)..I have no idea, only time will tell I guess!

I find all this absorption/wavelengths/concentrations rather complex, so I try to simplify the question and look for the simplest answer that I can be sure of.
So, in the question of do the so called GHG’s actually warm the atmosphere/planet. Rather than argue about the absorption/wavelengths/concentrations, surely there are data from detectors high up that directly measure the radiated energy (that CO2 & Methane would affect) leaving the planet?
Do they exist?
Are such data available?
Have they shown less energy reaching those heights as CO2 and Methane increased?
How would this explain the fact that the earth hasn’t warmed for over 17 years as CO2 & methane kept rising?
I’m thinking that the warming ‘blanket’ atmosphere is very very thick, adding another thin blanket (so to speak) will not have any effect.
Anyhow, the CO2 concentrations rise as the temperature rises as shown clearly by Salby & others.
So I’m guessing the radiating energy of wavelengths under question is already absorbed 100% by what’s there.
I think you could probably remove half or more of the existing blanket and the temperature/heat values in the atmosphere would stay the same.
Does anyone know if above said data have been collected?

this is a very informative comment stream. Would someone please explain, though, why we would care if the the upper atmosphere, which is where people seem to be saying the action of gas molecules like CO2 and Methane predominates, gets warmer? What does that have to do with the surface or near surface temperature. If what is absorbed and prevented from going out into space is then re-radiated in part downward, would it not randomly again be re-radiated in part upwards. Eventually everything goes out the top to space and the layer right next to space may be a little warmer but I am unclear by why other layers would be warmer. Just trying to understand how you possibly end up with a net warming at the surface if the “heat” capture is at the top of the atmosphere, which is a long way up.

Dr. Sheahen – 3 questions: 1) is it known whether there is any affinity associated with IR wavelength and each of the molecules in the overlapping bands? That is, because H2O, CO2, etc. are of different configurations and atomic weights, would a particular wavelength excite an H2O molecule “in preference” to a CO2 (or other) molecule? 2) has anyone quantified the IR energy being given off by Earth? That is, do we know how much energy the Earth is producing or reflecting back into the atmosphere at each wavelength? And 3) What happens to the excited molecule? I assume it almost instantaneously returns to its non-excited state and releases energy at an even lower wavelength.
I ask because, if there is an affinity and that affinity is stronger toward H2O, then other GGs are pretty much irrelevant. OR, if Earth is producing little or no energy in the wavelengths associated with CO2 or CH4 then, again, they are irrelevant.

I was pulled over by a policeman wearing a green hat the otherday and asked to blow in his fartometer. Most embarassing. Fortunately I’d followed the government’s new guidelines on keeping fart gas below the permissible volumes.

“Would someone please explain, though, why we would care if the the upper atmosphere, which is where people seem to be saying the action of gas molecules like CO2 and Methane predominates, gets warmer? What does that have to do with the surface or near surface temperature.”
The greenhouse effect requires the understanding of two separate bits of physics: radiation of heat in a vacuum, and the adiabatic lapse rate.
First, the Earth absorbs energy from sunlight, and radiates energy to outer space as thermal IR. The Earth warms or cools until the energy radiated by the emitting ‘surface’ balances the energy absorbed, which happens at a temperature of about -18 C. However, the surface emitting to space isn’t the solid ground, because the atmosphere is partially opaque at IR wavelengths. The emitting ‘surface’ of the Earth appears to be about 5 km up on average. (You can think of it as a bit like fog, visually. Obviously I’m hand-waving over a lot of technical detail, here, to calculate/interpret that average height.) So it’s the layer 5 km up that settles at -18 C.
The second bit of physics is that gases tend to increase in temperature when they are compressed, and cool when they expand. And pressure decreases with altitude. So as convection drives air round convective cycles, it warms as it descends and cools as it rises. This means that convection turns on and off as the vertical gradient exceeds or falls below the rate of compressive warming, and this acts as a sort of thermostat that holds the *gradient* very close to a constant called the ‘adiabatic lapse rate’. Note that only the gradient is fixed, not the offset.
We modify this slightly to account for the condensation/evaporation of water, which has a very similar altitude effect. The result is called the ‘moist adiabatic lapse rate’, and is about 6.5 C/km of altitude, although it varies a bit depending on humidity.
So the surface temperature will be warmer than the emitting layer by an amount equal to the gradient times the height difference between the two. The gradient is about 6.5 C/km, the average height difference about 5 km, so the surface is 33 C warmer than the emitting layer, or +15 C.
When you add greenhouse gases, the atmosphere becomes more opaque, and the emitting layer appears to be higher. The increase in altitude makes the surface warmer.
This is the official, mainstream mechanism for the greenhouse effect, as used in the technical literature. (e.g. Soden and Held 2000, Manabe and Strickler 1964, Sagan 1967, etc.). Accept no substitutes!
As several people have noted, at the top of the atmosphere there’s not much H2O, so other gases have a much stronger effect on emission altitude. Methane has a significant effect (I think) between 1200-1400 cm^-1 at the upper tail of the thermal black body distribution, raising the altitude of emission in this band significantly. Overall, it’s not a big deal. But its not zero.

Steve Case says:
“The climate sensitivity of CO2 is about 1.2C° per doubling in the atmosphere
The climate sensitivity of CH4 is about (___)C° per doubling in the atmosphere
Can anyone fill in the blank?”
The climate sensitivity of CH4 is about (_0.11)C° per doubling in the atmosphere.
The climate sensitivity of CO2 you gave of 1.2 C per doubling is the no-feedback response. The IPCC models give an average feedback multiplier of +2.75. The CERES data suggests the feedback multiplier is 0.4.
The IPCC WII TS page 52 says CH4 increased from 722 ppb in 1750 to 1803 ppb in 2011. The report claims this results in a direct forcing of 0.48 W/m2. Therefore, a doubling of CH4 would cause a forcing of 0.36 W/m2, calculated by 0.48 x ln(2)/ln(1803/722). The Planck response is 3.2 C/W/m2. Therefore, the no-feedback climate sensitivity of CH4 is 0.11 C, (0.363 W/m2 /3.2W/m2/C). This assumes you wait a thousand years of oceans to reach equilibrium. The transient climate response based on AR5 Table 9.5 would be 56% of that, or just 0.062 C. However, at the current CH4 growth rate of 0.2% per year, you would have to wait 347 years to double methane.

Phil. says:
April 11, 2014 at 12:21 pm
“Kirchoff’s law doesn’t say what you think it does! It just says that emissivity equals absorptivity.”
A distinction without a difference.

“If I were wrong the warmists would have their tropospheric hotspot but they don’t.”
The tropical hotspot has nothing to do with radiative physics. The theory is that a warmer atmosphere will be moister, and that will reduce the moist adiabatic lapse rate. A shallower lapse rate means that altitudes below the average emission-to-space altitude warm less and altitudes above it warm more. So a moister atmosphere partially cancels the greenhouse warming near the surface (i.e. lapse rate feedback is negative), while reinforcing it at higher altitude.
The lack of a tropical hotspot may be due to one of two things – either the surface temperature measurements are biased upwards, so we’re looking for a bigger effect than is actually there, or the atmosphere is not getting moister at the rate the models expect. This of course would imply that the water vapour feedback, that multiplies a 1.2 C/2xCO2 sensitivity to a scary 3.5 C/2xCO2 sensitivity, is likely not correct.
But it’s got nothing to do with radiative physics.

A couple of years ago I tried to postulate that the logarithmic nature of radiative forcing due to greenhouse gasses was independent of the species of gasses involved. All I got was grief. No one could understand what in the world I was talking about. I even tried to explain it by describing a simple experiment and stating the likely outcome. And I got grief over that. Everyone just assumed I was just some redneck without any scientific understanding. That assumption appears to have blinded them from actually reading what I was trying to say. This incident really soured me on the WUWT community. So now I tend to keep my comments to anti-Marxist snark.

So millions of beef cows are causing the climate to change…
Just over a century ago millions of buffalo were roaming the western plains of North America. Is it possible that their methane (flatulence) caused the current warming cycle?
Just asking…

Sorry I am tired, it should have read …’only ruminants burp and fart methane…”

Nullius in Verba says:
April 11, 2014 at 8:08 pm
####
Another thing, its not concentration (parts gas a / total parts atmosphere) that is impotent, but density ( parts gas a / volume).

I didn’t say this, the vegan diet tends to be very low in B.12. And they don’t produce any more CO2 than people on a balanced diet or vegetarians.

Another poster spoke to this, but the point needs a little expansion. As wavelength is directly related to energy, I prefer to use the term energy as it is less esoteric to most folks than the word wavelength.
When a photon is absorbed by an atom or molecule (a/m), the a/m gains energy and is in an excited state. The a/m does not like to be in this state and it will eventually try to return to its natural ground state. Time frames vary widely for when the energy will be lost, and may depend on other environmental conditions. There are a number of ways the extra energy may be lost. Remembering that energy is always conserved, here are some of the ways the a/m might lose the extra energy to get back to its ground state:
1) Emission of a photon. The emitted photon(s) may be of the same energy as the received photon, or may be of any other lesser energy value. The resulting photons are free to interact with another a/m.
2) Direct transfer of the energy to a different a/m. All or some of the energy may be transferred. The new a/m now has excess energy it needs to deal with. Sidebar: A radiation counting technique, liquid scintillation counting, takes advantage of direct energy transfer.
3) Re-arrangement of a molecule. The extra energy can be the catalyst for molecular transformation, e.g. breakdown, or to make the molecule susceptible to a chemical reaction with another molecule.
The gist of this article is that the factors influencing energy absorption and subsequent deposition of that energy are:
1) the atom or molecule’s energy absorption bands. Every atom or molecule has specific absorption bands. The molecule is opaque to all other energy bands. (I’m ignoring other methods of radiation interaction, such as particulate radiation, that may deposit energy within an a/m).
2) The quantity of a/m’s available. The more atoms, the greater the chance for photon interaction. there are a lot more H2O molecules in the atmosphere than CO2 molecules.
3) The quantity photons available in the specific absorption range of the a/m. Because there are fewer CO2 molecules, in a large field of specific range photons, each gains extra energy which will want to go somewhere, e.g. H2O molecules, any other molecule such as your skin (what we perceive as warmth is energy transfer from excited molecules), and even emission into space especially if the excess energy is emitted at a wavelength that is not in CO2’s energy range or the range of other GHG’s.
Honestly, except for climate folks like Leif, Anthony and many other good climate scientists, I think the interaction of radiation with matter is poorly understood by some really poor climate scientists, of whom we are acutely aware. I see many commenters here amazed that they have not heard about the crux of this article’s focus. I am not amazed at this reaction. About the only place you will find the study of radiation interaction with matter is within radiation physics, which few get. The interaction of radiation with matter is critical to an understanding of GHG’s role in our climate.
For any physicists who may want to get into electron energy levels, photon wave and particle functions, and all the other cool micro world theories, let’s not go there such that we may give the many here a basic understanding. Once they grasp the basics, they can go to folks like Lubl and get a deeper understanding if they like. I am very pleased with Sheahen’s effort to keep it simple in this article. Well done.

bushbunny says:
April 11, 2014 at 10:37 pm
I didn’t say this, the vegan diet tends to be very low in B.12. And they don’t produce any more CO2 than people on a balanced diet or vegetarians.
####
I said this mostly to be funny, but the truth is that vegetarians do indeed produce significantly more gas, which contrary to popular belief, is not mostly CH4, but CO2. And for the humor impaired, this is funny because the anti-meat activists are promoting the cattle – greenhouse gas connection as a talking point to attack the cattle industry.

Richard M at April 11, 2014 at 11:40 pointed out that cow farts just get recyled back into co2 and then back into the grass they eat, so they add nothing extra to the atmosphere. Good point. As for permafrost melting, the Russians who have most of it say that the permafrost is NOT melting.

@ Mike B – I’m having troubles finding your Nullius reference; could you post the URL for it?
Gymnosperm is referring to a broad spectrum of energies (wavelengths) such as visible light and is quite correct. For example visible light, generally defined in the 400-700nm range and which is not in the CO2 wavelength/energy absorption band, does get through CO2 – as does all the other wavelengths (including the other IR wavelengths) that CO2 does not absorb.
CO2 absorbs energy as photons which are in the IR range. IR has a longer wavelength, and therefore has less energy associated with the photon, than a visible light photon. It has a greater energy than a radio photon. (You may know this, but this is for others)
As a single CO2 molecule absorbs photon energy, it becomes “saturated”, meaning it will not absorb any more energy without releasing energy. It can and may hold the initially gained energy for awhile. However, the molecule does not want to stay in an excited stated of extra energy forever and depending on environmental conditions will eventually shed the energy by one of the routes I noted in my previous post. If the saturated molecule gets hit by another “correct” wavelength/energy, the highest probability is that the extra energy will be immediately emitted – in any direction – as a photon with the same energy in which it came.
I don’t know what you mean by a “fogbank” of CO2″. I’m assuming you mean a large area with lots of CO2 molecules in it, and only CO2 molecules, which are absorbing the right energy photons. Let’s say a box full. Let’s say IR light is coming from only one direction like (sort of, kind of) sun light does. As each CO2 molecule gets saturated, any further hits are transferred – in any direction. Other CO2 molecules might absorb this energy but then also become saturated. If all the molecules become saturated, any excess input energy will just depart from the box. There will be other energy losses such as other molecules getting excited via direct energy transfer or the molecules happen to absorb degraded (lesser energy) photons from the saturated CO2 molecules, which is why the box may feel hot as those molecules give up their energy. Even long before saturation of all the CO2 molecules, you will start seeing IR (in CO2’s absorptive range) above the fog, below the fog, and to the sides of the fog if an excess photon deflects and goes outside the CO2 fog area.
However, in the sense that all photons in CO2’s absorption range are highly likely to get absorbed, this is true, but not just because of CO2. Water will absorb in the same range. There are a LOT more molecules of water in the air and with a broader IR absorption range than CO2,
The concepts of radiative and energy transfer are fairly easy to grasp. However, it is what happens to the energy that starts boggling the mind. With even just one radiative transfer we can only imperfectly predict statistically as to where that energy will go, We cannot predict its actual endpoint with certainty. If we cannot do this with one interaction, how does anyone think we can do it in such a gigantic, complex system as our climate? CAGW from a physics point of view has to be the worst scientific hubris that mankind has seen.

“@ Mike B – I’m having troubles finding your Nullius reference; could you post the URL for it?”
He means this one:
http://wattsupwiththat.com/2014/04/11/methane-the-irrelevant-greenhouse-gas/#comment-1611098
The ‘fogbank’ concept is just a simplified image to aid intuition. If you could see in infrared, the atmosphere would appear semi-transparent, like fog, so you could only see part way through it. The idea is that the visible ‘surface’ you see from above is what emits radiation to outer space, and it is this fuzzy ‘surface’ that settles at the -18 C average temperature needed for the Earth to emit as much energy as it absorbs.
Perhaps it would be clearer using Venus as an example. Even in the visible spectrum, you cannot see the solid surface of Venus. It is shrouded in high-altitude clouds that look like a fuzzy opaque fog. The energy absorbed by Venus from the sun is all emitted by these cloud tops, and so it is the cloud tops that have to achieve energy balance with the outside universe. The temperatures there are actually pretty similar to Earth. But because the visible cloud surface is around 50 km above the solid surface, and the adiabatic lapse rate on Venus is about 8 C/km, there is a 400 C temperature difference maintained between the solid surface and the average altitude of emission to space.
Carl Sagan wrote a short paper back in 1967 estimating the surface temperature of Venus by this method, before they were able to send probes there to measure it. ( http://adsabs.harvard.edu/full/1967ApJ…149..731S ) In a convective atmosphere, the surface temperature is the temperature needed to achieve energy balance plus the adiabatic lapse rate times the altitude of emission to space. Everything else going on below that point cancels out.
Or if that still doesn’t convince, try working out the magnitude of the greenhouse effect in liquid water. Since water absorbs all thermal IR within about 20 microns, it acts as a super-intense ‘greenhouse fluid’. Sunlight shines through and is absorbed deep down, but then on re-radiating it is immediately absorbed and re-radiated and absorbed again. It’s fairly easy to calculate that if you only consider energy transport by radiation the temperature ought to be hundreds of degrees less than a metre below the surface.
The reason the oceans don’t boil is that the difference between the level at which sunlight is absorbed and the emitting surface is only tens of metres, and the adiabatic lapse rate in water is only about 0.1 C/km, because water is incompressible. With a negligible near-zero adiabatic lapse rate, you get essentially no greenhouse warming, despite water being tens of thousands of times more intense a ‘greenhouse fluid’ than air. If the lapse rate was negative, then adding more greenhouse gases would result in cooling! (As happens in the stratosphere.) Try explaining that one using the other explanation!

Harvard –
“A low cloud, however, has a temperature close to that of the surface due to transport of heat by convection. As a result it radiates almost the same energy as the surface did before the cloud formed, and there is little greenhouse warming”
We have established that with or without the effect of the lower cloud there is no extra warming, this is the sun’s maximum output and heat within the range of the lower cloud so why should any other gases in the atmosphere have any other effect within this range ( up to lower cloud) .
If there was an addition to the temp within this range from some kind of extra gas i want to know as i will fill my greenhouse with it and generate more energy from my thermal air pump.

Nullius in Verba says:
April 12, 2014 at 5:45 am
if i was building a house from scratch and had the grounds to do it i would without doubt go this route,
Castle Howard in Yorkshire, UK , have had great results from this method.

Steve Fitzpatrick says, April 11, 2014 at 8:24 am:
“The reason GHG’s reduce loss of heat to space is that absent GHG’s the surface would emit infrared photons directly to space (since the non-GHG’s in the atmosphere are essentially transparent in the infrared wavelengths), while space, with an effective temperature just above absolute zero, would emit essentially no photons back toward Earth.”
Steve, you forget about one thing. The troposphere is primarily warmed through convective processes (conduction/convection/evaporation), not solely by radiation as you seem to think. Absent ‘GHGs’, the troposphere would still be warmed convectively. It could however NOT adequately cool to space. It would thus ‘trap’ the energy (heat) transferred to it from the surface.
The so-called ‘GHGs’ do not enable the atmosphere to warm. It starts warming convectively as soon as it’s placed on top of a solar-heated surface. No, they enable it to cool, by ultimately radiating the acquired surface energy effectively to space.

Ron C. says, April 11, 2014 at 11:36 am:
“3) Bulk gases of the atmosphere, O2 and N2, are warmed by conduction and convection from the surface. They also gain energy by collisions with IR active gases, some of that IR coming from the surface, and some aborbed directly from the sun. Latent heat from water is also added to the bulk gases. O2 and N2 are slow to shed all this heat, and indeed must pass it back to IR active gases at the top of the troposphere for radiation into space.
This third pathway has a significant delay of cooling, and is the reason why our surface has the temperature it does.”
Any sane person would understand, if they only took the time to think it through, that the delay in energy OUT from earth’s surface relative to energy IN (from the sun) lies in the convective process, not in the radiative. The first one needs to physically move massive air against gravity. The second one needs no such thing.

Nullius in Verba says, April 12, 2014 at 6:31 am:
Nullius, you really wanna reopen this discussion …? With nonsensical statements like this: “The ALR controls the surface temperature (…)” you’re simply not one that can be taken seriously. It proves how you absolutely won’t understand the most basic rules of how the earth system works, how any surface/atmosphere system works. You are no skeptic, Nullius. You adhere to dogma. Try to think for yourself rather than just credulously echo all that the Masters of the Climate Religion enunciate to the world.
How would the solar-heated surface of the earth be -18C with an atmosphere on top of it that could be heated through conduction/convection (with the energy (and thus the temperature profile) distributed upwards along the ALR up to the tropopause) but NOT adequately cool to space via radiation?
Think, Nullius. Think.

“How would the solar-heated surface of the earth be -18C with an atmosphere on top of it that could be heated through conduction/convection (with the energy (and thus the temperature profile) distributed upwards along the ALR up to the tropopause) but NOT adequately cool to space via radiation?”
That’s easy. While the atmosphere cannot radiate to space, the surface can. It would warm or cool until the outgoing energy matched the incoming, which would be at -18 C.
The air in contact with it would rise at the equator and cool adiabatically with altitude, but when it came down again at higher latitudes it would warm again at the same rate to its original temperature, transfer its heat to the surface by conduction, and the surface would radiate it to space. All the energy that entered the system would leave it, just as it does now, but it would all leave from ground level. The atmosphere would help spread it around horizontally, but its net effect on surface temperature would be zero.
All of this I’ve independently figured out and checked for myself. But much of it was also previously developed in the 1960s, and constitutes the ‘mainstream’ mechanism used in the models, albeit with a different emphasis and slant to the usual ‘official’ explanations seen in universities. It’s perfectly orthodox, but I’m not accepting it just because it’s orthodox, but because on this occasion it happens to be correct, too.
The issue with CAGW theory has never been to do with the GHE mechanism itself, but with the feedbacks. Getting the basic GHE physics wrong just makes it easier for the warmists to discredit us. I wouldn’t ever suggest that you give up on expressing alternatives that you think are correct simply because it sets back the cause of scepticism – we should always argue these things out. But it can be frustrating sometimes when the discussion keeps on going round in endless circles.
I agree, we really don’t want to open up this discussion again. It annoys our host. So I’m happy to clarify things for people who are interested and want to understand something about it, but I’m not going to argue any further. I’ve said what I’ve said. It should be enough.

Nullius in Verba
Alarmism has worked in one way, the 30 year endless repetition that co2 causes warming.
This has to be countered again and again until the knuckles bleed, the following- below, but in some way that is easy to digest for the average person- me! so easy that newspapers can print it, in some visual form, there are some papers that would use it.
http://acmg.seas.harvard.edu/p…
In order to maintain a constant terrestrial blackbody emission integrated over all wavelengths, it would be necessary to increase the emission flux in other regions of the spectrum and thus warm the Earth. Contrast this situation to a greenhouse gas absorbing solely at 15 mm, in the CO2 absorption band ( Figure 7-8 ). At that wavelength the atmospheric column is already opaque ( Figure 7-13 ), and injecting an additional atmospheric absorber has NO significant greenhouse effect.

MikeB says:
April 12, 2014 at 7:55 am
“Having said that I think that the level of scientific debate on this site has improved recently. We still get the same stupid people making the same stupid comments of course but there seem to be more commentators who actually know something. Still in a minority, but growing.”
MikeB and Phil.; it looks like you are right and I was wrong. BUT now I have a question. It’s a serious one. Really.
How can there be talk of downwelling IR in the CO2 absorption spectrum IF the mean free path length at surface pressure is about 30m or so AND the probability of photon absorption and thermalization is WAY higher than the probability of dethermalization and photon emission? All these photons should vanish after a few dozen meters.

Nullius in Verba says, April 12, 2014 at 7:58 am:
<em"The issue with CAGW theory has never been to do with the GHE mechanism itself, but with the feedbacks."
Exactly. And that’s precisely why they can perpetuate their myth that CO2 warms the earth system with you ‘CAGW skeptics’ as their useful idiots. The proposed ‘GHE mechanism’ is pseudoscientific nonsense, but as long as you defend it with your life, we will never get rid of the festering boil that is the CAGW hype. The hypothesis of CAGW builds upon the hypothesis of AGW that in turn builds upon the hypothesis of the GHE. The latter one is what engendered the warped physics that created the basis for the other two. The two former ones actually by themselves have more going for them, they’re more based on real physics than the former one. The only reason they won’t work is that they build upon the self-construed physics of the apparently sacred ‘GHE hypothesis’.

“One little nitpick: Over much of the ocean there is thermally driven convection only near the surface (in the well mixed layer) because slow continuous upwelling of cold deep water…”
🙂 One little nitpick back – what causes that slow continuous upwelling? Isn’t it the pole-to-equator global convection cycle?
It’s actually a cute example – I was going to mention it earlier and then decided it was getting too complicated. The oceans are actually a pretty neat analogy for what would happen with a non-GHG atmosphere, only inverted – with the roles of heating and cooling, rising and falling, equator and poles swapped around. The deep water formation near the poles is analogous to the heating of a non-GHG atmosphere near the equator. The water descends into the deep like the air rises into the troposphere. With no way to gain or lose heat, the temperature then varies only adiabatically until it cycles round to the other end, where the water warms at the equator or the air cools at the poles, and flows across the surface to begin the cycle anew.
But given the difficulty I was having explaining the straightforward physics, I thought this inverted analogy would just cause people’s brains to explode. Nevertheless, and with a health warning, I offer it up now to anyone who wants to think a little more deeply about this stuff. If you didn’t follow what I said earlier, don’t bother with it. It’s not important.

Steve Fitzpatrick says:
April 12, 2014 at 10:30 am
One suggestion: There are some people who will forever refuse to be convinced that GHG’s can possibly cause warming. There are some people who will forever refuse to accept that burning fossil fuels causes atmospheric CO2 to increase.
=====
Just as there are people that use GHG’s and CO2 as if they are the same
….it is a waste of time to engage any of these folks.

Is that claim accurate? meaningful?
==
http://wattsupwiththat.files.wordpress.com/2010/03/co2_modtrans_img1.png

A number of posters up above reference Kirchoff’s law relating to absorption and emission of EM radiant energy.
It’s almost 60 years since I studied such things, but as I recall, the law applies to thermodynamic systems where an EM radiation field is in thermodynamic equilibrium with a physical medium, which is capable of exchanging energy between the medium, and the radiation field, at ANY possible frequency.
At thermal equilibrium, the spectral radiant emittance and the spectral radiant absorptance must be equal at each and every frequency present in the radiation field. It is not any integrated total energy exchange, it is a point by point match. And that implies that the medium is able to facilitate the movement of energy from one radiating frequency to another until they all are in balance.
That almost guarantees, that the radiation field must be a thermal radiation field, where the radiation spectrum, is a consequence of the equilibrium Temperature (which must be uniform throughout the system).
So it is highly unlikely, that Kirchoff’s law, can be applied to the case of absorption and emission of atomic or molecular resonant radiation frequencies, such as the GHG molecules. They are not capable of transmuting some photon energy into any arbitrary frequency present in some thermal radiation spectrum.
The “band” spectra of molecules and the line spectra of atoms, do not follow the same rules as the continuum spectra of thermal radiation such as black body spectra. In the case of atomic line spectra, some transitions from an excited state to a lower state are forbidden by selection rules, or are of much lower probability as a result. The excited state population inversions necessary for the operation of many laser systems, are a consequence of such restrictions.
Many sources of energy operate to warm the atmosphere; but it is what happens subsequently to that extra energy that is of interest for weather and the climate. In particular it can’t appreciably warm the ground; but additional sunlight energy that enters during the delayed exit of the LWIR, can. And the clouds will adjust to negate almost all of it.

Patrick, Yes, I had the same argument too, months ago with some troll, obviously young I felt. Enough carbon dioxide will kill you he reckoned. If one is shut up in a closed air tight room. Too little oxygen will kill you for sure, and carbon monoxide. But when I asked what were the proportions of gases that we normally breathe, he replied, ‘You tell me!” My son, a born again hippie and green, the youngest one, not the eldest, said the same. I replied, ‘Daarlink, 95% of Greenhouse gases is water vapor. We need it. They form those little fluffy things in the sky” If we didn’t have CO2 to breathe we’d be dead. Didn’t believe me of course.
I suspect it is easier to fool people than convince them they have been fooled. The thing is, nature has a way of balancing things, usually in her/him’s favor. On the one side we have the realists, and on the other – the political and naive greens who look at rainbows and think how lovely they are but don’t know what or how they are created.

Ron C. says:
April 12, 2014 at 4:39 pm
Rob, I was just having a bit of fun with Richard.
The real deal is that after the desert broils in the sun all day, the accumulated heat is rapidly convected away
————————————-
I don’t understand this , there is little moisture in the desert and yet the heat rapidly decreases.
“So, its clear that convection requires a medium (specifically, a non-solid medium). Unlike radiation, if there is no medium near the source, it cannot loose its heat simply using convection. (It can of course loose it via radiation.)

but if convection requires a non solid medium – ie- moisture is the key for convection, you would assume the tropics on a cloudless night with more moisture content would cool rapidly.

Mike B –
I didn’t mean to get your goat. Like you, I’m not convinced by Sheahen’s argument. I really couldn’t make out if you were attacking it from a warmist of a sceptic perspective. You’re quite right, it shouldn’t make a difference, but it helps to know if someone is going to blast the top of your head off for doubting CAGW.
Of course, if I followed this blog more often I’d have remembered seeing you before. Mia culpa!

Tom’s paper is right, that’s what I learned during my studies for my diploma in organic agricultural
production. How can it be 100 years out of date, mate? Change ruminants digestive system, they won’t like that, they will die.

Willis, the reason why Sheanen’s argument is wrong is that he fails to mention that the water vapor is limited to the lower troposphere by the temperature gradient. CH4 and CO2 are not. At the top of the troposphere the concentration of WV drops to the point where other GHGs are determining the escape of radiation. That’s why his claim that “the effects of CH4 are completely masked by H2O” is a straightforward flasehood. Either he doesn’t understand the physics involved, or he is being worse than disingenuous.
I’m glad to see that you know how to use MODTRAN. If you play around a bit more, you’ll find that doubling CH4 has about the same effect as increasing CO2 by around 50ppm. That is what is meant by the statement that CH4 is a potent greenhouse gas.

Dr. Tom:
Someone else may have pointed this out, but I don’t feel like looking through 219 responses to find it, so here goes. Looking at the absorption cross-section graph, it appears to me that 3.3-micron band for methane is not “narrow” at all, not compared to most of the other bands for other gases. Though the peak is not as “clean” as others, it appears that methane absorbs SOME infrared radiation over a range of from about 3.0 microns to about 3.8 microns. And in the upper end of that range, from about 3.6 to 3.8 microns, water vapor’s absorption is ZERO. Not only that, but none of the other GHGs absorb ANY infrared radiation between 3.6 and 3.8 microns. Granted, methane absorbs only 20-30% of IR in that portion of that band, and assuming (I highly doubt this is a valid assumption, but it’s all I have at this time) that the actual emissions of IR are evenly spread across the 1-16 micron range, then the .2-micron width of this methane-exclusive absorption range amounts to just 1.3% of all IR, and at 25%, methane, will absorb, at a maximum (full saturation) just 0.3% of all IR over and above what is or would have been absorbed by other GHGs. That’s just back-of-the-napkin calculations, and a more accurate calculation (including the actual distribution of IR emissions across the entire 1-16 micron spectrum) will likely result a different percentage. I’ll leave that calculation (and the analysis of whether that percentage, whatever it turns out to be, is “significant”) to people who know more about this than me. But if there is ANY IR emitted in the 3.6-3.8-micron range, then I don’t think it’s accurate to say that water vapor absorbs ALL the IR that methane might absorb.