3. Schools of Thought - Where does that IR Come From Anyway?

We're being told to eliminate our use of fossil fuels because they produce atmospheric carbon dioxide (C02) that progressively warms the Earth through a blanketing effect that holds expelled heat close to the Earth's surface and slowly raises its temperature. Classically the phenomenon is called the "greenhouse effect". 

Our C02 levels have risen from 280 to 415 ppm over around 150 years and this is blamed on man made emissions caused by our huge dependance and use of fossil fuels. It is claimed that temperatures have risen as much as 3 C over this time due to the accumulation of heat trapping C02 and that they will continue to rise as concentrations increase in the future. This is strongly disputed in scientific circles but unfortunately is widely accepted in political, media and special interest circles. 

HOW DOES C02 SUPPOSEDLY RETAIN IR HEAT EMITTED BY THE EARTH?

Atmospheric Carbon Dioxide  apparently absorbs the long wave infrared radiation given off by an Earth with a black body average global temperature of 255 K.  After a brief period where C02 holds the energy as an excited vibrational state it quickly re-emits that IR energy, returning itself to a more stable low energy "ground" state. The energy emitted heads off in all directions including sending it back to the Earth in "violation" of the Second Law of Thermodynamics. 

 This interruption of upwelling heat flow and throw back radiation (in spite of violating the second law of thermodynamics) results in a net rise in Earth's temperature over time.

Globalwarmist factions want you to imagine an Earth with waves of IR pouring out of its surfaces  upwards towards the sky and a wall of C02 gas intercepting it and 1. throwing it back to Earth, 2. sideways to warm other atmospheric molecules and 3. a much smaller percentage of it actually managing to continue going upwards where it is dissipated into outer space. 

In order to accept that C02 is performing in this manner, we must also accept that a significant amount of "compatible" infrared waves are being emanated from Earth and are being beamed upstairs to waiting C02 molecules. Warmists don't worry about such a thing - deniers such as myself become tangled up in whether this creation of compatible IR and delivery in significant quantity is even happening. 

This paper details some of the scientific limitations and questions as to how this molecule can possibly work in this manner. Specifically I look at absorption and emission if infrared energy and see if its properties for absorption are compatible with the Earth's ability for creation of those particular infrared waves of heat.

THE ABSORPTION PHENOMENON - HOW C02 TRAPS IR HEAT.

     1. FINGERPRINT ABSORPTION OF INFRARED BY THE CARBON DIOXIDE MOLECULE.

note: to convert wavenumber to wavelengh - multiply the wavenumber by 30 in order to get frequency. Use Wiens Law calculator below to convert frequency into wavelength.

Using this calculator, we can see that the frequencies that C02 displays dramatic absorption peaks (dips) correspond to 2.3, 4.5 and more importantly 15 um. 

     2. C02 HAS VERY NARROW ABILITY TO ABSORB IR RADIATION AND PROBABLY DOESN'T EMIT AT ALL. 

CO2 absorbs 3 narrow bandwidths of radiation. Two of the 3 are not relevant on Earth, corresponding to temperatures only found within volcanoes or white hot metal. The only remaining wavelength absorbed and emitted corresponds with a temperature of -80 C, about the temperature of dry ice. That's not going to raise earth's surface temperature by several degrees as claimed. The hypothesis that back radiation of infrared from atmospheric CO2 to earth's surface is DOA - dead on arrival."

C02 does not emit at 2.3, 4.5 and 15 microns. It only absorbs IR energy and this isn't high enough to reach energy levels whereby C02 will re-emit energized photons such as laser beams or even new 2.3, 4.5 or 15 um IR beams. Absorbed photons at those wavelengths don't excite the atom enough to create the high energy state that is required to shift electrons in the core; instead they only change its shape. Thus they convert their energy into kinetic / vibrational energy which is thought to later be emitted as general black body radiation at no particular wavelength or it is more likely lost through kinetic transfer to surrounding air molecules. 

     3. BUT - HOW CAN WE FORCE C02 TO SUPER HIGH ENERGY LEVELS? - CONSIDER THE C02 LASER.

I asked this question on Quora:

If carbon dioxide only absorbs and emits infrared at 2.3, 4.5 and 15 micron wavelengths, why does a C02 laser emit in the 10 micron range? 

Best Answer from Richard Seymour:  a "CO2 laser" is really a mixture of gasses: mostly Helium, plus 10 to 20% Nitrogen and 10 to 20% CO2. The transitions that produce the final laser light are between states of the CO2 molecule, and are not full transitions from an excited state to ground.

A generated electron impact mechanism excites the {v1(1)} vibrational mode quantum state of the nitrogen. Because nitrogen is a homonuclear molecule, it cannot lose this energy by photon emission, and its excited vibrational modes are therefore metastable and relatively long-lived. N2{v1(1)} and CO2{v3(1)} being nearly perfectly resonant (total molecular energy differential is within 3 cm-1 when accounting for N2 harmonicity, centrifugal distortion and vibro-rotational interaction, which is more than made up for by the Maxwell speed distribution of translational-mode energy), N2 collisionally de-excites by transferring its vibrational mode energy to the CO2 molecule, causing the carbon dioxide to excite to its {v3(1)} (asymmetric stretch) vibrational mode quantum state (ie. it heats it up). 

The CO2 then radiatively emits at either 10.6 μm[i] by dropping to the {v1(1)} (symmetric-stretch) vibrational mode, or 9.6 μm [i] by dropping to the {v20(2)} (bending) vibrational mode. The carbon dioxide molecules then transition to their {v20(0)} vibrational mode ground state from {v1(1)} or {v20(2)} by collision with cold helium atoms, thus maintaining population inversion.

SOURCE OF IR ENERGY - THE EARTH - TWO SCHOOLS OF THOUGHT.

  SCHOOL # 1 - EARTH IS A MASSIVE SINGLE BLACK BODY AND BEHAVES ACCORDING TO ITS "LAWS".

Once we know the temperature of the blackbody, we know how much radiation is emitted at a particular wavelength or frequency. There is a peak wavelength or frequency at which the greatest amount of energy (per unit time per unit volume) is emitted, as you can see from the curve below. That peak of radiation emission shifts to progressively shorter wavelengths as the temperature increases.  Also, what humans perceive as heat and visible light are both parts of the electromagnetic spectrum.

A black body is like having your cake and eating it too. 

On the one hand we say that a source at a particular temperature generates an IR wave of a very specific wavelength. If it changes temperature then it will generate IR at a different wavelength. 

We have laws and calculators that dictate what SPECIFIC wavelength, energy level and frequency will be generated by any (hot) specific body at a specific temperature. Most notable is the Wiens Law associated with a simple calculator that makes the math of conversion easy. (see above). 

Then - we invent a theoretical item called a black body. We assign it an "average" temperature and use a special formula (Planck's) to calculate a RANGE of wavelengths that it will emit simultaneously, IN SPITE OF the so called Wiens Laws that says one temperature = one wavelength. Problem is it's in complete opposition to the logic of electromagnetic wave generation. How can it produce icy cold or blazing hot photons simultaneously if it is only one temperature? It defies the law of common sense. See expanded argument:

HOWEVER - If we are forced to accept that black bodies do exist and that they can emit multiple wavelengths from one medium "average" overall temperature then we have to view the Earth as doing the same. If this is so, then we have to accept that a 300 K body (Earth) will be producing a significant level of 15 um radiation even though the temperature for generating such a wavelength is actually 195 K. 

These MODTRAN scenarios (note: not actual measurements, only modelling results) show curves that state that a black body of 300 K (room temp) may peak around 10um but along with that it will generate a significant amount of 15 um IR waves. It also calculates the absorption of these waves by three levels of carbon dioxide (0, 200 and 400 ppm). Very interesting how it loses efficiency as the concentrations increase.

They are beautiful charts particularly the overlay of "actual" emission graphs (not really) that show C02 working in a RANGE of wavelengths from 13 to 17 um instead of at the pure single wavelength of 15 um. Also the absorption effect is visually dramatic even if it doesn't increase dramatically as the concentrations are raised. 

It's a really good visual argument to accept the school that says Earth transmits absorbable IR upwards and that C02 does an admirable job of absorbing it. (no comments on what it does with it). Media love it.

ACCEPT OR DENY - This scenario is desirable if you are a global warming alarmist as it says that there is plenty of fuel being sent upstairs for C02 to capture and retain, leading to an overall temperature increase of the Earth. But there's just so much theory tied up in all of it  - even a black body is a theoretical object - you can't make one or find one anywhere. IR energy is being sent up that normally requires 195 K to generate it yet it comes from a body whose temperature is 300 K. How does that happen in the theoretical world of black bodies? 

The closest thing to an active black body in our World would be the Sun and it actually meets the criteria spelled out below more than it does the pure black body scenario.

 SCHOOL #2 - SUPPLY OF IR RADIATION COMES FROM AN INFINITE NUMBER OF TINY "EMITTERS" WHICH COMPRISE THE STRUCTURE OF THE EARTH.

Look at the texture of the Earth as being "granular". The bumpy irregular surface is composed of an infinite number of small "emitters" each generating a specific wavelength of IR according to its temperature. Collectively these rise up into the atmosphere as a potpourri if waves and either pass by the waiting molecules such as C02 or are absorbed by them. 

If we don't accept that Earth is a black body and we prefer to belong to school #2 then we have to look at the Earth to find objects that are 195 K / -89 C and consider just how many of these objects are present on the Earth compared to other objects within its average temperature of 300 K.  

We must also ask whether these cold bodies can cumulatively generate enough 15 um wavelengths to have any real effect on the total global warming scenario. This school #2 actually meets the law of common sense and also meets the requirements of Wiens law (but not Planck's solution which creates the theoretical black  body curves) and probably this is the case. 

But it just shuts down the C02 based global warming argument because you wouldn't create all that much IR as there just isn't very many objects that are 195 K on our earth. They are really only found in Antartica and even then on a cold day. There would be none in the majority of the Earth's surfaces. So what is C02 absorbing and why do we make such a fuss about it? A conundrum indeed.

SCHOOL #3 - THE CRITICAL 15 MICRON WAVELENGTH MIGHT COME FROM THE ATMOSPHERE.

Although Planck's formula shoots this idea all to hell, what if Wiens was right in that a particular wavelength of IR could only be produced by a body emitting from a very definitive temperature relating to it. This means - 80 C for creating a 15 micron wavelength. Other than Antarctica on a bad day we on Earth haven't got a lot of objects sitting at that temperature. If you go upstairs however we can reach this low. We know the atmosphere emits IR to outer space. If the temp was -80 C when it was doing this emitting, would it be giving off the compatible 15 micron. This could be the source of 15 micron IR measured by satellites, and there might not be that much of it compared to the 10 micron stuff that comes off the warmer Earth. The so called C02 absorption band would be miniscule and meaningless, because most C02 is close to the ground not way up in the sky.  Just sayin...

AND FINALLY, SCHOOLS OF THOUGHT ON WHAT C02 DOES WITH ITS HEAT.

It might all be meaningless depending on what C02 does with the heat it supposedly gains when IR is sent up and absorbed by it. The hole in the tracings above might indeed be true. IR doesn't get to the upper atmosphere where the satellite will measure it because the C02 filters it out and erases it. The question that must then be answered is - Does it retain the heat in some way and warm the Earth because of this or does it shift it's heat to the surrounding molecules through "collisional de-excitation" and send it off to space through the vehicle of convection and thermal rise to outer space? 

So much to consider.