Science a GoGo's Home Page Forums General Discussion Climate Change Forum Specific Heat Capacity

Please correct me if I'm wrong (as if I really had to say that;-)

The concept of Greenhouse Gas stems from an observation by Arrhenius a while back that the temperature of a glass cyclinder containing a gas rose as he shined a light on it.

We all agree that the Sun's radiant energy, of all wavelengths, strikes the surface of our planet, is absobed, warming the surface. That energy flows from the warmer surface to the cooler atmosphere, mostly in infra-red wave lengths. Without an atmosphere, that energy would just vanish quickly into space.

Although EM radiation can be correlated to temperature (as in the "background temp of the universe") only matter can really have temperature: it's a measure of the average kinetic energy of the molecules in the sample, and by extension, of their average velocity.

Empirical studies show that each different substance absorbs IR energy to a characteristic extent. The amount of energy needed to raise the temp of a standard volume of a given gas by 1degC is defined as that gas' specific heat capacity.

For the inert gases, all the heat absorbed by the single atom can only be used to increase the velocity of the atom (translational energy). The inert gases are all found to have sp heat cap very close to a single value, about 1.0 relative units.

For the di-atomic molecules, some energy absorbed is diverted to rotating the molecule about its center of mass, so it takes more energy input (also allowing for the higher mass) to get the temp up by the 1deg than for the inert gases. The sp heat cap of the di-atomics is about 1.3 relative units.

For tri-atomics, and additional degree of freedom occurrs with the geometry: not only can the molecule use absorbed energy to increase its translational and its rotational speeds, but now the angle between the three atoms can vary (vibrational energy), so it takes even more input to get the molecules up to speed for the 1 deg increase in temp. Sp heat cap for these is about 1.6 rel units.

I believe the GHG Theory suggests that having absorbed this energy, the gas molecules are free to re-radiate it off to another molecule. and the process is iterated, delaying the ultimate fate of each photon to be lost to space. But as each molecule re-radiates its absorbed photon, it slows back down, so when the neighboring molecule absorbs the second hand photon, the net change in the energy of the two molecules is zero. So, in the Grenhouse Phenomenon, the GHG doesn't "generate" energy, it just delays the loss of energy to space.

Secondly, note that sp heat capacity doesn't mean any given substance is "better" at absorbing energy, only that it takes more energy to get its temp up- ie- the "stronger" substances actually help to keep the temp lower for any given energy input.

This is where I believe GW theory has perverted the concept of sp heat cap. It claims CO2 is a more efficient absorber, whereas, it should only be stated that it helps keep temps down by absorbing energy not used to increase its translational velocity.

Now it may be a co-incidence, but if we use those relative sp heat cap figures above, the known concentrations of atmospheric gases, and an average world temp of 288degK, then it?s an easy algebra ?mixing problem? to calculate that a rise in CO2 from 300ppm to 600ppm results in an increase to about 288.5degK- consistent with the GHG Theory. If that?s how the experts are calculating it, then isn?t that wrong?

docT wrote:
"The concept of Greenhouse Gas stems from an observation by Arrhenius a while back that the temperature of a glass cyclinder containing a gas rose as he shined a light on it."

You asked to be correct so ... ok.

The greenhouse effect was discovered in 1824 by Joseph Fourier and first quantitatively investigated in 1896 by Svante Arrhenius.

What I think you are missing is that when a photon is reirradiated ... it is at a longer wavelength. Thus its properties are different.

Thanks for the improvement on the history.

The longer wavelengths are less energetic than the shorter. Sunlight is "white", all wavelengths represented. The surface re-radiates mostly in the infra-red range ("heat"). The photon re-radiated by the air molecule cannot be shorter (more energetic) than the one absorbed. The law of conservation of energy must be obeyed.

The GH effect works because the matter introduces a time factor, a delay, in the situation. It insulates. A house is kept warm by better insulation, not because it generates heat, but because it delays the heat loss to the outside air.

Even if we introduce the concept of resonance, I don't see how it expalins the problem. Resonance doesn't generate extra energy either, it just concentrates it. Mico-wave ovens are "tuned" to the H2O molecule so that most of the energy input goes to them and not to the air or walls of the oven.

If the earth's radiant loss is tuned to CO2, then it just means less energy goes to the other molecules, but the total energy absorbed by the air remains the same.

Beuhler? Anybody???

docT wrote:
"Even if we introduce the concept of resonance"

Resonance? Who said anything about resonance?

All wavelengths come in.

some of the energy is re-radiated at longer wavelengths absorbed by so-called greenhouse gasses that absorb them

And trap (DO NOT re-radiate) them.

Thus the energy is trapped.

This is all, rather simply, explained here:
http://en.wikipedia.org/wiki/Greenhouse_gases

If the special GHGs "trap- ie not re-radiate" the energy, then the theory really goes to pot. The "trapped" energy would be manifest as increased velocity of the molecule. If CO2 is represented as only 1 in 2500 molecules in the air (corresponding to about 400ppm), then how fast do they all have to be moving to get the average velocity of all air molecules high enough to correspond to an increased temp of 1deg? About 2500x faster. I don't think it can happen.

GH Theory says the special gases absorb energy and then pass it on to the other molecules, as if they couldn't do it for themselves. That's where typical illustrations use the micro-wave oven example of resonance.

docT wrote:
"If the special GHGs "trap- ie not re-radiate" the energy, then the theory really goes to pot."

And amazingly everyone with a PhD at NASA, NOAA, CSIRO, University of Washington, Harvard, CalTech, JPL, Stanford, MIT, Oxford, Cambridge, Yale, etc. can't figure that out but a semi-retired MD can.

As I said in my last reply ... I'm taking you at your word that you are a semi-retired MD. If so act like it. Otherwise you have self-identified as a troll and will be ignored henceforth.

Choice is yours ... make it wisely.

PS: I notice no response to my statement about Lidex and Topsyn. I put the chance of you being a real MD at about 2%. And that, sir, is being generous.

Thank you for your well thought out and opinionated response.

From your own Wikipedia citation: "Greenhouse gases also emit longwave radiation both upward to space and downward to the surface."

Your pompous butt doesn't even know the most basic points of the theory of GHGs, yet you have declared it as The Truth. I see no point in dealing further with those who treat their position like religious zealots such as you. You announce your opinions as uncontested fact, and denigrate as inferior beings anyone you should dare contest your authority. Yet your last several posts here demonstrate your meager knowledge of this subject. What's the color of the sky in your personal fantasy land? Have fun wallowing in your kngdom. Ciao ciao, bucadicolo.

Post deleted by Amaranth Rose II

docT wrote:
"Your pompous butt"

Ah a medical term. It doesn't take much expose a blivet these days.

First you claim to be an MD, old enough to be semi-retired no less. Then you don't understand the name, any MD would know, of one of the most successful anabolic steroids marketed in the 70s and 80s. And now you are reduced to adolescent 20 year old name calling while demonstrating an exposure to science that is, at best, grade-school level.

You have now joined JLowe, RicS, Canuck, and a few others by earning the designation of troll.

Goodbye YOYO!