Radiative Physics Simplified II
A guest post by Jeff Id
Radiative physics of CO2 is a contentious issue at WUWT’s crowd but to someone like myself, this is not where the argument against AGW exists. I’m going to take a crack at making the issue so simple, that I can actually convince someone in blogland. This post is in reply to Tom Vonk’s recent post at WUWT which concluded that the radiative warming effect of CO2, doesn’t exist. We already know that I won’t succeed with everyone but when skeptics of extremist warming get this wrong, it undermines the credibility of their otherwise good arguments.
My statement is – CO2 does create a warming effect in the lower atmosphere.
Before that makes you scream at the monitor, I’ve not said anything about the magnitude or danger or even measurability of the effect. I only assert that the effect is real, is provable, it’s basic physics and it does exist.
From Tom Vonk’s recent post, we have this image:
Figure 1
Short wavelength light energy from the sun comes in, is absorbed, and is re-emitted at far longer wavelengths. Basic physics as determined by Planck, a very long time ago. No argument here right!
Figure 2 below has several absorption curves. On the vertical axis, 100 is high absorption. The gas curves are verified from dozens of other links and the Planck curves are verified by my calcs here. There shouldn’t be any disagreement here either – I hope.
Figure 2 – Absorption curves of various molecules in the atmosphere and Planck curve overlay.
What is nice about this plot though is that the unknown author has overlaid the Planck spectrums of both incoming and outgoing radiation on top of the absorption curves. You can see by looking at the graph (or the sun) that most of the incoming curve passes through the atmosphere with little impediment. The outgoing curve however is blocked – mostly by moisture in the air – with a little tiny sliver of CO2 (green curve) effective at absorption at about 15 micrometers wavelength (the black arrow tip on the right side is at about 15um wavelength). From this figure we can see that CO2 has almost no absorption for incoming radiation (left curve), yet absorbs some outgoing radiation (right curve). No disagreement with that either – I hope. Tom Vonk’s recent post agrees with what I’ve written here.
Energy in from the Sun equals energy out from the Earth’s perspective — at least over extended time periods and without considering the relatively small amount of energy projecting from the earth’s core. If you add CO2 to our air, this simple fact of equilibrium over extended time periods does not change.
So what causes the atmospheric warming?
Air temperature is a measure of the energy stored as kinetic velocity in the atoms and molecules of the atmosphere. It’s the movement of the air! Nothing fancy, just a lot of little tiny electrically charged balls bouncing off each other and against the various forces which hold them together.
Air temperature is an expression of the kinetic energy stored in the air. Wiki has a couple of good videos at this link.
“Warming” is an increase in that kinetic energy.
So, to prove that CO2 causes warming for those who are unconvinced so far, I attempted a thought experiment yesterday morning on Tom Vonk’s thread. Unfortunately, it didn’t gain much attention. DeWitt Payne came up with a better example anyway which he left at tAV in the comments. I’ve modified it for this post.
Figure 3- Experimental setup. A – gas can of air with all CO2 removed at ambient temp and standard pressure. B – gas can of air diluted by 50 percent CO2, also at ambient temp and standard pressure. C ultra insulated laser chamber with perfectly transparent end window and a tiny input window on the back to allow light in from the laser. Heat exit’s the single large window and cannot exit the sides of the chamber.
Figure 4 is a depiction of what happens when C contains a vacuum.
Figure 4 – Laser passes straight through the chamber unimpeded and a full 1000 Watt beam exits our perfect window.
The example in Figure 5 is filling tank C with air from tank A air (zero CO2) at the equilibrium state.
Figure 5 – Equilibrium of hypothetical system filled with zero CO2 air from canister A.
Minor absorption of the main beam causes infrared absorption and re-emission from the gas reducing the main beam from the laser. This small amount of energy is re-emitted from the gas through the end window and scattered over a full 180 degree hemisphere.
What happens when we instantly replace the no-CO2 air in chamber C with the 50% CO2 air mixture in B?
Figure 6 – Air in C is replaced instantly with gas from reservoir B
From the perspective of 15 micrometer wavelength infrared laser, the CO2 filled air is black stuff. The laser cannot penetrate it. At the moment the gas is switched, the laser beam stops penetrating and the 1000 watts (or energy per time) is added to the gas. At the moment of the switch, the gas still emits the same random energy as is shown in Figure 5 based on its ambient temperature, but the gas is now absorbing 1000 watts of laser light.
Since the beam cannot pass through, the CO2 gains vibrational energy which is then turned into translational energy and is passed back and forth between the other air molecules building greater and greater translational and vibrational velocities. —- It heats up.
As it heats, emissions from the window increase in energy according to Planck’s blackbody equation. Eventually the system reaches a new equilibrium temperature where the output from our window is exactly equal to the input from our laser – 1000 watts. Equilibrium! – (Figure 7)
Figure 7 – Equilibrium reached when gas inside chamber C heats up to a temperature sufficient to balance incoming light energy..
The delay time between the instant the air in C is switched from A type air to B air to the time when C warms to equilibrium temperature is sometimes stated as a trapping of energy in the atmosphere.
“CO2 traps part of the infrared radiation between ground and the upper part of the atmosphere”
So from a few simple concepts, two gasses at the same temp, one transparent the other black (at infrared wavelengths), we’ve demonstrated that different absorption gasses heat differently when exposed to an energy source.
How does that apply to AGW?
The difference between this result and Tom Vonk’s recent post, is that he confuses equilibrium with zero energy flow. In his examples and equations, he has a net energy flow through the system of zero, which is fine. Where he goes wrong is equating that assumption to AGW.
What we have on Earth, is a source of 15micrometer radiation (the ground) projecting energy upward through the atmosphere, exiting through a perfect window (space) – sound familiar? Incoming solar energy passes through the atmosphere so we can ignore it when considering the most basic concepts of CO2 based warming (this post), but it is also an energy flow. In our planet, the upwelling light at IR wavelengths is a unidirectional net IR energy flow (figure 2 – outgoing radiation), like the laser in the example here.
Of course adding CO2 to our atmosphere causes some of the outgoing energy to be absorbed rather than transmitted uninterrupted to space (as shown in the example), this absorption is converted into vibrational and translational modes (heating). Yes, Tom is right, these conversions go in both directions. The energy moves in and out of CO2 and other molecules, but as shown in cavity C above, the gas takes finite measurable time to warm up and reach equilibrium with space (the window), creating a warming effect in the atmosphere.
None of the statements in this post violate any of Tom’s equations; the difference between this post and his, is only in the assumption of energy flow from the Sun to Earth and from Earth back to space. His post confused equilibrium with zero flow and his conclusions were based on the assumed zero energy flow. The math and physics were fine, but his conclusion that insulating an energy flow doesn’t cause warming is non-physical and absolutely incorrect.
Oddly enough, if you’ve ever seen an infrared CO2 laser cut steel, you have seen the same effect on an extreme scale.
————-
So finally, as a formal skeptic of AGW extremism, NONE of this should create any alarm. Sure CO2 can cause warming (a little) but warmer air holds more moisture, which changes clouds, which will cause feedbacks to the temperature. If the feedback is low or negative (as Roy Spencer recently demonstrated), none of the IPCC predictions come true, and none of the certainly exaggerated damage occurs. The CO2 then, can be considered nothing but plant food, and we can keep our tax money and take our good sweet time building the currently non-existent cleaner energy sources the enviro’s will demand anyway. If feedback is high and positive as the models predict, then the temperature measurements have some catching up to do.
Even a slight change in the amount of measured warming would send the IPCC back to the drawing board, which is what makes true and high quality results from Anthony’s surfacestations project so critically important.
This is where the AGW discussion is unsettled.
====================================
My thanks to Jeff for offering this guest post – Anthony
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
RE: cal says: (August 7, 2010 at 8:21 am ) “The argument made by the Hadley centre is that an increase in CO2 increases the effective radiating altitude (as discussed above) and this implies a drop in temperature.”
I believe the argument they are making is that increased CO2 in the atmosphere will increase the depth of the CO2 ‘cloud’ around the planet in which CO2 photons cannot escape to outer-space. This, in *their* view, will necessarily force the tropopause to move a higher level to re-establish the previous radiative equilibrium and the natural adiabatic lapse rate will translate this increased altitude to higher temperatures on the ground.
However, if the level and temperature of the tropopause are now largely being determined by H2O, then I think there should be little change at all until we really add enough CO2 to the atmosphere to overwhelm the radiative significance of H2O.
I suspect that the temperature of the tropopause is determined primarily by the equilibrium established by the amount of incoming solar energy that can be absorbed primarily by H2O and CO2 at that altitude.
“The difference between this result and Tom Vonk’s recent post, is that he confuses equilibrium with zero energy flow.”
After reading Tom’s post I agree with Jeff that this illustrates where Jeff made an error.
I don’t know for certain that Michael Dunn is wrong arguing (basically) that radiation absorption/emission is so fast that it would be equivalent to scattering of radiation which would not alter the temperature of the atmosphere, however this is not the argument that Tom made in his original post and I suspect it is incorrect.
So essentially the surface is a source of LW radiation and some of that radiation will be absorbed by greenhouse gases and some will pass through atmosphere and escape to space. If we increase the concentration of greenhouse gases then the atmosphere will absorb more of the radiation passing through (unless concentrations are already high enough to impede radiation to an extend that convection dominates) and this extra energy absorbed by atmosphere will translate into higher temperature of the whole air mass through collisions. The response to more absorption is to reach higher equilibrium temperature and therefore higher rate of emission.
Stephen Wilde says:
Both the changes in the height of the tropopause and the changes in the latitudinal positions of the air circulation systems are direct evidence of a change in the speed of the hydrological cycle as I have said boringly often before.
Stephen, I was very interested in your assertion that the latitude of the air circulation systems may change. I agree with you that an increase in CO2 will lead to little change in surface temperature because the effect is to change the effectiveness of the convective cooling system. However, one possible outcome from that increased effectiveness is that we could potentially see a change in the structure of the Hadley cells (which I assume is the same as you said).
To put it so it is understandable: the sun heats the equators, causing air to rise, it then is forced out from the equator at high altitude until it looses enough heat (via infra-red emission into space) for that air mass to descend and repeat the cycle. In the process you get rising moist air over the equator and descending dry air over the Sahara, the Sahara being situated at a position where the air has been exposed to the IR window into space just long enough for the air to loose enough heat to start descending.
Similarly, over the poles, you get excess cooling. Air masses cool excessively forming a bulk of dense cold air which then spreads out from the poles. As it moves away from the poles it picks up heat until it rises (above the UK) – it then is sucked into the polar region by the cooling-descending air in that region.
The result is an area of high pressure at the sahara and low pressure over the UK, and we therefore get an intermidiate Hadley cell bringing air from the high pressure over the Sahara latitudes up to the UK latitudes. The result is the classic three Hadley cell (6 when you count the south hemisphere)
In theory, however, it is possible to have any number of Hadley cells. They are afterall only cooling convective currents and so long as there is an odd number in each hemisphere you will get the dominant rising air over the equator and descending air over the poles. (In theory you could get only one cell!). If however you change the rate of COOLING, so that the equatorial air mass looses heat quicker by some added vector (CO2), the result could be to shift the high pressure-dry zone of the Sahara further toward the equator. As each cell is really a convection cycle of heat-uplight-IR emission, the addition of CO2 would reduce the average time it takes for the air mass to cool, thereby tending to reduce the size of each convective cooling-cycle cell.
So, whilst CO2 is unlikely to have much effect on temperature, it could conceivably affect the number of Hadley cells. The result would be to move the Sahara Southward (and shrink it), to move the typical UK weather Northward (an area of continual weather fronts) around iceland. We would then see two further zones: one of typical dry climate with high pressure at the North of the Med, and another south of the med with continual weather fronts as hot southerly winds and colder northerly winds meet.
In reality, Hadley cells are not fixed, and more than likely at certain times, we already get a five Hadley cell structure to the atmosphere.
However, I suppose that this explanation is missing something from Tom’s post. Increasing CO2 concentration would have cooling effect until the point where the CO2 is sufficiently ‘excited’. During this transient period collisions would have the net effect of transferring energy from non-greenhouse gases to CO2 (in form of vibrational excitation) until these modes are in equilibrium. Still, I don’t think that this transient condition has any impact on the final equilibrium condition where the higher CO2 concentration must result in greater absorption of surface LW and higher equilibrium temperature to restore balance of radiation in and out of the air mass.
On the issue of the “greenhouse” effect, many are tying themselves in knots by unnecessarily delving into confusing details. Try thinking of the problem this way:
If it is easier for solar energy to reach the Earth’s surface than it is for heat energy to be irradiated away from the Earth, then it will be warmer at the Earth’s surface.
If the resistance to inflow and outflow of energy were equal, it would be cooler at the Earth’s surface (Eg. the Moon, on average, is cooler than the Earth.)
1. Solar energy is mostly non-infrared.
2. Heat radiated away from the Earth is mostly infrared.
3. The atmosphere allows non-infrared energy to pass through more easily than infrared. Energy gets in easier than out.
4. Therefore there is a “delay” in heat escaping the Earth as a whole system (planet including atmosphere), hence heat builds up near the surface until equilibrium between inflows and outflows are reached.
5. The more resistant the atmosphere is to the infrared flow away from the Earth, the higher the equilibrium temperature.
6. If greenhouse gases increase, the infrared outflow resistance increases, hence the heat content of the system rises to a higher equilibrium
(7. There are undoubtedly negative feedbacks in the Earth system. Otherwise, the Earth’s system would not have oscillated by only a few percentage point in temperature (in degrees Kelvin) over the last billion or more years. A system dominated by positive feedbacks is inherently unstable and gyrates wildly. A system dominated by negative feedbacks acts like the Earth has.)
The details of the mechanisms of radiation absorption, reemission, conversions to and from the kinetic energy of moving molecules and the potential energy of excited electrons, saturation effects, bandwidth broadening, etc. are critical to quantitative evaluation and predictions of the the equilibrium temperature for various changes in albedo, GHG concentrations, etc.
The details are not important for understanding the simple existence of a greenhouse effect due to Earth having an atmosphere.
Let me clarify point by point.
Your original suggestion involved “ideal” things of all sorts and it is difficult to decide how these ideal things will work. In the case of the CO2 filled cavity the window will become hot through conduction with the CO2 gas. In the vacuum cavity it will become hot through contact with the structure of the tube, except the tube as stated has no conductivity (i.e. well insulated, you said) so what happens then? Look, it doesn’t matter because the window is ideal. It has perfect transmission, no reflection, and no absorption, so it has emissivity of zero. Doesn’t matter what its temperature is. It does not radiate.
Distant end of the CO2-filled tube heats more rapidly, perhaps, but at equilibrium both have the same temperature, as I will explain in a moment.
No, won’t be anything like the Moon. The sun is just a small object at the distance of the Moon, the materials of the moon do not absorb completely, absorptivity and emissivity are not the same value because the emission and absorption take place in different parts of the spectrum, and the moon radiates into a hemisphere.
The tubes, in contrast, as I have imagined them are perfectly insulated except for a small aperture. They gain and lose energy only through the aperture, and I assume the view through the aperture is only that of the Sun. So equilibrium will occur when the incoming and outgoing spectra are the same, and the tubes have reached a temperature equal to the sun. The OLR is not LR; it is thermal radiation at 5800K.
I have assumed this scenario, except, as I tried to explain, it has some awful ambiguities.
You are sceptical because you ought to be; the engine you describe would violate the second law. I have tried to explain why these two tubes, if allowed only interaction with the Sun, will reach the same temperature, and never be able to drive a heat engine. Each intercepts exactly the same energy from the Sun as does the other, at equilibrium each radiates back toward the sun the same energy, there is zero net to flow through the heat engine and no temperature difference to drive it.
If you want to make a heat engine, then you must allow the two tubes to exchange energy with more than just the Sun. This prevents them from reaching the same temperature, allows one of the two to supply net energy to the other through an engine, which the temperature difference will drive. As you have described this device, its CO2 filling doesn’t provide enough difference between the tubes to make much of an engine here even if you keep the two tubes from reaching equilibrium.
Now, if you really want a simple heat engine then make two radiating panels of different materials; one that gets very hot in the Sun and one that stays cool.
@winterkorn
‘The details are not important for understanding the simple existence of a greenhouse effect due to Earth having an atmosphere.’
But the details are of utmost import to understand why other planets, and some of their moons as well, in this same solar system also has warmed slightly just like earth the blue marble of the fried gaia.
And, personally, I’m getting pretty sure the other bodies around sol that has warmed slightly haven’t done so due to some thousands of a percentage increase of green house gases on earth. But of course, what if….
Bill Illis says
People get caught up in the absorption and emission bands of CO2 and H20 and do not understand there is radiation ocurring all over the spectrum. CO2 has specific frequencies where it strongly interacts with EM radiation but there is also base black-body radiation (that is not as strong or intense sometimes) but there is two kinds of radiation to be concerned about – the strong Absorption and Emission bands and the more general black-body radiation.
I thought I had covered this clearly in my last post. The radiation from the surface approximates to a black body ( it is not exact – if it were the sea would not be blue!).
So of the three radiating elements I mentioned the surface is a near black body radiator and the gases are absorbing and radiating at their characteristic wavelengths but with intensities that are dependent on temperature.
I like your charts. I have not seen the ones “looking up” before. However I am not sure what your commentary is trying to say. You keep using the words “as if” it were such and such a temperature whereas that is exactly what it is.
For example when looking down from 50M all the radiation at all wavelengths will reach the sensor from the surface or from gas molecules in between which will be very close to the same temperature as the surface. This is exactly the point that Tom was alluding to. Any radiation absorbed by CO2 for example will be re radiated. Since the temperature decline within 50M is small you will not see that the re radiation is slightly lower. So no absorbtion bands are to be expected. Water vapour bands are even less likely to be seen.
Looking up from 50M you will see energy radiated downwards from excited molecules in the atmosphere above. There will be very little in the atmospheric window around 10 micron since these wavelengths are not absorbed and therefore cannot be re radiated downwards.
At the other wavelengths you will see energy radiated downwards mainly by H2O and CO2. Because they are such powerful absorbers the level at which they will radiating downward will ( on average ) be not far above the 50M where you have placed your sensor. So the fact that they are radiating at -20C seems entirely plausible to me.
If you look down from 20Km you will see exactly the picture I was descibing where all the radiation is either from the surface at about 288K ( higher during the day in the tropics) or from CO2 and H2O at the temperatures you quote.
Looking up you will mainly see radiation characteristic of CO2 since this is by far the dominant radiating gas above the tropopause.
All the data you showed seem exactly as one might expect.
Maybe I missed something that you were trying to say.
The abstract physics discussions about how insulators insulate (or not for those who somehow believe insulators don’t insulate) and quantum mechanical accounting for every particle and photon is interesting it must ultimately agree with the observations.
If we accept the temp record from 1880 to 2000 as reasonably accurate and break it into two 60 year intervals we find temperature rose 0.4c in each interval.
If we accept an anthropogenic CO2 driven increase of 75ppm during that time we find that it rose 25ppm in the first period and 50ppm in the second.
If we accept that CO2 acts as insulator and does raise surface temps but as with any other insulator it becomes exponentially less effective per unit of increase then everything makes sense and we can make some predictions for the next 120 years.
Let’s assume we don’t repent our wicked ways and continue doubling how much fossil fuel we burn every 60 years.
Years +CO2 +temp
1880-1940 +25ppm +0.4c
1940-2000 +50ppm +0.4c
2000-2060 +100ppm +0.4c
2060-2120 +200ppm +0.4c
As near as I can tell from the observations and by accepting the CO2 vs. temp correlations as causation (for the sake of argument) there will be a CO2 doubling to about 650ppm in 120 years and a 0.8c temperature rise because of it.
This is not inconsistent with IPCC projections. In fact it is their best case scenario and it happens to be right on the money for the ten years from 2000-2010 that we didn’t analyze above.
Now we must compare the upsides to the downsides.
If we examine all nations that underwent industrialization during this 1880-2000 period in history, compare their fossil fuel comsumption to gross domestic product, we find another correlation – growth in fossil fuel consumption goes hand in hand with economic growth.
Slowing economic growth is a huge downside but that’s what limiting fossil fuel consumption will do absent a comparably cost/effective alternative energy source.
As well, scientific and engineering advances are driven by growing wealth. If there’s less economic growth there will be less wealth available to fund research and development, including research and development of alternative energy sources.
There’s another big downside but it will happen if we strangle our growing energy needs.
A warmer earth with a higher CO2 content is a greener earth. This is just indisputable testimony from the geologic column. Personally I prefer green plants and animals to bare rock and ice so I consider this an upside to continued exponential increase in fossil fuel consumption.
We can expect sea level to rise about 12″ from thermal expansion. This is the only downside. 120 years to deal with it makes it seem almost insignificant.
So the CAGW crowd basically wants to throw civilization under the bus to stop a “problem” that’s actually a great benefit to both the biosphere and standard of living for each human member of it.
I suspect the CAGW crowd is suffering a mass “messiah complex”. They want to save the world and be recognized for it. But there’s a big problem for them if the world doesn’t need saving. Thus we get the climategate chucklemonkey writing in 2008 “We can’t explain the lack of warming since 1998 and it’s a travesty that we cannot”.
Actually the IPCC did explain it. It just happens to be their best case scenario where nothing scary happens – the world doesn’t need saving – in fact the world gets better by burning more fossil fuels.
So there. I feel much better now.
Mike Haseler says:
August 7, 2010 at 10:06 am
Hello, Mike. Your post shows that you’ve got my point and that you see some of the implications.
As regards CO2 specifically though the fact is that we see quite large circulation changes from natural climate variability so any effect from CO2 is likely to be unmeasurable particularly since the response of the hydro cycle is highly scaleable by which I mean that the energy shifting efficiently of the latitudinal shifts would increase geometrically as the shifts become more extreme. After all over billions of years they have prevented permanent disruption of the system through ice ages and much warmer periods than we have now.
I haven’t yet thought through the precise consequences beyond the latitudinal movement of the jets but some of the possibilities are as you suggest.
Continuing my conversation with myself….
Thinking about it more I’m thinking Tom may be right and Jeff (and I) might be wrong. Maybe additional concentrations of CO2 does not directly warm the surrounding air:
1) Presumably in actual atmosphere the air does not radiate like a blackbody because greenhouse gas concentrations are small (ie. If there were no greenhouse gases the atmosphere certainly would not radiate like a black body.)
2) The Energy Equipartition law suggests that statistically energy will be distributed evenly across the different kinetic modes available for a molecule. Air is a mixture of different molecules, and not all molecules have vibrational modes available to interact with radiation. Larger concentration of CO2 impacts the characteristics of the air mass as a whole since there is now larger proportion of available vibrational energy state relative to translational.
3) Therefore, an air mass with larger CO2 concentration and SAME equilibrium temperature would be expected to absorb and radiate a larger amount of radiation.
I’m sure someone can tell me if I’ve made errors in my logic above (ie. my interpretation of black-body/ energy equipartition law or otherwise). If not then it seems the argument I made earlier that the temperature of the air mass would have to increase in order to balance the change in absorbed radiation is wrong. Moreover, I don’t see why an injection of CO2 would result in a net transfer of energy from vibrational excitation to translational. Greater opportunity for vibrational to translational conversions would be equal to greater opportunity for translational to vibrational conversions.
Note: Even if Tom is correct, this does not mean that greenhouse gases have no warming effect on earth or atmosphere. The GHGs still warm the surface and warming of the surface results in atmosphere reaching higher equilibrium temperature. It’s just that higher absorption of radiation in atmosphere (due to higher CO2 concentration) does not DIRECTLY warm the surrounding air.
This is a valuable “Assume the horse is a perfect sphere” experiment. The blogger says: My statement is – CO2 does create a warming effect in the lower atmosphere.” is incorrect. The blogger merely proves that CO2 absorbs 15um wavelength radiation and relaxes. Whoop de doo. Congratulations!! The “physicist” fails in his “perfect sphere” experiment by failing to ask the question, “is there any way that CO2 would cause cooling to be faster or cause net cooling in general?” The answer is an emphatic YES! The second question is, “Will the cooling forces (excluding convection) overwhelm the radiative heating mechanism. The answer again is YES. How do we know this?
Convective cooling using air is substantially more effective than conductive cooling using air. It’s why we blow air on hot soup to cool it faster…more air…more cooling (CO2 at higher concentrations than 400ppm).
Conductive cooling using air is substantially better than radiative cooling with no air. Radiative transfers of energy are slow, it’s why things stay hot or cold in a vacuum. FOR A LONG TIME!!!
If you were to add a small amount of CO2 and only CO2 to the interstitial space (area between the surface contacting the coffee and the outside surface) of a thermos for your hot coffee… guess what …it get’s colder faster. Go do the experiment in a glass thermos or any thermos. Since your coffee is radiating at LWIR, the CO2 gas doesn’t keep the coffee warmer. That is basic physics and thermodynamics. Also, since there is more Oxygen than CO2 in the atmosphere…and replacing Oxygen with a CO2, a gas with a lower heat capacity at constant pressure, the atmosphere will be more conductive and cool faster.
Jeff hedges his bets…and says….”I’ve not said anything about the magnitude or danger or even measurability of the effect. I only assert that the effect is real, is provable, it’s basic physics and it does exist.”… This is disingenuous. The conductive effects of added CO2 to the atmosphere will outweigh the absorptive effects. The net effect is cooling. When the physical effect is not measurable in the real world, is it necessary to account for it? If a measured effect contains both mechanisms…and one outweighs the other, do you use the net effect in the calculation? If yes, do you make conclusions based on the net effect or the only one of the components? If CO2 can absorb heat and do conductive/convective cooling and the net result is cooling, do you claim that CO2 causes heating if the net effect is cooling?? The “green house effect” is bogus. Don’t believe me… convince a nursery to pump in CO2 (800ppm final concentration ought to be enough) to keep it warm at night in the green house instead of turning on the heat when the temperature approaches freezing outside. Should be able to bump the temp up by 5C. For good measure…have Jeff bring his laser.
Mike Blackadder says: “Therefore, an air mass with larger CO2 concentration and SAME equilibrium temperature would be expected to absorb and radiate a larger amount of radiation.”
Equilibrium temperatures of chamber “C” are not the same for different CO2 concentrations. Yes, at larger CO2 concentration an air mass will absorb larger amount of radiation. The parcel of air will warm up to a level of temperature when absorbed and emitted radiation are equal, regardless if it is a black body or not, at which point the radiation will stop warming the air. What might be so confusing in this simple schema?
@Cal
For what it’s worth the following is what you see in the infrared spectrum looking upward and downward:
http://www.sundogpublishing.com/fig8-2.pdf
It’s from the 2006 textbook “A First Course in Atmospheric Radiation” by Grant Petty.
All the figures from the textbook may be viewed at:
http://www.sundogpublishing.com/AtmosRadFigs.html
Mike Blackadder
1 “Presumably in actual atmosphere the air does not radiate like a blackbody because greenhouse gas concentrations are small (ie. If there were no greenhouse gases the atmosphere certainly would not radiate like a black body.)”
Not true, the collisions are more numerous than radiation, you will get blackbody radiation.
3 – “Therefore, an air mass with larger CO2 concentration and SAME equilibrium temperature would be expected to absorb and radiate a larger amount of radiation.”
This is just confusing. If the equilibrium temperature is dependent on the absorbed radiation, then what you are saying is that — if your air has the same energy input with or without CO2……
“I don’t see why an injection of CO2 would result in a net transfer of energy from vibrational excitation to translational. ”
C02 is far more likely to collide than radiate. So the CO2 will absorb the energy, the molecules vibrate and collide, and you get heat. More CO2 means more capture. Maybe only slightly more, but still more.
winterkorn says:
August 7, 2010 at 10:43 am
“If it is easier for solar energy to reach the Earth’s surface than it is for heat energy to be irradiated away from the Earth, then it will be warmer at the Earth’s surface. ”
Nice.
Stephen Wilde: You replied, “Some of these links may help you.
http://search.orange.co.uk/all?q=jet+stream+shifts+1970+to+2000&brand=ouk&tab=web&p=searchbox&pt=todayweb_hp4&home=false&x=21&y=15”
Thanks for the link. But I don’t need links to search engine outputs. I’ve researched that. Specific data upon which you rely was what I was asking for. On the page you offered, there was little to document the global latitudinal variations you commonly refer to.
I will again suggest you learn to use the KNMI Climate Explorer:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere
For example, it would allow you create Hovmoller diagrams of CAM-SOPI precipitation data from 10S-20N, at different ocean longitudes, from 1979 to present. The following are samples, using 12-month averages to eliminate seasonal variations. I’ve thrown some lines on them to make it easier to identify the variations. Here’s one that captures the ITCZ over the Pacific at 180 long (also catches the SPCZ on occassion):
http://i36.tinypic.com/sbnfcg.jpg
And the ITCZ at 120W:
http://i35.tinypic.com/qprp1v.jpg
And the ITCZ for the Atlantic at 30W:
http://i33.tinypic.com/k5324k.jpg
ENSO appears to be the cause of the greatest year-to-year variability, as one would expect.
Sanctus simplissimus! The thought experiment of passing a laser through gases in a container (which itself may absorb IR) confuses signal transmitivity with the flow of thermal energy in the atmosphere, which in the geophysical setting is demonstrably more through non-radiative mechanisms than through terrestrial IR radiation. In that setting there is no radiative algebra that can determine the temperatures throughout the atmosphere, as the AGW proponents invariably imply. Like temperature itself, radiative intensity is a NON-CONSERVATIVE state variable, and not a flow variable! For a solid physical understanding of the problem, the conservation of enthalpy under the inviolable direction of entropy needs to be mastered. This is almost never seen in discussions on either side of the climate debate.
Like all strong absorbers, CO2 is also a strong emitter. Its effect thus cuts both ways. It’s not a generator of any energy. Those who are inclined to believe that CO2 has a rare ability to trap or store thermal energy, squirelling it away like gold coins, forget that its specific heat is less than that of aluminum. For them, I suggest finding a large aluminum post on a cold winter day and see for themselves how much their temperature is increased by standing next to it. In fact, if they would put their tongues on said post they would never again attempt to argue that a colder body, unsustained by any independent power source, raises the temperature of the warmer body.
Jeff, thanks for the reply. Bear with me for a minute, I’m still trying to sort this out.
“Not true, the collisions are more numerous than radiation, you will get blackbody radiation.”
So you are saying that we will get a fixed amount of radiation from a mass of air at given temperature regardless of the CO2 concentration? Just to clarify. Say you have two packets of air in a vaccuum and both are at the same temperature, but one packet has concentration CO2 like earth and the other twice the amount; would the packet with higher CO2 not emit more radiation to space? Also I don’t see why many collision events have any impact except that it gives opportunity for the air temperature to reach equilibrium in response to radiation events. In other words a CO2 molecule would presumably transfer vibrational energy to translational and vice versa many times between absorbing or releasing a photon.
I said: ‘I don’t see why an injection of CO2 would result in a net transfer of energy from vibrational excitation to translational. ‘
Jeff: “C02 is far more likely to collide than radiate. So the CO2 will absorb the energy, the molecules vibrate and collide, and you get heat. More CO2 means more capture. Maybe only slightly more, but still more.”
My point (and I believe Tom’s point) is that the converse is also true. More CO2 means that there are more molecules with the additional vibrational degrees of freedom. CO2 that isn’t excited that collides with another particle will result in translational energy converted to vibration of the CO2. Therefore, if we increase CO2 concentration and we don’t increase the amount of energy in the air packet then the temperature is lower (ie. if CO2 has no vibrational excitation there would be a transient effect of net translational to vibrational conversion until reached an equilibrium).
I suppose that where this thinking goes wrong is in the event that there is a very large amount of radiation. If everytime a CO2 molecule transfers vibrational energy to another molecule that it immediately absorbs another photon that with the many collisions we are effectively pumping radiation into the system. I could see in that case why there would be a net transfer of energy from vibrational to translational. That seems to be the case in the example that you’ve given and perhaps is true in the atmosphere.
Thank you Bob, very helpful.
When I retire from the day job I’ll make a start. In the meantime I suspect that new observing techniques and closer attention to the relevant observations may make such work unnecessary.
Have you given more thought to extending your work to mesh in with global rather than regional events ?
Dave Springer
Thanks for the interesting links
Rob Z
I am sorry but I cannot agree with your view that conduction is more powerful than radiation. A few things are known for certain and one of these is how much energy would be radiated by the earth at its current surface temperature if there was no atmosphere. This is far more than it currently radiates. Therefore if there were no atmosphere it would cool until radiation balance is achieved. So despite what you may feel intuitively the nett effect of the atmosphere is not a cooling one.
Your example of the thermos flask is not valid. The thermos is designed to remove all forms of heat loss. So the there are two walls of poorly conducting material where the inner surfaces are silvered to reduce radiation and the gas is removed to reduce conduction. I am pretty sure that the thermos would work better with silvered surfaces and 0.0003 bar of CO2 in the gap than it would with blackened surfaces and a perfect vacuum.
More importantly we can do the sums for the real thing. The maximum temperature gradient across the atmosphere is 8K per kilometre.The conductivity of air is 0.024W/mK so the energy lost by conduction is only a tiny fraction of a watt per square metre compared with the hundreds of watts lost by radiation.
In any event the issue is not really what the atmosphere is doing now but what it would do if you added more CO2. As I have said previously this will never be answered using a bottom up analysis. The micro models used by climate scientists today may work when we study gross changes that occur for short periods during weather events they don’t work for subtle changes over long periods relating to climate. Indeed I suspect subtle effects like an increase in any trace gas or aerosol will not be understood using any type of analysis until we have hard data from satellites correlating actual emissions with actual temperatures as the earth responds over time to changes in clouds, wind, convection currents, ocean temperatures etc. Then we can do real science.
Stephen Wilde says: “Have you given more thought to extending your work to mesh in with global rather than regional events ?”
ENSO and AMO are regional phenomenon with global effects. Have you forgotten my posts about OHC? I present and discuss things regionally because one can identify causes of variability–SLP, ENSO, etc. With global perspectives, one loses that ability, and assumptions made at the global scale may very well be incorrect, because of the noises created by the regional variations at different time scales.
Rob Z says:
August 7, 2010 at 12:14 pm
You got it.
Any increase of heat capacity of the working fluid improves the efficiency of a heat pump.
Mike,
from this link:
http://en.wikipedia.org/wiki/Planck%27s_law
you can see that intensity of emission I is based only on temperature. I really have a hard time following the rest of your post. Every time I think I’m getting it, I loose it.
Maybe an even simpler explanation.
The laser passes through clear stuff — it gets absorbed by black stuff. The CO2 is black stuff. If we consider all the other minor aspects of what happens, the black stuff is still black. The laser cannot pass — so it makes heat.
The rest of the consideration about re-emission time, how much light passes through and the rest only determines the level of heating, not whether it happens or not.
I hope that is helpful.
RE: Gail Combs: (August 6, 2010 at 4:45 pm) “I guess I was not clear. I thought that is what I said.”
I am sorry, I thought that was an isolated general question…
There is another dimension to consider here – “Time”. How fast does the radiation exit the Earth system? How much time does it spend moving from molecule to molecule.
When the Sun sets each night, the average surface radiation level falls from 418 W/m2 at the peak to 364 W/m2 just at sunrise or a decline of 10C.
So over the 12 hours, an average 4.5 W/m2 is lost to space each hour (obviously slower in the CO2 and H20 bands and faster in the windows.)
But if the Sun did not come up tomorrow, at 4.5 W/m2 loss per hour, it would only take 80 hours – a little more than 3 days – before the surface temperature in the centre of the continents approached that of the Cosmic Background Radiation – give or take some lag from water bodies.
Or one could also say, the average time that the energy represented by a visible spectrum photon from the Sun spends in the Earth system before it is lost to space is 40 hours – either a surprisingly long number or a surprisingly short number depending on your perspective. But at the speed of light and the average relaxation time for excited molecules, this means the photons are spending an extremely long period of time bouncing around from molecule to molecule. Maybe someone wants to take those numbers and calculate how many molecules each photon ends up in before it escapes to space – lots of Zeros in that number.