Guest post by Ira Glickstein
Albert Einstein was a great theoretical physicist, with all the requisite mathematical tools. However, he rejected purely mathematical abstraction and resorted to physical analogy for his most basic insights. For example, he imagined a man in a closed elevator being transported to space far from any external mass and then subjected to accelerating speeds. That man could not tell the difference between gravity on Earth and acceleration in space, thus, concluded Einstein, gravity and acceleration are equivalent, which is the cornerstone of his theory of relativity. Einstein never fully bought into the mainstream interpretation of quantum mechanics that he and others have called quantum weirdness and spooky action at a distance.
So, if some Watts Up With That? readers have trouble accepting the atmospheric “greenhouse” effect because of the lack of a good physical analogy, you are in fine company.
For example, in the discussion following Willis Eschenbach’s excellent People Living in Glass Planets, a commenter “PJP”, challenged the atmospheric “greenhouse” effect:
“The incoming energy (from the sun) you express in w/m^2, lets simplify it even more and say that energy is delivered in truckloads. Lets say we get 2 truckloads per hour. … when we come to your semi-transparent shell [representing greenhouse gases (GHG) in the atmosphere], you are still getting two truckloads per hour, but you say that these two truckloads are delivered to both the earth and to the shell — that makes 4 truckloads/hr. Where did the extra two truckloads come from?”
In that thread, I posted a comment with an analogy of truckloads of orange juice, representing short-wave radiation from Sun to Earth, and truckloads of blueberry juice, representing longwave radiation between Earth and the Atmosphere and back out to Space. A later commenter, “davidmhoffer” said “Ira, That was a brilliant explanation. …”
This Post is a further elaboration of my physical analogy, using a pitching machine and yellow and purple balls in place of the truckfulls of juice.
Graphic 1 shows the initial conditions. The Sun is a ball pitching machine that, when we turn it on, will throw a steady stream of yellow balls towards the tray of a weight scale, which represents the Earth. The reading on the scale is analogized to “temperature” and, with the Sun turned off, reads “0” arbitrary units.
TURN ON THE “SUN”
Graphic 2 shows what happens when the Sun is turned on and there are no GHG in the Atmosphere. The stream of yellow balls impact the tray atop the weight scale and compress the springs within the well-damped scale until equilibrium is reached. The scale reads “1”. This is analogous to the temperature the Earth would reach in the absence of GHG.
The balls bounce off the tray and, for illustrative purposes, turn purple in color. This is my way of showing that Sun radiative energy is mostly in the “shortwave” visible and near-visible region (about 0.3μ to 1μ) and that radiative energy from the warmed Earth is mostly in the “longwave” infrared region (about 6μ to 20μ). The Greek letter “μ” (mu) stands for a unit of length called the “micron” which is a millionth of a meter.
Since, at this stage of my physical analogy, there are no GHG in the Atmosphere, the purple balls go off into Space where they are not heard from again. You can assume the balls simply “bounce” off like reflected light in a mirror, but, in the actual case, the energy in the visible and near-visible light from the Sun is absorbed and warms the Earth and then the Earth emits infrared radiation out towards Space. Although “bounce” is different from “absorb and re-emit” the net effect is the same in terms of energy transfer.
If we assume the balls and traytop are perfectly elastic, and if the well-damped scale does not move once the springs are compressed and equilibrium is reached, there is no work done to the weight scale. Therefore, Energy IN = Energy OUT. The purple balls going out to Space have the same amount of energy as the yellow balls that impacted the Earth.
ADD GHG TO THE “ATMOSPHERE”
Graphic 3 shows what happens when we introduce GHG into the Atmosphere. The yellow balls, representing shortwave radiation from the Sun to which GHG are transparent, whiz right through and impact the weight scale and push it down as before.
However, the purple balls, representing longwave radiation from the Earth, are intercepted by the Atmosphere. In my simplified physical analogy, the Atmosphere splits each purple ball in two, re-emiting one half-ball back towards the Earth and the other half-ball out to Space. Again, you can assume that half of the balls “bounce” off the Atmosphere back to Earth like reflected light from a half-silvered mirror and the other half pass through out towards Space. In the actual case, it is “absorb and re-emit half in each direction” but the net effect is the same in terms of energy transfer.
OK, here is the part where you should pay close attention. The purple half-balls that are re-emitted by the Atmosphere towards Earth impact the tray of the weight scale and press against the springs with about half the force of the original yellow balls. So, at this stage, when equilibrium is reached, the well-damped scale reads “1.5” arbitrary units.
But, we are not done yet. The purple half-balls are absorbed by the Earth, and re-emitted towards Space. Then they are re-absorbed by the Atmosphere and once again split into quarter-balls, half of which head back down to Earth and re-impact the weight scale. Now it reads “1.75”. As you can see, the purple balls continue to get split into ever smaller balls as they bounce back and forth and half head out to Space. The net effect on the weight scale is the sum of 1 (from the yellow balls) + 1/2 + 1/4 + 1/8 + 1/16 and so on (from the purple balls). That expression has a limit of “2”, which is approximately what the scale will read when equilibrium is reached.
Again, the well-damped scale does not move once the springs are compressed and equilibrium is reached, so there is no work done to the weight scale. Therefore, Energy IN = Energy OUT. The purple balls going out to Space have the same amount of energy as the yellow balls that impacted the Earth. But the “temperature” of the Earth, as analogized by the reading on the weight scale, has increased.
DOUBLE THE GHG IN THE “ATMOSPHERE”
Graphic 4 is the final step in my physical analogy. Let us double the GHG in the Atmosphere. (NOTE: I am assuming that the doubling includes ALL the GHG, most especially water vapor, and not simply CO2!) This is represented by putting a second layer of Atmosphere into the physical analogy.
The purple balls emitted towards Space by the first layer of the Atmosphere are intercepted by the second layer, where they are absorbed, and smaller balls are re-emited in each direction. The downward heading balls from the upper atmosphere are intercepted by the lower Atmosphere and half is re-emitted down towards the weight scale that represents Earth. Once again, they compress the springs in the weight scale increasing the reading a bit, and are re-emitted back up. The purple balls get halved and bounce around up and down between Earth and the two layers of the Atmosphere, further increasing the reading on the scale once equilibrium is reached.
Again, the well-damped scale does not move once the springs are compressed and equilibrium is reached, so there is no work done to the weight scale. Therefore, Energy IN = Energy OUT. The purple balls going out to Space have the same amount of energy as the yellow balls that impacted the Earth. But the “temperature” of the Earth, as analogized by the reading on the weight scale, has increased due to the doubling of GHG in the Atmosphere.
WHAT I LEFT OUT OF THE PHYSICAL ANALOGY
Any simplified analogy is, by its very nature, much less than the very complex situation it is meant to analogize. Here is some of what is left out:
- My purple balls are re-emitted in only two directions, either up or down. In the real world, longwave radiation is emitted in all directions, including sideways.
- My purple balls are all totally absorbed by the Atmosphere and re-emitted. In the real-world, a substantial amount of longwave radiation is re-emitted from the Earth and the Atmosphere in the 9μ to 12μ band where the Atmosphere is nearly-transparent. A substantial portion of the radiation from Earth and the Atmosphere thus passes through the Atmosphere to Space without interception.
- My physical analogy addresses only radiative energy transfer. In the real-world, energy transfer from the Sun to Earth and Earth to Space is purely radiative. However, the Earth transfers a considerable amount of energy to the Atmosphere via convection and conduction, in the form of winds, precipitation, thunderstorms, etc. These effects are absent from my analogy.
- I represent the Atmosphere as a single shell, when, in fact, it has many layers with lots of interaction between layers.
- I represent doubling of GHG as adding another shell, when, in fact, doubling of GHG, if it occured (and if it included not just CO2 but also a doubling of water vapor and other GHG) would increase the density of those gases in the Atmosphere and not necessarily increase its height significantly.
- In my analogy, all the energy from the Sun strikes and is absorbed by the Earth. In the real-world, up to a third of it is reflected back to Space from light-colored surfaces (albedo) such as snow, ice, clouds, and the white roof of Energy Secretary Chu’s home :^). If a moderately warmer Earth, due to increased GHG, evaporates more water vapor into the atmosphere, and if that causes more clouds to form, that could increase the Earth’s albedo to counteract a substantial portion of the additional warming.
I am sure WUWT readers will find other issues with my physical analogy. However, the point of this posting is to convince those WUWT readers, who, like Einstein, need a physical analogy before they will accept any mathematical abstraction, that the atmospheric “greenhouse” effect is indeed real, even though estimates of climate sensitivity to doubling of CO2 are most likely way over-estimated by the official climate Team. When I was an Electrical Engineering undergrad, I earned a well-deserved “D” in Fields and Waves because I could not create a physical analogy in my overly-anal mind of Maxwell’s equations or picture the “curl” or any of the other esoteric stuff in that course. Therefore, those WUWT readers who need a physical analogy are in great company – Einstein and Glickstein :^).
I plan to make additional postings in this series, addressing some implications of the 9μ to 12μ portion of the longwave radiation band where the Atmosphere is nearly-transparent, as well as other atmospheric “greenhouse” issues. I look forward to your comments!
Frank Lee Meidere says:
February 23, 2011 at 1:02 pm
Yes, the bank transactions are a thumbnail sketch.
Q1. Did a cooler heat a warmer? A1. It’s against the law.
It’s true the law doesn’t pry that closely because they would find individual molecules becoming internally excited and having that excitement turn into external motion. If you go back up-thread Steve mentioned this.
It’s not appropriate to ask one molecule to represent all of his brothers and sisters because they are so independent-minded. At any moment a volume of air including water vapour for example has a temperature, but within that body, if you were really quick you could find a bunch of molecules so sluggish that they would qualify as ice and, right next door you’ve got some that would scald you. The reason they’re moving as they are is the collisions that have taken place. Incoming photons add some very, very local pepper but it doesn’t constitute heat until there’s a respectable amount of it. After all, there are others adjacent that are spitting out photons just as fast as they can, so that would be cooling. Except, it’s not. It’s all about the average.
In discussions we tend to visualize radiation across human-scaled distances but radiation occurs within volumes of stuff, not just between different things like “the surface” and “the atmosphere”. Conduction utterly overwhelms radiation within a steel bar. Many of us think it does in a gas at 1000 millibars.
Q2 Answered above, I hope, but the withdrawals would have to be pro-rated as the account dwindled.
Q3 Is he still missing?
You know, I think that does it. So in my banking analogy, we don’t consider the various profits and losses until the end of the day, at which point they would average out to what we would expect: BA-A ends up “cooler,” while the other two end up somewhat “warmer.” At least until equilibrium is reached.
Thank you Oscar, George, and Ira. This has helped a lot.
George, calm down, I’m not questioning your understanding of EM radiation.
Yes indeed the laser beams need to be coherent over the length of interest, and for a “stable” interference signal they need to be phase locked (most easily established from the same source, but not a necessary condition) etc. etc. This was intended to be a high level example of interference, not a detailed example including all of the caveats including; coherence length, phase matching, wavelength matching, etc. etc. My major point was that the energy at the location of destructive interference is not destroyed; it just shows up someplace else, in full compliance with the laws of thermodynamics.
This is supposed to be a “thought” experiment right ?
My point again is that the laws of thermodynamics apply everywhere (from molecules to the entire universe (however big that may be)). In some cases these laws have no apparent affect (i.e. EM waves in a vacuum). But they still apply, everywhere, everyplace, all of the time.
I do not care to get into a ——- match about who has more education and patents and experience, etc. I am glad to hear that your employer values your contributions, as does mine.
I never claimed to “know it all”, please note the beginning of my post where I said “AS I UNDERSTAND THEM”. I am certainly open to any information that increases my understanding of the laws. Telling me how many patents you have does not increase my knowledge about the laws of thermodynamics.
Cheers, Kevin.
George E. Smith, Kevin,
Thanks for your comments.
Seems even very knowledgable persons disagree on a lot of issues (or maybe the forum type of discussion can turn anything into an argument).
In my original post I tried to reconcile the observation that any form of shielding seems to slow the radiative cooling of an object, with the second law of thermodynamics which states that heat or energy only goes from hotter to cooler.
The idea that the shield is heated by the emitting object and then heats the emitter by radiation is not consistent with the second law unless you look at the process in detail like we just did.
I know this “backradiation thing” is slightly AGW-ish, (shudder) but facts are facts.
Brgds, Dan
Ira Glisckstein;
One of my favorite jokes is about the physics major and engineering major who are waiting for a bus outside a building. >>>
I think the first time I noticed this odd acceptance of mathematical results without thinking was when calculators first started becoming common. There’d be come calculation or other that needed to be done and all the slide ruler guys would say “four” just as the calculator guys would say “three point nine nine nine nine nine…”
I used to say “so…four?” and some of them would argue. I’d ask them to sell me what the difference was by subtracting four from their results on the calculator… and some of them STILL didn’t get it.
I developed a few quips over the years to make various points:
Q: If two trains are 100km apart, one going 30 km and our and accelerating at 1 km/hr/min and the other is going 20 kilometers an hour accelerating at the same rate, what will the speed of collission be?
A: What makes you think the rail company is stupid enough to have them on the same track?
For the physicists…
Q If I throw a ball straight up, and there are no other effects except gravity, what is the velocity of the ball at the peak of the trajectory?
Physicist; zero
Q Zero? Are you certain? Zero? Motionless?
Physicist; yes
Q So if it is motionless at the peak of the trajectory, how does it get back down?
And for the engineers:
Q can you model the suspension of a car with a capacitor, a resistor, and an inductive coil?
Mech Engineer; of course not
Elec Engineer; don’t be stupid
Q could you, Mr EE, write down the equations you would use to calculate current in that circuit on the white board? And could you Mr ME write down the equations for motion in a system with a spring, a shock absorber and a known coefficient of friction?
Ok, look at those equations side by side. Now, can I ask the question again?
And possibly my all time favourite
Q What is centrifugal force?
A Force outward on a body travelling in a circle
Q If I tie a string to a weight, and swing it around in circle, am I pulling on the string or pushing on it?
Hmmm, I had lots of problems with your analogy until I ready your explanation of what was left out. Now I think it’s pretty good. I think you left out something in your list of what’s left out. Maybe this has been pointed out already:
There is no heating effect merely from low-band light present in the atmosphere. In fact, you can bounce (completely “elastically”) as much IR as you like and it creates no heat. What creates the heat is the “inelastic” bouncing of IR. It strikes a surface (or a free-moving atmospheric particle) and LOSES some energy. This energy manifests as heat.
Thus your analogy is misleading as it represents the “collisions” as elastic, whereas the heating effect is entirely dependent on inelasticity. The analogy looks good insofar as it represents the amount of IR radiation passing through the atmosphere at every point but it fails at what some will consider to be the most critical point.
When I saw your first diagram I thought you were representing the heating effect as the momentum transfer from the balls bouncing off the scale. If that were the case one of your earlier questioners would have been right, in that you cannot manufacture further momentum simply by bouncing balls around in a closed system. Then as I read I decided you didn’t mean this. Then by the time I was finished, I was unsure.
Perhaps the analogy needs a “redo” taking this and a few other worthwhile objections from the comments into account. Our physical intuition concentrates, consciously or unconsciously, on momentum transfer in your analogy and this confuses the issue. In the radiative heating context momentum is practically a nonissue. I hate to tinker but perhaps you need balls with no momentum but finite weight (no, Galileo would turn over in his grave; he demonstrated that gravitational mass and momentum mass are interchangeable). Well, something like that. Or a weightless ball — someone suggested “flubber” above — that leaves “goo” behind when it bounces, and the goo has weight. the “weight” equals the heating effect. shortwave radiation leaves practically no goo, but longwave leaves much more.
Hmmm, looking at my suggestion it’s going to really mess up your simple analogy. I changed my mind. It’s a nice start, but perhaps you need a slightly different analogy, to avoid the problem with momentum.
I heard a version of that same joke during the slide rule days before calculators. For those unfamiliar with a slide rule, there are marks for two significant figures and then, to get more, you have to estimate the distance. (Like reading a clock that has no second hand and attempting to estimate seconds by the position of the minute hand.) Well, at our college, they installed really big slide rules (perhaps six feet long) at the front of the classrooms and the profs used them to demonstrate calculations. With the larger slide rule, some thought they could estimate to four or five or more significant figures.
Well the joke is that some profs got so used to the slide rules that they used them even for calculations they could do in their head. So, one time, when the prof had to multiply 2 x 2, he used the slide rule and announced the answer: "3.995, but, for convenience, we’ll call it 4.”
“”””” Kevin says:
February 23, 2011 at 8:13 pm
George, calm down, I’m not questioning your understanding of EM radiation. “””””
Is that one of those:- “Have you stopped beating your wife yet ?” statements ?
So what is your evidence that I am not calmed down; why would I be other wise ?
So where in any of my posts did I assert, or even hint that I might believe that the Laws of Thermodynamics do not apply everywhere in the Universe. Can you provide a reference for any such assertion by me ?
A similar situation is the statement often asserted by posters at WUWT, that the Heisenberg principle of uncertainty, only applies to microscopic things, and doesn’t apply in the macro world.
So those folks are asserting that in the macro world, you CAN ( in a macro situation) have dx . dp < h/2pi despite Heisenberg's assertion that you can't.
So, many folks including me, believe that the laws of Physics apply everywhere. Apparently string theorists believe that there is a separate universe for every conceivable different set of Physical laws. They of course have no proof of that; or even any evidence of such behavior; no basis whatsoever; which simply is NOT science.
So you apparently believe that not only do the laws of physics apply everywhere, but they also apply to everything; or every concept even. The question is, what experimental observational evidence accompanies the application of some physical laws; say the laws of Thermodynamics, to some physical situation, where they create no consequences whatsoever.
In fact you could rewrite the laws of thermodynamics to be anything you want them to be, and then get the same null experimental data when you apply them to some systems. You may choose to believe that those laws apply to that system; others may differ.
You may choose to have two laser beams interfere and produce zero amplitude at a specific point in space; and assert that there is no energy at that point; it is somewhere else, I believe you suggested.
Well may I counter with a suggestion that the total laser energy, at any point whatsoever in that region of overlapping laser beams, is also precisely zero. You won't find any energy at any such point whether the electric field there is zero or any finite value. And you won't find any even in a thought experiment; just as there is none there in real physical fields.
As for my quip about Patents, and such; was it not YOU who made a point of telling us that YOU are not a PhD; as if that message, was supposed to convey some important information to other readers.
Since it was you who raised the credentials issue for us all to wonder about, I simply chose to lay my cards on the table so readers can see, I have nothing up my sleeves.
One could make the point that PhDs tend to learn more and more about less and less. In my case, I elected to forgo advanced degrees, as having no value for my intended career path; and pursued a multidisciplinary career in Industry; where a working knowleedge of many subjects was of more use than an extensive knowledge of a very restriced specialty.
I have no problem with those in certain fields who DO have the need to have highly refined formal training in certain specialties.
Dr Laura has a PhD; she doesn't know anything about either EM radiation or Thermodynamics. I thought of getting one in Ice Cream Making; but couldn't find any job listings requiring that skill.
It's good that you have a job with an employer who appreciates your knowlwedge. So I don't have to worry about you coming after my job.
Thanks R. Craigen for you comments and thoughts. Physical analogies are always a problem because , if you account for everything, you end up with something as complex as the thing you are analogizing and the whole point of the exercise is to come up with somthing simpler to aid insight and understanding.
Let us consider the balls and the scale as a physical system only, in an idealized case with no gravity and perfectly elastic balls and tray. If I pitch a steady stream of balls at the tray of the well-damped weight scale, they will compress the springs. During that time period, the tray will be moving down against a force, which requires energy, so, even if the balls and the tray are perfectly elastic, and we ignore the effects of gravity, there will be energy consumed in compressing the springs, and, as a consequence, the balls bouncing off will have a little less speed than the balls coming down.
However, once the springs are compressed to the point that their force upwards exactly matches the force of the balls coming downwards, the tray will not move and there will be no energy consumed. So, the upward bouncing balls will have the same speed and energy as the downward ones.
I thought of the scale analogy while riding my bicycle, after having sketched up several versions, including one where the pitching machine was aimed horizontal and was impacting a hinged vertical plank such that it was no longer vertical. The scale analogy was pleasing because, in the case of the Sun and the Earth, when the Sun comes up and bathes the Earth in Sunlight, the portion of Sunlight absorbed slowly raises the surface temperature (like springs being compressed) until the point where surface temperature is such that an exactly equal amount of far-IR energy is re-emitted from the Earth. After that point, the Earth temperature remains constant (like the height of the tray on the weight scale) and an equal amount of energy comes into and out of the Earth (like the equality between the energy in the yellow balls and the purple ones).
Another thing I liked about the analogy is that, if I placed a fixed plank some distance above the tray, the upward-going balls would bounce off it in a downward direction, further compressing the springs until a new equilibrium was reached. To make the fixed plank more like an Atmosphere with GHG, which absorbs Far-IR energy and re-emits it in random directions, I considered having holes in the plank such that half the balls passed through (like the IR re-emitted upwards) and half bounced down (re-emitted downwards) . However, since the balls represent large quantities of energy (like the “truckloads” suggested by “PJP” whose question ignited the analogizing in the first place), I thought it better to have them split in half, going both up and down.
In any case, this thread seems to have got lots of us thinking, and some (but not all) have accepted the idea that GHG (mostly water vapor but also including CO2) in the Atmosphere are responsible for raising the temperature of the Earth above what it would be without GHG.
Some, however, seem to be so upset at the official climate “Team’s” distortions of AGW into CAGW (Catastrophic), that they do not want to accept the Atmospheric “greenhouse” effect in any way, shape, or form. In their mind, to do so, and admit that human-caused CO2 (burning fossil fuels) and land use (causing reduced albedo) are responsible for even a little additional warming, is to give AGW credibility.
I think disbelieving AGW is an error both scientifically and also in terms of winning the hearts and minds of the general public to the rational skeptic cause. I am skeptical about CAGW, not AGW. I think that CO2, per se, is not bad, and perhaps up to 1000 ppm or more might be beneficial. I think a modest temperature increase is, overall, beneficial (which is why I moved from NY to FL :^) and that the large majority of the warming we have experienced is due to natural cycles not under human control. Furthermore, the small part due to human activities is inevitable because, considering the inability of most government projects to work effectively, ther is no way we can change it much. I think it is prudent to conserve and use energy efficiently (hence my 40-50 miles/week on a bicycle and our use of an electric gold cart and a Prius hybrid) not so much for environmental reasons but because of the cost in blood and treasure to protect our access to foreign sources.
“”””” I think it is prudent to conserve and use energy efficiently (hence my 40-50 miles/week on a bicycle and our use of an electric gold cart and a Prius hybrid) not so much for environmental reasons but because of the cost in blood and treasure to protect our access to foreign sources. “””””
Ira, may I suggest that the cost (in blood and treasure) that you refer to is a domestic political decision; and not a global problem.
The US has plenty of fossil fuels to meet its needs. And our primary “foreign” source, is our nearest neighbor, Canada; with whom we share no hostilities. Our apparent shortages are of our own making; witness a dictator in Washington wh simply decrees on his royal sceptr that we shall not utilize our own energy resources.
And it isn’t for environmental reasons, because we will sit by and watch our industrial competitors, and even our enemies, come into our territorial sphere of interest, and pursue the very same resources that we refuse to use ourselves.
If you think an electric gold cart or a Prius, is an environmentally protective solution for you; then go for it. Some of us don’t see it the same way. Where I live it simply isn’t safe to commute by bicycle, although I have done that anyway.
Most of our blood and treasure expenditures go not to protect our sources; but to protect the sources of our “friends and allies” who simply won’t do it for themselves.
I would love it if we told our allies to protect their own sources of energy, and not rely on us to do it for them.
Dan, with respect;
You wrote;
“I know this “backradiation thing” is slightly AGW-ish, (shudder) but facts are facts.”
I don’t believe that I ever suggested that backradiation does not exist. I freely admit that it exists.
I also admit that “backconduction” also exists in solids (or liquids, or gases). Let me explain, a colder molecule is vibrating slowly and is in contact with a warmer molecule. The colder molecule does indeed transfer some energy (instantaneously) to the warmer molecule, however the warmer molecule transfers a WHOLE lot more energy (instantaneously) to the colder molecule. The Second law just says that the NET flow is from the warmer to the colder location; that’s all, nothing more. It does not say that energy can only flow one way, it says that the NET energy can only flow one way. Net needs to be calculated instantaneously, it is not permissible to apply “dampening” or “averages” to this calculation.
So the point is that there is nothing unique about “backradiation”. In any system energy flows in many directions all at the same time. Backradiation does not have the ability to create “extra” energy.
My point is that the AGW hypothesis calls for the creation of “extra” energy, (sometimes called “Net Energy Gain”), in the absence of better explanations from climate scientists this currently and always has violated the laws of thermodynamics.
My further point is that the fact that backradiation exists does not (by itself) demonstrate that it (backradiation) can cause a higher equilibrium temperature to be achieved. It may be able to achieve this feat, but there are many other factors that need to be investigated such as the “speed of heat” through the materials involved and the thermal capacity and volume of the materials involved.
I have a quick little analogy about AGW; I’m driving down the highway emitting mosquitoes out in front of my windshield. As this stream of mosquitoes strike my windshield they slow my forward progress and reduce my speed. So are these “extra” mosquitoes, or are the just sourced from my vehicle. This analogy is not much worse than measuring temperature with a scale (a device that only converts mass (when subjected to gravity) to a mechanical displacement).
Cheers, Kevin.
Ira says:
In any case, this thread seems to have got lots of us thinking, and some (but not all) have accepted the idea that GHG in the Atmosphere are responsible for raising the temperature of the Earth above what it would be without GHG.
Henry@Ira
Ira, the problem I have lies in the definition of a GHG. Take for instance ozone. It bounces off quite a bit of UV radiation but it also entraps some of earth’s radiation (especially at around 13um). We call ozone a GHG. But what do you say: if ozone increases in the atmosphere (which it actually does, lately), what is the net effect of this? Is it more cooling or more warming?
(straight answer please)
Henry;
You might like to specify high- or low-level ozone. They are quite separate in virtually all respects.
By “level” I mean altitude, of course, not quantity.
Ozone (O3) has a very narrow peak absorption in the longwave band of interest and is thus technically a GHG, even though its contribution to warming the Earth is miniscule and may be counteracted by its blocking of UV in Sunlight. I do not know what the net effect of an increase in O3 would be, but I am pretty sure it is very small either way.
When we speak of GHG in the context of any significant amount of warming, we generally mean H2O (water vapor), the most important and influential GHG, and CO2 (carbon dioxide), which is the next most heavy hitter. CH4 (methane) and NO (nitrous oxide) , along with O2 (oxygen) and your example O3 (ozone) are minor players with narrow peaks, as far as I know.
Water vapor, when it condenses in the Atmosphere, forms clouds that I and most other skeptics believe have a net negative feedback effect. The official climate Team models clouds as a positive feedback, which I believe makes their predictions incorrect. Their estimates of CO2 sensitivity (the increase in global mean temperature due to a doubling of CO2) are, IMHO, at least four times too big. They seem to believe that CO2 interacts with H2O in a way that multiplies its effect, and that may tie into their modeling of clouds as positive feedback. Some commenters in this thread seem to think that Atmospheric CO2 has a cooling effect, but I have not seen that confirmed. Is that answer straight enough?
henry @ur momisugly BrianH
We know that most ozone is made from naturally from oxygen and UV. We need that.
Henry@ur momisuglyIra
if you study the atmospheric aborption bands (excluding clouds) , you will find that ozone cuts a significant part (ca. 15-20%) of the sun’s radiation. It also makes a significant dent in the outgoing radiation of earth (@ur momisugly 13u).
so with the good comes some of the bad. Surely, looking purely at those graphs, I would say the net effect of more ozone must be cooling rather than warming. So why call it a GHG?
We should call it something else.
Co2 and even methane cool the atmosphere as well. You can find the proof here.
http://wattsupwiththat.com/2011/02/20/visualizing-the-greenhouse-effect-a-physical-analogy/#comment-605627
In the case of CO2, the question is what is the net effect, cooling or warming?
If the net effect is cooling, then why do we still call it a GHG?
HenryP;
As I mentioned elsewhere, Mars has 1% of Earth’s atmospheric density, but it’s pure CO2, making it 25-30X as much of a CO2 “blanket”. But the blackbody theoretical temp and the actual surface differ by only 0.1°C, and, IIRC, it’s LOWER on the surface than the bb number (280.0K vs 280.1K).
Oops!
Thank you Kevin for an interesting conversation.
Regards,
Dan
I’m pretty sure back-radiation exists. And back-back-radiation and back-back-back-radiation and even back-back-back-back-back-back-radiation.
Kevin;
My point is that the AGW hypothesis calls for the creation of “extra” energy, (sometimes called “Net Energy Gain”), in the absence of better explanations from climate scientists this currently and always has violated the laws of thermodynamics.>>>
I’m a hardcore skeptic and that is exactly what I believed when I first starting reading the science supporting AGW. I remain a skeptic, but the above is not the claim AGW science makes. In Ira’s model, and in the AGW claims, and in the IPCC reports, the increase in CO2 results in a perturbation of the system followed by a new steady state in which the rate at which energy leaves the system per unit of time is identical to what it was before the increase. Which is exactly what the physics says should happen unless the change also affects the amount of energy being absorbed.
What does change is the temperature gradient from earth surface to top of atmosphere. Interestingly, as seen from space, unless the size of the atmosphere changes, the temperature would be seen to be identical. But the “curve” from surface to TOA would be different, same net effect or average so to speak, but a different shape.
AGW theory says the shape of that curve results in much higher temperature at surface.
I say not freakin’ likely.
henry@BrianH
thanks, yes, that adds more weight to my argument. How is that on Venus, do you know? I vaguely remember that it should be even warmer if CO2 were a GHG.
henry@OliverR
I actually did some thinking about that. What I see is happening, is this: let some of the 14-15 um radiation be sent back to earth by the CO2. When it comes back (after that same radiation hits something on earth) it seems to be always coming back from earth at a longer wave length (mostly by-passing the CO2 at 14-15).
So, I would say no, there is no back-back etc. radiation. There is only (one) re-radiation (deflection) of the same photons…..
But I would like to hear the opinion of other people on this blog about this. Namely if what I say is true, then the whole idea of earth’s atmosphere acting like a giant greenhouse falls in the water. There is no entrapment. There is only somewhat delayed cooling. Is that the same as warming?
Sorry David, you posted almost at the same time as me, but your post does seem like an answer for me! Thanks!
I have said it several times; and I can repeat for those who may have missed that. The claim that there is no GHG “warming” effect, due to whatever trace gas, is for me, not a hill worth dying for.
That GHGs do capture some LWIR radiation that is emitted from elsewhere (surface or atmosphere), is known Physics, and that this results in raising the atmospheric Temperature, is also well understood. OK I don’t know how accurately this has ever been pursued to the extent that quantum theory can tell us precisely what happens; but I am personaly confident that it does warm the ordinary atmospheric gases through the molecular collisions that are the manifestation of heat. I think it is quite naive to deny that much.
What happens after that is far less certain; and to me far less interesting, because I am convinced beyond any reasonable doubt that whatever happens, will be ultimately regulated by cloud modulation. H2O is basically in control of the earth’s comfort region.
I know nothing of, and have little interest in (besides natural curiosity), the various ENSOS, el nino, la ninas, AMOs and the like. I know they are significant contributors to earth local climates. I’m happy that folks like Bob Tisdale, or Bill Illis, and others here keep track of those things and come here to explain them to us. So I don’t dismiss that stuff; it’s just my skillset is not oriented to studying that; so I’m glad they do.
But I see too much exposure to ridicule by the AGW crowd, because a lot of skeptics, don’t really understand enough quite basic science (Physics) to grasp the issues; and I refuse to believe it is because they are incapable of that. They are perfectly able to understand if it is explained to them in understandable ways. If I can help in that process, my time is well spent.
Well ALL Physical models (of the universe) and ALL mathematics, are pure fictional creations of our imagination.
There is nothing in any branch of mathematics, that actually exists anwyhere in the known universe; which after all, is all we care about. We made it all up out of whole cloth; a tool box !
And the equally fictional models of our theories, are already “analogies” if you want to use that word.
So I don’t see any point in trying to create some (presumably) simpler analogy to substitute for what is already a simple concept.
To do so, is to simply introduce confusion, and false leads to aspects of the “analogies”, that are NOT compatible with the already well accepted models.
Others much smarter than we are, have already reduced the “analogies” to about their simplest state. Heed the caution of that Einstein you mentioned; when he said (reputedly), that “scientific theories should be as simple as possible; but no simpler.”
Good words to live by. Better Ira, to use your imagination to try and make the accepted “models” understandable to lay persons; than to try and invent alternatives.
HenryP :
February 25, 2011 at 4:44 am
Henry, it is never the same photon. I could argue here but I will let Dr. Feynman do it for me by having you listenen to http://vega.org.uk/video/programme/46 at 80 minutes into the video (you can just jump to that position). He does not agree with your view of photons (light– radio waves, IR, visible, X-rays, etc.) but many thoughts you are having are getting closer. Maybe we can take the next step for I want to get to the bottom of this also but only by proper physics.
BTW: for some reason other Waynes began posting under this article, Wayne and JackWayne, they are not myself, just lowercase wayne.