Primer on greenhouse gases, I.

Objection to the scientific basis of greenhouse warming seems to be the gift that keeps on giving. That is, if you like getting the same gift over and over again and returning it because it's defective never works. Still, hope springs eternal that understanding something about it will make the disagreements clearer. So this will be the first post about the underlying science. There will be more. It's a primer, so if you know the science it's not for you. But understanding what's under the hood can be explained without requiring agreement on global warming. On the grounds that learning about science is an end in itself, we will plunge ahead. That's called idealism, folks.

First we have to do some elementary physics. High school level. The central theme is the interaction of electromagnetic (EM) radiation and matter. EM radiation is a mysterious thing that can pass through empty space and also through matter without interacting with it. That's how the sun's radiation gets to us and how its visible portion lights up our world. To get here it has to pass through the atmosphere without being stopped by it. But EM radiation can also interact with matter. Whether it interacts or not is what we have to talk about. It depends on the nature of the EM and the matter it encounters. Let's talk about the EM part first.

An electromagnetic field has two components. As its name suggests, one is the magnetic field and one the electric field. Electric fields are produced by separated or stationary electric charges. Magnetic fields are produced by moving charges. You can't see the fields but you can detect their presence. The electric field can be seen by putting an electric charge in it and seeing if it experiences a force. You can do the same by putting a magnet in a magnetic field or seeing what happens to a moving electric charge. The two components are different but intimately connected. Changing one causes changes in the other and vice versa.

The field can also transfer energy from one place to another. Here's one way to visualize this abstract idea. Energy is the ability to do work. Take a magnet in your right hand and hold a compass in your left hand. The magnet produces a magnetic field. Now wave the magnet around. By moving the muscles of your arm you are making the magnet move and with it the field. You are putting work into the field. Now watch as the compass needle wiggles back and forth as you wave the magnet. You are transferring the work from your arm to the magnet to the compass needle -- via the magnetic field. So the field can transfer energy.

Charges and moving charges produce electromagnetic fields that move. One way to do this is to send electrons (negative charges) racing up and down a long wire many thousands of times a second. The long wire is called an antenna, and the changing electromagnetic field it produces is called a radio wave. Think of a very tiny test or indicator charge at a particular point in space, like the magnet in our example. When the radiowave passes what you would see is the charge wiggling back and forth. The back and forth wiggling corresponds to the passage of an electromagnetic wave. The "width" of the wiggle is called the amplitude of the wave and how fast it wiggles per second is the frequency of the wave. The wave is usually pictured something like this:


Source: NASA

Think of this like a water wave (except you don't need the water). the test charge is a boat sitting on the water bobbing up and down as the wave "passes" through. The boat doesn't travel in the direction of the wave, which is really a disturbance on the surface of the water. The boat bobs up and down, moved by the energy in the wave. The test charge does the same thing at a point in space (no water needed) as the EM wave "passes through."

All EM radiation is like this (for our purposes we don't need to talk about the particle version of EM radiation). The different "kinds" of EM are related to differences in the frequency of field wiggling. The EM produced by power lines produces a wiggling back and forth pretty slowly, 60 times a second. Radiowaves produce a wigglng thousands of times a second.

Since the waves all travel at the same speed no matter their frequency (that's an empirical fact), we can also talk about them in terms of the crest to crest distance (the "wavelength"), which is an alternative to frequency as a way to classify them. Some of these distances are very long (miles) and some extremely short (billionths of a meter or less). Here's how that works. Think of standing alongside a railroad track. Consider two trains traveling at the same speed, say 80 miles an hour. The number of box cars that pass you a second is the frequency. If one train has much shorter box cars more will pass you in a second. The shorter the wavelength (the shorter the boxcar) the higher the frequency. Since we know the speed the train goes (which is always the same, the speed of light), knowing the length of the box car will also tell us how many will pass us in a second. And vice versa. So we could characterize the train either by the number of boxcars per second (the boxcar frequency) or the length of the boxcar (the wavelength). Confusingly, EM radiation can be characterized either in terms of its frequency (cycles per second or hertz) or by its wavelength (meters or some subdivision of meters like nanometers). They are equivalent in the sense that if you know one you also know the other.

We have familiar names for EM of various frequencies (alternatively, wavelengths). Here's another pic (using wavelength) from our friends at NASA, where you can also learn more about the various forms of EM (see links at bottom):


Source: NASA

What does all this have to do with greenhouse gases? It turns out that all matter both emits and absorbs EM radiation and the frequencies (or wavelengths) at which a gas does the emitting and absorbing is what makes something a greenhouse gas or not. We also need to discuss the frequencies (or wavelenghts) of the EM radiation emitted by the earth and the sun. That's coming up. Stay tuned.

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Oh, I'm going to have some questions for you !


By gilmoreaz (not verified) on 18 Jun 2008 #permalink

Very nice explanation, thank you. I can't wait for the next in the series!

Suggestion? Maybe if we submit our questions before you write, it may help address the main topics, in your primer, that deniers use to try to discredit global warming.

I'll start and give my devil's advocate question. How come the increasing CO2 is causing the warming when it is such a tiny component of the atmosphere, compared to say water vapour?

>I'll start and give my devil's advocate question. How come the increasing CO2 is causing the warming when it is such a tiny component of the atmosphere, compared to say water vapour?< RobT

The ocean sinks are filling; they possess a finite capacity to absorb CO 2 emissions. When that capacity is fully exhausted, CO 2 will no longer have any place else to be "warehoused," other than in the atmosphere. We are not very far away from that point, at the present time. The outcome is obvious. We are systematically denuding the planet of the environmental capacity to recycle CO 2; what do you think that the ultimate result of this will be?

How about the RF generated by the electrical field oscillation? The Ruskies several years ago said they could generate enough RF in a simulation over a pool of water using cellphones, high voltage wires, and various devices to cause the water to warm. Weapons technology from space. Use a solar panel to generate electricity to microwave a specific point or area. Cook them in their skins. The Mig-25 has a 600 Kw radar transmitter that they would low level in Afghanistan and do the locals with it. Kills them outright or makes them dumb or crazy.

As I recall the Swedes jumped on this and now in the EU you cant put a cellphone tower near a school. Why is that?

GW could be caused by many things but it gives me pause as the pulses generated by all these devices have to slide through multiple spectrum levels. Are we microwaving the earth? Another thing discounted...conveniently in the GW question. Do continue though Revere. I would like to hear the "consensus" position as to what the cause is.

RobT-Good question. Never completely answered, but it continues to generate even more questions when the GW's try to explain it. Its still much less dangerous than the Co. GW MIGHT kill you. The Co WILL kill you.

By M. Randolph Kruger (not verified) on 18 Jun 2008 #permalink

Gosh, MRK, ever hear of Microwave ovens? They actually let some folks buy those even though they easily could be turned into a dandy kilowatt microwave weapon.

Dylan, I don't want to give it all away but I'll give you a hint: Revere is going to take you through absorption and re-emission of EM at much shorter wavelengths than that. If you could see in the longer infrared wavelengths -- such as those the Sun-warmed Earth radiates out toward space -- CO2 gas would look black.

Look forward to the rest. My mind is open despite what follows.

I am no expert and do not deny there is global warming. There has been global warming, just as in the late 60's and 70's there was global cooling. How long this will last, nobody can say for sure. Is it man made?. Perhaps, in part, some estimates put it at 30-70%. The sun has gotten hotter, and IPCC by it's own admission says that it's confidence in solar forcing estimates is not very good.

What I find most objectionable is the certainty some express that CO2 is behind all of global warming and predict a disaster. Yet it seems not well supported by facts. Facts being good data and laws of physics and science. There are theories, and assumptions made to fill the holes due to lack of data or poor quality data, and depending on which assumptions and theories are adopted for the models, wildly differing projections are obtained, and worst case scenarios emphasized to terrorize people into accepting policies which pick their pocket.

The mean temperatures has increased 0.4 to 0.8 deg C over the last 120 years, so they say. Maybe it's more or maybe it's less, and is 120 years even significant?. Orbital eccentricities, axial wobble, solar brightness variation, cosmic ray flux, reductions in our magnetic field strength, volcanic events, even wars might affect climate (maybe all that nuclear testing in the 50's could have caused reductions in temperatures in the 60's and 70's that make temperatures today appear to be rising faster than they are).

In fact, we do not even know what the mean temperature today is, and it's not even clear that a global mean temperature is a particularly useful metric. It seems heat content would be more meaningful. But how much of the temperature rise or warming effect is due to man made CO2?
How much of the CO2 in the atmopshere is from man? Where is 1/2 of the CO 2 we have emitted that has disappeared go to. There are many theories, but nobody knows for sure.

I could argue that the main culprit is water vapour, but we don't have much historical data on water vapour. Human activity certainly releases a lot of water into the air and warmer temperatures should increase the water vapour. Water accounts for most of the greenhouse effect . Estimates of how much range from 60-80%! Big range.

They are unsure how clouds affect the amount of solar radiation reaching the surface of the Earth. There is a lot they don't seem to know. Also, we know several planets in our solar system have gotten hotter in recent years, suggesting the sun might be the main reason.

The other thing is CO2 and H20 are only able to absorb radiation in specific and overlapping wavelengths, and compete for the available energy. Carbon dioxide could absorb more than 3 times the energy it currently does if not for competition from clouds and water vapor for the same IR. Clouds could absorb 50% of available energy capture just 14%. So more CO2 does what? the atmosphere is already saturated with green house gasses relative to the amount of IR available to capture.

IPCC also seems to have forgotten some basic laws of Thermodynamics and Physics.

First of all, hot air rises. Last time I was on a plane it was -50 deg C at 30,000 ft (outside of course). IR emitted from the warmer surface is absorbed by CO2 and H20 in the lower troposphere, near the surface, trapping the heat, near the surface. This heats the air at the surface relative to the air above it. The air then rises, transferring heat upwards by convection to the cooler air above.

Some would like us to believe that the energy from CO2 absorbed IR is trapped within the troposphere, or transferred back to the surface, resulting in a net heating effect. They claim the IR absorbed by CO2 is released in all directions randomly, and does not get released back into space due to a temperature inversion at the tropopause. If so, it would seem we would see significant temperature increases in the upper troposphere, or at least the energy would be trapped there. How does that affect temperature on the surface? And any temperature increase should be associated with an expansion and raising of the troposphere, which would have a cooling effect.

But net global back transfer of IR is not possible thermodynamically, because heat transfer of the emitter is in the direction in which the absorber is colder. Energy transfer must flow downhill, from high to low energy. Hot to cold. There is a drastic temperature difference between the surface and the upper troposphere. That provides the driving force. Hot to cold is up.

With increasing altitude, the temperature declines due to the declining pressure, 0.7 to 1.0 deg C every 100 meters. Warm air is less dense than cold air, that means the heat is transferred by convection as well in an upward direction by IR transfer to the cooler CO2 above . I don't live at 30,000 ft. The way I see it, if it gets a bit warmer up there, who cares, since it won't affect the temperature on the surface. It may of course affect climate to some degree, maybe for the better, maybe for the worse, depending on where you live.

CO2 is essential to the earths cooling system, since it releases the IR that has been absorbed by the atmosphere into space, whereas water vapor is minimal in the upper troposphere. In fact, a case could be made that CO2 is more important in inducing an ice age due to low levels, more so rather than as a gas that increases temperatures dramatically at high levels. People point to Venus and it's hot surface due to it has 96% CO2. Yet what makes Venus so hot is it's enormous atmospheric pressure relative to Earth, and not it's CO2.

As CO2 makes up only 0.038% in the atmosphere, it accounts for only 4-8% of the entire green house effect (without any greenhouse gasses, the earth would be -18 deg C.), Some estimates put this at 26%. They are the same folks that say water vapour and clouds, with a 0.1-4.0% concentration, account for only 60% instead of 80% of the greenhouse effect. Such wide variations prove there is no real consensus. This is not an exact science.

Should we monitor CO2?. Absolutely. But we should not rush to judgement and deprive people of food and energy until the science can offer a greater certainty and a consensus of the scientists is reached. And eliminating the conflict of interest where politics seems to be influencing the debate would be helpful.

Idle-exactly my point. The US used to toss their klystron tubes into the trash for the TACAN's, ILS, Radar transmitters and a few things that I am not supposed to even mention. Those things were Amana's without a boresight on them. Even one that was off frequency was dangerous as it slipped in and out of the various frequencies and yes, it could be a directed weapon as a result. My point is though the looping of all of the power back and forth rising in and out of their frequency levels generates RF and it could be warming either the water or rock to give us a temperature rise. Its up only about 1/2 of a degree and thats significant but 1/2 of a degree of SST doesnt melt ice. That ice is being melted by something warmer than 32 deg. F. But there is nothing to point their fingers at and say that this is the reason. Not warm Co2 trapping heat at least.

A certain power failure in S. Florida in the 80's was attributed to a slightly off freq tube at a certain Air Force base as it resonated on the same level as the power grid and it was displaced off of the base.Disrupted things for about ten minutes before it burned out the transformers in a 20 block area. Categorically denied of course. Florida Flicker and Flash restored it within a day. But the possibilities are there. If humans are all turning on computers, walkmans, TV's, DVD's, telephones, faxes, speakers what is the total magnetic spectrum in gauss for the earth? What was it in the 50's and on up to now. This was one of the fields that wasnt even discussed but we do know it generates a helluva lot of heat.

By M. Randolph Kruger (not verified) on 19 Jun 2008 #permalink

"There are theories, and assumptions made to fill the holes due to lack of data or poor quality data, and depending on which assumptions and theories are adopted for the models, wildly differing projections are obtained, and worst case scenarios emphasized to terrorize people into accepting policies which pick their pocket."

Yeah, I'm sure it's all a huge conspiracy to rob us of our beloved money. All those evil scientist just want their climate research funded, so they terrorise us with their doomsday talk. Just like those astronomers who warn us of the long term dangers of asteroids just to get money for their stupid telescopes... OUR TAX MONEY! THINK ABOUT THAT.

Now they even go around telling us we should leave our cars (SUVs?) in the garage. Or even built more efficient cars (those crazy lunatics). Think about it. They tell us not to be as wasteful with our resources. It's the right of every American to do as he damn well pleases. Heh, sustainability, I've never heard anything as RIDICULOUS as that.

Matt -way to go!
Great refutation of all those silly facts, figure, and logic.

Pft - great summation on why it we have no clue about what's happening.

Charges and moving charges produce electromagnetic fields that move.

There may be a typo here. Charges that don't move produce fields that don't move. Only moving charges produce moving fields--and corresponding magnetic fields.

By Roger Sweeny (not verified) on 27 Aug 2009 #permalink