Primer on greenhouse gases, III.

By revere on June 20, 2008.

This is the third (and last) post in our primer of the science of green house gases (see the first two here and here). Our objective is to explain what makes something a greenhouse gas. Why is CO₂ a greenhouse gas and not O₂ (oxygen) or N₂ (nitrogen)? In the first two posts we set the table by explaining electromagnetic (EM) radiation, how we describe it and how it interacts (or doesn't interact) with matter. We pointed out that all physical bodies act like little transmitters of EM radiation and that they can also absorb EM radiation -- but only at the same wavelengths they emit it. Some physical bodies, like the earth and the sun emit EM at all wavelengths, although they emit most of it (peak emission) around a wavelength determined by the substance's temperature. The hotter the body the more EM radiation it emits and the shorter the wavelength at its peak.

The wavelength at peak emission is given by Wien's Displacement Law (see last post):

λ_max = a/T

where λ_max is the wavelength (in microns) of maximum EM intensity for a body of absolute temperature, T, in Kelvins. a is a constant with a value 2898. We discuss wavelength and absolute temperature in the first two posts.

What are the values of λ_max for the sun and the earth? The sun's effective temperature is about 5800 Kelvin, so λ_max = .5 microns = 500 nanometers. This is right in the middle of the "visible" range. This is quite nice because it allows us to see by the sun's light. Coincidence? Obviously not. Our visual system evolved to take advantage of the sun's peak EM radiation.

Let's do the same calculation for the earth. The temperature at the surface of the earth is about 300 Kelvins, so we have peak EM emission of the earth, λ_max = 2898/300 = about 10 microns. We can't see this EM radiation. It is in the far infrared. But the earth is still radiating energy away at this wavelength.

As explained in the earlier posts, the earth and the sun are called black bodies because they emit and absorb EM radiation at all wavelengths. Some substances, however, especially gases at atmospheric pressure, only emit and absorb at very precise, discrete frequencies. Most atmospheric gases let EM radiation in the visible range pass without any interaction (they are transparent to these wavelengths). Some gases, like methane, CO₂, N₂O (nitrous oxide) and a few others (but not the most abundant gases in the atmosphere, nitrogen and oxygen) will absorb radiation in the infrared. That's what makes them green house gases.

What happens now is something like those Chinese finger trap toys, the little tubes of crisscrossing fibers where you stick a finger from each hand in the ends easily enough but when you try to pull them out they get stuck as the tube closes down. EM energy from the sun comes streaming through the atmosphere with a peak at 0.5 microns. It easily reaches the surface of the earth because the atmosphere is transparent to visible light. About 30% of the sun's light is reflected and the other 70% is absorbed and heats up the earth's surface to a temperature of about 300 Kelvins. The earth then re-radiates the EM energy at 10 microns. But now instead of an unimpeded trip back to space, some of the gases in the atmosphere, the greenhouse gases, absorb in the 10 micron EM peak energy range. When a CO₂ molecule absorbs an EM wave it gets hotter. When it gets hotter it also radiates EM, some of it back down in the direction of earth, some of it "sideways" and some of it back out to space. Whatever portion gets radiated back to earth is a portion of the incoming EM energy that doesn't balance out the incoming stuff.

That's how the greenhouse effect works. It's not theoretical. Without the greenhouse effect the earth would be over 30 degrees Celsius cooler. Other planets also have pronounced greenhouse effects, notably Venus whose atmosphere of CO₂ keeps it at around 500 degrees Celsius.

This much everyone agrees on. The purpose of these posts was to make clear exactly what a greenhouse gas was. CO₂ is the most prominent but not the only one. Methane is an even stronger infrared absorber but there is much less of it in the atmosphere so its effects are overshadowed by the more prevalent CO₂. CFCs and ozone are also greenhouse gases, but also of lesser importance.

Almost all climatologists also believe that the marked increase in greenhouse gases since the dawn of the industrial era (18th century onward) is contributing to an accelerating warming of the earth as well. The simple, purely radiative greenhouse mechanism we have outlined is too simple. It doesn't take account of other important factors everyone agrees affect surface temperatures, most notably heat transfer by convection and the heat released or absorbed when water changes phase (the latent heat effects). Once we start considering these inter-related factors, things start to get complicated with feedback loops that can only be understood via computer simulations.

The computer simulations are absolutely necessary. It is not possible to rely solely on the historical record without some idea of the underlying mechanisms that affect global climate. The problem is not interpolation of the climatic record (estimating temperatures between measured points) but extrapolation -- estimating temperatures outside the range of recorded points. To do this it is necessary to posit a model, even if the model is the simple one "no effect" one that says the future will be like the past. It is tremendously important to take care, since the climate system is like a huge supertanker that cannot be turned around without huge effort. If it is sailing for an iceberg we won't be able to stop it.

An enormous amount of effort has been expended in trying to understand the consequences of allowing greenhouse gases to increase at the current rate. In our view, the problem is less in the science than in the inconvenient consequences of the science, but we won't settle this here. Our goal was much more modest. It was clear from the comment threads that not everyone understood what a greenhouse gas was. We've tried to remedy that small point.

More like this

Thanks for the primer. Nice blogging.

Yes, it is a good thing to explain the greenhouse effect. The global warming story is complicated, and can only be understood by understanding the building blocks that go into it.

http://www.aboutoilandgas.com/atce/2006/technical/documents/spe1029151…

Okay Revere, good stuff as usual. You students probably are amazed at what you can pull out of the can each week that they have never seen before.

Back to GW though.

Besides the other things that were discounted in GW and the IPCC this is one that really got my attention and I have been aware of this but looking for this paper or really primer on NMR imaging. As noted the imaging of the release of Co2 and other gases from limestone rock was created by the effects of drilling for oil.

OTOH and I havent found it yet, they were able to image that gas not unlike that NASA TERRA/MODIS satellite picture from a year or two ago of the total Co in the atmosphere. Said image shows that the US and EU are moderately polluting the atmosphere and that SE Asia is producing enough to cover the globe twice over.

In subsequent papers I have been poring thru there were a couple of guys who created an atmosphere and ocean a year or two ago that hit their little science project with oscillating RF. This wasnt the Russians, it was an expansion of their water heating experiment. They took the estimated RF (their estimation) and simply tried to re-create that condition in the experiment.

Results were that Co2 and just about every gas began to warm. More importantly, their water began to warm along with the rocks. I lost track of who these guys were. If you know who they are please let me know.

But to the end game. IF the sunlighters, and reflectivity buffs and we are making Co2, and other gases in quantity types are wrong about GW's causes, there has to be something else. Remember, I have never said even though others jump before their chutes are on said that GW wasnt happening. Nope, I agree it is happening even with the shitty instrumentations that are being used. What other causes could there be to heat the earth 1/2 of a degree. What could melt the ice in Greenland at such a huge rate.

Oceanographers and the more specialized ocean people cant explain it except to say as a maybe that the water hitting the ice is warmer. I watched it all last year and it wasnt very warm, or cold. Anomaly levels were constant for the previous years. Microwaves might explain it. Remember, Antartica got a lot colder in the last few years but ice is still breaking off there. The Arctic got warmer and had thin ice.

Could we be microwaving the water/ice off of the planet from power lines, cellphones, TV's, radio, etc. The graphs for EMR go up as much as the population does since the 50's and is increasing . The graphs laid over the NASA temp graphs show about the same thing. But here is my rub. A known heating element is out there in the environment and its not even in the IPCC report. De Nada. Now there is something that if the GW's are right about warming but wrong about the causes would absolutely floor them.

Would it be that if they did acknowledge that as the cause that it would mean the doom of man as we know him? We are denoted as sentients because we use tools. What happens if we cant tun on the tube?

Revere, nice reading.

Re the EM from the sun:

"It easily reaches the surface of the earth because the atmosphere is transparent to visible light."

and

"But now instead of an unimpeded trip back to space, some of the gases in the atmosphere, the greenhouse gases, absorb in the 10 micron EM peak energy range."

I would like to know why it is presented this way? As if methane, CO2, and N2O are not present for the incoming EM from the sun. The EM from the sun has to go through the same atmosphere as the EM that is being reflected back.

Thank you for your work.

Geers: That's the whole secret here. When the EM comes streaming in its wavelength is at .5 microns which is not absorbed by greenhouse gases. Its wavelength gets "downshifted" by its interaction with the earth and it goes back out at 10 microns, which is absorbed by the greenhouse gases.

...it goes back out at 10 microns, which is absorbed by the greenhouse gases.

So, the more carbon moved from the locked-up terrestrial reservoirs (coal, oil, natural gas, limestone) into the atmospheric reservoir, the more absorption occurs. QED.

You can see that a person really has to work at getting this wrong.

"It is not possible to rely solely on the historical record without some idea of the underlying mechanisms that affect global climate. The problem is not interpolation of the climatic record (estimating temperatures between measured points) but extrapolation -- estimating temperatures outside the range of recorded points."

If the problem is extrapolation, then you don't have a problem. In the past, the earth was much warmer than it is now. Proof? The now montane climate of the Florissant Fossil Beds was once warm enough to support tropical and coastal plants - and the best evidence shows it was about 8000 feet MSL at the time (34 million year ago) (as it is now). It was also much cooler - proof being the last ice age. So we are not at any extreme, hence interpolation of the data is all that is required.

Oh yes - the temperature has fluctuated many times (many ice ages, with warm periods between). As anyone who has studied control mechanisms knows, oscillations require a restoring force. Obviously there is one (or more). Do the current climate models include that? I don't know - but if they don't they are flawed.

Fantastic primer.

Thanks

Nobody disputes that CO2 is a greenhouse gas, or that there has been global warming.

But H2O is a more significant greenhouse gas, and both H20 and CO2 compete for some of the same energy. In fact, the earth is already oversaturated with greenhouse gasses, H20 and CO2. There is not enough energy being emitted in the discrete wavelengths that they can absorb for all of the CO2 and H20 in the air. Adding CO2 just increases the saturation of greenhouse gasses. Like adding more people to a famine, you just will have more hungry people. Not enough food to go around.

What is not pointed out is that according to the laws of thermodynamics, energy must flow downhill from a high energy state to low energy state, from hot to cold.

When cooler air above the warmer surface absorbs the IR emitted by the earth, it warms up and rises into the cooler air above and eventually into space. The greenhouse gasses do not trap the heat near the surface, because unlike a greenhouse, there is no roof on the earth trapping the heat in, and the heat is released from the surface. So the surface air has a huge heat sink above it. It's cold up there, the higher you go the colder it gets, due to lower pressure with increasing altitude. And warm air is less dense than cold air and rises.

If the surface is hotter than the air above it, then CO2 which previously absorbed IR from the surface will not emitthe IR back to the surface.

So CO2 either emits or absorbs, depending on its energy state relative to the surface, but it does not do both simultaneously, If it did, more and more heat would accumulate due to more and more CO2 being added to the atmosphere, and temperatures would rise. Thats the theory the Global Warming supporters want you to buy. But there is a Sheriff in town, it is the Law, the Law of Thermodynamics, especially the 2nd one. Any theory that violates this law, is debunked.

Now H20 in air and clouds, (ranges from 0.1%-4.0% concentration) accounts for 60-80 of the greenhouse effect, and CO2 (0.038% concentration) about 10%-20% (scientists do not agree on the numbers). Molecule for molecule, CO2 is a better greenhouse gas, but there are not so many relative to water. Water in the air is important.

Remember the coldest of the cold winter nights (say -10 to 10 deg F). What they all have in common is those nights are very low humidity. They are very dry, very low H20 content. When there is plenty of moisture in the air, such you might get when it snows, you tend to see temperatures at 20-35 deg F. In the desert, days are very hot, nights are very cold. This is due to the lack of water vapour in the air. CO2 in the desert at night, and in northern winters, is also lower since it has few plants releasing it.

Now consider the urban effect. Many of the temperature measurements used to determine the global average are biased upward by the urban heat effect. We know temperatures between urban and rural areas can differ by 1-5 deg C at most. Urban areas have a lot of asphalt that absorb heat during the day, and there are much higher CO 2 levels, almost twice the average CO2 of 0.038%. And while a bummer for those folks living in an urban environment, especially during the summer, as mentioned before, this is a localized effect, and the heat will dissipated vertically into that great heat sink in the sky in the evening.

Now as for Venus being very hot, since it has very high CO2 levels. They like you to believe that this is due to CO2 being a greenhouse gas. It's not so simple. The temperature of a gas is proportional to it's pressure. Venus atmospheric pressure is 92 times that of the earth, and it is much closer to the sun. So it's hot.

Now, what about that Global Warming. There has been global warming over the last 30 years at least. It's likely due to the sun, and more cities, larger cities that can absorb the additional radiation and reflect less. The suns magnetic field strength doubled over the last century, although there are disturbing signs this could reverse and possibly plung us into an ice age (the additional CO2 might help prevent this by slowing the amount of cooling near the surface).

This increased magnetic strength of the sun also reduced the amount of cosmic rays the Earth receives. Cosmic Rays are beneficial to low cloud formation, and there is evidence low cloud formation has been in decline since at least 1950. Clouds reflect light back to space. Thus the oceans and land absorb more radiation, water vapour remains in the air as a greenhouse gas (as opposed to low clouds which can reflect light), and this likely accounts for some of the global warming we have experienced.

There is another element that needs to be considered. Our own magnetic field strength is weakening. About 10% over the last 150 years, and this is accelerating. It is not clear to me yet how this might affect warming, perhaps by allowing more of the suns radiation in. A quick search did not reveal much insight.

More disturbing is that the sun is at the end of a 11 year solar cycle, the sunspots have not yet returned, being delayed for some unknown reason. Going back to the little ice age of 1650-1700, we find that the sun had undergone a Maunder Minimum, a period of low magnetic strength with little or no sunspot activity. An ice age might be looming if the same thing occurs.

One thing about Climate in our worlds history. Climate variability has proven to be the rule and not the exception. Man may be influencing the weather, but I just do not see CO2 as being the biggest factor. If anything, more CO2, as food for our plants, is improving crop yields and allowing more food to be created on less land. Might even lessen the impact of the next ice age, or even prevent it. More CO2 might be good.

sorry

4th para

...eventually EMITS THE IR into space

PFT you wrote "Nobody disputes that CO2 is a greenhouse gas, or that there has been global warming."
Excuse me but where have you been. Lots of people dispute that there is global warming, or if there is global warming it is effected by CO2. I don't know that anyone asserts that CO2 is not a greenhouse gas, but they assert that it is not causing GW for sure. Most of these people that write about it that I have researched receive funding from oil, coal or tobacco industries.

pft: People don't "point it out" because it is false. There is a thermodynamic roof over the troposphere. It is the stratosphere, where the environmental lapse rate is inverted. Thus packets of air cannot rise because the environmental lapse rate versus the adiabatic lapse rate is such that there is stability. It is a temperature inversion. You seem to have a very poor grasp of the science, which is why I wrote some posts giving an elementary explanation. It was not designed to convince you or anyone else about one side or the other of the debate. You advance a very crude climate model. It is, simply put, that the future of climate will be like the past. You have no argument for it except that you believe it. You neglect the changes that the industrial revolution have brought on because you don't like the policy consequences. So you deny their relevance, even though you don't understand the science. That's what makes you a denialist, not that you disagree with the scientific consensus.

Thanks revere, for the explanation but I don't think you've answered pft's assertions. For instance, I don't understand how a reversed adiabatic lapse rate at the statosphere equates to the physicality of a greenhouse roof, and if we are going to use the greenhouse metaphore as something more than just a metaphore shouldn't we expand it also to note that greenhouse farmers, in order to stimulate abundant growth, keep their CO2 levels much higher as they recognize that CO2 is a necessary requirement for healthy growing plants, the basis of our planet's food chain. Can you also address the H20 content in the atmosphere as a measure of the effectiveness of heat entrapment and its complex and the degree of dominance it plays in regulating thermal distribution. Is there a linear relationship with CO2 and heat entrapment or has the saturation point been reached so that concern over increased levels is unfounded? Do we know?
PFT points out the sunspot connection, cosmic ray and cloud formation aspect, the venus analogy fallacy, and the overall tendency for Earth to enter a global cooling as part of it's physical long-term natural history. Why are these criteria which I've often seen dismissed as minor and insignificant ignored but other insignificant and minor conditions elevated to "driving forces" in the argument?
I don't see pft's refutation of your assertion as being a "crude climate model" (if anything it seems more sophisitcated, and you're description of the model, while I wouldn't call it "crude" either, is in a number of ways too simple if it ignores these aspects of overall global climate which is singularly noteworthy with its hallmark being its complexity.
Finally, you used the "d" word, which has become very devisive and in actuallity derogatory for those who earnestly seek understanding. I much prefer the "h" word; heretic, which is a more accurate description of those who can plainly accept that the Earth's environment is under assault by man's impacts and is not in some thermal steady state. Heretics also recognize that Earth does warm and cool as it plainly has throughout its natural history, but recognize the robust dynamic equilibrium that the system displays with all its poorly understood feedback systems and limiting loops and that it plainly has been doing so (changing while "staying within certain states of equilibrium") in a robust manner for the last few hundred million years eduring many climate changing events from asteroid assaults and extreme vulcanism, to ice ages. Heretics are also likely to question not only the literal beliefs and the conclusions but the wisdom of policy makers as to how we should address those threats to what is seen as stability and heretics question the idea of just who's criteria should we define the word "benefit". Some don't necessarily accept the political aspect of the program as the next obvious step even if some of the initial assertions might be correct, particularly if the drive to bring about a mandate are provoked by a spirit of alarm.
Thank you.

doug: OK, you've asked for a tremendous amount in your questions. Let me do the best I can in this format to clarify. It's not possible to address it all because that would take a book length explanation, but since I didn't address those issues in my post and they aren't germane to what I was writing about I'll take the easy way out and only go to the specific issues pft (and you) raised relevant to the post. In particular, two things, the "roof" issue and the "model" issue (which includes the cosmic rays).

pft wanted to know what stops a warmed packet of air from just going up and up. He alleges there is no "roof" to stop it since the air gets cooler as we go higher. A rising packet that isn't exchanging energy with its surrounds (adiabatic conditions) expands and the energy it takes to expand comes from its internal energy, in this case its temperature. This makes the packet cool, on purely thermodynamic grounds at a rate called the adiabatic lapse rate. It is given by physics and doesn't vary (I'm simplifying a bit, so don't nitpick me here). In particular, it doesn't reverse. It is always the same. It is the environmental lapse rate that reverses in the stratosphere. The rate at which the surrounding air changes temp as we go up is given by conditions at that moment. The change in temp as we go up is called the environmental lapse rate. If the environmental lapse rate exceeds the adiabatic lapse rate (which is negative) then the packet of air will not rise. In particular, if temperatures increase as we go up (this is called a temperature inversion) then the air is stable for vertical motions, i.e., a packet of air that is displaced from its vertical position will tend to return to that position. Think of a marble at the bottom of a trough. If you push it up from the bottom it will tend to return to the bottom.

It is true that in the troposphere, where we live and up to say 30,000 or 40,000 feet, air temps tend to decrease as we go up (although under some meteorological conditions, like a subsidence inversion, such as we have about a third of the time in the LA basin) the air might be stable and air pollutants don't disperse but remain where they are emitted. But ordinarily, the air gets cooler, i.e., the environmental lapse rate is negative, although it might not be as negative as the adiabatic lapse rate, so that would also be a problem. At any rate, the usual temperature profile reverses in the stratosphere, where there temps normally increase as we go higher. Hence the stratosphere is like one large temperature inversion and rising packets of air stop rising when they get there, since the adiabatic expansion cools them but the surrounding air is getting warmer. Hence we have cool air in warm air, which sinks. That's the thermodynamic roof I was referring to.

Now for the "modeling" part. pft is using a very crude model for climate change. He doesn't know the details of the model but he asserts an algorithmic rule about how climate will change in the future. It is this. That whatever the details of the mechanism (and his cosmic ray scenario is purely descriptive but I'll allow someone could and probably has made some kind of computer model of the cosmic ray contribution), the increase in greenhouse gases since the industrial revolution does not affect it in any meaningful way and future emissions won't either. That's a strong assertion. It is possibly true. The question is, how likely is it to be true?

So it is not true that pft doesn't rely on models while the IPCC does. Both use models. The question is which one do you think is more reliable in this regard. If you examine the IPCC models you can't help but be impressed by the number of different things they have taken into account and the wide range of possible scenarios they consider in trying to bracket the impact of increase in green house gases. The system and its interactions -- which are quite clearly non-linear -- is not amenable to anything but computer modeling. This is required of any quantitative model of cosmic rays so it doesn't set the IPCC effort apart from pft's claims. Ed Lorenz's very simple of climate using only 8 simple equations put to rest the hope that we could use analytic methods to come up with a closed for solution to this. We are stuck with simulations.

So there remains uncertainty but the requirement to make a decision one way or another. We think nothing is going to happen so we decide to do nothing and live with the downside risk. Or we decide the downside risk is so large we'll take a chance and work to reduce green house gases. The IPCC has tried to quantify the risks on either side, and since some very powerful interests are involved there is controversy.

Finally, let's stop talking about Al Gore. The only reason Al Gore gets into a conversation about science is that he is readily identified in the public mind as a politician and opponents of the IPCC position want to say this isn't science but politics. Al Gore isn't a scientist, he has not contributed to the science. I don't even like him. But he's not the issue. Every time Al Gore's name is invoked in the argument it is a sign the arguer doesn't want to discuss the science but divert attention to the claim that climate science and climate scientists are corrupted by politics and are lying about their science. That's a strong claim and I won't argue it one way or another in this already too long response.

Disclaimer: I am not a scientist, just a concerned layperson.

You neglect the changes that the industrial revolution have brought on because you don't like the policy consequences.

This isn't just pft's problem, it seems to be a social trait of humans everywhere. As creatures of habits, we tend to go on doing what we have been taught to do all our lives. The evolutionary record is littered with species that could not change when change was demanded, and human history is littered with the corpses of civilizations that could not adapt to social or environmental changes thrust upon them in the space of 1 or 2 generations only.

The point isn't that we will suddenly cause our own extinction. That's possible, but not very probable. More likely, we'll trigger some level of ocean rising, and cause displacements of populations because the way they are used to living will no longer work as their climate shifts. Along with this expect more localized disasters like we have seen with flooding, tornados, and cyclones.

No big extinction, no huge smoking gun that convinces everyone once and for all, but more like the accumulation of small infections and injuries that, in time, seriously affect humanity.

I have friends from SE Alaska that dream of going up and living in their native villages when they retire. It's not possible because some of the villages are already threatened by melting permafrost and rising sea levels. That's not a theoretical outcome of GW, it's an actual one that has already happened.

We've probably all known diabetics that just can't seem to change their diets no matter how many doctors and family members tell them it's necessary or alcoholics who die due to the effects of alcohol rather than quit, and so on.

Understanding the science is crucial, and this blog's emphasis on educate, educate, educate is absolutely necessary.

But we have seen that even educated people can be denialists. So the challenge is also to be able to learn to do things differently than we have been taught all our lives. It isn't easy.

Imagine a bear cub, upon reaching adulthood, suddenly discovering the hunting and foraging techniques taught by its mother no longer provide enough food to maintain health. He will most likely die because he cannot adapt.

Humans, however face a thorny variation of that problem: we may cause ourselves a lot of suffering because we WON'T adapt.

This is also part of the challenge of dealing with GW.

Thanks, Revere. I do appreciate your taking the time here. Cheers.
Oh, and for yogi-one's friends who wish to live in Alaskan villages; it's true that some of them are in peril for a number of reasons such as subsidence, beach erosion, and some possible sea-level rising but a lot of the villages are not. Keep in mind that the villages were themselves originally the product of policies designed to change native traditional lifepatterns to ones that were "settled" and more compatible with European concepts of civilizations, such as missionary activity and commercial activity. Any number of those villages shouldn't have been put on those exposed areas in the first place...and quite a few of them are inland along major rivers and as we know, rivers with or without global climate change are ever changing landscapes and permanent human habitation along them, no matter where or when, is done with human timescales in mind, not nature's. I think that they'll still be able to find villages that will be available for them to move into, but no matter which one, there is always the possibility that those villages will encounter something of Alaska's unpredictability.Good luck to them and to us all.

Revere. I have a 12 hr time difference so do not usually respond, but this issue interests me.

First of all, "You advance a very crude climate model. It is, simply put, that the future of climate will be like the past."

I never said that or even implied it. We do not fully understand what the climate was in the past, and have trouble knowing what the climate is today, let alone the future. The past has shown climate variability is the norm, not the exception, well before the Industrial Age.

I accept that the industrial revolution has resulted in higher CO2, but do not accept it is a bad thing. While it may contribute some to the current warming, it seems unlikely it is the main contributor.

"That's what makes you a denialist, not that you disagree with the scientific consensus."

I only deny that which I can prove to be untrue. I have yet to see scientific consensus on climate change. At least, not near enough to radically change our living standards. The consensus I see is that CO2 is a greenhouse gas, it is increasing, it may contribute to global warming, but how and to what extent is unknown.

I also recognize some of the same people pushing global warming on us in MSM are the same who gave us the lies about the GWOT and Iraq. The beneficiaries of carbon cap and trading in the war on climate change will be the same people who finance conventional wars. Until recently, I was on Al Gores side, but having looked into it myself, I am reversing course. I am officially a skeptic of the religion of global warming, not necessarily a denier, as denial like atheism, requires an act of faith.

Now, about that roof. Well, we know there is some limited mixing between the troposphere and stratosphere, so the roof has some holes. But simplifying the model, I would assume that if heat is accumulating at the roof, the temperature of the upper troposphere would rise, and the CO2 that is unable to emit the IR due to the temperature inversion of the stratosphere, would rise to some levels of the stratosphere, and upon reaching the top of the stratosphere, it would emit it's IR into space, and reverse course.

http://www.atmosphere.mpg.de/enid/20c.html

"Cooling of the stratosphere isn't just the result of ozone destruction but is also caused by the release of carbon dioxide in the troposphere. Therefore, global warming in the troposphere and stratospheric cooling due to ozone loss are parallel effects."

So we know the stratospheric cooling is due to CO2 from the troposphere.

Anyways, your elementary explanation proved CO2 was a greenhouse in an environment which there is no greenhouse.
And thats fine. But those accepting the Hansen and Gore worst case threats do so as a matter of faith, and not science.

pft: I am mystified by your rendition of the elementary science. The "roof" has nothing to do with infrared radiation. It has to do with vertical mixing of gases and explains why warm packets of air don't just keep rising. If that were true there would be no atmosphere. Think about it. Yes, there is some mixing but it takes years for CFCs to make their way to the stratosphere. It is possible because they are almost inert in the troposphere.

Heat is not accumulating at the roof. What I am calling the roof is the thermodynamic barrier to vertical mixing created by the atmosphere's vertical temperature profile. You seem to be very confused about EM radiation, greenhouse gases and the structure of the atmosphere. It is essential to understand these things if you want to have an informed opinion about the matter. The greenhouse effect has nothing to do with greenhouses. It is well known and stated everywhere that what keeps a greenhouse warm is not what we call the greenhouse effect. The term is a historical misnomer but it seems to have confused you, judging from your second to last sentence. A confusion among many.

You say you do not accept that carbon dioxide (and methane, which has increased as a result of agricultural practice) has any meaningful effect on climate. That means you have some kind of mechanism or model that tells you that. Or are you just stating it? Why else would you say it? It means that whatever the mechanism of the climate system was in the past, it remains the same mechanism now. You don't know what that mechanism is but you feel confident that carbon dioxide can't be a significant factor. I'm mystified. Is this faith based climate science?

Your main argument seems to be you don't trust the science because it comes to you through the main stream media and they are tools of the oligarchs or something like that. So we get Al Gore again. I'll say it again. The science has nothing to do with Al Gore, any more than it has to do with James Imhofe, the Senate's chief climate change denialist.

Climate scientists have actually thought about the issues and they actually do understand the science. That's something to ponder. You don't think there is a consensus but most people who have looked at this seriously do. I'll leave it at that.

Revere "The "roof" has nothing to do with infrared radiation."

It certainly does, since a "roof" implies there is a barrier preventing the IR absorbed by CO2 in the troposphere from being released to space.

Revere "It has to do with vertical mixing of gases and explains why warm packets of air don't just keep rising."

I never said a particular packet of air continuously rises. Certainly a warmer packet of air rises a finite distance and stops when it comes into equilibrium with the air at X altitude.

Revere "Think about it. Yes, there is some mixing but it takes years for CFCs to make their way to the stratosphere. It is possible because they are almost inert in the troposphere."

Not sure why we are talking about CFC's (the article I linked did but the point it makes about CO2 IR being released from the stratosphere was the key to the discussion). Back to CO2. The troposphere is extremely well mixed and CO2 concentrations are essentially the same in the upper troposphere and through the stratosphere as at measurement sights like Mauna Loa. What the article shows is that CO2 as a greenhouse gas does not stop the heat being released into space, it is releasing so much the stratosphere is cooling. In any event, what CO2 does is it simply delays the heat from being released back into space. Also, unlike water which is present in very low levels at high altitudes, CO2 is essential to cooling the planet. If there was no CO2 and all IR absorbed by CO2 were absorbed by H20, there would likely be significant global warming, and not the beneficial warming we have seen over the last 120 years. Thats why I pointed out that H20 may be the most important factor in global warming, unfortunately, we have little historical data to know if it has increased or not. Water vapour being unable to form into low clouds as a result of less cosmic rays is also a concern, since less light gets reflected.

Revere "You say you do not accept that carbon dioxide (and methane, which has increased as a result of agricultural practice) has any meaningful effect on climate. That means you have some kind of mechanism or model that tells you that. Or are you just stating it? Why else would you say it? It means that whatever the mechanism of the climate system was in the past, it remains the same mechanism now. You don't know what that mechanism is but you feel confident that carbon dioxide can't be a significant factor. I'm mystified. Is this faith based climate science"

If you stick to what I did say this could be an easier discussion. But you say I said something I did not, and then go on to rebut it. You didn't go to school with Bill O'reilly by any chance (LOL).

What I said was " I accept that the industrial revolution has resulted in higher CO2, but do not accept it is a bad thing.[I do not deny that it could be bad]. While it may contribute some to the current warming, it seems "unlikely" it is the main contributor....... The consensus I see is that CO2 is a greenhouse gas, it is increasing, it may contribute to global warming, but how and to what extent is unknown due to their are too many uncertainties."

And I have pointed out, that CO2 is already at saturation levels, and more CO2 could not absorb more energy at the surface, although the absorption of IR by more C02 would be completed at lower altitudes. In a rural area at 380 ppm CO2, this absorbtion takes place within 10 meters. In the city, CO2 levels are as much as 2 times higher at the surface, and the asphalt and concrete had absorbed so much IR than the earths natural surfaces do, thus release much greater amounts of IR to the plentiful and hungry CO2. So absorbtion takes place within a couple of meters, and temperatures are 1-5 deg C hotter in the city in the early evening, yet by early morning, the warm air has risen, and temperatures are closer to those in rural areas, as the heat and the high levels of CO2 has dissipated vertically upward.

What CO2 and other greenhouse gases do, when looking at the troposphere as a whole, is they delay the emission of absorbed IR into space. Some of the energy is degraded due to the work expended in adiobatic expansion.

But how much of the warming we have had is due to man made CO2?. And since 1880, the temperature has increased 0.6 deg C (+.-0.2 deg C) despite CO2 rising from 280 ppm to 380 ppm. How much did CO2 contribute to this, and how much normal variability?. Even the low ends of estimates of a future doubling of CO2 do not sound that bad, say 1.2 deg C.

Revere "Your main argument seems to be you don't trust the science because it comes to you through the main stream media and they are tools of the oligarchs or something like that."

Hardly my main argument, but when the pundits agree on an issue and hype it, and seem to talk with one voice, you have to look closer. I did. I mean, even the republicans are going green, that must make you nervous.

Revere "Climate scientists have actually thought about the issues and they actually do understand the science."

Understanding the science and having pondered it does not mean there is a consensus that man made CO2 is the primary driver of global warming, and what the long term effects are going to be, or that the consensus is correct. At one time they had a consensus that the earth was flat. What is consensus anyways, majority rule?. Who was it that said "when scientists say they have reached a consensus on anything you should reach for you wallet".

Interesting article here on consensus. I don't have time to discuss further.

http://mclean.ch/climate/What_consensus_col.pdf

If you don't put anymore words in my mouth, should you respond, I will agree to disagree.

revere - one point re methane - how do we know that it has a) increased, and b) increased due to agricultural practice? (at a global level). There were millions of bison once throughout North Amercia - they must have farted too? And while we now raise livestock intensively, there were always some other herbivores and methane producing bacteria?

pkiwi: There are methods involving carbon isotopes that allow us to estimate it. Here is one piece related to your question: http://www.slate.com/id/2178595/

I am sure there are others (and given the controversy, probably some that say it's not a problem).

revere,
I would like your opinion on the following paper.

"Falsification Of The Atmospheric CO2 Greenhouse Effects
Within The Frame Of Physics"

http://arxiv.org/pdf/0707.1161v4

This paper starts where your elementary description starts and then takes it to the real world of physics.

Unfortunatly, your writeup is overly simplistic and comes to the wrong conclusion.

I would like to see you response to this body of work.

ReadOn: I'll likely not get to it soon as there are some other things going on (you may have noticed). Tell me what you what conclusion you object to.

This

"When a CO2 molecule absorbs an EM wave it gets hotter. When it gets hotter it also radiates EM, some of it back down in the direction of earth."

This is the crux of the C02 warming theory, but does not appear to be supported by physics. You are talking about something -60C radiating Heat back to earth (33C). Now I understand that the lapse rate and number of layers of the atmosphere has bearing on this, but NET, the heat transfer back to earth is nil.

Also see this recent Blog.

http://jennifermarohasy.com/blog/2009/03/radical-new-hypothesis-on-the-…

Readon, I looked at the paper you cited and it is nonsense. He uses lots of technical terms but doesnât understand what they mean or how to apply them. He takes great pains to dispute the simplistic (and technically wrong) explanations that have been given as metaphors to try and convey the message of global warming to non-technical individuals who donât have the background to understand the precise technical details. He doesnât understand the precise technical details either.

The author doesnât seem to appreciate that the only way that the Earth loses heat is by radiation. The relative thermal conductivity of air with differential amounts of CO2 is essentially completely irrelevant. That thermal conductivity does influence the details of the temperature profile of the atmosphere, but it is the radiative properties of the Earthâs surface and of Earthâs atmosphere that dominate the temperature of the Earth in equilibrium with the radiation it absorbs from the Sun, geothermal heat and the radiation it radiates into space.

He is correct that in glass greenhouses the heat transfer is not dominated by radiation, and in that (very narrow and hypertechnical) sense the âgreenhouseâ metaphor is a poor one.

He goes on to deny the reality of conservation of energy by saying that the entire concept of there being an energy balance for the entire Earth is wrong (see figure 23). Figure 23 is wrong because it doesnât address geothermal heat.

He brings in first and second law of thermodynamics but uses them incorrectly to dispute that there can be transfer of heat from the atmosphere to the surface when the atmosphere is colder than the surface. Technically that is true, but that is not how actual models calculate the heat transfer. Because the atmosphere is both partially transparent and partially opaque to electromagnetic radiation of different wavelengths, treating it as a simple âlumpedâ parameter with constant properties at a constant temperature is an inappropriate modeling technique. Everyone doing such calculations knows that.

In equation 136 he writes down what he says is the heat balance, but leaves out heat transfer by radiation. Later he adds a few more equations and then says he has the complete equation (he doesnât), and that no terms depend on CO2. He is correct that no terms depend on CO2 because he deliberately left them out. Maybe he is fooling himself, he isnât fooling anyone who knows about radiative heat transfer.

Revere, I would recommend that you donât waste your time reading this; it doesnât contain any serious or valid arguments against global warming. Your time is much better spent on H1N1/2009 flu.

ReadOn, the definition of a black body is something that absorbs all radiation that falls on it. That includes radiation emitted from something colder than the black body.

A black body at -60 C does emit radiation characteristic of that temperature. When that radiation falls on a black body at 30 C, that radiation is absorbed. That is the definition of a black body. The black body at 30 C emits more radiation that a black body at - 60 C, so the net heat transfer is from the hotter body to the colder body.

The atmosphere is not a black body. It is partially transparent, so not all radiation that passes through it is absorbed. CO2 makes the atmosphere less transparent to infrared radiation so that more of the radiation emitted from the Earth is absorbed, and then re-emitted in all directions. The net effect is to reduce the radiation emitted from the Earth (because some is absorbed, then re-emitted, and absorbed by the Earth's surface).

This is radiation heat transfer 101, not stuff that is complex or controversial.

You did not even read the paper. You are so quick with your ad-hominem attacks. Typical, right out of the play book.

Yes, figure 23 is wrong, and that is what he says. He was using that as an example of bad science. You completely missed the point.

"Figure 23) are scientific misconduct since they do not properly represent the mathematical and physical fudamentals." and "A schematic diagram supposed to describe the global average components of the Earth's energy balance. Diagrams of this kind contradict to physics."

You are not making sense on any of your other rambling points. I cannot take you seriously if you are just a skimmer.

revere,

Do you rely on people like daedalus2u for input? I hope not. He is sort of closed minded, and does not want to consider ideas contrary to his own AGW belief system.

How can he be considered seriouly when he just skims material. But then again, he knows the science is settled.

If he really wants to get his panties in a wad, he should read the Michael Hammer Blog

http://jennifermarohasy.com/blog/2009/03/radical-new-hypothesis-on-the-…

ReadOn: I am not paying attention because of the press of other matters, but for the record, daeduls2u is a frequent commenter and has excellent scientific credentials of his own. I don't rely on my commenters here, but I respect them.

ReadOn, I read about half of it, it isn't short or easy to read. It is attempting to contradict things that have been well known in physics for over 100 years using analogies that are not apt and which are frequently wrong. It isnât worth my time (or anyoneâs time) to read it carefully. When I find multiple wrong ideas is a paper which attempts to contradict things that are well known, I donât bother reading it in detail unless I am looking for the data that the authors generated. There is no data in this paper and many of the premises are wrong.

I consider this paper to be an example of shotgun argumentation; many arguments on many different aspects of global warming when those arguments could be considered separately.

http://en.wikipedia.org/wiki/Shotgun_argumentation

Primer on greenhouse gases, III.

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