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Climate Hustle

Is CO2 a pollutant?

Posted on 11 February 2010 by John Cook

We commonly think of pollutants as contaminants that make the environment dirty or impure. A vivid example is sulphur dioxide, a by-product of industrial activity. High levels of sulphur dioxide cause breathing problems. Too much causes acid rain. Sulphur dioxide has a direct effect on health and the environment. Carbon dioxide, on the other hand, is a naturally occuring gas that existed in the atmosphere long before humans. Plants need it to survive. The CO2 greenhouse effect keeps our climate from freezing over. How can CO2 be considered a pollutant?

A broader definition of pollutant is a substance that causes instability or discomfort to an ecosystem. Over the past 10,000 years, the level of atmospheric carbon dioxide in the atmosphere has remained at relatively stable levels. However, human CO2 emissions over the past few centuries have upset this balance. The increase in CO2 has some direct effects on the environment. For example, as the oceans absorb CO2 from the atmosphere, it leads to acidification that affects many marine ecosystems. However, the chief impact from rising CO2 is warmer temperatures.


Figure 1: CO2 levels (parts per million) over the past 10,000 years. Blue line from Taylor Dome ice cores (NOAA). Green line from Law Dome ice core (CDIAC). Red line from direct measurements at Mauna Loa, Hawaii (NOAA).

Rising CO2 levels causes an enhanced greenhouse effect. This leads to warmer temperatures which has many consequences. Some effects are beneficial such as improved agriculture at high latitudes and increased vegetation growth in some circumstances. However, the negatives far outweigh the positives. Coast-bound communities are threatened by rising sea levels. Melting glaciers threaten the water supplies of hundreds of millions. Species are becoming extinct at the fastest rate in history.

How we choose to define the word 'pollutant' is a play in semantics. To focus on a few positive effects of carbon dioxide is to ignore the broader picture of its full impacts. The net result from increasing CO2 are severe negative impacts on our environment and the living conditions of future humanity.

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Comments 51 to 100 out of 252:

  1. In my lectures on light pollution I say that light (man-made, at night) and CO2 are similar pollutants: both have been considered as harmless 30 years ago, both are very harming. The main cure for both is a large reduction of energy use.

    Needing to define such pollution properly, I wrote a text 'What is light pollution, and how do we quantify it?': http://amper.ped.muni.cz/light/lp_what_is.pdf

    It discusses the concept of pollution thoroughly, ending with a note on pollutants, commenting on religious connotations etc. Pollution in a modern sense should be not taken emotionally, being a rather scientific term. I touch the history of the concept at p. 2 of my paper. The very beginning of the paper reads:

    'Generally, pollution is an impairment of the purity of the environment. As a pure,reference state of the environment, its natural state is to be considered, if applicable and adequate.'

    I owe that scientific, non-emotional approach to terminology, which is so useful if not indispensable to understand the problem properly, to Pierantonio Cinzano, see the hyperlink in the paper. I admit that it took me a year or more to identify myself with it. A good friend of mine, a topmost expert in LP, did not accept such attitude... I hope my text might help you in studying the issue and decide for yourself.

    Jenik Hollan, http://amper.ped.muni.cz/gw
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  2. The article makes a lot of good points, but it still sounds like quite a 'stretch' to classify CO2 as a 'pollutant'.

    However, given the political climate, and the pressing need to regulate CO2 emissions (and other GHGS), it is a 'stretch' we should be willing to live with; the alternative is much worse.
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  3. Westwell writes: "Oceans don't acidify because of CO2 absorbed from the atmosphere".

    I have heard 'skeptics' make this claim before. The only argument they can make to support this claim is poor memories of high school chemistry coupled with unshakeable faith in the absolute power of buffers.

    Yes, of course it is 'buffered'. But even buffers can be overwhelmed. Did it ever occur to Westwell that this might be exactly what is happening?

    Nor is a large change in pH necessary to explain the current problem known as "ocean acidification". Even a very small change is enough to interfere with shell formation -- especially when the small pH change is accompanies by a large change in carbonate ion concentration.

    A detailed explanation of why Westwell is wrong is hard to find on the open Internet, but when the Royal Society says we already have a 0.1 reduction in pH due to atmospheric CO2, it takes more than the word of a biased skeptic to overturn their scientific authority.
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  4. RSVP writes:
    ...And yes, I am aware that Mars only gets about half the sunshine as the Earth, however, shouldnt all that CO2 be keeping the planet a little warmer?

    The short answer to your question is: No. There are too many other variables contributing to the "greenhouse effect" such as planetary albedo, which is very different in the case of Mars and Earth.

    Besides: -40C IS a lot warmer than the cold of space. So the greenhouse effect IS keeping Mars warmer than it would otherwise be. Just not by so much.
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  5. On Mars:

    there is some greenhouse, but just a faint one, several kelvins only. This is due to CO2 being the only gas there, even if a bit more abundant (I mean mass per column) than on the Earth. And, due to the very low air pressure, so that spectral lines remain very narrow, lacking the so-called pressure (or collisional) broadening.

    Low pressure and almost no water vapour give but a faint greenhouse effect. Albedo has nothing to do with that effect, nor sunshine: the effect is the difference from such temperatures, which would result from the existing albedo and sunshine in the absence of GHGs.

    Still, it is amazing there is no paper which would evaluate the 'deltaT' due to CO2 for Mars... just some old, outdated crude estimates. Maybe, no GCMs for Mars exist yet. So we don't know how many kelvins it is for Mars. Science may not need it, but education does.

    jenik hollan, http://amper.ped.muni.cz/light
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  6. Mars is also very dry and subject to intense dust storms which have a cooling effect. There's no possible comparison between the earth and Mars just because there some CO2 in both atmospheres.
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  7. Riccardo
    "There's no possible comparison between the earth and Mars "

    I just made one, precisely because using this example isolates factors such as the effect of water vapor.

    Mars is perfect laboratory for testing greenhouse theories, and yet, in reading replies of MattJ, jenikhollan for instance, one encounters resistance in the form of ...not enough atmospheric pressure, you need help from water vapor, Mars has a different albedo, dust storms....etc.

    In a way Riccardo, you are right. This is a bad comparison because it tends to show AGW is not related primarily to "anthropogenic" CO2, especially when you continue looking closer at this particular example, as CO2 on the Earth is thousands of times more diffuse, which means IR surface emissions have even less chances of being affected by it.
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  8. Jenik Hollan writes: "Maybe, no GCMs for Mars exist yet. So we don't know how many kelvins it is for Mars. Science may not need it, but education does."

    Actually, NASA-Ames has a Mars GCM.

    RealClimate has discussed the climates of Mars and Venus, though neither post is very satisfactory IMHO. When I was in graduate school we did a Earth/Mars/Venus comparison in one of my global climate courses, and it would seem like a natural topic for a post.
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  9. RSVP writes: "In a way Riccardo, you are right. This is a bad comparison because it tends to show AGW is not related primarily to "anthropogenic" CO2, ..."

    We've been round and round this before. Elsewhere on this site there are multiple cogent explanations of the evidence that CO2 is the primary (but not sole) driver of anthropogenic climate change. It gets a bit tedious to have to keep answering the same spurious objections over and over again.

    See these links to other posts on this site:
    (1) http://www.skepticalscience.com/How-do-we-know-CO2-is-causing-warming.html
    (2) http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm
    (3) http://www.skepticalscience.com/CO2-is-not-the-only-driver-of-climate.html

    The Martian climate differs from that of Earth in a number of respects, none of which contradicts the physics of greenhouse gases in the terrestrial atmosphere.
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  10. I'm surprised my comment which was numbered 8430 was removed . The second half presents the relevant data :
    While the effect of a little more CO2 on the spectrum and therefore mean temperature of the planet is minor ( see http://cosy.com/Science/LogCO2effect.jpg ) , its enhancement of plant growth is profound : http://cosy.com/Science/CO2-pineGrowth100120half.jpg .

    Interested people will have to go to my forum to see the first half which is effectively they conclusion and consequences .
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    Response: Note that this version of your comment, which has been stripped of the political rhetoric, has not been deleted.
  11. Ned wrote in 60:
    We've been round and round this before. Elsewhere on this site there are multiple cogent explanations of the evidence that CO2 is the primary (but not sole) driver of anthropogenic climate change. It gets a bit tedious to have to keep answering the same spurious objections over and over again.

    See these links to other posts on this site:
    (1) http://www.skepticalscience.com/How-do-we-know-CO2-is-causing-warming.html
    (2) http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm
    (3) http://www.skepticalscience.com/CO2-is-not-the-only-driver-of-climate.html
    Thank you. I will check them out. There are usually some pretty good links -- and the writing usually isn't that bad, either.
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  12. MattJ said
    "Besides: -40C IS a lot warmer than the cold of space. So the greenhouse effect IS keeping Mars warmer than it would otherwise be. Just not by so much. "

    When you say "greenhouse effect" are you talking about the rewarming of the surface of Mars due to the CO2(i.e. the slowing down of loss of heat), or simply the heat that the atmosphere there acquires?

    These would be separate I assume. If for instance, Mars had an atmosphere of pure Nitrogen, and the average temperature was -39.5C, the only "greenhouse effect" would associated with the 0.5 C temperature difference.

    This is what I am talking about when I refer to "primary" contributor. Maybe the definition gets used too loosely in these discussions.
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  13. RSVP,
    i think no one has ever said that CO2 is the greenhouse gas. You are arbitrarly assigning this role to it. Indeed, CO2 is responsible of roughly 30% of the whole effect.
    Even considering AGW, we all know that CO2 alone would not lead us to 3 °C of warming, may half of it or even less.
    So it is the interaction between the various part of the whole earth climate system that matters. On the contrary, Mars has an almost "dead" climate system. This is why your parallel between the two is wrond, not becaus it "is a bad comparison because it tends to show AGW is not related primarily to "anthropogenic" CO2", which it does not show.

    "CO2 on the Earth is thousands of times more diffuse, which means IR surface emissions have even less chances of being affected by it."
    You should look a little bit closer at how the radiative balance in the real atmosphere works. Even the zeroth order aproximation would tell you that as far as the absorbtion is concerned what matters is the integral over the whole atmosphere. On this respect, it does not matters if it is diffuse or not.
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  14. should read "i think no one has ever said that CO2 is the MAIN greenhouse gas
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  15. What I perhaps left out in #63...

    I mean to distinguish heating of the atmosphere through
    1) convection from surface,
    2) IR emanating from surface that is picked up by atmosphere

    Only #2 should be considered greenhouse heat.

    The result of #2 is:
    a) slightly warmer atmosphere,
    b)a slightly higher surface temperature (due to slightly less convection, which in turn (by definition) can only be attributed to #2).

    I was convinced by poster Gord, that an item c) is not real (so I leave this out here). It has to do with IR emanating from the atmosphere and warming the surface (those arrows that point down out of the sky in greenhouse diagrams).
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  16. I do not believe I have just read the "Mars atmosphere" argument again.

    Aside from the massive difference in solar flux it experiences due its comparative distance from the sun, it also lacks much of an atmosphere at all. Certainly it doesn't have any significant amount of water vapour - the other important greenhouse gas on Earth. So the feedback effects are just not even in the same ballpark.

    It doesn't even qualify as an "apples vs oranges". It's comparing apples with.....durian!
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  17. Mike, the atmosphere on Mars is nearly pure CO2.

    As I explained in my first post in this article, I calculated the height of what a pure CO2 atmosphere would be on Earth if all other gases were removed. This would leave a CO2 cover on the entire Earth with between 7 and 30 meters, much as exists on Mars.

    In any case, greenhouse effects of water vapors would be apples, and that CO2 oranges. Are you implying that CO2 acts as a greenhouse catalyst for water vapor?
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  18. Bob Armstrong:
    "While the effect of a little more CO2 on the spectrum and therefore mean temperature of the planet is minor ( see http://cosy.com/Science/LogCO2effect.jpg ) , its enhancement of plant growth is profound : http://cosy.com/Science/CO2-pineGrowth100120half.jpg ."

    OK. "a little more" CO2 would be fine with most, I think. What we are discussing, is how to avoid a doubling, we are already about 40% on the way. If you are saying that a 40% increase in CO2 has minor impact on the mean temperature, and think that is backed by physics, you should do a careful checking of the physics. Because it does not seem to be backed by observations. Assertions of CO2 saturation, almost complete overlapping with H2O etc seem to be, in general, false.

    On the contrary, observations so far indicate a CO2 sensitivity far above the basic 1 degC/doubling, i.e. a considerable positive feedback. We just don't know how big it will turn out to be - far too little observations on the radiation balance of Earth for that.
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  19. SNRatio
    "We just don't know how big it will turn out to be "

    Making that determination is one excercise. The other would be a series of projections in seeing how mankind could fare by actually following a prescription for reducing CO2 emissions into the near future. Has anyone done this, with detailed consideration to all its consequences?

    There was this book called The Limits to Growth. It only looks at the negatives of growth but provides no recipes nor describes the actual consequences of pulling back on fossil fuel consumption. We are already seeing problems with a floundering world economy without even starting.

    Obviously, you could start however by reducing tourism for example. Cut out frivolities such as the movie industry. Motocross and car racing. What else?

    You dont see much talk about this here. All you see are blank statements about the need to reduce CO2.
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  20. RSVP, 70:

    "Obviously, you could start however by reducing tourism for example. Cut out frivolities such as the movie industry. Motocross and car racing. What else?

    You dont see much talk about this here. All you see are blank statements about the need to reduce CO2. "

    This is not a forum for discussion of social and economical issues, and, luckily, what it takes to develop in a sustainable way is no longer a scientific or technological problem - so that's really not in the scope of what is important to discuss here.

    Basically, we have no lack of resources, not really of knowledge either, what we have is a lack of skills and will. And it's not about not using energy, it's about the forms and the smartness. Therefore, please stop talking about bans on motocross or whatever. It's complete nonsense.

    What you _could_ talk about, is incentives to electrify the transport sector faster. Like some money to make me complement my solar collectors with a few solar panels. So I could, for instance charge my car from them. The collectors, flat plate and vacuum tubes in series, work like magic. Right now: -5 outside, the sun sets in a few minutes, and it's still 10 degC in and 50 degC out from the collectors. (Latitude 60.20 N) Pre-heats domestic water, heats the house, regenerates the soil collector for the heat pump.

    Please don't talk about this being so difficult. Either you haven't really tried, or you lack skills.
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  21. SNRatio
    Replacing old technologies with new technologies on a global scale can not happen in a vacuum. To name just a few issues:
    1) Actual benefits of new technologies (to what extent can they allay global warming or other negatives to the environment)
    2) Time for transition. Is the rate possible to make a difference while fossil fuels are running out anyway. In other words, what is the optimal pace for minimizing global warming.
    3) Which technologies should we actually be choosing?
    4) ETC.

    Assessing these questions lends itself very much to science (or engineering if you will). I never advocated any measures, in fact, just the opposite. On the other hand, you have already prescribed howt others might follow your lead. A very scientific question would be, "What would the world be like if everyone setup solar panels?". Solar panels actually trap solar radition that would otherwise reflect back into space my friend.
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  22. RSVP, your reference to Mars' atmosphere is obtuse. What are you trying to say?
    Mars' surface is warmer than it would otherwise be without its CO2 atmosphere. Earth benefits from the GH effect of CO2, water vapor and other gases. Obviously, if it had only CO2, it would be a lot colder, yet still warmer than space, so what exactly is your point?

    On this:

    "What would the world be like if everyone setup solar panels?". Solar panels actually trap solar radition that would otherwise reflect back into space my friend."

    Interesting idea. By all means, elaborate. That radiation actually would be relected only if it strikes a high albedo surface, which makes up little of the total surface and virtually none of the suitable areas for solar panel installation. So, in fact, it would heat up the surface and be re-radiated upward as IR. If instead that energy is captured, transformed and converted into various kinds of work, does it somehow add to the total energy? Will it somehow inject more heat into the system? Where will the "trapped" energy end up going, eventually?
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  23. jenikhollan wrote in 56:
    On Mars:

    there is some greenhouse, but just a faint one, several kelvins only. This is due to CO2 being the only gas there, even if a bit more abundant (I mean mass per column) than on the Earth. And, due to the very low air pressure, so that spectral lines remain very narrow, lacking the so-called pressure (or collisional) broadening.
    I just bumped into a classic from 1950, almost 60 years ago:

    Strong, J. & Plass, G. N. (November 1950) The Effect of Pressure Broadening of Spectral Lines on Atmospheric Temperature. Astrophysical Journal, vol. 112, No. 3, p.365-79
    http://articles.adsabs.harvard.edu//full/1950ApJ...112..365S/0000365.000.html

    Of course if others are interested in something more recent:

    Pressure broadening
    Thursday, July 05, 2007
    http://rabett.blogspot.com/2007/07/pressure-broadening-eli-has-been-happy.html

    High Pressure Limit. . . .
    Sunday, July 08, 2007
    http://rabett.blogspot.com/2007/07/high-pressure-limit.html

    Its great what you can find online nowadays. For example, I have found several of the classics in pdf on Spiegelman's monster by Sol Spiegelman and Manfred Eigen from the 1960s-70s. (One of my interests is the RNA world and the role of retroelements in evolution.)
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  24. Timothy Chase,
    great! I really love this good old papers. Thanks a lot.
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  25. Philippe Chantreau
    What is my point?

    Mars and Earth have "equivalent" amounts of CO2, (plus Mars also an almost 24 hr rotation), the difference being that on Mars the CO2 is not diluted as on Earth. These conditions appear to lend themselves to a useful comparison. Aside from this potential, given that at average temperature of the planet is around -43C, (and gets to around -120C) on the outset, it doesnt appear that the CO2 is doing a whole lot of warming on its own other than buffering temperatures any gas would.
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  26. PS to 74 If anyone is wondering, yes, the address on the Plass paper...

    Strong, J. & Plass, G. N. (November 1950) The Effect of Pressure Broadening of Spectral Lines on Atmospheric Temperature. Astrophysical Journal, vol. 112, No. 3, p.365-79
    http://articles.adsabs.harvard.edu//full/1950ApJ...112..365S/0000365.000.html

    ... actually has those dots in it. There is a pdf available as well. Incidentally, one of the points that I find interesting is that while they understood that quantized states of molecular excitation are responsible for the absorption bands and lines -- they mention a pure rotational bands (as opposed to rovibrational) of water vapor in "the region beyond 17μ on page 368 -- they were relying upon a fair amount of in the field observations as well as laboratory studies which were being carried out at the same time. For example, they state:
    Data on Absorption in the Infrared in the Stratosphere

    We are fortunate in having certain high-altitude measurements of the transmission characteristics of the upper atmosphere in the infrared which shows the bands that are important for our considerations.

    Figure 2 gives a curve representing the transmission of the atmosphere from 8 to 26 μ above 33,000 feet altitude...

    ibid., pg 368
    ... and:
    50 μ H2O Band

    Experimental studies of the absorption of this band in the region of 10-30 μ, which will be adepquate for the purposes of this calculation, are just now being carried out. It is uncertain whether the main absorption in this region is from lines or from the wings of very strong lines at 50 μ...

    ibid. pg375.


    The lack of convection in the stratosphere is explained as a consequence of pressure broadening (or lack thereof) and high rate thermal emission, mention of how absorption takes place according to the square root rather than the logarithm at lower pressures. I would assume that the high altitude measurements were being performed by the military at the time for the development of fighter infrared vision or something along those lines. If anyone knows...
    *
    One other point that may be of interest. In:

    Pressure broadening
    Thursday, July 05, 2007
    http://rabett.blogspot.com/2007/07/pressure-broadening-eli-has-been-happy.html

    ... Eli gives a link to the Spectral Calc. It is no longer there at that address. The new address is:

    Spectral Calc
    http://www.spectralcalc.com/calc/spectralcalc.php

    There if you are so inclined you can calculate their own absorption spectra if they are so inclined. The graphs that get produced are below the fold.

    Anyway, hard to imagine people arguing with physics and data which is more than half a century old. Then again, some of the science behind the greenhouse effect is more than a century old, and they will argue with that as well, and I was on the evolution/creationism front for several years... I guess I really shouldn't find it that hard to believe.
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  27. Thanks for your explanation carrot eater.
    I will try to examine the more sophisticated model.
    You must admit though that people are entitled to be sceptical when they are told of;
    A greenhouse effect which we are then told is nothing like a greenhouse at all.
    An atmosphere radiating back to the Earths surface explained by using the Stephan Boltzman equation, but then saying that this was not meant to be taken seriously.
    I think that we can all agree on open science with open data and traditional honesty where criticism is welcomed and not seen as a threat.
    As Mao once said "let a hundred flowers bloom, and a thousand thoughts contend"
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  28. RSVP at 02:08 AM on 14 February, 2010

    Even letting aside Phillipe's good point regarding the whole issue of net albedo effects of solar capture systems, we don't really need to worry about the little ways we can redirect or reject energy arriving from the sun at various solar capture systems. Any changes we can make in that department are a microscopic iota compared to others we're already accidentally promoting.

    Here's an illustration. Considering the loss of Arctic sea ice since circa 1980, on a typical summer day in the present the Arctic ocean is absorbing more additional energy than the entire world electrical generating capacity, by a large amount. Total global electrical demand is about 16TW. Back of the envelope calculation by a favorite skeptic of mine shows -at least- 40TW of additional energy being sucked up by the Arctic ocean on a summer day as a result of ice loss. What that tells us is that the amount of energy sloshing around here is so gigantic that any effects we may cause by tweaking a few km2 of albedo with capture systems are vanishingly small.

    This confusion probably has a little to do with the white roof/pavement schemes being promoted for reducing energy demand. Those are aimed at cutting air conditioning costs so as to reduce fossil fuel consumption thus reducing C02 pollution. They're not about increasing the total albedo of the planet.
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  29. RSVP:

    Mars and Earth have "equivalent" amounts of CO2


    Earlier you've been told:

    Due to the very low air pressure, so that spectral lines remain very narrow, lacking the so-called pressure (or collisional) broadening.


    Either you don't understand what is meant by collisional broadening, in which case you should go read one of the links provided above ...

    Or you're intentionally throwing out well-known, 60 year old, physics, pretending it doesn't exist.

    Which is it? The first possibility is curable.
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  30. RSVP, I don't understand why you're still on this 'Mars has carbon dioxide so it should not be cold' bit.

    Look at effective temperatures, that is the temperature the planet would have based solely on the amount of radiation hitting it and its albedo, vs mean surface temperatures;

    Eff Mean
    Venus: 227 K 735 K
    Earth: 255 K 287 K
    Mars: 217 K 227 K

    So, all three planets have some amount of additional heat which has to come either from internal thermal activity (which is VERY low on Mars) or a 'greenhouse effect' in the atmosphere, which is in fact responsible for nearly all the 'extra' heat in all three of these cases.

    Like Mars, the atmosphere of Venus is over 95% carbon dioxide. The two planets also have very similar effective temperatures. The vast difference in mean temperature is because Venus has a very thick dense atmosphere and Mars a very thin diffuse atmosphere.

    Earth's atmosphere bears virtually no resemblance to that of either of these two other planets... either in density or composition. The 32 C of greenhouse warming observed here is primarily due to water vapor. If all greenhouse gases with overlapping spectra were removed than CO2 would contribute about 26% of the Earth's greenhouse effect. The usual estimate of how much it actually contributes currently is about 9%... or a little under 3 C. On Mars CO2 is responsible for virtually all of the 10 C greenhouse warming.

    So where is the problem? Mars is warmer than it would be without the CO2 greenhouse effect. If the atmosphere were not so thin it would have a stronger greenhouse effect (cf. Venus), but even as it is Mars experiences much more warming from CO2 than Earth does.
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  31. suibhne wrote in 45:
    I still cannot get my head around the idea that co2 gas with two significant quantised IR bands can radiate in a way explained by Stephen Boltzman equation!


    carrot eater wrote in 46
    It doesn't, really. That's why detailed radiation transfer calculations are necessary, explicitly considering the full spectrum of wavelengths, and therefore those spectral lines. Planck's Law gives the maximum possible radiation at any given wavelength; S-B integrates that over all wavelengths. To deal with something with quantised bands in the context of Planck's Law, you'd have to introduce a wavelength-dependent emissivity.


    suibhne wrote in 78:
    Thanks for your explanation carrot eater.
    I will try to examine the more sophisticated model.
    You must admit though that people are entitled to be sceptical when they are told of;
    A greenhouse effect which we are then told is nothing like a greenhouse at all.
    An atmosphere radiating back to the Earths surface explained by using the Stephan Boltzman equation, but then saying that this was not meant to be taken seriously.


    suibhne, when you write, "You must admit though that people are entitled to be sceptical when they are told of;
    A greenhouse effect which we are then told is nothing like a greenhouse at all," it helps to realize that the greenhouse effect is actually a lot like the way that a greenhouse works -- in that while it permits energy to enter the system due to transparency to visible light (in the case of the greenhouse by means of transparent glass but in the case of the greenhouse effect due to the transparency of the atmosphere itself), it reduces the rate at which thermal energy is able to leave.

    Yes, of course there is the difference between the greenhouse that reduces moist air convection and the greenhouse effect which reduces the loss of heat due to "gasp!" invisible light. No, the earth's atmosphere doesn't have a glass roof -- but using such images (or the image of a blanket -- whether it is made of wool or one of the reflective space blankets that works primarily by reducing the loss of heat by thermal radiation) but people typically find such images and metaphors more helpful than an explanation that typically presumes a bachelor's degree or higher in physics.

    When you write, "You must admit though that people are entitled to be sceptical when they are told of; ... An atmosphere radiating back to the Earths surface explained by using the Stephan Boltzman equation, but then saying that this was not meant to be taken seriously," judging from carrot eater's explanation it is meant to be taken seriously -- but it is the Stephan Boltzmann law of blackbody radiation -- and this presupposes an absorptivity/emissivity of 1 (meaning that the object is completely black at all wavelengths).

    If you want to apply it to objects that are grey then you need to take into account how the absorptivity will be less than 1. If you want to apply it to realistic bodies that have an absorptivity that varies with wavelength then you need to take into account the fact that the absorptivity isn't a constant with respect to wavelength. The absorption and emission of radiation by a true black body as a continuem of constant absorptivity and emissivity lies at one end of "the spectra," the absorption and emission lines of certain alloys, crystals, dusts and greenhouse gases at the other end.

    But from one end to the other it is all thermal radiation. You want to really understand the reasons for the differences? Be prepared to take courses in thermodynamics, quantum mechanics, statistical mechanics and radiation transfer theory. You aren't really interested in going that far? Then you really don't have much reason for complaining that the science is opaque. Nevertheless...

    I think that we can all agree on open science with open data and traditional honesty where criticism is welcomed and not seen as a threat.
    As Mao once said "let a hundred flowers bloom, and a thousand thoughts contend"


    ... there is a great deal of science that is online.

    For example, the infrared imaging of the AIRS (Atmospheric InfraRed Sounder) instrument has an entire website devoted to it here:

    AIRS
    http://airs.jpl.nasa.gov

    ... and extensive catalogue of online images here:

    AIRS: Multimedia
    http://airs.jpl.nasa.gov/multimedia/multimedia_toc/

    ... documentation, specifications, an online database of all the peer reviewed articles that have made use of its data, a selection of available articles -- all of which I have linked to here. All documentation and data is open access and free to the public -- or at least those members of the public that are willing to take the time and look for it.

    You have climatologists making available detailed explanations for the laymen, a number of which I linked to here specifically regarding how thermal radiation laws apply to greenhouse gases. You can even download entire climate models -- one version after another as they are developed by NASA GISS.

    Heck, one recent go at explaining the radiation transfer theory that underlies our understanding of the greenhouse effect by a climatologist was made less than a week ago and can be found here:

    Another Try
    MONDAY, FEBRUARY 08, 2010
    http://rabett.blogspot.com/2010/02/another-try.html
    0 0
  32. Science and Skepticism, Part II of II

    But there are rather severe limits to what someone can be taught if they have no desire to learn, and beyond a certain point flood of requests for details and data that no one is likely to use simply becomes an instrument by which to waste people's time.

    As Gavin Schmidt wrote in a private letter to Ben Santer:
    The contrarians have found that there is actually no limit to what you can ask people for (raw data, intermediate steps, additional calculations, sensitivity calculations, all the code, a workable version of the code on any platform, etc) and like Som-ali pirates they have found that once someone has paid up, they can always shake them down again.

    Elizabeth May: An Informed Look at the East Anglia Emails
    3 December 09
    http://www.desmogblog.com/elizabeth-may-informed-look-east-anglia-emails
    ... and this seems very much to be the case given certain orchestrated campaigns.

    And it has recently been taken to any entirely new level by the Competitive Enterprise Institute:
    Here's just one part of the request:

    1. of all records, documents, internal communications, and other relevant covered material created by, provided to, received, and or sent by an official or employee of NASA including but not limited to NASSA GISS, that in any way relate to the, receipt, handling, processing, or disposition of "Freedom of Information Act," or "FOIA" requests;...

    CEI requests a significant percent of all records produced by NASA
    Thursday, February 04, 2010
    http://backseatdriving.blogspot.com/2010/02/cei-requests-significant-percent-of-all.html


    It is helpful to keep in mind the fact that many of the same organizations which are "encouraging" skepticism with regard to global warming are the same organizations that were encouraging skepticism with respect to the link between tobacco and health problems. I put together a list here:
    For those who are interested, here is a list in alphabetical order of 32 organizations involved in both the denial campaign surrounding tobacco and that surrounding Anthropogenic Global Warming:

    1. Acton Institute
    http://www.sourcewatch.org/index.php?title=Acton_Institute
    http://www.exxonsecrets.org/html/orgfactsheet.php?id=5

    2. American Legislative Exchange Council (ALEC)
    http://www.sourcewatch.org/index.php/American_Legislative_Exchange_Council
    http://www.exxonsecrets.org/html/orgfactsheet.php?id=10
    ...
    Comment 855 of Real Climate's "Unforced Variations"
    http://www.realclimate.org/index.php/archives/2009/12/unforced-variations/comment-page-18/#comment-151461
    Guess what?

    The Competitive Enterprise Institute is on there as number 10.

    With respect to skepticism regarding the conclusions of established science, it is helpful to keep the following quote from an internal Brown and Williams document in mind:
    Doubt is our product, since it is the best means of competing with the “body of fact” that exists in the mind of the general public. It is also the means of establishing a controversy.

    Smoking and Health Proposal (1969)
    http://tobaccodocuments.org/landman/332506.html
    0 0
  33. CBDunkerson
    "The vast difference in mean temperature is because Venus has a very thick dense atmosphere and Mars a very thin diffuse atmosphere."

    What about the distance from the Sun? Should I continue reading?
    0 0
  34. dhogaza
    "Earlier you've been told:
    Due to the very low air pressure"

    "Air on Mars?". That's interesting. I guess I know what you meant.

    Why not just quantify the difference pressure makes and we can get on with it.

    However a poster name Gord was saying, that only CO2 at a lower temperature would absorb IR. This would be CO2 at higher altitudes which I assume would also be at a lower pressure.

    And, by the way, I never said CO2 isnt a greenhouse gas. All I have ever challenged is the idea that such a rarified gas in our atmosphere is modulating ice age cycles, and or acting as the main cause of a current global warming trend.
    0 0
  35. RSVP,
    distance from the sun is included in the calculation of the mean effective temperature CBDunkerson showed; just for info, planetary albedo is also included. Go on reading then, or should i say go back reading?
    0 0
  36. One commenter said:

    //If CO2 is "pollutant" what term would you reserve for e.g. dioxin, the stuff involved in the Union Carbide disaster, Bhopal, India, 1984? Thousands perished.//

    It seems that you are confusing "pollutant" with "toxin". They are not the same thing, and "toxic" may or may not both apply to a pollutant.
    0 0
  37. RSVP wrote in 84:
    CBDunkerson
    "The vast difference in mean temperature is because Venus has a very thick dense atmosphere and Mars a very thin diffuse atmosphere."

    What about the distance from the Sun? Should I continue reading?
    Here is the distance of Venus from the Sun:
    Orbital Semimajor Axis: 0.72 AU (Earth=1 AU)

    Venus Statistics
    http://www.windows.ucar.edu/tour/link=/venus/statistics.html
    The albedo of the earth:
    For example, the albedo of the Earth is 0.39 (Kaufmann) and this affects the equilibrium temperature of the Earth.

    Albedo of the Earth
    http://hyperphysics.phy-astr.gsu.edu/HBASE/phyopt/albedo.html
    The albedo of Venus due to the highly reflective sulfuric acid in its upper atmosphere:
    The bond albedo of Venus is 0.75. Albedo is a measurement of the reflectivity of an object.

    Albedo of Venus
    http://www.universetoday.com/guide-to-space/venus/albedo-of-venus/
    Put those numbers together and the temperature of Venus without a greenhouse effect would be roughly the same as earth's without a greenhouse effect: -16°C as opposed to -17°C. The actual temperature of Venus is 457°C and the actual average temperature of the earth is 14°C.
    0 0
  38. PS

    That's right: just going off of the albedos and distances from the sun, Venus should be just one degree warmer than the earth -- where we omit the greenhouse effect of both planets due to their greenhouse gases.
    0 0
  39. RSVP: "Air on Mars?" That's interesting. I guess I know what you meant.

    Why should you find that "interesting" unless you knew nothing about Mars in the first place? Is there no "air" on Mars? If so, photographs from the Mars rovers showing dust storms and dust-devils on the surface are indeed mysterious.

    There is already plenty of information in the responses here and elsewhere on this website to show that the Mars/CO2 sceptical argument is wrong, or misleading, or irrelevant (actually a bit of each). What is interesting, is that you still want to use it.
    0 0
  40. RSVP, Mercury is closer to the Sun than Venus, yet it's not as hot. Also, if I recall right, although Venus always presents the same side to the Sun, there is not that much difference between the sunny and shady side temperatures.
    0 0
  41. CBDunkerson wrote in 81:
    Look at effective temperatures, that is the temperature the planet would have based solely on the amount of radiation hitting it and its albedo, vs mean surface temperatures;

    Eff Mean
    Venus: 227 K 735 K
    Earth: 255 K 287 K
    Mars: 217 K 227 K
    Thank you CBDunkerson. You've got the wrong figures -- and my attempt was seriously out of wack. 1 minus the albedo for the absorbed, fourth power of the temperature for the watts implying fourth root of watts to get the temp...

    I found the following that shows the right approach to calculating what the temperature of a planet minus the greenhouse effect = the effective temperature.

    What is the Effective Temperature of Venus
    Atmoz 18 Jul 2007
    http://atmoz.org/blog/2007/07/18/what-is-the-effective-temperature-of-venus/

    I shoulda known better. Would have if I hadn't been in such a hurry.
    0 0
  42. CORRECTION:

    I meant "Thank you CBDunkerson. You've got the right figures -- and my attempt was seriously out of wack...."

    Jesh!
    0 0
  43. Mike
    Air is what we breath here on Earth. "Air" by definition is a specific a mixture of gases, which by the way is changing over time as we can see from the graph.
    0 0
  44. CBDunkerson
    So where is the problem?

    Riccardo prompted me to "go back reading". I did.

    This is what I understood. On Mars, the greenhouse effect due to CO2 contributes to a 10C increase in temperature. On Earth a 3C increase. If I didnt get that right, please correct me.

    Now, my turn. I was saying earlier that Mars and Earth actually have "equivalence" of CO2 in their atmospheres in the sense that if you remove all other gases from that of the Earth, you would have about the same coverage of CO2 on the Earth as on Mars. In fact, as Earth is a larger planet (perhaps, and in this I am not hold my hand to any flames), there is even more CO2 volumetrically. But at any rate, these planets are at least par in some sense. Furthermore, both planets have the same rotation of around 24 hrs.

    Even though Mars is further from the Sun, according to you, the greenhouse effect is 3 times as high. Other posters have actually alluded to there not being enough pressure to activate the CO2 for spectral broadening etc. Perhaps the albedo is lower on Mars than the Earth, which I assume would favor more surface IR and more greenhouse heating.

    So, I dont think there is any problem, however, I do think it rather unfair to dismiss these questions as irrelevant, especially when a lot of the marketing behind the deleterious effects of CO2 has been based on image of the greenhouse effect on Venus.

    By the way, one last comment. With all that rocket science, astronomy, physics, chemistry, etc., apparently the situation on Venus came as a surprise when they actually sent probes over there. It should have been predictable. What fundamental science was missing at that time to have required the loss of so many space probes?
    0 0
  45. RSVP at 18:39 PM on 14 February, 2010

    "What fundamental science was missing at that time to have required the loss of so many space probes? "

    Not science, data, such as what was the atmospheric pressure at the surface, the temperature, things like that.
    0 0
  46. RSVP, the '3 C increase from CO2 on Earth' is only partially correct. It is impossible to give an exact figure because many of the bands of radiation retained by different greenhouse gases overlap... so did a particular photon get retained by CO2... or water vapor... or ozone? The 9% estimate is computed by looking at average concentrations, location (e.g. CO2 can be found higher in the atmosphere than water vapor and thus accounts for more IR absorption there), circulation, and so forth. However, if we could somehow magically remove the overlapping IR bands from other greenhouse gases (while retaining all other bands they absorb) then CO2 would account for 26% of the 32C greenhouse warming... 8.32 C. That is a better comparison for Mars in terms of greenhouse potential since there are few other greenhouse gases there. Of course, Mars also has more CO2... but less atmospheric pressure. So you've got alot of conflicting variables in play here.

    Also, it was the greenhouse effect itself which disguised Venus for so long. All that CO2 in the atmosphere preventing heat from escaping means that the surface of Venus is very hot... but that heat doesn't escape out to space where we could observe it. The greenhouse effect keeps the heat contained and the upper layers of Venus's atmosphere actually seem quite hospitable and Earthlike. It was the probes which showed otherwise.
    0 0
  47. Which is the More Powerful Greenhouse Gas?, part I of II

    RSVP wrote in 95:
    This is what I understood. On Mars, the greenhouse effect due to CO2 contributes to a 10C increase in temperature. On Earth a 3C increase. If I didnt get that right, please correct me.
    Consider yourself corrected...

    The greenhouse effect results in the earth being 32°C warmer than it would otherwise be.

    See:

    What is the Effective Temperature of Venus
    Atmoz 18 Jul 2007
    http://atmoz.org/blog/2007/07/18/what-is-the-effective-temperature-of-venus/

    Now there are two ways of calculating how much a given greenhouse gas is responsible for of this warming.

    First, remove the gas in question while holding the other greenhouse gases constant -- and see how much the greenhouse effect would be reduced -- and attribute that amount to the greenhouse gas that was removed.

    For carbon dioxide one gets 9%, or 2.9°C. Methane 4% or 1.3°C. Water vapor 36% or 11.5°C and Ozone 3% 1°C. Grand total? 52% or 16.6°C.

    Second, remove all the other greenhouse gases while holding the greenhouse gas in question constant -- and see how much of the greenhouse effect remains.

    For carbon dioxide one gets 26% or 8.3°C, methane 9% or 2.9°C, water vapor 70% or 22.4°C, ozone 7% or 2.2°C. Grand total? 112% or 35.8°C.

    See:

    Gases released by human activity that contribute to climate change and global warming.
    http://www.opencarbonworld.com/wiki/greenhouse-gas.html

    ... for the figures. Why the difference? Because the absorption bands overlap. Remove one gas and at least some of the absorption and consequent greenhouse effect that the gas was responsible for will be taken up by the others. Remove the others and at least some of the absorption and consequent greenhouse effect that gas was responsible for will be taken up by the gas that is left. (Gavin Schmidt explained this at one point but I will have to look up the exact reference.)

    However, water vapor is a fast feedback. When we say "hold it constant" while changing the amount of carbon dioxide in the atmosphere this really is nothing more than a thought experiment and corresponding calculation.
    0 0
  48. Which is the More Powerful Greenhouse Gas?, part II of II

    Water vapor that is in the atmosphere tends to be rained out very quickly having a half-life of about 10 days -- and the same is true of tropospheric aerosols as they tend to fall out with the rain. If it weren't for the corresponding process of evaporation the atmosphere would rapidly dry out.

    Moreover the amount of water vapor in the atmosphere is very sensative to temperature. If you raise the temperature by 1°C the absolute humidity will quickly rise by 8% due to the higher rate of evaporation, and if you raise the temperature by 10°C the absolute humidity will double. But if you raise the amount of water vapor in the atmosphere without raising the temperature right away then you will increase the rate of precipitation without a corresponding increase in the rate of evaporation. And it takes a while for the climate system to warm given the large thermal inertia of the earth's oceans and consequent characteristic time scale that is about thirty years.

    Please see:

    Spencer’s Folly
    July 28, 2008
    http://tamino.wordpress.com/2008/07/28/spencers-folly/

    But a large part of a "slug" of carbon dioxide injected into the atmosphere will remain in the atmosphere for years, decades, centuries and even millenia. As such it remains in the atmosphere long enough to maintain an imbalance between the rate at which solar radiation is being absorbed and the rate at which thermal radiation escapes the atmosphere, reducing the later. With the reduced rate at which thermal radiation escapes the temperature will rise, increasing the rate of evaporation which acts as a positive feedback, increasing the temperature still further, and once the new short-term feedback Charney equilibrium is achieved, while a doubling of carbon dioxide would raise the temperature by a little more than 1°C by itself, all the feedback will likely add about 2°C to this, bringing the total warming to 3°C.

    Please see for example:

    Skeptical Science: "Water vapor is the most powerful greenhouse gas"
    http://www.skepticalscience.com/water-vapor-greenhouse-gas.htm

    David Archer & Victor Brovkin (2008) The millennial atmospheric lifetime of anthropogenic CO2, Climatic Change 90:283–297
    http://geosci.uchicago.edu/~archer/reprints/archer.2008.tail_implications.pdf

    So which is more powerful? Carbon dioxide or water vapor. The first because it leads the latter.

    Please see:

    Richard Alley – The Biggest Control Knob: Carbon Dioxide in Earth’s Climate History
    December 19, 2009
    http://thingsbreak.wordpress.com/2009/12/19/richard-alley-the-biggest-control-knob-carbon-dioxide-in-earths-climate-history/
    0 0
  49. One thing:

    CO2 rose 100 ppm since Industrial Revolution 200 years ago.

    BUT:

    CO2 ALSO rose 20-30 ppm since 6000 years ago until 1700 AD.
    Could this be a result of the AGRICULTURAL Revolution(i.e from land use change)?
    0 0
  50. suibhne:

    "An atmosphere radiating back to the Earths surface explained by using the Stephan Boltzman equation, but then saying that this was not meant to be taken seriously."

    It's to be taken seriously, inasmuch as it shows the basic concept of how back-radiation from the atmosphere can cause the surface to be warmer than it otherwise would be. In order to show that basic concept, you don't need spectral detail.

    Any source that uses this cartoon model should make clear that it is making a lot of simplifications: using a single-slab atmosphere, and ignoring temperature variations within the atmosphere (the lapse rate), ignoring convection, ignoring wavelength-dependent detail. Once you add all this in, you end up with a fully fledged climate model, with thousands of lines of code.

    But that doesn't mean simple models aren't of any value.

    So, you seem to say you found a website where a very simple model is presented, without those caveats telling the reader there is much being left out. If you tell us what website this is, perhaps we could have a look, and suggest to the author that a couple sentences be put it, to that effect.
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