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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 1 to 50 out of 252:

  1. Anything can be a pollutant, in the wrong concentration. Even if it´s a naturally occurring substance.

    Take any substance that´s part of a biological cycle, vary it significantly and voila! You get undesirable consequences.

    Double Oxygen, anyone?
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  2. Got to agree with Alexandre. Somewhere along the way we have forgotten the concept of enough.
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  3. I would reserve the term "pollutant" to stuff that

    1. has got an immediate, direct harmful effect to human health and/or to quality of local environment in a way that substantially decreases property value
    2. can be traced back to individual polluters, actual deed and the damage done being provable at court

    None of these conditions hold for carbon dioxide.

    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.

    There should be a difference in legislation and multilateral treaties regarding the two kind of substances, otherwise not even overt criminals can be brought to justice. Cases like that can never be cured by taxation, virtual bonds, persuation & speeches.

    Also, humans do breathe out CO2, a substantial amount of it (up to 300 kg/year/person, ~2 Gt/year for mankind). If polluting is declared a criminal act (as it should have) and human breath is a pollutant, then it follows the very act of breathing should be punished. Each living person is amenable to law, judge included. Forget freedom, establish breathing permits ("breathing is not a right, it is a privilege").

    More likely this policy would meet some resistance. It could bring down all legislation against "pollutants" and evil/irresponsible guys involved in the act of "polluting" (i.e. killing/robbing people). Collateral damage of the most undesirable kind.

    Invent another term, please.
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  4. Re:"as the oceans absorb CO2 from the atmosphere, it leads to acidification that affects many marine ecosystems."

    This is not true. The oceans are buffered and the acidification does not rise from increased absorption of CO2.
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  5. Yes it is semantics. But playing politics is something we do everyday, wether at work, school, internet, etc. It seems like in the USA and UK we do it for sport. But the bottom line is we have to move foward so it doesnt matter if you call it klem kaditlehopper as long as something gets done
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  6. Using figures from the graph, one can estimate the comparable height of a pure CO2 Earth atmosphere removing all other gases. For intance, if you assume an air atmosphere 20 km high, with a concentration of 0.0274 CO2 (how it used to be), you would have a CO2 atmosphere of 5.5 meters covering the Earth. If you assume 0.0387 vppm, that pure CO2 atmosphere grows to 7.8 meters. Assuming continual doubling, to 0.0774, you get 15.5 meters. If you dont like 20 km and wish to consider a higher atmosphere of 40 km for instance, then these results simply get multipled in linear fashion, so that at worst, you get roughly around 30 meters of pure CO2 covering the Earth.

    Ironically, that basically describes the atmosphere of Mars, which has a composition of nearly pure CO2.

    ... and Mars is a very cold place.

    I derived these figures assuming the Earth as a perfect sphere, using the formula for calculating the volume of a sphere and applying it to an assumed Earth radius of 6378.1 km. No rocket science required, but I did use a computer spreadsheet.
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  7. I think a key factor here is timing. We tend to think of something being a pollutant or poison if it has an immediate negative effect, as someone mentioned above.

    I think this is a precarious view, though. When we're talking about a substance that hangs around in the atmosphere (at least the portion not absorbed by the oceans, plants, etc.) for a very long time and can therefore build up over decades and centuries to a dangerous level, I would say that still qualifies as a pollutant.

    As for the "too much of anything is bad" idea--of course that's true, but if we consistently apply that guideline it leaves us doing nothing about any pollutant. The only rational approach is to distinguish between critical and non-critical levels of substances. If we call the damaging levels of something a pollutant, regardless of its source *e.g. sulfurous emissions from volcanoes), then I think that's fine.

    Westwell: Oceans don't acidify because of CO2 absorbed from the atmosphere? Really?
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  8. Westwell, a acidification is a decrease in pH. Nobody is suggesting the oceans will become acidic!

    You could take a look here ( if you are genuinely interested in learning about the issue.
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  9. Argh, typo. Should just say "acidification is a decrease in pH".

    Relatively small changes in pH are associated with significant alterations to ocean carbonate chemistry, which affects the ability of calcifying organisms (such as corals) to build their skeletons
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  10. Republican Rep. Mike Noel (Utah): "Are you stating on record that CO2 is a pollutant? Are you saying that CO2, carbon dioxide, is a pollutant, are you saying that?”

    Professor Joseph Andrade: "I'm saying that carbon dioxide has a unique molecular structure which absorbs infrared radiation, and that that is in part responsible for the effects that you're concerned with, Representative Gibson is concerned with, and Representative ...."

    Noel: "I want to get this on the record, ok? Are you saying that we have to rid the planet of carbon dioxide?"

    Andrade: "Of course not!"

    Noel: "It's not a pollutant then, it's not going to kill you. It's not going to kill plants. Is that correct? I also have a degree too, professor. So I want to get this straight. Is it a pollutant?"

    (The conversation becomes a verbal skirmish, and the committee chairman breaks it up.)

    Noel: "I'm sorry, I'm sorry ... It got out of hand."
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  11. Part of the ambiguity in the term "pollutant" is that a distinction needs to be made between the [quantity of] CO2 represented by the flat part of the curve above versus the incremental CO2 introduced as a by-product of human activity ("anthropogenic CO2"): same molecule, different origin. We encounter an analogous (intentional?!) ambiguity when skeptics use the term "global warming" to describe all warming that has occurred: a) since the last glacial maximum (~22,000 years before present) or b) since the LIA. It is not simply CO2 but A-CO2 that is interpreted to be driving anthropogenic warming (AGW), and thus is acting as a "pollutant".
    The other potential ambiguity is that the harmful impact of A-CO2 needs to be measured relative to the "status quo", which refers specifically to the climate and environment that has existed for the several thousand years prior to human impact on climate. This is a "blink of an eye", geologically. During the time period preceding the curve shown depicted above, both CO2 and temperature varied substantially in response to natural drivers. This partly explains why many geologists see climate change in different context.
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  12. CO2 can actually be toxic to humans at or above 50,000 ppm.

    See link:
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  13. In many posts on many websites, deniers try constantly to make the people concerned about human impact on the climate admit that they think of CO2 as a pollutant (which is of course why John addressed the question here). Their reasons then become clear when, with denier's glee, they come back with, "...but it's necessary to support life on Earth!"

    It's just another of the many carefully rehearsed tricks that deniers use against those with a shaky understanding of the causes of climate change, in order to undermine their trust in the findings of climate scientists.

    Unfortunately at the moment the science of the 'blindingly obvious*' used by deniers seems to be winning the battle for public opinion.

    *'blindingly obvious' is the phrase used by arch-denier Lord Monckton to describe the evidence against AGW.
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  14. This entire discussion is missing the required context. People may differ on how they use the word 'pollutant', but in the US the issue goes back to this Supreme Court case:

    The Supreme Court found that CO2 qualifies as a pollutant, as defined by the Clean Air Act.

    Regardless of whether you want to use the word 'pollutant' or not, increased CO2 levels have adverse effects which qualify them for regulation under the Clean Air Act.
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  15. RSVP - I don't see what the point of your Mars atmosphere comment was. Can you clarify your purpose with that comment?

    CoalGeologist - as you point out, "pollutant" also depends on source. An example I like to use is fixed nitrogen. It's a vital soil nutrient - but becomes a pollutant when there's too much of it spread on fields and the excess flows down the Mississippi and into the Gulf of Mexico, where it fuels algae blooms and a massive dead zone.
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  16. As with so many other aspects of the climate change debate, the question of whether CO2 should be regarded as a pollutant has become more an issue of politics and ideology than of science. An interesting analysis and discussion can be found in the United States Supreme Court decision in Massachusetts et al. v. EPA et al.:
    At the time, the U.S. Environmental Protection Agency, acting on behalf of the Bush Administration, declined to regard CO2 as a pollutant that could potentially be regulated under the Clean Air Act. The Supreme Court split 5-4, along ideological lines. See p. 26 for discussion of the term "pollutant".
    The political nature of this dispute is further evident in that the plaintiffs included 11 (2004) "Blue States" plus one Red State (New Mexico), while the EPA was joined by 9 (2004) "Red States" plus one Blue State (Michigan, capital of the auto industry!).
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  17. Venus, too, like Mars, has an atmosphere of nearly pure carbon monoxide. Yet it, unlike Mars, is hellishly hot.

    RSVP, do you suppose, that, just maybe, distance from the sun has some slight influence here?
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  18. "angliss at 05:35 AM on 12 February, 2010
    RSVP - I don't see what the point of your Mars atmosphere comment was. Can you clarify your purpose with that comment?"

    While I believe there is such a thing as thermal environmental pollution, I am personally not convinced (yet) that anthropogenic CO2 is the main cause of global warming. One way to look at this is by comparing the situation on Mars, which happens to also have a 24 hr day, and an atmosphere of pure CO2 that is just about the same as would exist on the Earth if all
    other gases from our atmosphere were removed (which is the point of explaining my calculations). On Mars, the average temperature is down around -40C. And yes, I am aware that Mars only gets about half the sunshine as the Earth, however, shouldnt all that CO2 be keeping the plantet a little warmer?
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  19. Anything which causes damage to an ecosystem when it grows too concentrated is a pollutant. Thus we have "light pollution" and "noise pollution" despite light and sound being 'naturally occurring' and generally harmless things. Early in the planet's history "oxygen pollution" wiped out alot of species.

    A single molecule of CO2, or just about any other substance, is not going to noticeably harm the environment in any way... but 80,000 ppm CO2 would kill off most life on the planet. Thus, somewhere between those extremes CO2 logically MUST be considered to become a pollutant.

    It is a measured fact that increased CO2 emissions have changed the pH of the shallows of the world's oceans. This change has clearly had an adverse impact on species living there. Thus, human CO2 emissions have become a pollutant for the ecosystems of the upper portions of the world's oceans. Likewise, rising global temperatures have been linked to the increasing atmospheric carbon dioxide level... and those rising temperatures are having adverse impacts on countless ecosystems all over the world.

    Thus, atmospheric CO2 has reached levels where it has become a pollutant for many parts of the planet. Granted, there are many other areas which have suffered no significant adverse impacts from increasing CO2 levels yet. However, since CO2 released in one part of the planet can mix throughout the atmosphere in a matter of mere months this means that release of CO2 anywhere on the planet is contributing to the harm in areas being polluted by it... similar to acid rain from sulfur dioxide (another naturally occurring substance which only becomes a pollutant at high concentrations) appearing far removed from the emissions source.
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  20. RSVP, it is true that the atmosphere of Mars is 95% carbon dioxide... but the mass of the Martian atmosphere is only 0.5% that of Earth.

    Further, Mars does not have any significant component of water vapor in its atmosphere. That, combined with Mars getting about 43% as much sunlight is responsible for its cold temperatures.

    The high percentage of CO2 in the Martian atmosphere DOES provide a greenhouse effect. Just not enough to overcome the low amount of sunlight and lack of much more potent water vapor greenhouse warming.
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  21. RSVP at 05:21 AM on 12 February, 2010

    For chronic exposure, even lower. Some folks become symptomatic at less than 2,500ppm after a relatively brief time, but if we were to somehow hit that we'd all be cooked anyway.
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  22. CO2 is toxic to subwater organisms, because the following reaction occurs:

    H2CO3(ac)= H+(ac) + HCO3-(ac)

    Yes, seawater has a natural pH buffer thanks to all the salts there(the so-called alkalinity), but the quantity of CO2 we emit is so big that this buffer is overwhelmed.

    In consecuence, oceanic pH has dropped 0,1 pH units from pre-industrial times(pH used to be 8,2. now is 8,1).

    This is equal to roughly 30% increase in acidity!(don't forget that pH is a logarithmic scale).

    More acidic water means that shelled creatures like corals, pteropods, diatoms, etc, will lose their shells and die.

    This alone is more than enough to consider CO2 a pollutant, even if we ignore global warming!
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  23. Alexandre writes: "Anything can be a pollutant, in the wrong concentration."

    This is a good way to look at it, and an excellent analogy is to think of drugs and other medications. In the correct dosage, a drug can save your life. But too much of it can kill you. Same with CO2
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  24. Thanks for putting in this topic John. It is one of those pieces of semantic nonsense (how many CO2 molecules could you fit on the head of a pin?) that are trotted out by deniers as if discovering some new universal truth hitherto covered up by the secret scientific brotherhood.

    On a practical level my understanding is that the American EPA, and possibly other countries are in the same position, can only regulate to reduce "pollutants" in air soil and water. It was never envisaged when such bodies were being established that CO2 would be become the most important issue of all and need controlling. The simplest thing would be to rewrite legislation to say "control pollutants AND CO2" and that would get us away from semantic games.

    I mean clearly CO2 isn't a pollutant in the classical sense. Nor is water. And yet water, after a flood, or a landslide, or a tsunami, damages human environments as much as any chemical released from factory or oil tanker. So too much water, too quickly, in the wrong place at the wrong time, is a damaging agent in the same way that pollutants from an oil tanker crash, or a factory fire, are damaging agents.

    It is all reminiscent of the old debate about what is a "weed". Definitions usually break down at some point and we are usually left with just the idea that a weed is a plant growing rapidly in the wrong place. So perhaps it would be helpful to refer to CO2 as a chemical weed rather than a pollutant.

    That might stop the deniers dancing on the heads of pins.
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  25. David Horton at 08:05 AM on 12 February, 2010

    David, I get what you're saying, but the analogy with water from a tsunami or other natural event really does not work.

    I even disagree with our host when he says:

    "How we choose to define the word 'pollutant' is a play in semantics."

    The CO2 in question here is an effluent from human activities.

    Our C02 emissions are an outcome of our engineered products, something we now realize is a serious imperfection.

    As another example, C0 is found naturally occurring in the atmosphere yet we have spent a lot of money improving our motor vehicle engineering so that we do not emit too much C0. We do not accept that because C0 is a naturally occurring atmospheric constituent that we may ignore the C0 we produce as a byproduct of our activities.

    EPA's job is going to be explaining that simple fact, but the job of explanation is going to be very difficult given the call to confusion they'll be facing from industry.
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  26. Thank you for the explanation, RSVP. That's what I thought you probably were going for, but I wanted to be sure before I attempted to respond with a scientific rebuttal.

    However, CBDunkerson has already made the very points I would have made and I feel no need to reiterate his points.

    Ed Seedhouse - I think you meant carbon dioxide, not carbon monoxide.
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  27. Posted by John Cook at 22:54 PM (main article):
    "as the oceans absorb CO2 from the atmosphere, it leads to acidification that affects many marine ecosystems"

    Seawater is nowhere near to being acidic, not even neutral. It is alkaline. No conceivable CO2 levels could turn it into an acid. Acidification is a misnomer, designed to conjure scare up.

    The process can honestly be described as dealkalinification, at best.

    All the surface waters of the world are carbonate-saturated. The lysocline, where calcium carbonate solubility starts to increase sharply is somewhere around 3700 m. The CCD (Carbonate Compensation Depth), below which no limestone deposition occurs is at 4200-5000 m.

    It didn't change much during glacial periods, when atmospheric CO2 levels are supposed to be considerably lower than today. Kinda enigma, see:

    Glacial/interglacial variations in atmospheric carbon dioxide (review article)
    Daniel M. Sigman & Edward A. Boyle

    With water warming, lysocline goes down, not up.

    If all else fails, we can put some limestone into oceans to balance CO2. There are several million gigatons of it in crust, a tiny little percentage would suffice.
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  28. "The net result from increasing CO2 are severe negative impacts on our environment and the living conditions of future humanity."

    I agree with the general view that if most climate scientists are right, the net effects of c02 will be very negative. However, the issue here is a general philosphical one. By labelling and demonising something natural and essential to life as a 'pollutant', is a dangerous and misleading policy. It creates a dogmatic, one-sided political perspective.

    As David Haughton points out, you could also call water a 'pollutant' using this sort of labelling. If too much is ingested in the lungs, one drowns, it can form hurricanes which kill thousands of people, it can form tsunami waves that kill thousands, etc etc, so should we call 'water' a pollutant and form policies against it? Of course not. It is misleading and dangerous to do such a thing, regardless of its overall net positive or negative effects. Labelling C02 a pollutant may achieve political goals, but at the expense of also creating a dogmatic perspective. What this sort of general policy does to the mind (as also with Plato and with his concept of a Republic run by an elite-he never asked what such an arrangemnet does to the mind of those involved), is that is creates systematic bias and extremism.

    It is the same kind of problem with eg demonising dissent, dissent of course can be very wrong, but it can also have value, but the demonisation of dissent as a general policy is what is wrong.

    I'm sorry, but it is just another case of 'lumping' which is a general philosophical issue that some people have a valid disagreement with.
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  29. "Acidification is a misnomer, designed to conjure scare up."

    No, you're wrong.

    Regardless of where on the scale of pH a change takes place, a decrease of pH reading is best and most concisely termed "acidification". A lower pH reading is more acid, a higher pH reading is more alkali and there is no threshold for the use of either term. A change in pH reading from 10 to 9 is considered acidification even though the resulting number describes a base. Just so, a change from a reading of 2 to 3 is considered alkalinification (or the less used "basification") even though the result is still acid.

    Researchers using the term "acidification" have little choice in the matter. The alternative would be to use the more clumsy phrase "reduction of pH value" or a variation thereof. I don't think these folks care enough about politics to do that, they'll instead stick with the accepted parlance.
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  30. I agree with thingadonta #28.
    It will end up being a net negative for those seeking to prevent "climate change".
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  31. People like to make a big deal of whether or not acidification can occur above pH 7. It's silly. As are claims that "acidification" was designed for alarmist purposes (look at the alternative labels for the phenomenon). What matters is deviation from conditions to which organisms have evolved. This is certainly changing, and rather rapidly too. Industrial activity has increased the activity of hydrogen ions near the ocean's surface by about 25% I believe.

    Whether or not carbonate is at saturating levels is not the only concern, although it is certainly something to consider. It's expected that for aragonite the saturation horizon will go from 730 m up to the surface over the course of this century and from 120 m up to the surface in the sub-Arctic Pacific (apparently in Orr et al 2005 -- I haven't read it yet). In the North Atlantic, 2600 m up to 150 m is expected. These changes pose a very serious challenge to many calcareous animals.

    But effects will be seen long before the saturation horizon ascends to shallower depths than where the creatures live. See this Wooten et al paper in PNAS for example:
    Look at Figure 2B. Now think about what's going to happen when atmospheric CO2 is at 500 ppm? Very big changes to ocean chemistry and consequent effects on ocean creatures. And we're headed there much too quickly.
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  32. "All the surface waters of the world are carbonate-saturated."

    Yes, you'll find a nice diagram illustrating just that on p.7 of the Royal Society report (link at 8, above).

    What's your point?
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  33. Not to belabor a point, but it seems we're continuing to make tangelos out of tangerines and oranges here.

    Fish oil in a fish is natural, part of the natural world, undoubtedly necessary and good.

    5000 gallons of fish oil spilled in a harbor is a pollutant, damaging, and is under the purview of the EPA.
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  34. Ugh. There's nothing worse than misplaced pedantry. Would somebody please inform the sceptics that they aren't being clever when they harp on the usage of the word 'acid'. If the pH is decreasing, something is becoming more acidic. Period.
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  35. thingadonta: I don't follow your point. The EPA labeling something as a pollutant, under the language of the Clean Air Act and with the approval of the Supreme Court, has no particular philosophical implications. It merely sets the process towards the EPA being able to regulate its emissions.

    And Berenyi, breathing is completely irrelevant to the topic. What's relevant are activities that introduce extra carbon to the carbon cycle. Breathing merely re-circulates carbon that's already in the system.
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  36. re carrot eater
    "The EPA labeling something as a pollutant, under the language of the Clean Air Act and with the approval of the Supreme Court, has no particular philosophical implications".

    I disagree. It's labelling, and leads to systematic bias and dogma. You can regulate something without labelling it, eg cars arent labelled a 'dangerous moving object', and yet they are still regulated.
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  37. The point, here, is that we're adding CO2 into the system which was *removed* from the system hundreds of millions of years ago. It is this CO2, alone, which we need to regulate. Its also much easier to do than some would have us believe. If we used bio-sequestration, we could significantly reduce the net CO2 emissions of coal & natural gas power stations. If we increase our use of non-fossil fuel derived sources of fuel & electricity (solar, biogas, wind, tidal etc etc) then we could significantly reduce the gCO2/kw-h that our economies create. Lastly, if we become much more *efficient* in our use of fuel & electricity, we can significantly reduce the amount of kw-h/$ of GDP necessary to sustain our economy.
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  38. John Gribbin's book "He Knew He Was Right" states that one of NASA's criteria for off-Earth life involves "looking for planetary atmospheres with a low percentage of CO2". Mars doesn't have much of an atmosphere but what is there is mostly CO2 (so no life). Venus has a hot thick atmosphere with high levels of CO2 (so no life).

    On Earth, plant life far outweighs the animal life so low levels of CO2 along with high levels of O2 mean that the plant life is successfully converting the former into the latter (along with cool oceans sinking much of the balance of CO2). When temperature gets too hot, the oceans can't hold very much gas so CO2 gets much higher. Likewise volcanoes belch a lot of CO2 and this can add to the imbalance.
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  39. There is a lack of carbon-14 in fossil fuels and the isotopic ratio of CO2 in the atmosphere due is changing as a result of its release into the atmosphere. If you could some how bring in the labeling of "pollutant" with regard to this changing ratio that would make more sense.
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  40. Referring to the graph, it should be noted that proponents of AGW do not attribute global warming to 380 ppm CO2, but to the 100 ppm difference in concentration relative to where it was 200 years ago.
    (All AGW positive "radiative forcing" is coming from the extra 100 ppm, not 380 ppm.)

    Going back to my spreadsheet, 100 ppm yields a 2 meter coverage of CO2 over the Earth (as calculated assuming 20 km of normal air).

    Again, keeping in mind the situation on Mars, try to imagine how much warmer the Earth would be with and without those 2 meters of CO2.

    As on Mars, for all practical purposes, the effect would be nil.

    However, since the Earth would be receiving more sunlight, and is covered with water, the situation would be very different. It would be a warmer place, not because the CO2, but because of the water.
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  41. It is interesting to note that if the graph in the article extended back another 2000 years or so it would show that in that time period CO2 levels rose just about the same amount, 100 ppm, as they have in the past 200... which was the difference between the coldest part of the last ice age and the warmth of the current interglacial. We humans have now pushed CO2 that much higher again in 1/10th the time it took to happen naturally. At the current rate of increase it'll only take about 60 years to hit ANOTHER 100 ppm increase.

    Those insisting that this CO2 is not a 'pollutant' or that the effect it is having on the oceans should not be called 'acidification' are in truth attempting to redefine the longstanding accepted meanings of both terms.
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  42. RSVP:

    "Again, keeping in mind the situation on Mars, try to imagine how much warmer the Earth would be with and without those 2 meters of CO2."

    Or better yet, lets use actual climate sensitivity estimates!


    Also this -
    "All AGW positive "radiative forcing" is coming from the extra 100 ppm, not 380 ppm"
    is untrue.

    There are even more powerful anthropogenic greenhouse gases (but their concentrations are much lower)

    You are at the right place - click "arguments" and find your answers.
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  43. #35 carrot eater at 12:13 PM on 12 February, 2010
    "Breathing merely re-circulates carbon that's already in the system"

    Carbon atoms are not labelled. If you are to decrease CO2 levels, it is as good to push carbon into a resevoir as to stop pulling it out from another.

    Provided we stop breathing, we would not need freedom fries either. Potatoes could be dumped into anoxic abyss of the Black sea and the planet would be saved.
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  44. 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!
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  45. thingadonta: Your premise is actually wrong. The EPA can't regulate CO2 emissions unless they are found to be covered under the language of the Clean Air Act. Perhaps that has some philosophical consequence for you, but it's really just a legal question.

    Berenyi: Carbon atoms aren't labeled, but you know if any given activity is re-circulating carbon, or introducing new carbon. Breathing is recirculating carbon that was already in the climate system, so it's irrelevant to the discussion. Digging up and burning coal is adding carbon that had been removed from the climate system. This is a very simple concept.

    suibhne: 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.
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  46. Actually, carbon is labeled in a way, as 12C, 13C or 14C, and that enables some interesting calculations for tracking carbon as it comes into and goes around the cycle. But that isn't really relevant to the point.
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  47. BP writes: If all else fails, we can put some limestone into oceans to balance CO2. There are several million gigatons of it in crust, a tiny little percentage would suffice.

    CO2 in the oceans and atmosphere will be out of equilibrium for a long time to come. By your suggestion we would need to start a long-term program of continuously manipulating the chemistry of the world's oceans. I guess that could be run by the same international agency that is responsible for continuously injecting aerosols into the stratosphere to increase the planetary albedo, right?

    This is ridiculous. We have two choices:

    (1) Burn lots of fossil carbon now, postponing the inevitable switch to nuclear and renewable energy for a few decades, and leaving future generations the burden of dealing with our mess (radiative forcing of climate, ocean acidification) for millennia to come;


    (2) Start transitioning to a low-carbon energy economy now, thus creating less of a mess for future generations to have to clean up.

    It seems to me that advocating (1) is the height of selfishness.

    The other, ironic point here, is that BP and others ought to think seriously about the implications of their glib suggestion that we can geoengineer our way out of the climate and ocean-chemistry impacts of our wasteful fossil fuel consumption.

    In my experience many so-called "skeptics" make a big deal about the dangers of letting a big, impersonal agency control our lives via cap-and-trade systems, carbon taxes, or whatever. But planetary geoengineering would require an international entity with the power to "adjust" the climate by whatever actions it sees fit, and with the power to impose taxes to pay for its activities.

    So "skeptics" are essentially rejecting a market-based solution (reducing CO2 emissions by cap-and-trade or carbon taxes, thus letting the market itself develop more efficient ways of generating power) in favor of a command-and-control solution (geoengineering).

    Once we start injecting sulfate into the stratosphere and grinding up carbonate rocks to dump into the ocean, we need to keep doing that effectively forever. Who's going to take responsibility for that? And who's going to decide how much aerosols to put in the stratosphere, and thus what the global temperature should be? I imagine that India and Canada might disagree about that. Are we going to take a vote?
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  48. carrot eater .................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......

    I agree, but then why do advocates of AGW theory frequently cite an atmosphere radiating back to the Earths surface using the Stephan Boltzman equation to justify their calculations?
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  49. suibhne: Those are extremely simplified cartoon illustrations, to help show people the basic concepts of the energy balance without having to write thousands of equations. Most people aren't interested in seeing the actual line-by-line radiation transfer codes, which indeed carry all the wavelength-dependent detail you are worried about, or the variation with altitude (a single-slab atmosphere is not sufficient for serious calculations).

    If you want to get into those details yourself, you can start with this interface with the MODTRAN model.

    You can see that the quantised nature of absorption and emission are very much considered. Note that this isn't a climate model, but just radiation code. In it, you fix the Earth's surface temperature and the composition of the atmosphere, and the code then figures out how radiation propagates around.
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  50. One of the problems with geoengineering is one of logic.

    In order to accurately counteract the effects of anthropogenic CO2 on the global climate and biosphere, you need accurate models of what the effects are going to be, where's going to be hit the worst, where you get the most bang for your metaphorical buck. In other words, you need models that can project effects, the very thing that most AGW skeptics (and most geoengineering proponents) say we don't have at present.

    So if the current models aren't good enough to accurately project a problem, then they're not good enough to accurately project a solution either. And if they're good enough to project the problem, then they're good enough to accurately project a solution. And in fact, the "best" solution projected thus far is not geoengineering, but rather retooling human energy consumption to not be carbon-based.
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