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Global warming question

  1. Oct 28, 2009 #1
    Is there any proof that it is the CO2 levels that cause the temperature increases, and not that increasing global temps by themselves increase CO2 levels? It seems to me that the warmer it gets the more things would grow as long as they had sufficient water, if more things are growing then more things would be dying and decaying, which would release more CO2 into the atmosphere. I have seen a few studies that said that with increases in CO2 levels plants produce more so imo the higher production would lead to more carbon being released when the produce is used or dies, so it looks to me like even the effects of CO2 on plants could be responsible for higher CO2 levels. How wrong am I?
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  3. Oct 28, 2009 #2

    Chi Meson

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    Moonbear should be taking this one, but...

    You are talking about increasing the frequency of a full cycle. Plants convert CO2 to O2 as they live, then decay back into CO2 when they die (over-simplified, of course). So increasing the rate at which they grow will increase the rate they die. This should maintain equilibrium. For the CO2 side of the equation to rise, the dying would need to be greater than the growing.

    This is what is essentially happening. Not just a reduction in rain-forest canopy, but the carbon that has been taken out of the cycle (fossil fuels) has been reintroduced.

    Another flaw: If your notion were somehow true anyway, the additional quantity of vegetation would at first create a net decrease of CO2, since there would be a lag between growing and dying. The recordings of CO2 quantities in the air are under debate, but I don't think a fall has been detected.
  4. Oct 28, 2009 #3
    Let me see if I am understanding this correctly, over their lifetime plant sequester the carbon and release the O2, then when they die they decompose and put all the carbon they captured back into the atmosphere? Do evergreen trees capture CO2 even during winter? Or do they need to be growing to capture carbon? The reason I ask is with the winters warming wouldnt things still be decaying where when winters are colder the would not decay during winter, allowing evergreens to remove more during winter without decomposition putting some CO2 back in? It seems to me if I am not to far out in left field that allowing a tree to grow and capture carbon then cutting that tree down and building a house or some other product out of it would keep all that CO2 locked up, but left to its own in nature once they died the would negate what they removed by putting it back into the atmosphere through decomposition?

    According to my reading rainforests decay at a far higher rate than coniferous forests, because of the canopy keeping most sunlight off the floor of the rainforest. Would we be better off cutting down the canopy trees and building houses or something else out of them capturing the carbon and allowing the new growth to thrive as well as reducing the decomposition rate? I have heard that new growth removes far more carbon than old growth is that true?

    I am not saying i'm right science is wrong(i am nowhere near that smart), i'm saying I dont understand how this is supposed to be working and am trying to get some help from all the intelligent people in this forum. Lately it seems that questions are not allowed as far as anthropegenic(?) climate change goes and thats what is scary to me, if the facts show what we are told they show why is it dangerous to discuss those claims? As I see it there is no danger in making false claims as long as those claims can be discussed and refuted. Its when there is no futher discussion neccesary or allowed that we will start going down the wrong road and will travel further down that road than we would of otherwise imo. Thanks Chi Meson for your help.

    Edit: I just realized my thread had been moved to a more appropiate forum, thanks.
  5. Oct 28, 2009 #4

    That's exactly the problem with scary claims, trying to fix non-problems things that can't be fixed.

    So if you argue that it's better to cut down the rain forests for whatever reason to solve CO2 issues, then you simply have no more rainforests. How would that loss relate to the fraction of a degree change in global temperature.

    You can see here in what small order of magnitude the rainforest contributes in the dynamic equilibrium of the carbon cycle


    maybe not a good idea to panick and destroy one of the most precious heritages of earth.

    I would love to see that question answered.
    Last edited: Oct 28, 2009
  6. Oct 28, 2009 #5

    Chi Meson

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    as I understand it (and not claiming to be the expert here) that is more or less the case.

    I dunno.
    you are right in center field, but I wouldn't use that as an excuse to chop down all the trees. Keep in mind that a mature tree used for lumber would take 100 years to grow. It could also take nearly that long to fully decompose if it lay by itself in the woods. If it were turned in lumber, how long would it remain a "house" ?

    I can't imagine that this would be a good thing.
    I think so, but please don't cut down the trees. I like them. I want them to stay, thank you. Why? I told you, I like them. Hemp is one of the most effective CO2 removers. That's hemp, the original cannabis, used for rope, not the modified stuff used for pot.

    right click the word for spelling suggestions
    that's not the case here is it?
    Sometimes false claims just get exhaustive, and if there is no basis for the claim, then it becomes another form of trolling and monkey wrenching. Not that I see that your questions are such.
    again, that's not the case here at PF, is it? I persojnally have the opinion that global temperature is rising. The melting polar regions and retreating glaciers on every continent are satisfying evidence of that. I also think that mankind is contributing to it. But as I have stated in the past, it's like spitting into a bucket. I personally don't believe that our contribution is principal "cause."
    Hy-o Silver! Away!
    Last edited: Oct 28, 2009
  7. Oct 28, 2009 #6
    Changes in temperature should alter CO2 levels by influencing gas solubility in water, perhaps wind patterns and ocean upwelling, changes in the biosphere, permafrost and ice extent changes, etc. It shouldn't be surprising that the carbon cycle can be perturbed if you change the underlying climatic boundary conditions.

    Changes in CO2 levels effect temperature due to radiative transfer. That simple.
  8. Oct 28, 2009 #7


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    There are two separate questions here.
    • What causes CO2 levels to rise?
    • Are rising CO2 levels the cause of increasing temperatures?

    The answer to the first is industrial CO2 emission. This is confirmed by a wealth of evidence and is not in any serious doubt.

    The answer to the second is that rising CO2 levels do indeed have a major contribution to rising temperatures, by basic physics. There are other factors contributing as well, and the complexity of the Earth's climate system is such that we only know approximately how much temperature rises in response to all these forcing factors; but carbon dioxide does stand out as the largest contributing factor for changes over recent decades.

    Here is a bit more detail on how we know this.

    The cause of the current rate of increase in atmospheric carbon

    Atmospheric carbon dioxide is currently increasing at about 1.7 to 1.8 ppm per year. Each ppm is 2.13 PetaGrams of carbon (a PetaGram is also a GigaTon), and so the increase is about 3.75 Pg/year.

    The burning of fossil fuels is currently adding about 6.5 Pg/year to the atmosphere. The effect of the carbon cycle is to redistribute the additional carbon, so that about half of what is being added goes into carbon sinks in the ocean and the land.

    There are several additional lines of evidence the help sort out how carbon is moving through the carbon cycle. As well as direct measures of carbon in the atmosphere and the ocean, two important supplementary measurements are the ratio of 12C and 13C isotopes, and the amount of oxygen in the atmosphere.

    There has been a marked fall in the ratio 13C/12C. This is because plants and fossil fuels have significantly smaller ratios, due to the preferential take up of the lighter isotope in plants. As carbon from deforestation and fossil fuels mixes into the atmosphere, the ratio falls there as well.

    Addition of carbon to the atmosphere comes with a removal of oxygen; and different processes remove different amounts of oxygen. Fossil fuel burning removes about 1.4 mol of O2 for each mol of CO2 produced; but respiration from plants removes about 1.1 mol of O2. Also, carbon dioxide is much more soluble in the ocean than oxygen. This means data from oxygen levels in the atmosphere, determined by the ratio N2/O2 can help sort out the sources and sinks of carbon.

    There has been careful study of these measurements in recent times, as scientists attempt to sort out details of the carbon cycle. There's no real question that rapidly rising atmospheric carbon levels are far and away being driven by industrial CO2 emissions; but there are open questions about where it gets distributed through the carbon cycle.

    A good reference here is
    From table 1 in the paper, on page 101, there are estimates of carbon sinks. Using the first row for most recent results by the authors, from 1993-2003, the following rates are indicated:
    • 6.48 Pg/year carbon added by fossil fuel burning.
    • 3.75 Pg/year carbon increase in the atmosphere. (1.76 ppm/year times 2.13)
    • 2.24 Pg/year carbon increase in the ocean.
    • 0.51 Pg/year carbon increase in the land.
    There are further details in the paper, and the major open question being address is how the 3.75 Pg/year that does not remain in the atmosphere is distributed between oceanic and land sinks. The first two numbers are known quite accurately. Note that the land is actually removing some of the carbon from the atmosphere. Increased plant growth works to remove atmospheric carbon, not add it.

    For your question, the bottom line is this. The amount of carbon being added into the carbon cycle from fossil fuel burning in the present is very large, and much more than the rise in atmospheric carbon. This, by far, is certainly the cause of rising atmospheric carbon levels in the present.

    The cause of rising temperature

    Carbon dioxide levels have increased dramatically over the last century and they continue to increase now. It is a straightforward consequence of basic thermodynamics that this leads to an increased greenhouse effect, with a "forcing" of increased energy supplied to the Earth's surface. There are other many other forcings that also play a part in Earth's energy balance, both positive and negative, but in the present epoch carbon dioxide stands out as the largest single forcing at work.

    There is a thread for explaining more of the background physics on this, with plenty of references, at [thread=307685]Estimating the impact of CO2 on global mean temperature[/thread].

    What is uncertain

    There are, of course, lots of open questions and uncertainties in this whole topic.

    It's quite definite that CO2 levels in the atmosphere are rising rapidly, and that this is caused by industrial emissions.

    There are significant open questions about how the extra carbon being added gets redistributed through the carbon cycle; and in particular how much is ending up in the ocean and how much in terrestrial carbon sinks.

    It's quite definite that increased CO2 levels in the atmosphere give a significant forcing to drive increased temperatures; and indeed the forcing involved is known quite accurately.

    There are significant open questions about other less well understood forcings that are at work; but it is highly unlikely that there is any unknown forcing of a comparable magnitude to the greenhouse forcing which has escaped everyone's notice.

    As well as this, there are very significant open questions about the response of the Earth to forcings. The amount of temperature increase for a forcing is a consequence of climate sensitivity, which is known only approximately.

    Felicitations -- sylas
    Last edited: Oct 29, 2009
  9. Oct 28, 2009 #8
    I never argued anything of the sort. I do however think it would be possible and could be benificial to thin out the forests by removing some old growth as well as under growth allowing the younger trees and plants to thrive. I am not a fan of clear cutting in any way whatsoever.

    Looking at the numbers on your illistration I was surprised to see the bigger numbers accorded to soil, where does the CO2 in the soil come from? Is it transfered from the plants through the roots or does the dirt absorb CO2 on its own? I am just asking questions I am not trying to pull an aristotle by getting the forum to reexamine their beliefs by asking questions.

    Never said it, never implied it.
  10. Oct 28, 2009 #9
    Mainly it comes from dead plants.

    If you want to know more here is a good place to start.

    http://ohioline.osu.edu/aex-fact/pdf/0510.pdf [Broken]
    Last edited by a moderator: May 4, 2017
  11. Oct 28, 2009 #10
    I am not looking for an excuse to chop down trees(i like trees), I am trying to understand how the whole process works so that I can either agree with AGCC or have a better idea of why I dont. So far I am leaning towards conservation over enviromentalism, I am wondering if it might be more productive and successful to manage the forests better instead of just making laws to "protect the forests" by keeping humans out.

    Like I said before I am not looking to clearcut all the forests to keep them from releasing their carbon just trying to understand the mechanisms of nature. I never realized hemp was that effective of a CO2 remover, i'm all for using hemp for ropes instead of nylon or plastic as I understand it hemp also makes durable clothing. Isnt hemp a short lived(not much time to absorb CO2) or can it grow for years and years?

    It is most definitely not the case here at PF, if it was I sure wouldnt waste my time even asking I feel this site is one of the jewels of the internet. I wasnt trying to indict the forum with my remarks, I was speaking more to the national government and the media, I guess I should know by now I have to be very precise when making remarks or asking questions around here.
    I am not arguing that the earth isnt warming I most definitely understand that it is, i'm just wondering how much were to blame if any and trying to see if some other remedy makes more sense to me than taxing CO2(not eliminating it just taxing it). There is so much I dont know I am just trying to reduce that number a little.
  12. Oct 29, 2009 #11
    what type of vegetation uses up the most co2?
  13. Oct 29, 2009 #12
    Most by what metric?

    Fastest growing, most efficient, or long term sequesters.

    Bamboo is considered to be one of the best absorbers of CO2 since it grows fast and doesn't decay rapidly after it dies. Algae also grows fast, but it decays rapidly.
  14. Oct 29, 2009 #13


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    I believe he meant harvest the tree, build the house, and grow another tree in place, which apparently can http://weyerhaeuser.com/Businesses/WoodProducts/BuildWithWood" [Broken]
    More like http://weyerhaeuser.com/pdfs/businesses/sustainableforestry/rgb.pdf" [Broken] in the Southern US, with thinning as early as 12 years, for managed softwood forests used in the majority of construction, longer in the NW and Canada.
    Last edited by a moderator: May 4, 2017
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