Comments 1 to 11:

1. witsendnj at 21:24 PM on 9 May, 2011
   This graph begs the question - What happens when the trees and perennial vegetation die off? Wait - why would they? Well, aside from deforestation, droughts, disruption of the nitrogen cycle, and wildfires, they are being slowly poisoned by air pollution. It's well established science that at current ambient levels of background tropospheric ozone, annual crops yields experience stunted growth in the range of 10 - 20%. The quality and viability of seeds and nuts is also impaired. (See this research: http://feeds.bignewsnetwork.com/index.php?sid=368143) As background levels continue to rise, it is expected that a concurrent increase in damage will result. With a burgeoning population and other adverse extreme weather impacting crops, we could see widespread famine soon. Aside from annual crops it seems reasonable to wonder what effect ozone has on longer-lived species like trees and shrubs, which are exposed to high summer levels season after season. And yet very few people do wonder, because since many species of trees can live for centuries, and can become so large, and because there is no control atmosphere for comparison with ambient levels of ozone, there is no funding and almost no research into the impact on mature trees, and in general, which leads to a sense of resignation and total apathy about their fate in a world where they, in essence, cannot breathe or photosynthesize. I expect that when we run out of oranges, avocados, peaches, cherries, apples, pecans, walnuts and maple syrup, not to mention lumber and paper, perhaps then people might notice that our trees are suffocating in a poisonous brew of toxic volatile organic compounds and stop blaming opportunistic insects, disease and fungus. And then maybe some enterprising scientist will get funding to study exactly what difference the mandated addition of ethanol and the resulting acetaldehydes and peroxyacetyl nitrates mean for emissions, because all indications are that the longer-lasting resultant ozone isn't being accounted for in models currently in use. I hope that happens before we run out of oxygen.
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2. WSteven at 21:42 PM on 9 May, 2011

   This graph begs the question - What happens when the trees and perennial vegetation die off?

   I don't think it does, the graphic is specifically about the respiration carbon cycle. Ozone pollution would be a separate topic.
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3. WSteven at 21:48 PM on 9 May, 2011
   (Oops, hit the submit button too early) On the other hand, surface O₃ and other pollutants will still need to be dealt even if we do successfully limit our CO2 productions @John Cook The graphic looks good. You're not finished making the graphics for this important rebuttal I take it?
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4. seeohtoo at 00:54 AM on 10 May, 2011
   The graphic leaves out an important part of the carbon cycle: plant cellular respiration. Plants burn the sugar they make for their own energy needs, returning part of the photosynthetically-fixed carbon to the atmosphere as CO2.
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5. r.pauli at 01:40 AM on 10 May, 2011
   Why is a big cow in the center? Is it that important?
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6. DSL at 01:45 AM on 10 May, 2011
   COW - CO2 = W2. In the U.S., a W2 is a tax statement. Therefore, the hidden message in the cow is that we need a carbon tax.
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7. F. Murdoch at 04:13 AM on 10 May, 2011
   @4 seeohtoo I think that would unnecessarily complicate a simple graphic which drives the concept home with little more than a glance. Best just to think of the arrows as net contribution.
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8. Paul D at 04:26 AM on 10 May, 2011
   rpauli@5 The cow is I assume a food source, a carbon/energy input for humans. One could also say it is third hand solar energy, after the tree (second hand).
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9. Bibliovermis at 06:20 AM on 10 May, 2011
   rpauli (#5), The graphic neatly displays my standard response to any breath-related dismissal, e.g. "You breathe out CO2, stop breathing if you want to do something about CO2 emissions." All exhaled carbon recently came from the atmosphere. Plants absorbed it from the atmosphere and were then eaten. If you don't eat plants, you eat animals that ate the plants.
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10. cwatts at 09:49 AM on 10 May, 2011
    This isn't a bad graphic, but it might well be misinterpreted by some members of the farming community. There are a number of myths that seem to be quite peculiar to agriculture—or at least Australian agriculture, with which I'm most familiar. These include that methane levels have stabilized while livestock numbers have continued to rise and hence there is no connexion between the two. Or, that because methane is short-lived it isn't a problem (this one actually renders methane a priority for mitigation efforts). Another is founded on a fundamental misunderstanding of chemistry and physics: 'My cow is made of carbon and simply recycles the carbon dioxide it breathes out.' That this 'argument' completely misses key facts about enteric fermentation and methane is beside the point; it's out there, in the community, and being spouted by the leaders of peak farming lobby groups. The graphic might reinforce these myths, particularly the last one.
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11. sailrick at 12:02 PM on 22 May, 2011
    Shouldn't the graphic include water as part of the active carbon cycle?
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