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More Carbon Dioxide is not necessarily good for plants.

Posted on 18 April 2011 by villabolo

An argument, made by those who deny man made Global Warming, is that the Carbon Dioxide that is being released by the burning of fossil fuels is actually good for the environment. Their argument is based on the logic that, if plants need CO2 for their growth, then more of it should be better. We should expect our crops to become more abundant and our flowers to grow taller and bloom brighter.

However, this "more is better" philosophy is not the way things work in the real world. There is an older, wiser saying that goes, "Too much of a good thing can be a bad thing." For example, if a doctor tells you to take one pill of a certain medicine, taking four is not likely to heal you four times faster or make you four times better. It's more likely to make you sick.

It is possible to help increase the growth of some plants with extra CO2, under controlled conditions, inside of greenhouses. It is based on this that 'skeptics' make their claims. However, such claims are simplistic. They fail to take into account that once you increase one substance that plants need, you automatically increase their requirements for other substances. It also fails to take into account that a warmer earth will have an increase in deserts and other arid lands which would reduce the area available for crops. 

Plants cannot live on CO2 alone. They get their bulk from more solid substances like water and organic matter. This organic matter comes from decomposing plants and animals or from man made fertilizers. It is a simple task to increase water and fertilizer and protect against insects in an enclosed greenhouse but what about doing it in the open air, throughout the entire Earth?

What would be the effects of an increase of CO2 on agriculture and plant growth in general? The following points make it clear.

1. CO2 enhanced plants will need extra water both to maintain their larger growth as well as to compensate for greater moisture evaporation as the heat increases. Where will it come from? Rainwater is not sufficient for current agriculture and the aquifers they rely on are running dry throughout the Earth (1, 2).

On the other hand, as predicted by Global Warming, we are receiving intense storms with increased rain throughout of the world. One would think that this should be good for agriculture. Unfortunately, when rain falls down very quickly, it does not have time to soak into the ground. Instead, it builds up above the soil then floods causing damage to the crops. The water also floods into creeks, then rivers, and finally out into the ocean carrying off large amounts of soil and fertilizer.

2. Unlike Nature, our way of agriculture does not self fertilize by recycling all dead plants, animals and their waste. Instead we have to be constantly producing artificial fertilizers from natural gas which will eventually start running out. By increasing the need for such fertilizer you will shorten the supply of natural gas creating competition between the heating of our homes and the growing of our food. This will drive the prices of both up.

3. Too high a concentration of CO2 causes a reduction of photosynthesis in certain of plants. There is also evidence from the past of major damage to a wide variety of plants species from a sudden rise in CO2 (See illustrations below). Higher concentrations of CO2 also reduce the nutritional quality of some staples, such as wheat.

4. The worse problem, by far, is that increasing CO2 will increase temperatures throughout the Earth. This will make deserts and other types of dry land grow. While deserts increase in size, other eco-zones, whether tropical, forest or grassland will try to migrate towards the poles. However, soil conditions will not necessarily favor their growth even at optimum temperatures.

5. When plants do benefit from increased Carbon Dioxide, it is only in enclosed areas, strictly isolated from insects. However, when the growth of Soybeans is boosted out in the open, it creates major changes in its chemistry that makes it more vulnerable to insects, as the illustration below shows.

Figure 1: Plant defenses go down as carbon dioxide levels go up, the researchers found. Soybeans grown at elevated CO2 levels attract many more adult Japanese beetles than plants grown at current atmospheric carbon dioxide levels. Science Daily; March 25, 2008. (Credit: Photo courtesy of Evan Delucia)

Figure 2: More than 55 million years ago, the Earth experienced a rapid jump in global Carbon Dioxide levels that raised temperatures across the planet. Now, researchers studying plants from that time have found that the rising temperatures may have boosted the foraging of insects. As modern temperatures continue to rise, the researchers believe the planet could see increasing crop damage and forest devastation. Science Daily; Feb. 15, 2008.

Figure 3: Global Warming reduces plant productivity. As Carbon Dioxide increases, vegetation in Northern Latitudes also increases. However, this does not compensate for decreases of vegetation in Southern Latitudes. The overall amount of vegetation worldwide declines 

In conclusion, it would be reckless to keep adding CO2 to the atmosphere. Assuming there are any positive impacts on agriculture in the short term, they will be overwhelmed by the negative impacts of climate change.

It will simply increase the size of deserts and decrease the amount of arable land. It will also increase the requirements for water and soil fertility as well as plant damage from insects.

Increasing CO2 levels would only be beneficial inside of highly controlled, enclosed spaces like greenhouses.

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Comments 101 to 150 out of 228:

  1. 97 - Berényi Péter

    "It means the curve up to the point where I've clipped it can be checked using actual data, beyond that it is pure fantasy."

    It would, of course, be important to see the source research behind the graph... but I doubt that the lines up to 'now' are composed of data sets which have been gathered between 1860 and now, from the whole world... How was the graph composed?

    You know, Science is about understanding the evidence presented, not making unverifiable claims about the meaning of the bit of a graph that happens to take your fancy.
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  2. "maybe the defenses of the particular species they studied are weakened by more CO2 - but they don't give the final result on the total yield (do the damages made by beetles offset the increased yield or not ?)"

    Gilles, that's because its only an article *about* the study, not the full study itself. I doubt the study would have gotten published *unless* they included full results &-judging from what they say in the article-the results don't tell a great story for the yield effects of beetle infestations on soybean plants grown in enriched CO2 conditions. Also, consider the increased cost of pest management, given the increased life-cycle & breeding times of beetles under enriched CO2 conditions-costs which will definitely be passed onto consumers. Seriously, your ability to ignore data that doesn't fit your agenda is quite astounding.
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  3. Let's see some real science.

    Journal of Experimental Botany (2009) 60 (10): 2859-2876.
    doi: 10.1093/jxb/erp096
    First published online: April 28, 2009
    Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE
    Andrew D. B. Leakey, Elizabeth A. Ainsworth, Carl J. Bernacchi, Alistair Rogers, Stephen P. Long & Donald R. Ort

    Lessons:
    1. carbon uptake is enhanced by elevated [CO2] despite acclimation of photosynthetic capacity
    2. photosynthetic nitrogen use efficiency increases at elevated [CO2]
    3. water use at both leaf and canopy scales declines at elevated [CO2]
    4. dark respiration is significantly stimulated in soybean leaves grown under elevated [CO2]
    5. stimulation of carbon uptake by elevated [CO2] in C4 plants is indirect and occurs only in situations of drought
    6. the [CO2] ‘fertilization’ effect in FACE studies on crop plants is less than expected

    The upshot is there is considerable general improvement due to elevated carbon dioxide levels, even if it is a bit less than in a fully controlled environment.

    Increased carbon uptake (biomass production), more efficient nitrogen & water use and enhanced drought resistance (even in C4 plants!) are particularly important factors.
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  4. I love the medication analogy in the article. It is a simple example that most people will easily understand and from there see the obvious fallacy of the 'more CO2 is always good' argument.

    As to the impact on plants specifically... it is well known (unless one is an evolution denialist also) that all lifeforms evolve to best survive within the environment around them. The longer a particular element of that environment is relatively stable the more time lifeforms will have to evolve to adapt to it.

    Atmospheric CO2 levels had been constrained to a range between about 180 and 280 ppm for millions of years. Every plant on the planet has therefor been evolving towards the ability to best survive within that CO2 range for millions of years. There is no way that they will all now be able to adapt to radically different CO2 levels within a matter of decades. Some will retain characteristics from higher CO2 periods in the past which will allow them to cope, but others will not.

    Thus, even without considering global warming's impact on water resources, pests, and other things which will impact plants... the changing atmospheric CO2 level alone will alter (likely already is altering) the growth patterns of plants all over the world.

    Another analogy: Humans require oxygen to live. However, we have evolved to process oxygen at the levels currently found in the atmosphere. If the partial pressure of atmospheric oxygen increased to four times current, oxygen toxicity would kill every human being on the planet (unless they were in some sort of environmentally controlled space).

    Given enough time, plants (or humans) could evolve to adapt to radically different levels of essential 'life giving' gases in the Earth's atmosphere. However, we are causing these changes on a scale measured in decades while those kinds of evolutionary changes would require millennia.
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  5. Until these FACE trials are able to mimic *all* the conditions expected to exist in an enriched CO2 world (including more extreme hydrological cycles & increased temperatures), then there is only so much relevant information that can be gleaned from them. What can be gleaned is that, even in ideal conditions, its unlikely that the rather modest long-term biomass increases seen so far will be sufficient to offset losses due to all the other detrimental impacts of global warming. Also, the results of FACE trials-even under ideal conditions-as regards disease & pest infestations, not to mention nutritional value, don't exactly paint a very pretty picture for our future.
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  6. JMurphy at 18:36 PM on 18 April, 2011

    Re PETM

    BTW, I find the PETM a fine example to contrast natural variance of temps and CO2 with the present anthropic one.

    There we had a ~5ºC variation in 10 to 20 thousand years, and that was a specially wild and fast variation in Earth's climate, specially if we consider we were not coming out of an Ice Age. It affected so much Earth's ecology that it caused a lot of species to shift in occurrence, adapt or be extinct.

    Now we're doing it over one order of magnitude faster: 5~6 degrees in one or two centuries (maybe more, if you consider the 200 year span). Species are not free to roam through the continents, as most ecosystems are fragmented by human occupation, even if species could move this fast.

    And we see people trying to argue how will this be benign to the planet, or that the variance is natural.
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  7. Anyone else get the feeling we are just wasting our time answering this kind of stuff? That the responses can keep getting produced, over and over, and back will come the same old nonsense, over and over. Time really is up for all this. Ten years ago we argued because we thought there was a chance of bringing facts to bear, changing minds, influencing people. The last ten years have shown that there are a core of people who will never stop resisting in order to prevent any political and economic action. And feeding off them are the politicians like Abbott, telling people they can be better off because he won't "tax" them to save the planet, fools like Howes demanding no change at all to the present economic structure, and the big corporations demanding the same. All just a game, as if we can decide not to respond to greenhouse gases and then everything will be alright.

    I am tired of that game.
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  8. David Horton at 22:24 PM on 18 April, 2011

    I'm with you.
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  9. Got to be said, that FACE stuff is interesting.

    The plots look log (asymptotic) or, at best, log-linear; not exponential (that's the 'up shot') and compatible with point 6. of the blog post.

    As has been mentioned, one can expect some improvement when one or another resource becomes more abundant, allowing other resources which are already abundant to be utilized and that will self-limit... in system like that, you'd expect an asymptotic improvement in the absence of any negative influences (increase in premeditation etc.)

    Good data.
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  10. 107 David Horton "Time really is up for all this"

    Maybe we need a new form of refereeingmoderation?

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  11. David Horton wrote: "Anyone else get the feeling we are just wasting our time answering this kind of stuff?"

    I try to keep mental note of the people who have proven themselves completely beyond reason and ignore them.

    Granted, that leaves whatever nonsense they post 'un-rebutted', but any such can always be addressed later should anyone suggest that it could have validity. Besides, if the thread remains short then the moderators usually have sufficient time to put in links to existing posts which give reality based evidence.
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  12. CBDunkerson

    Atmospheric CO2 levels had been constrained to a range between about 180 and 280 ppm for millions of years. Every plant on the planet has therefore been evolving towards the ability to best survive within that CO2 range for millions of years.

    < a href =http://meetingorganizer.copernicus.org/EGU2011/EGU2011-10649.pdf>Long-term effect of elevated CO2 concentration on temperature optimum of photosynthetic CO2 assimilation in two tree species, Holisova et al., 2011.:

    “The eight-year-old trees were grown in glass domes at the experimental research site Bílý Kˇríž in the Beskydy Mts. and they were exposed for three growing season to ambient (AC; 380 _mol(CO2) mol-1) and elevated CO2 concentrations (EC; 700 _mol(CO2) mol-1).”
    “Our data thus support the initial hypothesis that long-term growth of plants under elevated CO2 concentration leads to the acclimation of photosynthesis and other related processes to higher temperature.”

    Cited above species of trees live unchanged for millions of years - probably the "something" they need „the acclimation of photosynthesis” do „700 _mol(CO2) mol-1” ...

    Optimum photosynthesis for most species of C3 plants is 400-600 ppmv CO2. It is higher at higher temperatures .
    C4 formed as a response to unusually low levels of CO2 (<350 ppmv CO2). At 180 ppmv CO2 - some C3 species stop growing - less than 150 ppmv CO2 - the most die back (knowledge of "textbook").
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  13. les at 22:58 PM on 18 April, 2011

    That's a great system :-)
    Specially in these days of Science As A Contact Sport.
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  14. I give up on this post. There is so much non-science splattered around the comments and that includes the original posting.The whole thing is a scattergun target. How about a reality based and referenced article/post on actual science for a change?

    [personal attack snipped]
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    Moderator Response: [Dikran Marsupial] Please read the comments policy and keep constructive criticism impersonal.
  15. @100 LukeW:

    ""And you want those La Ninas to get stronger?" YES PLEASE !!
    Would make us billions ! (with some collateral damage too but life wasn't meant to be easy)

    You would like another 20 year drought cycle instead ...?"


    I can see you're not Australian (Please tell me that your not). "Collateral damage"? Is this the military?

    Do you seriously think what they went through is worth a bumper crop of wheat; assuming it doesn't get ruined? Perhaps a cold blooded cost analysis is in order? How much lost in damage to homes and infrastructure versus how much gained by, what, a 10 or 20% increase in yield?

    Having mentioned billions of dollars to be made, please tell me how many billions will be lost?

    I believe I said it before; any hypothetical benefits to agricultural growth will be more than diminished by property and infrastructure damage; not to mention lives lost.

    Who gets to be the "winners and losers" in this scenario? Those who eat versus those who drown?

    If one were to play God then the wish would be for moderate La Ninas. But that's not what's going to happen.

    As for contrasting that with 20 year drought cycles, I really see that as a difference without a distinction. It's like having this choice:


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  16. BP said..."It means the curve up to the point where I've clipped it can be checked using actual data, beyond that it is pure fantasy."

    You can claim that if you like but you need justification for making such a claim. By any standard you very definitely don't clip the way you did without noting that you've done so and explaining why you did it. I'm surprised that you're defending what you did instead of apologizing.

    Quite honestly, I'm going to have a very hard time taking anything you say seriously from here out.
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  17. @104 CBDunkerson:

    "As to the impact on plants specifically... it is well known (unless one is an evolution denialist also) that all lifeforms evolve to best survive within the environment around them. The longer a particular element of that environment is relatively stable the more time lifeforms will have to evolve to adapt to it.

    Atmospheric CO2 levels had been constrained to a range between about 180 and 280 ppm for millions of years. Every plant on the planet has therefor been evolving towards the ability to best survive within that CO2 range for millions of years. There is no way that they will all now be able to adapt to radically different CO2 levels within a matter of decades. Some will retain characteristics from higher CO2 periods in the past which will allow them to cope, but others will not."


    Excellent point. I was worried that a quick and easy "Skeptic" response would be to say something like; "In the good old Dinosaur days, plants did just fine with elevated CO2".

    The quick and easy rebuttal would be to say that plants had tens of thousands of years with which to evolve adaptations. Then one could bring up the Paleocene-Eocene Thermal maximum took 20,000 years to develop and yet major catastrophes ensued.

    As for the oxygen analogy, it would be better to revise it for basic level readers. Something like; "If the percentage of oxygen were to double, it would allow for massive fires. Even wet forests would burn."
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  18. David Horton @ 107... Yes, it's worth going through this over and over and over (IMHO). I always say this: It's not about changing anyone's mind who is posting here. We will never change Gilles, BP, or any other of the minds that are already made up. But in responding to their claims and debating their positions we have the opportunity to change the minds of others who come to SkS to read about this issue.

    Think of it as a public debate with a large audience. When you post here you are up on the stage making a point. You don't need to convince the person at the other podium whom you're responding to. You need to convince the audience.

    I would contend that the audience is always changing too. Even though we might have the same discussions here repeatedly with the cast of characters, there are more and more people reading SkS all the time. New minds ready to learn more about climate science.

    One of the great things about this site is the heavy moderation. When I go read WUWT it's more like you walked into a clubhouse where everyone thinks alike and is slapping each other on the back, and attacking anyone who doesn't think like they do. Here at SkS there is a more hearty, genuine debate.
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  19. Rob Honeycutt@116 For me the issue is that BP was using a graphic from a source that contradicts his position without mentioning that fact. It is a bit like taking a quote from a paper out of context to support an argument, where the paper as a whole supported an opposing position. Using a graphic or a quote from a report implicitly suggests that the report provides some support for your position.

    Somehow I don't think it would have passed without comment if say James Hansen had used a cropped picture from a climate skeptic report that was cropped in such a way as to ignore the central message of the report.
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  20. I would like to highlight a couple of things for readers,

    Arkadiusz made a post @83, trying to convince us that higher temperature will not be bad for the tropical forests. Two readers who took the trouble to dig a little deeper into the paper find that the results are not relevant to the current and future situation-- 200 years versus 10 000-20 000 time span. Now what does the skeptic do? Does he acknowledge this and cede the point? No, he ignores the critique and simply posts another paper @92.

    And nice try BP @97, but please do not insult our intelligence. You have been told repeatedly that this is not so much about where we have been or are but where we are headed if we continue under BAU. Your fraudulent graph was misleading and ignored the fact that its assessment agrees with the topic of the post-- moderate CO2 increases (and warming) favour an increase in biomass, but if CO2 goes way up, then vegetation does not fare well. Too much of a a good thing may very well be a bad thing. Try consuming a cup or two of salt to find out.


    Luke @100,

    Yes, you were speculating, thanks for confirming. I do not need links on how ENSO and IPO affect rainfall thanks, that is not what is at issue here so much as you claiming that we are headed for a period of more frequent La Ninas. That may or may not be true, but unless backed up by some science, it remans simple speculation. With that said, you seem to be basing your projection on the work of Verdon and Franks (2006).

    At least one of the papers that you cited has not helped you case:

    "Although there appears to be no overall trend toward wetter or drier conditions [over Queensland], the reconstructions suggest that the variability of rainfall and river flow has increased during the twentieth century with more very wet and very dry extremes than in earlier centuries, as projected for the region as a consequence of global warming."

    An increase of rainfall variability is not conducive for better crop growing conditions. And their work validates the IPCC projections.

    And I should have not have to point this out, but flooding (as was associated with this past La Nina) is clearly not conducive for agriculture either. Too much water is also a bad thing for crops and and other vegetation.
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  21. DM @ 119... Totally agreed. You might say that BP "Moncked it up."
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  22. @107 David Horton:

    "I am tired of that game."

    We need to play another game.
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  23. @111 CBDunkerson:

    David Horton wrote: "Anyone else get the feeling we are just wasting our time answering this kind of stuff?"

    I try to keep mental note of the people who have proven themselves completely beyond reason and ignore them.

    Granted, that leaves whatever nonsense they post 'un-rebutted', but any such can always be addressed later should anyone suggest that it could have validity.


    In echoing that sentiment let me emphasize that we have to address ourselves to the general public with the idea in mind that a "Skeptic' will be looking over their shoulders and spouting off his nonsense.

    That means that we don't really need to emphasize technical arguments/rebuttals but instead simplify the issues in order to "innoculate" the public.
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  24. BP @103,

    "Let's see some real science."

    What a truly bizarre statement to make, especially after what you have done earlier on this thread. And since when is "your" science "real" science?

    I'll give the paper a read......good gracious I did not even have to get past the abstract. BP, please tell us why you chose to leave out this lesson from your list (which was so important that they included it in the abstract)?

    "Finally, the stimulation of yield by elevated CO2 in crop species is much smaller than expected."

    Oh and this, from the same paper:
    "Most important though will be understanding why our major food crops fail to achieve the improved production under elevated [CO2] that can be achieved in protected environments and by some non-crop species."

    There is some hope though:
    "Overcoming this could deliver a 10–15% increase in crop yields by 2050, an increase that could be critical with an anticipated 3 billion increase in global population coupled with climatic change adverse to crop production. "

    Yet from their final paragraph:
    "Overwhelmingly, this has shown that data from laboratory and chamber experiments systematically overestimate the yields of the major food crops, yet may underestimate the biomass production of trees."

    The authors clearly fail to see the hearty optimism of the 'skeptics'.
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  25. Well, according to the 'skeptics', because we have increased CO2 by 40% above pre-industrial levels drought should no longer be much of an issue at all. But this is what is really happening on the ground during extreme drought:



    [Source]

    "Analyses of rainfall across 5.3 million square kilometres of Amazonia during the 2010 dry season, published tomorrow in Science, shows that the drought was more widespread and severe than in 2005. The UK-Brazilian team also calculate that the carbon impact of the 2010 drought may eventually exceed the 5 billion tonnes of CO2 released following the 2005 event, as severe droughts kill rainforest trees. For context, the United States emitted 5.4 billion tonnes of CO2 from fossil fuel use in 2009."

    Talk about a positive feedback! And more "cheering" news:

    "The authors suggest that if extreme droughts like these become more frequent, the days of the Amazon rainforest acting as a natural buffer to man-made carbon emissions may be numbered."

    A PDF of Xu et al. (2011) can be found here.
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  26. Albatross#125: "Talk about a positive feedback!"

    Here's another: Texas Co-ops Threatened by Wildfires.

    In an interesting ironic twist, the governor who wants to do away with environmental protection and has threatened to secede now is crying for federal protection: A Major Disaster Declaration makes the state eligible for response and recovery assistance from the federal government.
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  27. BP: "a bit less"
    Author: "much lower"

    Good idea to look at that paper, indeed.
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  28. I think it needs to be pointed out that the paper Berényi Péter at 21:23 PM was commenting on, Journal of Experimental Botany (2009) 60 (10): 2859-2876.
    doi: 10.1093/jxb/erp096 is one of the papers Chris S at 19:54 PM recommended as a must-read paper about the FACE experiments, Journal of Experimental Botany http://jxb.oxfordjournals.org/content/early/2009/04/28/jxb.erp096.full

    Apparently apart from myself and BP few others have bothered to read any of those recommended, otherwise they would know that the points made by BP were taken directly from the paper referred to including point 6, which he specifically commented on.

    Point 6 also confirms a point I made earlier, as well as often previously, about how FACE trials are the only means by which modeling based on laboratory enclosure experiments are able to be assessed for the first time in real world open air field conditions.
    It seems that in most cases, as already elaborated on, the modeling generally fails to predict the actual outcomes, and thus, before they, the models, can be relied on to provide any useful predictions as to what might happen under future real world conditions, they need to be able to first accurately predict the outcomes of FACE trials.
    Indeed, this is one of the main purposes of the FACE trials, but many casual observers seem ignorant of this aspect.

    I think this should also be kept in mind whenever modeled projections are discussed, until they are confirmed by observations in the real world, they are at best only theories based on opinions.

    Overall the paper supports arguments generally made by many sceptics, but it first needs to be read throughly by those capable of absorbing and understanding the contents, or at least holding some small knowledge of the subject under discussion, but therein lies the problem.
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  29. 125, Albatross,

    So according to BP, one study growing two species of trees in glass domes shows that trees are going to love the new CO2 age.

    On the other hand, a huge swath of the Amazon is dying right before our eyes.

    Gee. I wonder what I should believe.
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    Moderator Response: (DB) Perhaps wise investors should place their money in glass dome manufacturing plants.
  30. johnd - I completely agree, it's well worth reading the literature.

    Reading this particular paper, I was struck by statements such as:

    "A comparison of wheat yields from five different crop models with FACE results showed that the mean response ratio to elevated [CO2] was overestimated by more than a factor of two in the model projections .... Thus model parameterization and validation with summary data from FACE and non-FACE studies show that the quantitative differences in how crops respond to CO2 in the field compared to in chambers has important consequences for global food supply projections. Equally FACE has revealed factors operating in the open field situation that were not or cannot be identified by chamber experiments, for example, increased herbivory and performance of herbivore populations .... Most important though will be understanding why our major food crops fail to achieve the improved production under elevated [CO2] that can be achieved in protected environments and by some non-crop species."

    Emphasis added, references (in original) snipped for space issues and because I didn't want to copy their bibliography.

    FACE experiments are very useful - sadly, what they are revealing is that the skeptical predictions of greatly increased crop yields do not hold up under real conditions of CO2 increase, let alone accompanying heat stress and hydrology changes that will be factors as well.
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  31. JohnD @128,

    Yes, BP did grab those section titles from the paper-- but he did not provide full context and did not draw people's attention to the other key (negative) findings made by the authors. It is unfortunate that that BP and now you intent on not being true to the primary conclusions of the paper. They are optimistic only if they can figure out why the plants are not responding favourably to elevated CO2 levels-- maybe b/c they have not had time to adapt to those levels to take advantage...who knows...they don't seem to know.

    I could be wrong, but I think that you would be hard pressed o find a lead author on the paper who thinks that continuing wit BAU is acceptable in view of the evidence.

    Again, not all the lessons point to a negative outcome (that is also stated in the IPCC), at least when viewed individually, but this paragraph from the paper under discussion should be cause for concern for those who are prudent and risk averse:

    "More broadly, the stimulation of seed yield in response to growth in elevated [CO2] is ∼50% lower in FACE experiments than in enclosure studies for the world's four most important crops (Long et al., 2006; Ainsworth, 2008; Ainsworth et al., 2008a)."

    Now let us look at some of Dr. Leakey's earlier work:

    SP Long, EA Ainsworth, ADB Leakey, J Nosberger & DR Ort (2006) Food for thought: Lower than expected crop yield stimulation with rising carbon dioxide concentrations. Science 312:1918-1921

    ADB Leakey, M Uribelarrea, EA Ainsworth, SL Naidu, A Rogers, DR Ort & SP Long (2006) Photosynthesis, productivity and yield of Zea mays are not affected by open-air elevation of CO2 concentration in the absence of drought. Plant Physiology 140:779-790

    Again, the prudent path here is to prepare for the worst rathe than wishful thinking that we can overcome the problems identified in the FACE experiments. And that means reducing GHG emissions.

    Sorry, but BP has scored quite the own goal, and your post is not helping him.

    It is not clear to me that the FACE experiments considered heat stress. I found no specific reference to the impact of heat stress in the body text.
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  32. KR at 04:09 AM, the FACE experiments are useful in that they identify which modeling based on laboratory enclosure experiments is wrong or totally useless, something that needs to be kept in mind for all modeling perhaps.
    As always it is what happens and observed in the real world that counts.
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  33. Increased carbon dioxide in the air actually decreases the amount of water needed by plants, because most water lost by plants is lost by transpiration. When plants can access carbon dioxide more efficiently, they "breathe" less and emit less water vapor.

    In response to the questioning of the "clipped" chart -- obviously the author cut it off where he did because everything past that point was a projection, not a measurement. Proponents of global warming are learning that projections can't be trusted.
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  34. Volunteer#133: "projections can't be trusted."

    They sure can't; things are worse than they were projected to be. See the new thread Do the observations match the models?
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  35. Wow, some people are just not reading this thread and literature being cited properly (Volunteer I am looking at you).

    The doctored figure. Can you imagine the fuss the "skeptics" would make if say, the decline was removed from a certain dendrochronology. Oh wait, we have been there, and they are still screaming about that one even though in that case they were valid reasons for ding so. But I digress, BP was hiding the decline. Someone ought to tell the self-procliamed auditors at a certain blog ;)
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  36. johnd - I agree, "As always it is what happens and observed in the real world that counts."

    Why is it, then, that you continue to push the idea of greatly increased crop yields with CO2 increases, when FACE trials indicate that those optimistic projections are not correct?
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  37. @125 Albatross:

    Thank you, Albatross. It would be nice if this thread changed topic to other aspects of my post like the one you mentioned.

    I can see that posters here are beginning to repeat issues that have already been answered in detail. One good example is #133.
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  38. #133 Volunteer:

    "Increased carbon dioxide in the air actually decreases the amount of water needed by plants, because most water lost by plants is lost by transpiration. When plants can access carbon dioxide more efficiently, they "breathe" less and emit less water vapor."

    I and others have already responded to that issue. If you do not believe that are responses are accurate, by all means, tell us why. To return to the original statement, however, is to communicate with the rest of us as if we never responded. Please pick up your discussion of the issue from where it was last left. There is no need to reinvent the wheel.

    "In response to the questioning of the "clipped" chart -- obviously the author cut it off where he did because everything past that point was a projection, not a measurement. Proponents of global warming are learning that projections can't be trusted."

    Volunteer; it is totally irrelevant that BP cut out a section that he believed did not apply to his point. That is grossly unprofessional.

    If he does not believe in its relevancy or accuracy, the proper thing to do is to post the entire image and then to explain why he believes that particular portion of it is not relevant.

    To do as he did is to represent the evidence in a way that the originator of the did not intend. It also causes those who look at the chart to have faith in the assumption that nothing has been taken out of context; intentionally or not.

    Finally, your quote marks on the word clipped is disingenuous.
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  39. KR at 04:35 AM, you obviously missed the results of the FACE trials I referred to in johnd at 19:31 PM on 18 April, 2011.

    The science isn't settled just yet, plant genetics is moving at a fast pace.
    The irony is that some red necked croppers involved in commercial seed trials is going to know where the science is at years before you get to read about it in some peer reviewed study available free online.
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  40. 128 Johnd
    "modeled projections are... at best only theories based on opinions."

    No. Some are based on well understood models and data while other are not so good. BPs assertion that the famous clipped diagram shows an exponential rise was clearly a theory based on opinion which the data in the FACT paper didn't uphold.

    Personally, I think he did a great job of correcting himself and supporting the blog post.
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  41. Albatross - be careful interpreting the increased variability. Land clearing in reef catchments has increased runoff which is what the coral proxy study is based on. And land clearing itself can accentuate droughts when they occur.

    Villabolo - you really are trying to stop the tides - yes I am Australian and your basic knowledge of our climate history isn't very good. (1) don't build homes and infrastructure on flood plains - lessons of 1974 forgotten to be rediscovered in 2011 (as the lessons from the 1800s were also forgotten). Is it that surprising that flood plains ... errr ... flood ! It is absolutely stunning that Australians are surprised by the floods.

    (2) any Aussie crop physiologists and modellers worth their salt knows that episodic droughts and floods make production problematic. We live on the receiving end of ENSO - you HAVE and WILL get episodic droughts and floods. And any ecologist knows the big wets are the resets for decades of low rainfall years. If you don't like it - don't live here. Are you trying to suggest none of this has happened before. In fact probably historically much worse in the 1800s. Those who don't learn from history are doomed to repeat it. And the ENSO x IPO story is written large in the rainfall history, sediment cores and corals.

    Not enjoying such variation Aussies mitigate against drought and flood using a thing called "dams". How many billion dollars do you think full dams and rivers are to agriculture?
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  42. @Berényi Péter #103

    Speaking of real science and given that you speak of every branch of science as if you know it. Can you explain how those FACE experiments could keep the CO2 enrichment in wind conditions, which accounts for a great deal of water strain? Also, can you comment the fact that the vegetation studied is mainly for human use, directly or indirectly, that is, varieties have been enhanced to maximize growth and productivity and to resist drough by every possible way, thus they might "be expecting" more CO2? Why don't we humans enrich our environment with 28% Oxygen just to feel good? Why don't we add some 30% food to our diets, just to thrive? (Oh, we do! and the only thing that thrives is our spare tyres -those in the middle and with a navel in front-)

    About your snippets -the sort of figures and phrases that you are recently laying in any imaginable nest- you selected the image on the right from a brochure that also contains the image at the bottom.

    At this time you should know better and get some graphic with margin errors in it, proper attribution and a dataset. Also checking the source, a very poor one -no matter who did it- no matter it is just a brochure. In the image below they only speak of drought. No single place becomes any wetter and even a new dessert is born in southern Chile ... wait! the scale is wrong: 40% doesn't mean 40% less rainfalls, just a 40% probability of the place going dryer, hence a 60% probability of it going wetter. How do I know? Because it's what Mahli et al (2008) says, and that's why a source is needed. I can also tell that the season name is the NH's though most of the area represented is in the SH.




    The fact is that the brochure is a very poor one and unfortunately some very serious works are misinterpreted or depicted in a wrong fashion. There are also not so serious works, but all of that is outside the importance of that brochure to the present topic.

    On the practical side, the image equals you simply saying "raising CO2 has made soils and vegetation richer in Carbon during the last +100 years". How do we know? Just because if you have had a better source you would have used it, and that, sir or madam, that almost equals a confession.
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  43. johnd - "KR at 04:35 AM, you obviously missed the results of the FACE trials I referred to in johnd at 19:31 PM on 18 April, 2011"

    Actually, I did look at the second article you linked. From their conclusions:

    "Overwhelmingly, this has shown that data from laboratory and chamber experiments systematically overestimate the yields of the major food crops, yet may underestimate the biomass production of trees."

    More wood, but less food?

    Again - the FACE experiments you have pushed, with more realistic testing then lab/greenhouse work, do not show the crop amplification you have suggested will occur.

    As to redneck commercial growers and new seed varieties - great, let us know when they have something. In the meantime, the data indicate that CO2 is not going to boost crops the way skeptics have claimed.
    0 0
  44. "As to redneck commercial growers and new seed varieties - great"

    Reminds me of the Chicago Cubs fan who, every fall, says "just wait until next year!"
    0 0
  45. johnd - My apologies; I had looked at the second reference you made in this post, defending BP, not your earlier post the day before.

    From that PowerPoint on Australian FACE experiments (only), Slide 14:

    "Increases and Decreases in Yield

    BUT

    Despite experimental yield increases, due to future predicted changes in rainfall and increases in temperature:

    - Semi-arid zone: Yield LOSS (-10 to -20%) in North West Victoria
    - HRZ: Yield GAINS (+10 to +20%) in the South West"


    (Capitalization as in original)

    Looks like a wash to me - any CO2 based increases nullified by resulting temperature and hydrology shifts. You are not making your case.
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  46. A rhetorical question:

    Why do some people think that cherry-picking quotes and numbers from the middle of presentations and papers, while ignoring the summary and conclusions sections that provide the take-home message for all the data, is in any way an acceptable tactic?
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  47. KR at 06:06 AM, I'm not sure what crop amplification you think I have suggested, as all my arguments in this thread and all others previously have always been based on what the FACE trials indicate.
    Unlike perhaps yourself and many others I don't have a lot of faith on modeled projections that have not, or cannot be validated by real world observations.
    The only exception to the FACE trials has been the use of CO2 enrichment in commercial greenhouses where it has been an established practice for several decades.
    0 0
  48. dhogaza at 06:23 AM, for your analogy to be true, it means you are referring to fans watching replays of a season oblivious that the games were played a decade earlier.
    I can certainly see how that might actually be happening.
    0 0
  49. KR #146
    For the same reason you didnt answer the question about the social security analogy?
    0 0
  50. @100 LukeW:

    ""And you want those La Ninas to get stronger?" YES PLEASE !!
    Would make us billions ! (with some collateral damage too but life wasn't meant to be easy)"
    (Emphasis mine)

    Luke; concerning your response at #141 to my post #115.

    I am very well aware of Australia's variable climate throughout history. You are assuming my ignorance, in what I believe is an attempt to dodge my basic premise.

    As you yourself stated, La Ninas will become stronger and more frequent. I was simply stating that there will be more devastation than blessing as a result.

    An obvious example is what you saw happen to your wheat crop last season. That you admitted that production in Australia is problematic runs against the grain of your original statement in #100.

    You were describing the heightened effects of La Nina as if it were a cornucopia while grossly downplaying the destructive side. Recent events and rational intuition should give you an idea of what you country's future really has in store.

    More severely fluctuating weather than before, with more drastic effects than before.

    By the way, you can try out this thinking experiment:

    All percentages are based a previous average.

    Year 1: 130% bumper crop.

    Year 2: 50% crop devastation.

    Year 3: 70% harvest; 10% complete crop loss; 20% crop dwngraded to animal feed status.

    Question. What is the average harvest of crop fit for human consumption?
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