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Effects of Elevated CO2 and Temperature on Rice Crops

In the ISCID Brainstorms forum Emeritus Professor of Biology John A. Davison challenged my assertion that atmospheric CO2 increases are a good thing for plant growth. He said while it might apply to trees it doesn’t apply to grasses such as rice which don’t yield more grain in an elevated CO2 environment. He then went on to say that only in the laboratory can benefits be observed from elevated CO2 where other potentially limiting factors (sunlight, nutrients, water) aren’t an issue. Sorry John, but that’s just wrong on all counts.

Rice grain yields increased 60% in outdoor field tests with elevated CO2. Yield peaked at 28C and then declined 10% for each additional degree. Even the global warming hysterics readily admit that average temperatures will only increase a few degrees at most. The cool thing about temperature though is you can compensate for an undesirable increase by shifting either your growing season and/or your latitude. In any case the actual grain yield increase obtained from elevated CO2 are still double any losses engendered by projected temperature increases.

Source: Journal of Experimental Botany
Temperature Effects on Rice at Elevated CO2 Concentration

In addition to increased grain yield elevated CO2 also reduces the impact of drought. Rice grown in the field at elevated CO2 levels consumed 10% less water.

Source: USDA Agricultural Research Service
Impacts of Drought, High Temperature and Carbon Dioxide on Rice Physiological Processes

It is hard to believe, isn’t it? :roll:

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12 Responses to Effects of Elevated CO2 and Temperature on Rice Crops

  1. The global warming debate is SO not over. Al Gore just wishes it was over. The fact of the matter is the crapass bandwagon science underpinning global warming hysteria is sinking faster and farther than a lead weight dropped in the Marianis Trench.

  2. I was reading about this yesterday. Plant growth slows at CO2 concs of 220 ppm and stops at 150 ppm. Above 220 ppm there is a steep rise in the growth rate up to about 500-600 ppm then it levels off. Sorry I can’t give you the refs but I googled it up on the net so no doubt others who know (much) more than me can expand on this. I find the narrow band of CO2 concs in which accelerated plant growth occurs and that plant growth stops at a level not far below that which we have today intriguing.

  3. From today’s Aussie press

    Australia and US are right to reject Kyoto: British experts Thu Oct 25, 2007 10:05am AEST

    UK experts say the Kyoto protocol has failed to deliver results

    Two researchers in the UK have backed Australia’s decision not to ratify the Kyoto protocol, saying it has failed to deliver cuts to carbon emissions.

    http://www.abc.net.au/news/sto.....069716.htm

  4. A few months ago I saw a program on TV about this sort of thing. Can’t recall which channel but I think the fellow was growing citrus trees and the difference between those grown in an enriched CO2 environment and those grown in normal air was spectacular. They were about twice the size. Their increased tolerance to water stress was also noted.

    Tried to find it but, instead, found this article which states in part,

    one of the best ways we know to improve plant resistance to environmental stresses is to enrich the atmosphere with carbon dioxide. Is it possible that this phenomenon also improves the nutritional quality of the food we eat? We have long felt that it may indeed do so; and there is now another reason for believing that that hypothesis has merit.

    The first of the foundational elements of this CO2-induced, plant-stress-relieving, human-health-promoting hypothesis was established by Idso and Idso (1994), who demonstrated that environmental stresses due to air pollution, high temperature and lack of water are all significantly mitigated by atmospheric CO2 enrichment. In some experiments involving high temperatures, in fact, they noted that supplying plants with extra CO2 actually made the difference between the plants living or dying (Idso et al.,1989, 1995)

    So, not only do plants grow bigger and tolerate water stress better but they may also be more nutritious! Looks like a win, win situation to me.

  5. mad doc

    Plants exhibit a linear response to CO2 increases up to about 600-700 parts per million. However, increased growth rate keeps continuing up to concentrations of 1500ppm. The current average concentration in the atmosphere is near 380ppm, up from 320ppm 50 years ago. There isn’t enough fossil fuel in the known reserves to raise the concentration up anywhere near even the top of the linear response range of 600ppm. As the oceans warm they release CO2 and they can increase CO2 levels far over the top of the linear response range. This is the basis of some of the doomsday scenarios. The logic goes that CO2 is a greenhouse gas and the more in the atmosphere the warmer the earth gets and the warmer the earth gets the more the oceans release CO2. This positive feedback mechanism is feared to produce a so-called runaway greenhouse.

    The problem with this scenario is that for the majority of the earth’s history it has been much warmer than it is today. We’re in an ice age today near the warmer end of the range between the coldest and warmest it gets during an ice age. The Medieval Warming a thousand years ago (when Greenland was actually green and hence the name) was the warmest end of the range. The Little Ice Age which occured 300 years ago was near the low end of the range. If history repeats we should expect to see Greenland become green again like it was 1000 years ago.

    The earth has never experienced a runaway greenhouse but there is much evidence that it has become a runaway deep freeze in the past – the so-called “Snowball Earth” where glaciers cover the entire planet. No one knows what the mechanism is that ends a snowball earth as there’s also a positive feedback effect from snowcover – snow reflects light back into space efficiently so the more snowcover the colder it gets and the colder it gets the more snowcover. Some think that decreased cloud cover is a negative feedback factor that eventually tips the scales and reverses the freeze. The negative feedback from cloud cover is what probably stops the runaway greenhouse from happening. As the earth warms cloud cover increases and clouds reflect sunlight back into space thus cooling it off again. The oceans reabsorb CO2 as they cool and this accelerates the cooling even more.

    What we end up with is pendulum effect with the climate swinging back and forth from one temperature extreme to another. The equilibrium point is in the middle of the range but inertia (or something else – solar variation, cosmic ray variation, and orbital idiosyncracies are suspected factors) pushes it through that point keeping the pendulum in motion.

    The earth has however spent the majority of the time near the equilibrium point and that point is much warmer than today.

    Coming back to plant response to CO2 it’s thought that because the earth has spent most of its time in a warmer climate with higher CO2 concentration in the atmosphere plants have evolved (or perhaps were designed) to function at their peak in that higher CO2 environment. There is such a thing as an optimum climate for the biosphere and it’s almost certainly at the point where plants grow most efficiently. I consider plant growth response to CO2 a smoking gun pointing to the optimum climate for the biosphere.

    So almost certainly global warming is a good thing for the biosphere. Plants are the primary producers in the food chain. When they grow faster everything higher up the chain has more food available. Global warming may be inconvenient for mankind in the short run. Oceans WILL rise and cause problems for coastal cities built near sea level. For the rest of the biosphere this causes no problem as no animals except humans have built huge immovable cities near sea level. All the other animals just migrate inland to higher ground and if it gets too warm for them they migrate to higher latitudes. As the higher latitudes become free of ice there’s plenty of new area opened up for them to migrate into.

    So even if you’re a tree hugger you should be glad global warming is happening. It’s a natural thing. We shouldn’t try to stop it we should instead adapt to it like all the other life on the planet will do and has been doing for a billion years.

  6. …don’t have the reference handy but recently scientists at North Carolina State university placed some plants in a type of oxygen chamber. They increased the oxygen level to a greater percentage than in our present atmosphere and the growth rate and size of the plants were well above the present average.
    I wonder; could this type atmosphere have contributed to the large size of some of the dinosaurs (the sauropods)?

  7. DaveScot said,

    So even if you’re a tree hugger you should be glad global warming is happening. It’s a natural thing. We shouldn’t try to stop it we should instead adapt to it like all the other life on the planet will do and has been doing for a billion years.

    While I’m far from being a treehugger, and I readily acknowledge that the current hysteria over global warming is in serious need of moderation, it must be remembered that the ability to adapt is tempered by the amount of time needed to do so, and climatic events have resulted in mass extinctions in the past. Whether or not we have the ability to do anything about the current trends is seriously in question, but as a Christian myself, to suggest that we shouldn’t do anything *if we can* doesn’t seem like good stewardship to me.

  8. DaveScot

    Thanks Dave.

  9. Mickey

    We once thought, not very long ago, that preventing forest fires was “good stewardship”. We know it isn’t now. Preventing forest fires causes fuel to build up to unnatural levels and when the inevitable fire does happen its intensity causes death and destruction on an unnatural scale. As well, there are many species that thrive on land where a fire has swept through. Without regular fires coming through they don’t get their turn at bat. The earth’s climate naturally swings between cold and warm epochs. Is it good stewardship to try to prevent this natural change? Probably not.

  10. DaveScot,

    There’s a difference between humans starting forest fires by carelessness and fires started by natural causes, such as lightning strikes. I think we *should* prevent the former when possible, but not always the latter, as you suggest. My suggestion was that if there is significant anthropomorphic contribution to climate change, it would be irresponsible not to do something about it, with the understanding that I acknowledge that the jury is still out.

  11. #10

    Mickey Bitsko

    Please give me some evidence for “anthropomorphic contribution to climate change,” otherwise enough!.

  12. 12

    mad doc

    Certainly you don’t deny that there’s evidence?? Whether or not the evidence is reliable is what’s in question, not whether there is any evidence.

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