Climate change: Models ‘underplay plant CO2 absorption’

Oct 17, 2014

By Matt McGrath

Global climate models have underestimated the amount of CO2 being absorbed by plants, according to new research.

Scientists say that between 1901 and 2010, living things absorbed 16% more of the gas than previously thought.

The authors say it explains why models consistently overestimated the growth rate of carbon in the atmosphere.

But experts believe the new calculation is unlikely to make a difference to global warming predictions.

The research has been published in the journal Proceedings of the National Academy of Sciences.


 

Read the full article by clicking the name of the source located below.

15 comments on “Climate change: Models ‘underplay plant CO2 absorption’

  • Sigh!

    Handing a fully serviceable craft to those wanting to navigate up a certain river in Egypt.

    I will hear about this on one of my q and a sites today. Of course the question will gratuitously include the name of Al Gore!



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  • On the other hand, we are destroying vast tracks of vegetation, particularly the Amazon. The end point is easy to predict. The speed with which we get there is not.



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  • changes with the age of plants and nutrient availability.

    Nice link. It’s obvious when you think about it. C02 is not the only determining factor for plant growth. There’s probably a long list of essentials, but nutrients and water are two obvious ones. A plant might have more C02 available to support growth, but without the rest of the list, it’s not going to happen.

    On the same theme, sooner or later someone will post. “The world will be better place with more C02 because the plants will grow faster and bigger giving us more food.” So before anyone does, this is what happens to a food plant that feeds a third of the world’s population when you increase available C02.

    So why would a plant have less protein in a raised carbon dioxide environment? In the process of photosynthesis plants convert carbon dioxide into sugars using a protein called RuBisCO to capture the CO2 from the atmosphere. If carbon dioxide levels increase plants will need to produce less RuBisCO to capture the same amount of carbon dioxide. Less of this protein means a less nutritious meal. And the plant’s extra resources can then be diverted in to protecting the plant. Plants protect themselves using spines and thorns or make themselves less appetising by producing toxic chemicals. Eucalypts produce phenols.

    AND

    Cassava is a staple food for much of the developing world. But if it is not prepared properly it can cause a serious lifelong disease called Konzo. Julie Cliff has been a medical doctor working in Mozambique since the 70’s and has seen the effects of cyanide in cassava first hand.

    Dr Julie Cliff In Mozambique the disease that gives us most problems is a disease called Konzo and that’s a permanent paralysis. And they get that when they eat too much cassava. The first time it happened was 1981. We went to investigate it and we got a message saying it was polio. But we soon realised it wasn’t polio because the symptom was quite different.

    NARRATION Back in the lab Ros’s group have been looking at how rising CO2 will affect the cyanide levels of cassava.

    Dr Ros Gleadow We grew cassava at three different concentrations of carbon dioxide. Today’s air, one and a half times the amount of carbon dioxide and twice the carbon dioxide of today. And we found that cyanogen concentration in the leaves increased.

    Dr Graham Phillips So as we get more Carbon Dioxide in the atmosphere these will contain more cyanide?

    Emeritus Prof. Howard Bradbury More cyanide yes. The yield from the roots which is the main thing, will go down. So that is the most worrying aspect.

    Dr Ros Gleadow I feel sort of slightly uncomfortable with having discovered something so bizarre that the plants actually made less tubers when we grew them at elevated carbon dioxide. But they did. It is all very highly balanced in plants, the ratio of the proteins and the toxins. When you grow plants at elevated carbon dioxide the plants are more efficient so they can grow really well. And at the same time allocate more of their resources to defence.

    The full article can be viewed here:-

    http://www.abc.net.au/catalyst/stories/2891924.htm



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  • David R Allen Oct 18, 2014 at 9:44 pm

    Nice link. It’s obvious when you think about it. C02 is not the only determining factor for plant growth. There’s probably a long list of essentials, but nutrients and water are two obvious ones. A plant might have more C02 available to support growth, but without the rest of the list, it’s not going to happen.

    The classic case is the tropical open ocean.
    There are “blooms” of algae etc. when there are run-offs from land, or up-wellings of nutrients, but once the photosynthesising organisms have used up the mineral resources and sunk into the depths, there is a “blue desert” of water and dissolved CO2 refreshed by waves.

    http://www.seashepherd.org.au/toxic-gulf/specialisation-in-the-blue-desert.html
    The open ocean is often referred to as ‘the blue desert’. Nutrients are low, and plankton and other primary drivers of the food chain cannot exist at high enough quantities to support life on the kind of scale we see around the coasts.



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  • 9
    inquisador says:

    Agree with Nitya, David;

    fascinating stuff. It would be interesting to see the results of experiments on a range of other staple crops such as legumes, rice, potatoes, beets, brassicas and fruits…to get an idea of what higher rates of co2 would do to all of those and more.

    Is there a possible role here for genetic modification?



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  • David R Allen Oct 18, 2014 at 9:44 pm

    On the same theme, sooner or later someone will post. “The world will be better place with more C02 because the plants will grow faster and bigger giving us more food.” So before anyone does, this is what happens to a food plant that feeds a third of the world’s population when you increase available C02.

    The one-dimensional thinking denialists, have already done that, and quoted enhanced levels of CO2 in commercial glasshouses, as evidence that CO2 is “a nicey nicey plant food”, which is great for the atmosphere, along with “a bit of extra warmth”!
    Their concept of climate measurements showing future consequences, can be estimated as zilch, which is why they copy rubbish, from illiterate or dishonest denial websites, to massage their cognitive biases!!



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  • @op link – By analysing how CO2 spreads slowly inside leaves, a process called mesophyll diffusion, the authors conclude that more of the gas is absorbed than previously thought.

    Between 1901 and 2100 the researchers believe that their new work increases the amount of carbon taken up through fertilisation from 915 billion tonnes to 1,057 billion, a 16% increase.

    Absorption rates are irrelevant in the long term, unless the trees in which carbon is stored are preserved beyond their normal lifespan (40 to 400 years) .
    What matters is the balance between absorption and release, together with the CO2 retained in living and residual biomass.
    With mass burnings, logging and forest clearances, a substantial quantity of this carbon + more, has already been returned to the atmosphere.

    Likewise where forest has been replaced by agriculture, the carbon in the crops is quickly recycled back to the atmosphere through consumption and breakdown of organic matter.



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  • Alan4- Question

    Long separated from my biology classes- I thought much of the CO2 absorbed by plants combines with other things, releases some of its oxygen and is no longer CO2. Shouldn’t the amount released upon death and decay be far less than the total CO2 consumed and used over the plant’s lifetime?



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  • rjohn19 Oct 20, 2014 at 11:34 am

    I thought much of the CO2 absorbed by plants combines with other things, releases some of its oxygen and is no longer CO2. Shouldn’t the amount released upon death and decay be far less than the total CO2 consumed and used over the plant’s lifetime?

    The chemical equation for photosynthesis is: 6CO2 + 6H2O = C6H12O6(sugar) + 6O2

    Some of the sugars will be consumed and released as CO2 by the plant respiring, when it is not in sunlight.
    Any other carbon in the sugar, starch, or wood, of the plant, will be converted back to CO2 by animals which have eaten it, fires consuming it, or by microbes and fungi breaking it down after the plant dies, provided that oxygen is present for these processes.

    The exception is where oxygen is excluded, as in the formation of peat or coal, or in swamps devoid of oxygen where biomass ferments to methane.
    Carbon is also temporarily removed from the cycle where wood etc. is preserved – as in timber buildings for their duration.

    If all the plant material is decomposed in oxygen, the CO2 produced, will be equal to that absorbed to produce those carbohydrates and sugars in the first place.



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  • Well gee, this won’t encourage misunderstanding among deniers at all.

    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.

    Added CO2 will likely shrink the range available to plants while increasing the size of deserts. 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.

    How long do you give it before this paper is cited by denialists as evidence for this particular trope?



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