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Thread: doubling of CO2

  1. #1 doubling of CO2 
    Forum Radioactive Isotope sculptor's Avatar
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    Apr 2012
    CO2 doubling causes an increase in radiance to earth’s surface of 3.7 watts/meter squared, which in turn raises temperatures about 1 degree Celsius.
    Still considered accurate?

    Of course, it ain't just CO2 with which we're enriching the atmosphere, and every atmospheric component has it's own contribution to positive and negative temperature effects.

    And, then
    we get myriad positive and negative feedback loops from the changing biom. (eg: if more greenery is enriching the atmosphere with more O, what effect would we expect?)

    Is it possible to look at the potential interplay of effects dispasionately? Or is everybody trapped within their cognitive predispositions?
    It seems that atleast for "climate science" on the web, most people have lost the ability for dispassionate objectivity.

    (I'm thinking I'll post part of this in psychology--------ok?)

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  3. #2  
    Life-Size Nanoputian Flick Montana's Avatar
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    Quote Originally Posted by sculptor View Post
    every atmospheric component has it's own contribution to positive and negative temperature effects.
    Elucidate, please.

    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
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  4. #3  
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    I don't understand the question.

    The various contributions of the different greenhouse gases are set out quite clearly in the IPCC reports as well as in the literature. As I understand it there's absolutely no question at all of that measurement for CO2 alone.

    All the complexities and difficulties and general faffing about arise from trying to measure the relevant effects of aerosol emissions among other things. We have a pretty good history from volcanic eruptions to work from, but actually measuring the great brown cloud from Asia and its effect is a bit of a headache. Similarly for the effects of the loss of albedo in the Northern Hemisphere - pretty good but could be better.

    The real hassle comes from

    1. calculating the impact of feedbacks rather than forcings. Water vapour being the biggie here. And not just the quantitative effect but the timing of those effects. The IPCC talks about transient climate sensitivity and equilibrium climate sensitivity but there's no real guidance on how we judge those. (Of course that's probably irrelevant for as long as we continue to put our thumb on the scales of the CO2 balance in the oceans and atmosphere.)

    2. calculating when and how much the accumulated CO2 and/or energy will trigger some of the more serious irreversible (on human scales) events. It's one thing to observe the "drunken forests" with trees collapsing higgledy piggledy as the permafrost thaws for the time being. It's another thing entirely to calculate the amount of ghgs and their possible effect on climate that will (when exactly?) be released when the whole lot thaws right through.

    3. And not noticing strange impacts from things we can actually see. Like that great brown cloud from Asia. If we're thinking that CO2 is necessary for plant growth we also have to acknowledge the necessity of sunlight. We see the pictures of the cities under their smog blankets. What about the agricultural areas? Turns out that crop harvests in many regions of China is substantially reduced because of the smoke haze. (I thought the item was on Science Daily but I can't see it there just now.) How many other cascading effects are there that we've not thought about or measured even though they're right in front of us?
    Lynx_Fox, PumaMan, PhDemon and 1 others like this.
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  5. #4  
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    I'll quote a pretty good authority, and then discuss the details. The authority is the IPCC's AR5.

    The current sensitivity is estimated to be between 1.5°C and 4.5°C per doubling. You will find that figure in the SPM.

    In the interval between AR4 and AR5, both Hadley and GISS started adding oceanic heat transfer models to their GCMs, making AOGCMs. The oceanic models are still not as detailed as the atmospheric ones, since we know less about the deep ocean than anyplace else on Earth but beneath the crust. This has caused the models to temporarily increase their range of output, due to the larger uncertainties introduced by the ocean models. However, we can expect these ocean models to improve to approach the atmospheric models in the next few years, and when all is said and done we will have much tighter estimates.

    But at this point, it looks like 3°C is the median likely sensitivity.
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  6. #5  
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    Unfortunately the AR5 did not include some of the best research over the past year that looked at how models treat water vapor mixing and cloud distribution. When the models referred to in the IPCC are examined those that simulate these processes best match observation and suggest a range of 3 to 5 C sensitivity for doubling of CO2. And it appears we'll be well above doubling by mid century. Probably the best paper on subject is:
    Schneibster likes this.
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  7. #6  
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    Mar 2014
    Sure, @Lynx_Fox, it was only published in 2013, you can't expect them to have stuff from the last half of 2012 much less the year of publication. It's not a single paper, it's a compilation.

    Good question though. It illuminates the limits of the process.

    And you are perfectly right to add the cloud coverage modelling which people have been complaining about for years. That will be as important as the ocean models, but not in terms of the total heat, at least according to the current results. It's more important to the perception, because it's been talked about so much.
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