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Thread: What are the relative causes of current climate change?

  1. #1 What are the relative causes of current climate change? 
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    To what extent are the general symptoms of climate change (more extreme weather, natural disasters, increased surface temp, animal/plant migrations, spread of invasives, drought, floods) being caused by the following factors: GHG emissions; deforestation, desertification and other types of land-use change; watershed degradation; topsoil loss, habitat fragmentation etc.?


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    exchemist
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    Quote Originally Posted by mrtorrence View Post
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    To what extent are the general symptoms of climate change (more extreme weather, natural disasters, increased surface temp, animal/plant migrations, spread of invasives, drought, floods) being caused by the following factors: GHG emissions; deforestation, desertification and other types of land-use change; watershed degradation; topsoil loss, habitat fragmentation etc.?
    What do you mean by "watershed degradation"?


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    General disruptions to the hydrological cycle, and there is some overlap with the other items I mentioned. For instance, topsoil loss is certainly a form of watershed degredation given how much water healthy top soil can hold. Reduction in vegetative cover (whether that's deforestation or otherwise). Dams. Channelization and putting rivers into concrete canals or pipes. Increase in impervious surfaces whether concrete or otherwise.
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    exchemist
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    Quote Originally Posted by mrtorrence View Post
    General disruptions to the hydrological cycle, and there is some overlap with the other items I mentioned. For instance, topsoil loss is certainly a form of watershed degredation given how much water healthy top soil can hold. Reduction in vegetative cover (whether that's deforestation or otherwise). Dams. Channelization and putting rivers into concrete canals or pipes. Increase in impervious surfaces whether concrete or otherwise.
    Oh I see. That's a far broader interpretation of watershed than I am used to.

    I must say it seems a very open-ended question and not one for a one paragraph answer. Obviously GHG increase is the root cause, but I do not know to what extent that increase is due to emission from burning fossil fuel and to what extent it is due to destruction of GHG sinks. From everything one reads it seems that emission is the biggest contributor.
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    Well let's be scientific about it, I don't think it is obvious that GHGs are the "root" cause. I think it is the primary or majority cause, but I think it's possible it might only be responsible for 50 or 60% of current climate change symptoms. I think it will likely be responsible for a greater percentage in the future if we keep emitting at this rate, but I'm just trying to get at the relative causes currently. Take a look at this research and how important photosynthesis and evapotranspiration are to modeling the climate . And they say it is very uncommon for vegetation to be factored into climate models! That is insane! And then check out this research by climatologist Dr. Rosa Maria Dos Santos looking into the river that flows in the clouds above the Amazon rainforest, it contains more water than the Amazon river itself. Don't you think there's some chance that has more of an effect on the local climate than GHG concentration in the atmosphere?
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    exchemist
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    Quote Originally Posted by mrtorrence View Post
    Well let's be scientific about it, I don't think it is obvious that GHGs are the "root" cause. I think it is the primary or majority cause, but I think it's possible it might only be responsible for 50 or 60% of current climate change symptoms. I think it will likely be responsible for a greater percentage in the future if we keep emitting at this rate, but I'm just trying to get at the relative causes currently. Take a look at this research and how important photosynthesis and evapotranspiration are to modeling the climate . And they say it is very uncommon for vegetation to be factored into climate models! That is insane! And then check out this research by climatologist Dr. Rosa Maria Dos Santos looking into the river that flows in the clouds above the Amazon rainforest, it contains more water than the Amazon river itself. Don't you think there's some chance that has more of an effect on the local climate than GHG concentration in the atmosphere?
    Yes, let's be scientific about it.

    On the local climate, yes, of course, local factors will have more influence than anything else. That is how we get local climate in the first place. But if you speak about the root cause of global climate change, that seems almost unquestionably to be due to the experimentally observed fact that greenhouse gas concentrations have increased considerably over the last 200 years.

    The way the science on this developed, as I understand it, was that this increase was the initial observation, rather than any change in climate. Knowing that these gases absorb strongly in the IR, predictions were made about increased heat retention and hence climate change. So rather than seeing climate change and then looking for explanations for it, we saw change in gas concentrations, and predicted climate effects before any had been identified. Now of course we seem to be seeing some of the predicted effects in reality, e.g. shrinkage of glaciers and the polar icecaps.

    That prediction remains the core prediction, whatever subtleties we introduce into our models to estimate more accurately the quantitative effects of it.

    The first article is certainly very interesting on the need to model more accurately surface evaporation, as this affects the balance between heat input raising the temperature vs. increasing the humidity. But I don't read this as saying global climate change is actually caused, in the first place, by changes in the global leaf cover of the Earth.

    If it did say that, then this would have to be added on top of the core prediction due to the greenhouse gas effect. The greenhouse gas prediction is not going to be altered by discovery of another effect, unless that effect can definitively be said to mitigate it. The article does not suggest that at all, so far as I can see.
    Last edited by exchemist; May 13th, 2019 at 02:56 AM.
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