Not-so-green hydroelectric dams give off more methane than anyone thought

Hydroelectricity is the only renewable that produces any meaningful amounts of energy on a global scale (about 16% of all electricity, compared to the paltry cumulative total from all other renewables of less than 3.5%). Oh the dilemma, hydropower turns out to release more methane than people realized. New research suggests dams are the main source of methane from rivers, and they could potentially lift global freshwater emissions by 7%.

There are 50,000 large dams around the world, but many, many more smaller ones.

Maeck’s team decided to take a look at methane releases from the water impoundments behind smaller dams that store water less than 50 feet deep.

They describe analysis of methane release from water impounded behind six small dams on a European river. “Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7 percent,” said the report. It noted that such emissions are likely to increase due to a boom in dam construction fostered by the quest for new energy sources and water shortages.

From the paper:

Sediment Trapping by Dams Creates Methane Emission Hot Spots

Inland waters transport and transform substantial amounts of carbon and account for 18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (0.23 mmol CH4 m–2 d–1 vs 19.7 mmol CH4 m–2 d–1, respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.

Life is so complicated if you are trying to save the planet. Still, someone’s got to do it.

The Bureaucrat’s burden… (like “The White Mans burden” all over again).

h/t Science Daily

REFERENCE

Andreas Maeck, Tonya DelSontro, Daniel F. McGinnis, Helmut Fischer, Sabine Flury, Mark Schmidt, Peer Fietzek, Andreas Lorke. Sediment Trapping by Dams Creates Methane Emission Hot Spots. Environmental Science & Technology, 2013; : 130715152553007 DOI: 10.1021/es4003907 [Abstract]

8.4 out of 10 based on 30 ratings

97 comments to Not-so-green hydroelectric dams give off more methane than anyone thought

  • #
    wayne, s. Job

    It is a bit hard to comment on BS like this, why are we spending money allowing idiots, scientists maybe, but idiots non the less, swilling in the trough of other peoples money?
    Maybe the memo about falling levels of methane in the atmosphere did not reach them.

    When you look at the land area of dams and the small amount of vegetable matter involved
    compared to the ongoing reclamation and draining of swamps, peat lands and mangroves, the dams are doing diddly squat.

    Have these people any education in the real world? The big bad bogey of dams and the green
    effort to stop them is a sight to behold. David Bellamy is a victim of these idiots.

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    • #
      Dave

      Agree,

      The main problem with sedimentation is:

      1. Loss of water capacity over years.
      2. Damage to turbines from sediments.

      Also in 1986 it was estimated around 1,100 cubic kilometers of sediment had accumulated in the world’s reservoirs, consuming almost one–fifth of global storage capacity and these guys are worried about Global Methane emissions. I don’t know what it is today?

      But the problem of sedimentation is definitely not methane, that’s the least of a hydro and storage dam worries.

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    • #
      Sceptical Sam

      Maybe the memo about falling levels of methane in the atmosphere did not reach them.

      Fugitives from that fact, perhaps?

      Is it still a fact?

      30

    • #
      Mark D.

      Thank you Wayne, s. Job. Your comment sums up exactly what I was thinking. Mother nature does this on a scale that dwarfs human effects. Another example of the “humans bad” meme.

      20

  • #
    Lank of the damned

    How do the emissions from this hydrogeneration compare with equivalent coal or gas power generation?

    10

    • #
      Heywood

      Actually a very interesting question.

      A coal and/or gas fired power station emits primarily CO2, but methane has been regarded as having 25 times the “warming” properties of CO2 so a comparison would be interesting, especially when broken down to emissions per MWh produced basis.

      Perhaps TonyfromOz can help us out with some figures.

      20

      • #
        Olaf Koenders

        Methane (CH4) rapidly decays to CO2, which has little if no warming effect compared to water vapour and CH4 itself is of no consequence as its absorption bands are already saturated by water vapour.

        http://stevengoddard.wordpress.com/2013/07/31/runaway-braindamage-effect-strikes-climate-scientists

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      • #
        Olaf Koenders

        I should expand a bit on this. Current levels of CH4 in the atmosphere about 1800 parts per BILLION), being regarded (likely erroneously) as some 23x the greenhouse disaster potential of CO2, equates to just around 42ppm CO2. In other words, bedwetting over nothing.

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        • #
          Lank of the damned

          The amount of atmospheric methane has varied over earth life time. During the first billion years of earth life it may have been considerable (%?). Of course there was no oxygen around then, sulphur gases were at much higher levels and water was probably more than we have today. Even so, isotopes etc suggest temperatures were probably ‘habitable’ at some places on the globe in the Archean.
          Hard to compare the affect of greenhouse gases over earth time when you consider how air composition has evolved.

          00

    • #
      Otter

      The CO2 would be Moister. (sorry, had to find a joke in there)

      20

  • #
    markx

    Surely any vegetation/organic matter which now settles in dams would have simply settled somewhere further downstream in the absence of the dam, and there decayed and released methane?

    30

    • #
      AndyG55

      Not quite Mark.

      Normal decomposition is mostly CO2, you need trapped anaerobic (lack of oxygen) decomposition of sediments for CH4.

      But once the CH4 is released into the atmosphere, it converts to essentially the same amount of CO2 that would have been released.

      30

    • #
      Otter

      I think when they say ‘hot spot’ in this article, they are meaning a concentration of methane. Allowing it to settle downstream would normally mean it is spread out and has very minor effect. But a ‘hot spot’ could be similar to those lakes that suddenly release massive amounts of CO2, doing a fair bit of harm to the local surroundings?

      50

  • #
    Otter

    I seem to recall reading somewhere recently, that greens like the idea (when they aren’t actively opposed to it, meaning, when anyone else proposes it) of building small hydro dams all over the US- without any concern, apparently, for the environmental damage they might do, re: what this article relates, just for starters.

    40

    • #
      AndyG55

      Sort of like the Greens not giving a rat’s ar** about the massive avian damage done by wind turbines.

      The Greens are environmental vandals of the highest order.

      81

      • #
        Dave

        And,

        Wind turbine construction, service roads etc cause soil erosion because of the lax government (GREEN) regulations.

        The Tehachapi Pass Wind Turbine Farm in California, for example, has deep gullies created by the force of rain sweeping off access roads and around wind turbine foundations, all straight into catchment areas and then sedimentation.

        WINDMILLS cause methane.

        10

      • #
        Olaf Koenders

        Agreed AndyG. There’s no such thing as a happy greenie. They’re the sand in the gears of modern civilisation – and they intend to be.

        40

  • #
    Rereke Whakaaro

    … water impounded behind six small dams on a European river …

    And this is taken as a proxy for all dams, globally?

    How much land, either side of the river, upstream of these dams is given over to livestock grazing? Do any manufacturing facilities have waste water systems that could feed back into the river? Does the upstream river flow through any populated area, or recreational area open to the public? Are there any places upstream, where trees and other vegetation enter the river? What material represents the bed of the river? Is it sand or shingle? Or is it mud and decaying vegetation? And finally, what is the population of fish and other aquatic organisms in the river?

    In other words, is the methane natural or man-made, or some combination of both, and if the latter, what are the proportions?

    50

  • #
    Peter Miller

    This has got to be some of the stupidest ‘climate research’ ever conducted.

    Vegetation either rots directly into carbon dioxide, or indirectly into carbon dioxide via methane.

    The carbon dioxide is either released in fresh water (sometimes in dams) or in the sea.

    A very small amount of carbon, once it has entered the land drainage system, is permanently fixed in anaerobic sediments.

    Like most ‘climate science’ this is just scary BS about a non-problem.

    50

  • #
    blackadderthe4th

    This seems to be a minor problem! But at least you recognise the danger of releasing GHG from ‘buried’ sources. When you consider the amount of sediment in the worlds oceans and permafrost. Which will be released as GHG as GW increases due to higher levels of co2, which will in fact be a positive feedback. Which in turn will release even more GHG and the cycle will continue until it is too late!

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    • #
      Heywood

      The IPCC says :

      a “runaway greenhouse effect”—analogous to Venus– appears to have virtually no chance of being induced by anthropogenic activities.

      http://www.ipcc.ch/meetings/session31/inf3.pdf

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      • #
        Olaf Koenders

        That’s right Heywood. In fact, Carl Sagan actually hypothesised there might be Earth-like conditions on the surface of Venus. I doubt he publicly recanted once the Russian Venera’s landed.. 😉

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      • #
        blackadderthe4th

        @Heywood

        ‘a “runaway greenhouse effect”—analogous to Venus’

        Who said anything about Venus? Down with your straw arguments!

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        • #
          Heywood

          “which will in fact be a positive feedback. Which in turn will release even more GHG and the cycle will continue until it is too late”

          This is describing a “runaway greenhouse effect” is it not?

          Nice try dickhead.

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          • #
            blackadderthe4th

            ‘This is describing a “runaway greenhouse effect” is it not?’ no just serious positive feedback! Look in a mirror and see what is on your head, clue, its not a wart!

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            • #
              Heywood

              So a “serious positive feedback” will eventually result in what?

              Nice comeback. You respond to being called a dickhead by calling me…… a dickhead. 10 points for originality tosser.

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              • #
                blackadderthe4th

                ‘So a “serious positive feedback” will eventually result in what?’ very difficult climate conditions!

                PS have you looked for any errors in my vids, because if you have I’m ready to make alterations if there is any! Ah, thought not!

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              • #
                Heywood

                I haven’t watched them. I’m not going to. I don’t indulge thread bombers and spammers. No views from me I’m afraid.

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              • #
                Mark D.

                PS have you looked for any errors in my vids, because if you have I’m ready to make alterations if there is any! Ah, thought not!

                Not so fast Udderly4th!

                The teeter-totter explanation of forcings was…um…good for 5th grade. You have some explaining though, no credible scientist talks about GH effect as causing a runaway temperature. Your video, on the other hand, suggests (propaganda style) that the result of imbalanced forcing will be runaway. In other words, the little round weight falls off the teeter (naturally the video stops at that moment leaving the viewer to fill in the future with their now manipulated mind.

                So Udderly4th, tell me why you suggest a runaway scenario with your video?

                While you are at it, create a video that accurately (at a level of understanding above grade 5) places weights on the teeter totter where other forcings have their concurrent effect would you Pleeeese?

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              • #
                blackadderthe4th

                ‘naturally the video stops at that moment leaving the viewer to fill in the future with their now manipulated mind’

                No don’t think so! But here is another one of Potholers recent videos on the the same subject!

                http://www.youtube.com/watch?v=zQ3PzYU1N7A&list=PL82yk73N8eoX-Xobr_TfHsWPfAIyI7VAP&index=27

                Watch and weep!

                03

            • #
              AndyG55

              Would rather watch “World’s funniest videos”. (which I don’t, btw)

              The quality is FAR better from the 10 seconds of each I have bothered with.

              30

            • #
              blackadderthe4th

              @Heywood

              ‘I’m not going to’ well that figures! Because in the kingdom of the blind the one eyed are kings, I’m not one eyed but you are blind to the truth! So that will be game set and match to me then! I accept your admission of defeat!

              014

              • #
                Mark D.

                Why do I get the feeling that the Warmist camp has determined that video is the best way to convey their propaganda campaign?

                It’s like the back room at Craptical Seance has created a special list of links to flood the blog world and their minions are off spreading it like HIV infected semen.

                70

              • #
                blackadderthe4th

                ‘Why do I get the feeling that the Warmist camp has determined that video is the best way to convey their propaganda campaign?

                Because it is best to use simple truthful clips so that the AGW anti-science mafia can at least have a chance to comprehend them!

                013

              • #
                Heywood

                “So that will be game set and match to me then! I accept your admission of defeat!”

                Bwahahahahaha.

                That’s what it is all about with you isn’t it. Point scoring. You are another typical warmist who WANTS it to warm, because being proven right is much more important than the fate of the planet.

                You measure success by the number of views on your YouTube channel. I am sure it is a reliable metric of consensus. /sarc

                So, no. No ‘victory’ for you.

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              • #
                Mark D.

                Huh! At least blackudderly4th freely acknowledges that it IS PROPAGANDA…..

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              • #
                AndyG55

                Victory ONLY in your own feeble little mind.

                No doubt you would consider that if you only just passed a junior high science exam that would be a major victory.

                10

              • #
                crakar24

                Mark D,

                Why do I get the feeling that the Warmist camp has determined that video is the best way to convey their propaganda campaign?

                That would be cameras powered by batteries that were charged by a hampster running in a little plastic wheel i hope otherwise it would be called hypocrisy.

                Oh by the way just another example of the omni potent force of a trace gas

                http://www.pipestonestar.com/Stories/Story.cfm?SID=43732

                Coldest July day in 102 years

                20

              • #
                Mark D.

                Thanks Crakar but you don’t need to tell me, I’m already living the cold. We had a frost warning for most of northern Minnesota a week ago. This is summer in farming country! This year was among the snowiest protracted winters in history together with the lousiest summers I can remember. The heat came on in the house several days last week with outside temps in the low 50’s F.

                Damn it, the warmists want me to think cold is because of warming……

                F-them!

                30

              • #
                crakar24

                Mark,

                The correct statement is

                “It might be cold where you are but trust us it is hot everywhere else”

                20

              • #
                blackadderthe4th

                @Heywood
                August 2, 2013 at 8:29 am

                ‘who WANTS it to warm’, WRONG its what the true science is saying!

                PS Have you found any valid errors in my youtubes yet? Guess not! Well put up or shut up.

                03

              • #
                Heywood

                Yes. It is true. The earth could boil but you would die with a smile on your face in bed next to Richard Alley because you did it, you have the biggest hit count on YouTube.

                Feel safe in the knowledge though, that I didn’t contribute to your views. I don’t follow the directions of warmist wankers so you can demand that I critique them as much as you like, but I won’t be wasting my time.

                10

              • #
                blackadderthe4th

                ‘but I won’t be wasting my time’ because you lack the comprehension to understand them! Sad, but true.

                02

              • #
                Heywood

                Lol.

                It just eats you up inside doesnt it? You really don’t like it when someone doesn’t play your game. Stiff.. Bwahahaha.

                Loser.

                20

        • #
          Ace

          Shedloads of MSM journos have been saying it for years.
          Who primed them with that?
          Who ever corrected them?
          Has Twattadder ever gone on an alarmist blog and corrected these “straw men”?

          30

      • #
        AndyG55

        except there is NO runaway greenhouse affect on Venus, despite 96% CO2

        The surface temp is due mostly to the massive atmospheric pressure.

        At similar atmospheric pressures as found in Earth’s atmosphere, Venus’s atmosphere is almost EXACTLY what it should be for its relative distance from el Sol.

        There is NO effect from that 96% CO2 on Venus

        50

    • #
      Rereke Whakaaro

      … amount of sediment in the worlds oceans …

      Most of which are very deep, on the basis that sediment moves downwards, and gets washed downwards by deep currents, and is therefore at a temperature is fairly constant and very cold, and impervious to temperature changes near the surface.

      … and permafrost.

      Permafrost is called permafrost because it has been there a long time. Do you know just how warm the ambient air temperature would have to be, before it melts? And don’t just parrot 0oC, because permafrost is not just water.

      40

      • #
        blackadderthe4th

        ‘the ambient air temperature would have to be, before it melts?’ no! So this must not be happening then?

        Permafrost Melting due to Global Warming

        http://www.youtube.com/watch?v=6ql2QFFbGFE

        015

        • #
          Heywood

          “Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years. Most of Earth’s gas hydrates occur at low saturations and in sediments at such great depths below the seafloor or onshore permafrost that they will barely be affected by warming over even 10000 yr.”

          Published Science, as opposed to BlackIdiotThe4th’s BBC inspired YouTube channel.

          160

          • #
            Bob in Castlemaine

            Maybe why the “great catastrophy” failed to eventuate during recent [warmer] interglacials aye?

            00

    • #
      Olaf Koenders

      Blackadder4, the greatest greenhouse gas is water vapour. All others already have their IR absorbtion bands saturated by it. Get a hobby.

      http://stevengoddard.wordpress.com/2013/07/31/runaway-braindamage-effect-strikes-climate-scientists

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      • #
        blackadderthe4th

        ‘the greatest greenhouse gas is water vapour’, it may be the biggest, but that doesn’t mean it is the most critical! Because co2 is more active at the IR frequencies that block heat escaping into space. hence the planet is warming!

        WV and co2 as heat vents into space.

        http://www.youtube.com/watch?v=_RdAKIN6Y6k

        017

        • #
          Ace

          This add-a-twat goon is the most incredible ding-bat….even though its patently his most vulnerable point that he relies on You Tube for his world-view, he goes on advertising the fact.

          Its like that guy Axhilles going about shouting “look, my heels, my heels, no sandals everyone, my heels”.

          100

          • #
            blackadderthe4th

            ‘ts like that guy Axhilles [sic] going about shouting “look, my heels, my heels, no sandals everyone, my heels” yep those sandals would be good protection against those arrows! Just like the AGW anti-science mafia using the temperature rise and the 800 years co2 lag as a debunk for AGW, when it is in support of AGW.

            The reason for the temperature rise and the co2 800 year lag.

            http://www.youtube.com/watch?v=S8r46j2WrNk

            09

            • #
              Ace

              “sic” indeeeeed..what a completly pompous prick, and then he gos and advertiss his You Tube weakness.

              BTW, he might one day look up the Cyrillic of Axhilles.

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              • #
                Ace

                …clue, its Greek, not English, pillock.

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              • #
                blackadderthe4th

                ‘clue, its Greek, not English’ sorry I thought we were posting in ENGLISH, pillock!

                08

              • #
                Ace

                A Greek name is still Greek in any language…doh!
                Hence there is no “correct” spelling in English of a Greek name which would be in an entirely different alphabet. Hence your “sic” being so utterly pretentious and hollow.

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        • #
          Myrrh

          blackadderthe4th
          August 1, 2013 at 8:36 pm ·
          ‘the greatest greenhouse gas is water vapour’, it may be the biggest, but that doesn’t mean it is the most critical! Because co2 is more active at the IR frequencies that block heat escaping into space. hence the planet is warming!

          Carbon dioxide is fully part of the Water Cycle, which is absent from the AGW Greenhouse Effect, water has a residence time in the atmosphere of 8-10 days – all natural unpolluted rain has a pH of around 5.6-8 because water in the atmosphere combines with carbon dioxide. The AGW GHE does not have rain in its Carbon Cycle.

          Real physics of what water in the atmosphere does, when it gets heated it expands and evaporates, lighter than air it rises and takes that heat away from the surface, where it cools and condenses back into ice and liquid water.

          Temperature of the Earth with atmosphere mainly the real gases nitrogen and oxygen: 15°C

          Temperature of the Earth without any atmosphere at all: -18°C

          Compare with the Moon without atmosphere: -23°C

          Earth with atmosphere in place, but minus water, think deserts: 67°C

          The real gas atmosphere of mainly nitrogen and oxygen is the real thermal blanket around the Earth, not the trace gas practically all hole in the atmosphere carbon dioxide..

          And, water is the great cooling mechanism through the Water Cycle, but it is also the gases nitrogen and oxygen, air, which cool the Earth from the extremes of heat reached on the Moon without them.

          They do this also in heat tranfer by convection, as they are heated at the surface their individual volumes expand and they become lighter than surrounding air and so rise taking the heat with them. When they cool in the heights they condense and become heavier than surrounding air and so sink, these are called convection currents, winds.

          Combined individual volumes of heated air expanded and form areas of low pressure, because their weight is spread over a greater area as they take up more room.

          Combined individual volumes of cold air form areas of high pressure, because the take up less room when they condense so their weight is greater because there are more of them in the same amount of space. High pressure areas weigh more heavily on us, low pressure areas weight lighter on us.

          Hot air rises, cold air sinks. Winds flow from high to low.

          10

        • #
          Graeme No.3

          That has to be the most stupid statement I’ve read on this site.

          Unfortunately you don’t seem to know anything about the greenhouse effect, infra-red absorption/radiation or logic so you won’t ever realise how stupid. HINT if water vapour is radiating it must have absorbed it first.

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    • #
      Otter

      And exactly WHY has this never happened before? The world has been much warmer in the past, as recently as 1000 years ago.
      Or is it your contention that these ‘buried sources’ never existed until humans came along?

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      • #
        blackadderthe4th

        ‘And exactly WHY has this never happened before?’and it has!

        700 million years ago snowball Earth followed by Hothouse Earth

        http://www.youtube.com/watch?v=Xrm1KXttqDA

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        • #
          Heywood

          More referrals to your own YouTube channel? I am surprised that Jo and the mods still allow you to use this blog a a promotional platform for your propoganda.

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          • #
            blackadderthe4th

            ‘I am surprised that Jo and the mods still allow you to use this blog’ is it because they are so full of the truth? If you have any evidence they don’t then please let me know and I shall make alterations!

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          • #
            AndyG55

            Its not propaganda. Its JUNK, impure adulterated JUNK. !!

            Meaningless dribble.

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        • #
          Otter

          Your response doesn’t even come Close to having anything to do with what I asked about.

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    • #
      AndyG55

      The yapping Chihuahua returns.!

      Hi Baldrick.. and to quote the real BlackAdder..

      “Every village has an idiot, and if all those idiots were brought together in one village, you, Baldrick, would be the idiot of that village.”

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    • #
      • #
        blackadderthe4th

        ‘Try this: I mean, can you read big words?’

        http://www.nature.com/scitable/knowledge/library/methane-hydrates-and-contemporary-climate-change-24314790

        And goes on to say in BIG WORDS!

        ‘but CH4 concentrations have risen by ~150% since pre-industrial times, compared to only ~40% for CO2 (IPCC 2001). Rising atmospheric CH4 concentrations lead to more rapid depletion of the hydroxyl radicals needed for oxidation, longer CH4 residence times, and thus increased CH4-induced warming (Lelieveld et al. 1998)’

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        • #
          MemoryVault

          . . . more rapid depletion of the hydroxyl radicals needed for oxidation, longer CH4 residence times, and thus increased CH4-induced warming (Lelieveld et al. 1998)’

          Is that why it has gotten so much warmer, globally, these past 15 years or so?

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        • #
          Sceptical Sam

          Not only does he not understand what he reads, but he can’t count either.

          Blackie, 1998 came before 2011.

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    • #
      AndyG55

      And no , its is NOT a problem at all. Sediments in lakes have always released methane, and always will.

      The permafrost farce has been proven to be a total red herring, a non-existent problem.. just like trace amounts of CO2 in the atmosphere will NEVER be a problem, unless they are not there.

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      • #
        AndyG55

        ps.. It is very important for the current population level that CO2 levels keep climbing. They must never be allowed to drop back down to the plant subsistence level of around 280ppm.

        We must overcome this nonsense of the CO2 haters and bring the level up to at least 700ppm, for the sake of sustaining human life on Earth.

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  • #

    An excerpt from The American Thinker’s Why Environmental Professionals Hate All of the Above:

    What’s behind this change of heart about natural gas? Maybe it’s the need to continue the struggle. Admitting that natural gas is clean and that America has enough of it to power the country for a century — where would that leave the leaders of environmental groups that now raise hundreds of millions in donations? It might leave them having to make a living like everyone else.

    Maybe the environmental pros are more interested in their own survival than that of the planet. To maintain their constituency’s support and the generous donations that go with it, environmental groups must always protest something. And to expand their donor base, they must expand their protest. If coal, oil, and natural gas are “dirty,” so are hydro and ethanol, and, soon enough, wind, solar, and biomass may be as well. There is literally no end to the anti-growth agenda of the environmental left.

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  • #
    Turnedoutnice

    It’s a big mistake to get sedimental about methane.

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  • #
    Chris Schoneveld

    The mouth of the Barrow river in Cairns used to be a large wedge of sand, almost like a delta, protruding from the coast. After they dammed the river the mouth became sediment starved, the sand bank disappeared and the beaches that used to be fed with sand from the Barrow river, through long shore currents, started gradually disappearing. Now they are trying to protect the coast line by dumping big blocks of rocks (Clifton Beach etc.) but this makes matters worse since the waves hitting the rock wall will create violent turbulence that would prevent any new sedimentation that might be brought through wave action from sand further offshore. They should consult the Dutch how to replenish sand starved beaches.

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  • #
    Ace

    But without it conditions could become Fresian.

    20

  • #
    Backslider

    What relevance does this have?

    Whether the methane is release behind a dam wall or somewhere further down the river/sea, what difference does it make? It will still be released.

    I see this as just another attempt to boost Greeny arguments in their quest to prevent the building of dams.

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  • #
    Brian G Valentine

    Well, if a marsh is created by damming something up, who wouldn’t expect marsh gas to be released.

    The methane is oxidized promptly to CO2 and water in the atmosphere, anyway.

    30