Mr Methane

Posted by William M. Connolley on September 24, 2008
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Various wild excitement about methane emissions from the Arctic shelf… Hot Topic, Inel and The Indescribably Overhyped, which latter reveals “exclusively” what Magnus translated several weeks ago.

Inel, very sensibly, asks for context: what are we to make of “millions of tons of a gas 20 times more damaging than carbon dioxide”? I think the best thing to look at would be the global methane concentration. If that isn’t going up strongly, then this isn’t a big thing at present. Whether or not its a sign for the future is another matter. Unfortunately I couldn’t find the current methane concs on the wub, so I thought I’d ask you lot.

[Update: pulled out from a comment by C (thanks):

http://pubs.giss.nasa.gov/abstracts/2003/Schmidt_Shindell.html

"Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates" Shmidt/Shindell 2003.
From Table 2.1:

M ..... T
1 ..... 8.4
2.5 ... 10.1
4 ..... 11.5
7 ..... 13.4
10 .... 16.7
40 .... 26.9
100 ... 41.1
200 ... 42.5
M = multiple of current concentration.
T = CH4 lifetime (years)

Shakhova states there's 540 Gt total at least and 50 Gt of CH4 ready to go on the Siberian shelf (see Gareth above). So that could double residence time.]

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  2. #2 Magnus W
    2008/09/24

    I’m involved in to much political stuff at the moment… something which could take an abrupt ending soon… so shortly I haven’t heard any numbers or even estimates just the “”This may be of the same magnitude as presently estimated from the global ocean,” he said. “Nobody knows how many more such areas exist on the extensive East Siberian continental shelves.” part… which I guess if I dear to say don’t look catastrophic but not good either.

    http://en.wikipedia.org/wiki/Methane

    An as far as I have looked no runaway… super killing mega bombs… However I haven’t looked very far.

    http://www.google.se/search?hl=sv&client=firefox-a&rls=org.mozilla%3Asv-SE%3Aofficial&hs=LKI&q=god&btnG=S%C3%B6k&meta=

  3. #3 Magnus W
    2008/09/24

    (think my post got stuck… but basically just said that well… don’t look catastrophic but bad… see: “This may be of the same magnitude as presently estimated from the global ocean,” he said. “Nobody knows how many more such areas exist on the extensive East Siberian continental shelves.”)

    http://en.wikipedia.org/wiki/Methane#Methane_in_Earth.27s_atmosphere

    and

    http://scholar.google.com/scholar?hl=en&lr=&safe=off&q=%22ice+cores%22+%2Bconcentration+%2Bincreases+%2Bmethane+&btnG=Search

  4. #4 Dave Rado
    2008/09/24

    Talking of indescribably overhyped, there was a lot of hype not long ago about methane from cows being a serious issue for climate change – yet as silence says, it seems there’s been a decade or so of reasonably steady methane concentrations. So was the cow hype just hype or was there a germ of a serious issue?

    Dave

  5. #5 James Annan
    2008/09/24

    There is certainly the germ of a serious issue: if meat consumption increases (and with it, the global herd) and if we do not work out how to reduce methane emissions (which people are working on, it is not technological pie in the sky but a matter of nutrition science and waste management, with a direct economic payback to motivate the work irrespective of climate change considerations) then we can expect the global methane level to increase and with it global warming.

    But at the moment, there doesn’t seem to be any real sign of this – certainly far less than people anticipated in the emissions scenarios used even as recently as AR4.

    Methane also has the nice property that it does not hang around for long, so it can reasonably be put off to future generations to handle these emissions (in sharp contrast to CO2 where our emissions will hang around for generations). I’m not losing any sleep over it.

    [Agreed re scenarios. Someone (Eli?) suggested that a sufficiently large methane pulse would overcome the sinks and hang around for longer. I don't know -W]

  6. #6 Dave Rado
    2008/09/24

    Thanks James, that’s really helpful – although as far as its not hanging around for long is concerned, as I understand it, it gets converted to CO2 and it then does hang around as CO2; so it’s still a long term problem, surely, albeit less serious than if it persisted in the form of methane.

    Dave

  7. #7 Dave Rado
    2008/09/24

    Sorry, I’ve just realised that what I wrote in my previous post, although applicable to permafrost methane, isn’t applicable in the case of cows, because of the fact that in the case of cows, the resulting CO2 is just part of the natural carbon cycle. Sorry about that.

    Dave

  8. #8 Magnus Westerstrand
    2008/09/25

    My comment got stuck as spam yesterday! Didn’t know you had a quality filter! ;)

    [Anything with a URL seems to do it. Sorry, approved now. You should be trusted as a known contributor but the filters here seem to be a bit rubbish. I've just marked you as trusted, but I doubt it will help -W]

  9. #9 Magnus Westerstrand
    2008/09/25

    Oh the Irony…. the link was not supposed to be… what it was in my first post… this might be more appropriate.

    http://scholar.google.com/scholar?hl=en&lr=&safe=off&q=%22ice+cores%22+%2Bconcentration+%2Bincreases+%2Bmethane+&btnG=Search

  10. #10 Gareth
    2008/09/25

    I’ve been blogging this since earlier this year (the methane tag should get all my relevant posts, but my tagging history’s peripatetic). The first paper to sound an alarming note was given by Shakova et al at the EGU (abstract): money quote…

    …we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time.

    So, what’s abrupt?

    Depends on how many methane chimneys there are. And that is surely well worth finding out.

  11. #11 Magnus Westerstrand
    2008/09/25

    Gareth, interesting that sounds more alarming… that would mean that methane would pass CO2 as the most important greenhouse gas if I remember the numbers correctly? But I don’t find any papers of this happening before, anyone?

  12. #12 silence
    2008/09/25

    Magnus: The arctic is a tough place to get to, and not everybody who has been there has been on the lookout for undersea methane releases. A lack of data about past releases in this area doesn’t mean that they haven’t been happening for centuries.

    Since these methane chimneys allegedly show up on an echo sounder, the would presumably be visible to submarines’ sonar. This means that there’s a good chance that the US or Russian military would have data on their past existence. Anybody know how good the odds of getting that kind of data declassified are?

  13. #13 Magnus Westerstrand
    2008/09/25

    Yes I know that this is the first expedition to go there with good equipment. What I’m fishing for is older data ice cores and such.

  15. #15 CobblyWorlds
    2008/09/25

    [....Someone (Eli?) suggested that a sufficiently large methane pulse would overcome the sinks and hang around for longer. I don't know -W]

    http://pubs.giss.nasa.gov/abstracts/2003/Schmidt_Shindell.html
    “Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates” Shmidt/Shindell 2003.
    From Table 2.1:

    M ….. T
    1 ….. 8.4
    2.5 … 10.1
    4 ….. 11.5
    7 ….. 13.4
    10 …. 16.7
    40 …. 26.9
    100 … 41.1
    200 … 42.5
    M = multiple of current concentration.
    T = CH4 lifetime (years)

    Shakhova states there’s 540 Gt total at least and 50 Gt of CH4 ready to go on the Siberian shelf (see Gareth above). So that could double residence time.

    I’m obviously a delusional alarmist old fool because frankly I’m scared by this.

    PS,
    just taken me an ages to post this because I’ve been looking at CH4 13C fraction here: http://www.esrl.noaa.gov/gmd/ccgg/iadv/
    But after a 12 hour day at work I’m getting nowhere.

  16. #16 Dave Rado
    2008/09/25

    Has anyone come up with a suggestion of why methane concentrations levelled off starting about a decade ago?

  17. #17 Eli Rabett
    2008/09/25

    The issue came up in discussing a paleopaper where there was a large methane pulse. I took the position that the pulse should quickly pass, but one of the authors pointed out to me that while methane destruction is autocatalytic wrt OH, (OH –> HOx –> OH) this can be saturated if there is a ton of methane about, e.g. the amount of methane sets a limit on how much OH can be regenerated. In that case the destruction rate is limited, and the CH4 can live a long (centuries) time.

    Can’t find the article or the post

  18. #18 Eli Rabett
    2008/09/25

    Of course, Cobbly found the article. Thanks.