Methane Data

Posted by William M. Connolley on September 25, 2008
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AL (and V1S, sorry!) pointed me to http://www.esrl.noaa.gov/gmd/aggi/, which lead me to http://www.esrl.noaa.gov/gmd/ccgg/iadv/, from which I selected Barrow, as being in the Arctic, and CH4, as being methane, and 2000-2008, as being a small enough interval that you can see whats going on, and I got:

i-f55b85ea17081c40765e0f113a9db880-methane-image-2000-2009.png

So there you have it: methane isn’t shooting up precipitously. Its a bit higher this year than last. OK, I know, those are preliminary data. But I think thats enough to rule out any major changes.

Its worth pointing out (JA has said this, but I forget where) that methane is an awful long way below the “std” BAU scenarios. I can’t find a recent one now, but the IPCC ’90 BAU scenario would have us at about 2200 ppbv by now.

BTW, Nuture says that CO2 [corrected] *emissions* are now increasing at 3.5 % a year, which is higher than it was. Don’t immeadiately know what concentrations are increasing at.

[Update: Small side note: here we have Nature linking to wiki. I didn't know they did that -W]

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  1. #1 silence
    2008/09/25

    I gave you http://www.esrl.noaa.gov/gmd/ccgg/iadv/ a good 20 hours earlier. :P

    [Corrected. Sorry -W]

  2. #2 Magnus Westerstrand
    2008/09/25

    Yes, but the interesting part must be possible future scenarios?

  3. #3 crandles
    2008/09/25

    OK compare:

    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/alt/alt_ch4_ts_surface_00210.png

    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/zep/zep_ch4_ts_surface_00475.png

    and

    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/mlo/mlo_ch4_ts_obs_03397.png

    The first two show more or less straight line increases in concentration from 1820 to 1870 nmol/mol over the period from 1995 to present.

    Mauna Loa shows show more or less a straight line increase in concentration from 1760 to 1790nmol/mol.

    The higher concentration at higher latitude is expected

    http://en.wikipedia.org/wiki/Image:Ch4rug_multicolor.png

    but why does the higher latitude increase by 50 compared to Mauna Loa increase of 30? Would this suggest an extra local source providing 20nmol/mol?

  4. #4 David B. Benson
    2008/09/25

    How is 3.5% a year less than 1%/y?

    [It isn't, my typo. But 3.5ppm/y (out of 384) is less than 1%/y -W]

  5. #5 James Annan
    2008/09/25

    when one is the rate of increase of emissions (or maybe rate of increase of the annual increment of concentration), and the other is the rate of increase of CO2 concentration…

  6. #6 crandles
    2008/09/26

    Agree with James that 3.5 is % for emissions

    The link says

    Most striking is that, despite years of effort, carbon dioxide emissions are increasing at an alarming rate of 3.5% a year- faster than the 2.7% predicted by the IPCC in their worst case scenario, and miles ahead of the 0.9% annual rise in the 1990s.

    [My f*ck-up. Nuture says *emissions* are increasing at 3.5%/y. They don't mention concentrations. I've corrected myself, again -W]

    Meanwhile I think I was looking cross-eyed at those graphs I linked. It is nearer 10 than 20 for the difference.

  7. #7 ice
    2008/09/26

    does anyone have a good explanation for why the minimum of the CH4 seasonal cyle is in summer (which should be the max of wetlands emission) ? is it totally driven by the photochemical sink?

  8. #8 crandles
    2008/09/26

    >Don’t immeadiately know what concentrations are increasing at.

    Nature links
    http://www.globalcarbonproject.org/carbontrends/index.htm

    which says
    “Atmospheric CO2 growth
    Annual mean growth rate of atmospheric CO2 was 2.2 ppm per year in 2007 (up from 1.8 ppm in 2006), and above the 2.0 ppm average for the period 2000-2007. ”

    and

    “Anthropogenic CO2 emissions have been growing about four times faster since 2000 than during the previous decade, and despite efforts to curb emissions in a number of countries which are signatories of the Kyoto Protocol. Emissions from the combustion of fossil fuel and land use change reached the mark of 10 billion tones of carbon in 2007. Natural CO2 sinks are growing, but more slowly than atmospheric CO2, which has been growing at 2 ppm per year since 2000. This is 33% faster than during the previous 20 years. All of these changes characterize a carbon cycle that is generating stronger climate forcing and sooner than expected.
    ”

    Nature says
    “For the first time, we have hit 10 billion tonnes of carbon emitted annually.”

    which seems to fit with 8.5 from fossil fuels and cement and 1.6 from land use.

    But
    “CO2 removal by natural sinks
    Natural land and ocean CO2 sinks have removed 54% (or 4.8 PgC per year) of all CO2 emitted from human activities during the period 2000-2007. The size of the natural sinks has grown in proportion to increasing atmospheric CO2. However, the efficiency of these sinks in removing CO2 has decreased by 5% over the last 50 years, and will continue to do so in the future. That is, 50 years ago, for every ton of CO2 emitted to the atmosphere, natural sinks removed 600 kg. Currently, the sinks are removing only 550 kg for every ton of CO2 emitted, and this amount is falling. ”

    Hmm 4.8PgC/10.1PgC (not compaable years) is only 47.5% not 54% natural removal suggesting falling removal. Doing a few unjustifiable calculations and assuming sink increases in proportion to excess CO2 over 280ppm then I get for 2000 7.9GtC emissions 4.46GtC natural removal which is 56% natural removal. For 2007 I get 5.13GtC natural removal; 51% natual removal. Natural removal falling from 56% to 51% in just 7 years does not sound good but I am probably stretching the figures too far.

  9. #9 Ice
    2008/09/26

    Another question, then:
    does anyones have a plot of the observed evolution of CO2 atmo concentration versus the concentrations used in the Ipcc models ?
    are we above the forescast in terms of concentrations just as we are in terms of emissions ?

  10. #10 Steve Bloom
    2008/09/26

    Barrow is a bit distant from the ESS. To what extent weuld we expect methane measurements there to reflect a sharp increase over the ESS?

    Also, Nature just posted a detailed-ish public access (for now) article on all of this. I have to say I didn’t find the quote from the AWI guy entirely reassuring.

  11. #11 CobblyWorlds
    2008/09/26

    Ice,

    Sorry no pics, but:
    SRES tables here.
    http://www.grida.no/CLIMATE/IPCC_TAR/WG1/531.htm

    NOAA Global CO2 halfway down this page.
    http://www.esrl.noaa.gov/gmd/ccgg/trends/

    2007 was about 382.71, call that 382. Currently about 2ppm per year, so that’s 6ppm extra to get a ballpark 2010 level. Just zip along the 2010 line of the SRES table and compare with 388ppm CO2.

    As for your earlier question, sounds reasonable. But as I can’t explain the rise in d13C CH4 (e.g. Barrow vs Alert, Mt Waliguan China, Mace Head Ireland) I’ve decided it’s time to do some reading.

  12. #12 ice
    2008/09/27

    @cobby
    thanks for the sres link, very interesting.
    Taking your 2010/ 388ppm level, looks like we are not out the way yet – but i need to read carefully about isam and berncc..

  13. #13 CobblyWorlds
    2008/09/27

    Anyone know why the 13C content of CH4 rose in 2007/8?

    If it were clathrates surely it should fall… Or can someone educate me?

    Alert.
    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/alt/alt_ch4c13_ts_surface_00210.png
    Barrow.
    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/brw/brw_ch4c13_ts_surface_00011.png

    Mace Head Ireland might suggest it’s not localised to the Arctic.
    http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/mhd/mhd_ch4c13_ts_surface_00025.png

    What data there is in the southern hemisphere shows less of a deviation, as is to be expected.

  14. #14 David B. Benson
    2008/09/27

    ice — Rotting biomass produces CH4.

  15. #15 Steve L
    2008/09/28

    Interesting discussion, thanks. David Benson, I’m also interested in ice’s first question. Your answer confuses me, though, because I would assume Alaska to be too frozen after about September to support much rotting. Is the methane wafting up there from somewhere else?