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Much ado about methane

Filed under: — david @ 4 January 2012

Methane is a powerful greenhouse gas, but it also has an awesome power to really get people worked up, compared to other equally frightening pieces of the climate story.

What methane are we talking about?

The largest methane pools that people are talking about are in sediments of the ocean, frozen into hydrate or clathrate deposits (Archer, 2007). The total amount of methane as ocean hydrates is poorly constrained but could rival the rest of the fossil fuels combined. Most of this is unattractive to extract for fuel, and mostly so deep in the sediment column that it would take thousands of years for anthropogenic warming to reach them. The Arctic is special in that the water column is colder than the global average, and so hydrate can be found as shallow as 200 meters water depth.

On land, there is lots of methane in the thawing Arctic, exploding lakes and what not. This methane is probably produced by decomposition of thawing organic matter. Methane could only freeze into hydrate at depths below a few hundred meters in the soil, and then only at “lithostatic pressure” rather than “hydrostatic”, meaning that the hydrate would have to be sealed from the atmosphere by some impermeable layer. The great gas reservoirs in Siberia are thought to be in part frozen, but evidence for hydrate within the permafrost soils is pretty thin (Dallimore and Collett,1995)

Russian gas well

Is methane escaping due to global warming?

There have been observations of bubbles emanating from the sea floor in the Arctic (Shakhova, 2010; Shakhova et al., 2005) and off Norway (Westbrook, 2009). The Norwegian bubble plume coincides with the edge of the hydrate stability zone, where a bit of warming could push the surface sediments from stable to unstable. A model of the hydrates (Reagan, 2009) produces a bubble plume similar to what’s observed, in response to the observed rate of ocean water warming over the past 30 years, but with this warming rate extrapolated further back in time over the past 100 years. The response time of their model is several centuries, so pre-loading the early warming like they did makes it difficult to even guess how much of the response they model could be attributed to human-induced climate change, even if we knew how much of the last 30 years of ocean warming in that location came from human activity.

Sonar images of methane plumes, from Westbrook

Lakes provide an escape path for the methane by creating “thaw bulbs” in the underlying soil, and lakes are everywhere appearing and disappearing in the Arctic as the permafrost melts. (Whether you get CO2 or a mixture of CO2 plus methane depends critically on water, so lakes are important for that reason also.)

Methane bubbles captured in freezing lake ice in Alaska

So far there hasn’t been strong evidence presented for detection enhanced methane fluxes due to anthropogenic warming yet. Yet it is certainly believable for the coming century however, which brings us to the next question:

What effect would a methane release have on climate?

The climate impact of releasing methane depends on whether it is released all at once, faster than its lifetime in the atmosphere (about a decade) or in an ongoing, sustained release that lasts for longer than that.

chronic vs catastrophic release cartoon

When methane is released chronically, over decades, the concentration in the atmosphere will rise to a new equilibrium value. It won’t keep rising indefinitely, like CO2 would, because methane degrades while CO2 essentially just accumulates. Methane degrades into CO2, in fact, so in simulations I did (Archer and Buffett, 2005) the radiative forcing from the elevated methane concentration throughout a long release was about matched by the radiative forcing from the extra CO2 accumulating in the atmosphere from the methane as a carbon source. In the figure below, the dashed lines are from a simulation of a fossil fuel CO2 release, and the solid lines are the same model but with an added methane hydrate feedback. The radiative forcing from the methane combines the CH4 itself which only persists during the time of the methane release, plus the added CO2 in the atmosphere, which persists throughout the simulation of 100,000 years.

response of carbon cycle / hydrate model to fossil fuel CO2 forcing

The possibility of a catastrophic release is of course what gives methane its power over the imagination (of journalists in particular it seems). A submarine landslide might release a Gigaton of carbon as methane (Archer, 2007), but the radiative effect of that would be small, about equal in magnitude (but opposite in sign) to the radiative forcing from a volcanic eruption. Detectable perhaps but probably not the end of humankind as a species.

What could happen to methane in the Arctic?

The methane bubbles coming from the Siberian shelf are part of a system that takes centuries to respond to changes in temperature. The methane from the Arctic lakes is also potentially part of a new, enhanced, chronic methane release to the atmosphere. Neither of them could release a catastrophic amount of methane (hundreds of Gtons) within a short time frame (a few years or less). There isn’t some huge bubble of methane waiting to erupt as soon as its roof melts.

And so far, the sources of methane from high latitudes are small, relative to the big player, which is wetlands in warmer climes. It is very difficult to know whether the bubbles are a brand-new methane source caused by global warming, or a response to warming that has happened over the past 100 years, or whether plumes like this happen all the time. In any event, it doesn’t matter very much unless they get 10 or 100 times larger, because high-latitude sources are small compared to the tropics.

Methane as past killing agent?

Mass extinctions like the end-Permean and the PETM do typically leave tantalizing spikes in the carbon isotopic records preserved in limestones and organic carbon. Methane has an isotopic signature, so any methane hijinks would be recorded in the carbon isotopic record, but so would changes in the size of the living biosphere, soil carbon pools such as peat, and dissolved organic carbon in the ocean. The end-Permean extinction is particularly mysterious, and my impression is that the killing mechanism for that is still up for grabs. Methane is also one of the usual suspects for the PETM, which consisted of about 100,000 years of isotopically light carbon, which is thought to be due to release of some biologically-produced carbon source, similar to the way that fossil fuel CO2 is lightening the carbon isotopes of the atmosphere today, in concert with really warm temperatures. I personally believe that the combination of the carbon isotopes and the paleotemperatures pretty much rules out methane as the original carbon source (Pagani et al., 2006), although Gavin draws an opposite conclusion, which we may hash out in some future post. In any case, the 100,000-year duration of the warming means that the greenhouse agent through most of the event was CO2, not methane.

Could there be a methane runaway feedback?.

The “runaway greenhouse effect” that planetary scientists and climatologists usually call by that name involves water vapor. A runaway greenhouse effect involving methane release (such as invoked here) is conceptually possible, but to get a spike of methane concentration in the air it would have to released more quickly than the 10-year lifetime of methane in the atmosphere. Otherwise what you’re talking about is elevated methane concentrations, reflecting the increased source, plus the radiative forcing of that accumulating CO2. It wouldn’t be a methane runaway greenhouse effect, it would be more akin to any other carbon release as CO2 to the atmosphere. This sounds like semantics, but it puts the methane system into the context of the CO2 system, where it belongs and where we can scale it.

So maybe by the end of the century in some reasonable scenario, perhaps 2000 Gton C could be released by human activity under some sort of business-as-usual scenario, and another 1000 Gton C could come from soil and methane hydrate release, as a worst case. We set up a model of the methane runaway greenhouse effect scenario, in which the methane hydrate inventory in the ocean responds to changing ocean temperature on some time scale, and the temperature responds to greenhouse gas concentrations in the air with another time scale (of about a millennium) (Archer and Buffett, 2005). If the hydrates released too much carbon, say two carbons from hydrates for every one carbon from fossil fuels, on a time scale that was too fast (say 1000 years instead of 10,000 years), the system could run away in the CO2 greenhouse mode described above. It wouldn’t matter too much if the carbon reached the atmosphere as methane or if it just oxidized to CO2 in the ocean and then partially degassed into the atmosphere a few centuries later.

The fact that the ice core records do not seem full of methane spikes due to high-latitude sources makes it seem like the real world is not as sensitive as we were able to set the model up to be. This is where my guess about a worst-case 1000 Gton from hydrates after 2000 Gton C from fossil fuels in the last paragraph comes from.

On the other hand, the deep ocean could ultimately (after a thousand years or so) warm up by several degrees in a business-as-usual scenario, which would make it warmer than it has been in millions of years. Since it takes millions of years to grow the hydrates, they have had time to grow in response to Earth’s relative cold of the past 10 million years or so. Also, the climate forcing from CO2 release is stronger now than it was millions of years ago when CO2 levels were higher, because of the band saturation effect of CO2 as a greenhouse gas. In short, if there was ever a good time to provoke a hydrate meltdown it would be now. But “now” in a geological sense, over thousands of years in the future, not really “now” in a human sense. The methane hydrates in the ocean, in cahoots with permafrost peats (which never get enough respect), could be a significant multiplier of the long tail of the CO2, but will probably not be a huge player in climate change in the coming century.

Could methane be a point of no return?

Actually, releasing CO2 is a point of no return if anything is. The only way back to a natural climate in anything like our lifetimes would be to anthropogenically extract CO2 from the atmosphere. The CO2 that has been absorbed into the oceans would degas back to the atmosphere to some extent, so we’d have to clean that up too. And if hydrates or peats contributed some extra carbon into the mix, that would also have to be part of the bargain, like paying interest on a loan.


It’s the CO2, friend.


  1. D. Archer, "Methane hydrate stability and anthropogenic climate change", Biogeosciences, vol. 4, pp. 521-544, 2007.
  2. N. Shakhova, I. Semiletov, I. Leifer, A. Salyuk, P. Rekant, and D. Kosmach, "Geochemical and geophysical evidence of methane release over the East Siberian Arctic Shelf", Journal of Geophysical Research, vol. 115, 2010.
  3. N. Shakhova, "The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle", Geophysical Research Letters, vol. 32, 2005.
  4. G.K. Westbrook, K.E. Thatcher, E.J. Rohling, A.M. Piotrowski, H. Pälike, A.H. Osborne, E.G. Nisbet, T.A. Minshull, M. Lanoisellé, R.H. James, V. Hühnerbach, D. Green, R.E. Fisher, A.J. Crocker, A. Chabert, C. Bolton, A. Beszczynska-Möller, C. Berndt, and A. Aquilina, "Escape of methane gas from the seabed along the West Spitsbergen continental margin", Geophysical Research Letters, vol. 36, pp. n/a-n/a, 2009.
  5. M.T. Reagan, and G.J. Moridis, "Large-scale simulation of methane hydrate dissociation along the West Spitsbergen Margin", Geophysical Research Letters, vol. 36, 2009.
  6. D. Archer, and B. Buffett, "Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing", Geochemistry, Geophysics, Geosystems, vol. 6, pp. n/a-n/a, 2005.
  7. M. Pagani, K. Caldeira, D. Archer, and J.C. Zachos, "ATMOSPHERE: An Ancient Carbon Mystery", Science, vol. 314, pp. 1556-1557, 2006.

148 Responses to “Much ado about methane”

  1. 51
    Hank Roberts says:

    You can’t see methane. How could you see a methane plume and know its size from a ship? If there are measurements, they’ve yet to be published.

    What can see methane? GOSAT/IBUKI
    The satellite coverage is shown here:

    Barrow data points are provisional and that site warns against using them.

    There are known other sources, including much closer to Barrow, e.g.
    You want scary? what’s known is plenty — e.g. see that paper:

    “… we have conducted [more than] 200 point measurements of methane emission and ecosystem respiration rates on the Arctic coastal tundra within the Barrow Environmental Observatory. These measures reveal that methane emission rates are log-normally distributed, but ecosystem respiration rates are normally distributed. The contrast in frequency distributions indicates that methane and carbon dioxide emission rates respond in a qualitatively different way to their environmental drivers: while ecosystem respiration rates rise linearly with increasing temperature and soil moisture, methane emissions increase exponentially….”

    Could that biological change be happening in the ocean as well as on land?

  2. 52
    Hank Roberts says:

    ps for wili — did you check that provisional methane data at Barrow lately?

    Look at it repeatedly. Once the orange data points are checked, if they’re valid, they stay on the chart. and choose parameter “methane”

    Remember: “Data shown in ORANGE are preliminary.”
    This is a snapshot: — date generated in lower right corner.

  3. 53
    prokaryotes says:

    You always have to look at the big picture and look on the capacities of earth natural carbon sinks (input/output). The natural sinks it seems, are over loaded and degrade from all kinds of anthro involvements. And then there are feedback mechanismic which are not accounted for too. For instance the Jenkinson effect.

    The big picture is also that we are on path to an ice free planetary state, thus the entire hydrocyle is put on steroids. Hence why extreme weather, especially with increased precipitation is the new normal.

  4. 54

    #53–Appreciate the concern for accuracy, Hank–but you can certainly see methane bubbles break the surface.

    And what are the chances that a professional expedition looking for methane wouldn’t have the appropriate gear to image–and measure–it?

    You’re right of course that the results aren’t published yet; but they surely will be coming in the nearish future. And no doubt they’ll be eagerly perused when they do show up in the literature.

  5. 55
    CM says:

    Thanks for this, the issue’s been bubbling up a lot on the open threads.

    [Response: :)

    > although Gavin draws an opposite conclusion, which we may hash out
    > in some future post

    Might one hope for a preview? I finally got around to reading David’s Carbon Cycle (warmly recommended), so I might even be able to follow you this time.

  6. 56
    Hank Roberts says:

    > Jenkinson effect

    “… strongly dependent on the rate …. long-term warming equivalent to 10°C per century could be sufficient to trigger compost-bomb instability in drying organic soils.”

    Note that —> 10 degrees C per century
    High compared to anything we know about, e.g. (hat tip Tamino via Romm)

    Sure, we know when topsoil dies it produces lots of CO2 (as does anything that dies if not promptly eaten by something).

    My impression was that screwed up Biosphere II — I recall they rushed closure, didn’t bring in mineral soil below a layer of topsoil and duff; instead, they used all topsoil. Of course that part buried too deep died.
    Of course CO2 went way up.

    So we _know_ that already.
    Would we be so stupid …

    Oh, right.

  7. 57
    wili says:

    Thanks for pointing out that the methane spike has now been scrubbed from the Barrow, Hank. Usually don’t they replace the aberrant orange dots with little green crosses? This time they seem to have been left out completely. Is that a usual practice, as far as you know?

    I would really like to hear what people are thinking of Semiletov and Shakhova. It seems to me that we either have to say, in spite of their impressive credentials and experience in the area, that they are essentially delusional, or that they are right but that the monitoring stations and some other sources are faulty. Is it possible that large quantities of methane would not have made it to monitoring stations hundreds of miles away by now? Or is there some super sink that could have gobbled up all the methane that S&S (and others) report seeing bubbling from the ocean? Could it be that something else was bubbling up?

    In short, should we really just ignore the statements of these experienced scientists? Do they have a reputation for making things up that we should know about?

    [Response:I think they’re doing important, necessary work and I’m grateful to them. David]

  8. 58
    George Spiegelman says:

    Relating to #4 and #18. Some may be aware that there is a lot of debate on the topic of having municipalities separate organics from non organic in the waste stream (separate collection from households and businesses). Millions are being spent or are being considered.

    There are lots of components to these debates. The one I want to raise (and that is always included) is that organics sent to landfills generate methane (ignore capture, since it is so inefficient) and this is significantly worse than separating them so they can be composted which would produce CO2-and compost.
    Does the short half life of methane fatally weaken this argument?


    [Response:No, since methane is more powerful than CO2 it would have a stronger climate impact until it decays to CO2. The main fear of CO2, though, is that it will build up and cause much more severe problems in the decades ahead. Methane vs. CO2 is less relevant to that concern. David]

  9. 59
    Pete Dunkelberg says:

    It took just hours to get back to methane alarmism. But nice try David.

  10. 60
    wili says:

    To George @ 58–I think it is still a cogent argument. Even over the period of a century, methane has global warming potential 35 times CO2. It also argues for slow composting with less turning since this leaves more of the carbon in the compost (and produces more compost).

    Our landfills have been a way that we have very temporarily and ineffectively been sequestering carbon, but that carbon has been and will be coming back to us in the very powerful form of methane.

    Your point reminds me of another issue–any large burst of methane in the next few years and decades is especially bad since it makes it that much more likely that other feedback loops will be kicked off or kicked into high gear before we have started reducing CO2 emissions and bringing down CO2 levels.

    Again, even a remote possibility that significant amounts of methane could come from the Arctic sea and land should be a spur to set us on an emergency path to drastically reduce GHG emissions. Actual findings that certainly parts of the tundra and reportedly parts of the ocean are starting to release increasingly large amounts of GHGs should not be minimized or swept under the rug, but shut set policy makers hair on fire to find every remotely reasonable way to reduce our own emissions. But instead we have the very weak tea that is the results of the Durban talks. Very sad for ourselves and for our progeny.

  11. 61
    Anonymous Coward says:

    #58 George Spiegelman:
    “Does the short half life of methane fatally weaken this argument?”
    Weaken, yes. Fatally, no.
    The lifetime of methane in the atmosphere is already taken into account in most accounts of the importance of methane as a GHG. But these accounts depend critically on the timeframe being considered.
    Lower methane emissions would yield less methane in the atmosphere (everything else being equal). That would allow more heat to reach outrespace, which would of course be welcome.

    But, strategically, you’ve got to wonder if millions should be spent going after methane at this stage…
    If one were solely concerned about the next few years, going after methane would make sense. But, if you take the long view, any harm that methane could do in 10 years, CO2 will do in 30 years anyway (arbitrary numbers for illustration only).
    Deep cuts in CO2 emissions would not stop warming immediately because the implied loss of aerosols. In my opinion, that’s the point at which it would make the most sense to play all available cards. That’s the point at which one could start talking about avoidable warming.
    As long as CO2 is being emitted at anything like the current pace, I fear schemes to reduce methane emissions driven by arbitrary and short-sighted CO2e values effectively amount to yet another excuse for inactivism on the central issue.
    But that’s just my opinion. The fact of the matter is that reducing methane emission would have a positive impact.

  12. 62
    Mike Roddy says:

    Methane is too spooky for many scientists to wrap their heads around. It’s one thing to talk about adding 2 ppm CO2 per year and +.3C per decade, it’s quite another to talk about strangely behaving chemical monsters from the deep. Methane has stimulated more cautious and even wrong scientific opinion from quality scientists than any topic I’ve observed in the last decade.

    In any case, we will all have to await Shakhova and Semilitov’s paper, due sometime around April, last I heard. Whatever it says, or at least that which survives peer review, could lead to the conclusion that emergency measures are called for. This will require government action, something dreaded by the Kochs and Boyces and now, thanks to their media massaging, much of the public as well.

    All I ask is that Gavin et al keep an open mind, something that was not apparent in Archer’s piece. Many of us depend on you. And yes, the Arctic measurements taken so far were done with state of the art instruments, by an international team of supremely qualified scientists. Preemptive attacks and pooh poohing are uncalled for, and belong on Fox News, not here.

  13. 63
    David B. Benson says:

    George Spiegelman @58 — Many landfill operators flre the expressed methane.

  14. 64
    Lynn Vincentnathan says:

    Here’s another comment from that skeptic — could you answer this, David?

    I wrote: A portion of CO2 can remain in the atmosphere up to 100,000 years.

    His comment: Your knowledge of CO2 is flawed. You keep repeating this claim – I keep asking you for your evidence.

    [I provided links to some articles and books by D. Archer for him.]

    His comment: CO2 is heavier than the atmosphere. CO2 is much heavier than Methane.
    CO2’s Molar mass [ molecular weight ] is 44.0096 g/mol. It has a net atmospheric lifetime of about 5 years.

    Methane’s [ CH4 ] Molecular weight : 16.043 g/mol. It has a net atmospheric lifetime of about 10 years.

    I responded: That’s an interesting point, but I’m thinking it is not the weight, but the fact that CH4 is less stable and degrades for why it stays in the atmosphere a much shorter time than CO2.

    I’ll ask David Archer about it….

    [Response:He thinks that gases settle out of the atmosphere, so heavy ones have a shorter lifetime than light ones? That’s a new one. You are spending time reading this person’s wisdom, why? The five year lifetime for CO2 he quotes could be an exchange time scale, how long an individual CO2 molecule stays in the air before it moves into a plant or the ocean. But exchange fluxes don’t affect atmospheric CO2, only net uptake fluxes. David]

  15. 65
    Hank Roberts says:

    > … capture, … so inefficient
    numbers? what’s done is done and needs to be checked; are there new designs that successfully make clean enough methane an output?

    > organics
    As in organic chemicals, not organic farming

    > compost
    I’m much happier getting compost made from household food and yard waste that’s been piled and turned (by bulldozers admittedly) so it stays aerated, doesn’t make methane, and gives back a fairly clean compost product.

    If there weren’t cities collecting food and yard waste, what alternate source of compost would likely be used on at least the public lands — sewage biosludge?

    It’s happening. And that seems less than good practice from the results so far.

  16. 66
    Hank Roberts says:

    Well, you can feed it to rabbits.
    But what then?

  17. 67
    Hank Roberts says:

    Oh. Well, here’s some numbers on BTU contents of SEWAGE SLUDGE: A FASCINATING FEEDSTOCK FOR CLEAN ENERGY … (PDF)

  18. 68

    #57–“Is it possible that large quantities of methane would not have made it to monitoring stations hundreds of miles away by now?”

    Sure. If the methane were to disperse uniformly (and remain in a ‘flat’ layer), concentrations would drop as the square of those ‘hundreds of miles.’ If not, it’s quite likely the wind wouldn’t blowing in quite the right direction–there’s many more vectors that don’t lead to the monitoring station than ones that do.

    IIRC, S & S were unsurprised that their plumes weren’t being detected at large distances.

    [Response:The air mixes longitudinally fairly quickly, so if there is an ongoing new large source in the high latitudes, going for more than a few months I guess, it would be detectable in the interhemispheric gradient of methane. David]

  19. 69

    #58–Also, there has been and is a lot of work on using “landfill gas”–about 50% methane. In the US, according to the source linked below, about 20% of landfills are already harvesting energy from LFG, with roughly another 20% as good candidates for the utilization of this technology.

    The technology is reasonably common in parts of Europe, and projects exist pretty much around the world.

  20. 70
    Hank Roberts says:

    > Is that a usual practice, as far as you know?
    You should inquire.

  21. 71
    Hank Roberts says:

    > do you know
    A far better response: Wili, you should click their Help button, upper right.

  22. 72

    I like this essay except it doesn’t show where the methane sources are on a map. I know only about the Beaufort sea . I would say dominant wind direction causing an El-Nino like warming of the more open coastal Arctic ocean should have been modeled, otherwise the time scales proposed here are very conservative. I would caution anyone coming to absolute conclusions without a model simulating current Arctic sea ice melts as well.

  23. 73
    David B. Benson says:

    Lynn Vincentnathan @64 — Carbon dioxide is a well mixed gas in the atmosphere (with a mixing time of about 2+ years between the northern and southern hemisphere). In other words, even carbon dioxide is sufficiently light that a combination of Brownian motion, turbulence and simple convection keeps it aloft and well, but not perfectly, mixed.

    Furthermore, at water surfaces it quickly equalizes the partial pressures of dissolved in the water and free in the air. So while a tracked molecule of carbon dioxide in the atmosphere will eventually dissolve in watr another molecule will ‘evaporate’ to replace it.

    David Archer’s “The Long Thaw” has rest of the carbonate story; its not such easy chemistry.

  24. 74
  25. 75
    Susan Anderson says:

    On slime, until recently I did a lot of painting at the shore (wind on water, waves in motion, hence current fascination with water vapor maps, and you could add in chaos and celtic etc. imagery if you like that kind of thing). It got discouraging as rocks began to be covered regularly with black and green slime, making the light dark and unappealing; there was a similar deterioration in England’s west country, and they’ve had a good few floods as well.

    A variety of Earth Observatory satellite images show various blooms; I’ve even adopted one labeled Ostrov Kolguyev for my desktop. I may be imagining things, but news of these does seem to be on the increase. It fits with land-based observations of more insect pests as seasons lengthen.

    It does seem that even a smaller temporary amplification of polar methane, accompanied as you say by a larger effect closer to the equator, cannot be good news.

    In any case, a very informative article and discussion for which I thank you all, yet again.

  26. 76

    @Wayne, you can see the levels at 400 mb for the Northern Hemisphere for the month of November for years 2011, 2010 and 2002, on my blog, where I put them up so people can compare. The difference between 2002 and 2011 is pretty large:

  27. 77
    Edward Greisch says:

    51 Hank Roberts: Seeing methane: Try an infrared camera. Somewhere on the web I saw a video of methane leaking out of a valve.

  28. 78
    sidd says:

    There is a nice depiction of hydrate stability zone breakdown at Barrow
    from the University of Alaska,Romanofsky and Osterkamp

  29. 79
    Geoff Beacon says:

    Thank you Wili, Hank and Tenney Naumer. You have summarised the present situation enough for me to wait a bit before I hassle the policy makers I can contact – probably until I hear more about what Shakova and Semiletov saw and measured.

    Another side of the methane discussion is it’s role as a short(er) term forcing agent. Anna #37 mentioned one of Hansen’s papers but the paper avoids mentioning the difficult issue of beef. Does anyone give any credibility to Livestock and Climate Change by the World Watch Institute. The authors, Robert Goodland and Jeff Anhang, say

    Livestock are already well-known to contribute to GHG emissions.

    Livestock’s Long Shadow, the widely-cited 2006 report by the United Nations Food and Agriculture Organization (FAO), estimates that 7,516 million metric tons per year of CO2 equivalents (CO2e), or 18 percent of annual worldwide GHG emissions, are attributable to cattle, buffalo, sheep, goats, camels, horses, pigs, and poultry.

    That amount would easily qualify livestock for a hard look indeed in the search for ways to address climate change. But our analysis shows that livestock and their by products actually account for at least 32,564 million tons of CO2e per year, or 51 percent of annual worldwide GHG emissions.

    A very large component of their GHG emissions is methane.

    [Response: there are many errors in this report which ends up greatly overstating the role of methane. That is not to say methane is negligible, but rather it has to be seen in context – the ipcc report is much better than this. – gavin]

  30. 80
    Pete Dunkelberg says:

    Lynn @ 64, I see that David has given a very good straightforward
    answer. I want to add: Your knowledge of co2 is not flawed. It may be limited but that’s a different thing. The other party’s knowledge is flawed, or in other words the problem is what he knows that isn’t so, or in other words he’s an idiot. Is he really one oft those people who thinks co2 falls out of the sky because of it’s molecular weight?

    Anyway, you might want to read:

    VO2 Rising by Tyler Volk


    The Carbon Cycle by David Archer.

    Those are both short books. Archer’s is more technical.

    Finally, the evidence that when the CO2 fraction is elevated, it stays elevated for a long time comes from paleo-studies of CO2 concentration. Ask your “skeptic” what takes CO2 out of the air. Just ask him and see what he says. That’s enough for now.

  31. 81
    Joseph O'Sullivan says:

    #79 (Geoff Beacon and Gavin)

    On environmental blogs like Grist the FAO report came up.

    Environmentalists who are vegetarians/vegans said the equivalent of “we told you so” and urged all environmental groups to push meat free diets. As a meat-eating environmentalist I wondered how robust the arguments for livestock’s contribution to AGW in the FAO report were.

    I have a question about Gavin’s reply. Which report has many errors, the FAO report or the World Watch Report? What are the errors?

    Any light that could be shed on this issue would be greatly appreciated.

    [Response: the worldwatch report is the one with the problems. This came up a few years ago when it was published, and the errors involve double counting, including things that are actually carbon neutral, and some large over-estimates of individual terms. But in any attribution excercise, there are many different ways of slicing things and many of the comparisons that are made are down using inconsistent accountings (ie using full life cycle analysis vs not), and so many of the headlines are a little misleading at face value. – gavin]

  32. 82
    SecularAnimist says:

    Gavin, if and when time permits, I would love to see a RealClimate analysis of both the FAO and the WorldWatch studies of GHG emissions attributable to animal agriculture a.k.a. livestock production.

    The FAO study attributed nearly 20 percent of anthropogenic GHG emissions to animal agriculture. Even though that’s less than half of what the WorldWatch study found, it is still comparable to the transport sector — which gets a lot more attention.

    Looking at the issue another way, there was a study a few years back (I’ll try to find a link later) that compared the GHG footprint of the average American diet to that of a vegan diet, and found that the reduction in GHG footprint from switching from a conventional American meat-heavy diet to a vegan diet was comparable to the reduction from replacing a conventional gasoline-fueled car with a Prius.

    Given that adopting a vegan diet costs far less than buying a Prius (and in fact most likely will save you money), and that it also benefits your health, reduces your contribution to other very serious environmental impacts of meat production, and addresses animal welfare concerns as well, it certainly seems like an appealing option for anyone who wants to take personal action on global warming.

    And yet, for some reason, many environmentalists seem to really get their hackles up when this is suggested.

  33. 83
    Anonymous Coward says:

    #81 Joseph O’Sullivan,
    About livestock, the methane issue is a distraction (for the time being anyway). It’s carbon neutral and the impact goes away as soon as the methane degrades to CO2 in the atmosphere.
    The main issue with livestock is that raising grain-fed beef (and similar species) has a significant carbon footprint, in part because fossil fuels are used for inputs and operations in the farms which raise the grain. It takes a lot of grain to get a little meat on your table and you would get a lot more nutrition out of the grain if you ate it directly. The impact of the extra fossil fuel combustion isn’t going away because a fraction of the CO2 is likely to remain in the atmosphere a very long time…
    Livestock which simply roams the countryside for food does not have that problem.

  34. 84
    Anonymous Coward says:

    #82 SecularAnimist,
    “comparable to the reduction from replacing a conventional gasoline-fueled car with a Prius”
    There are conventional cars which consume less (depending on the test) than a Prius, a very heavy car. The Prius’ efficiency in traffic jams can’t be beaten by conventional cars however.

  35. 85
    D Goin says:

    Maybe I missed it, but how is bio-activity accounted for; whereby melting of permafrost initiates biological activity, heating the surrounding permafrost, causing deeper melting and composting, etc.? Intuition (which is not the best way to analyze things) makes me thing that these types of runaways would not have such a long lag.

    [Response:Interesting question. I tend to think of soils in the active (seasonally melted) zone of permafrost or around Arctic lakes as just plain cold, but I’ve never actually been to the Arctic, what do I know? David]

  36. 86
    Killian says:

    David wrote: “The only way back to a natural climate in anything like our lifetimes would be to anthropogenically extract CO2 from the atmosphere.”

    I’d love to see an RC thread on this.

    [Response:Good idea, watch this space. David]


    Please be good enough to include the much saner, easier, healthier and more sustainable methods that have nothing to do with extracting more fossil fuels. I’ve posted them many times. Let me know if you need the links, David.

    Quick hit: Geo-engineering based in technology is a Very Bad Idea. unintended consequences and all that… nature-mimicking solutions much preferred.

  37. 87
    Geoff Beacon says:

    Thanks Gavin for your comment in #81.

    I am quite prepared to accept that the World Watch report has problems but the authors do have certain plausible arguments for increasing the CO2e footprint of livestock-related activity set out in the FAO report.

    I’m surprised that you did not comment on the FAO report’s choice of GWP for methane as 23 – the Kyoto figure was 21. The excellent paper by Shindell, Schmidt et al., Improved Attribution of Climate Forcing to Emissions gives a value of GWP100 for methane of 33. Measured over 20 years this paper gives methane a GWP of 105 times carbon dioxide. The GWP20 of methane here is thus five times the Kyoto figure of 21 and almost five times that used in the FAO report.

    I was surprised to reread the World Watch report again and find

    The Intergovernmental Panel on Climate Change supports using a 20-year timeframe for methane.

    Is that correct?

    Should we then use a methane GWP of 105 for policy purposes?

    The World Watch authors only used 72. Would the use of a higher figure of 101 cancel some of their “over-estimates of individual terms”?

    [Response: No. GWP estimates, which as you note, are being revised upwards due to the indirect impacts of methane on atmospheric chemistry and aerosols, are all for comparing the integrated effects of a future emission of a kilo of CH4 compared to a kilo of CO2. The claim in the WW report was related to forcings today (which are the net effect of many past emissions), so they aren’t really comparable. In the Shindell et al (2009) paper we look at both attribution and GWP, but the conclusions on attribution would need to be further broken down by full lifecycle sector-by-sector emissions to get at the FAO claim. I haven’t done that, but my reading of the FAO claim is that is a reasonable estimate. The WW claim is not, nor is their claim of IPCC backing for an exclusive use of the 20 year timescale – IPCC gives those numbers but also those for 100 year timescales. – gavin]

  38. 88
    Killian says:

    Beef: The issue with raising beef has some to do with how you raise them. When they are grass fed and part of whole system designs in which they are used in healthy land management, they produce less methane themselves and help sequester more via the greater biological biomass of the healthier, balanced systems.

    Here’s some stuff under way:

    I’d post some permaculture-ish stuff, but that’s not what most would consider science.

  39. 89

    #68 inline–“[Response:The air mixes longitudinally fairly quickly, so if there is an ongoing new large source in the high latitudes, going for more than a few months I guess, it would be detectable in the interhemispheric gradient of methane. David]”

    Thanks, that is helpful. After opining to willi, I did a very rough-and-dirty back of the envelope calculation, which suggested that concentration excursions comparable to the annual cycle amplitude would be quite conceivable. (Yeah, I should have done that first!)

    Do we have an idea roughly how large would “large” have to be in order to affect the interhemispheric gradient?

    [Response:I’m not sure how big an event or new degassing source would have to be before you could see it. If it were in were near the equator you’d never see it. David]

  40. 90
    Lynn Vincentnathan says:

    RE #64, thanks, David, and others who made suggestions. I posted all your comments about CH4 & CO2 (minus certain phrases) on that site. I’m not writing it for the skeptic — I don’t think anything could convince him — but for other readers who might be bamboozled by him. Catholic Answers Forum is a huge forum with over 500,000 threads, over 9 million posts, and over 300,000 members (not that a whole lot would be reading that particular thread on “Radical Environmentalism: Now Global Warming Causes Prostitution?”).

    Another of my pet projects is the Catholic TV channel, EWTN, which reaches some 1.5 million homes. It has had a number of skeptic and denialist comments and screeds (despite 21 years of the popes writing that it’s everyone’s duty to mitigate climate change). I got another top climate scientist to help me with their weekly news program, The World Over, where they sometimes have as guest-speaker Fr. Sirico, head of the Exxon & Koch-funded Acton Institute for the Study of Religion and Liberty. At least that program is no longer promoting climate change skepticism anymore, and that environmentalists are a bunch of neopagan-pantheistic-atheist-communist-totalitarian-genocidal maniacs out to destroy the world.

    And we thought too much CO2 and CH4 in the atmosphere was was bad.

  41. 91
    Pete Dunkelberg says:

    Lynn on long lasting CO2 again –
    1. Contrary to what I said earlier the studies on how long some fraction of fossil fuel CO2 will last are model studies, not paleo studies. Of course the paleo record does show that once CO2 is raised it does not come back down quickly.
    2. Note that only some of our CO2 stays in the air out to 100 K years. It may be less than 10 percent.

  42. 92
    Geoff Beacon says:

    Thanks again Gavin.

    I’m not ashamed to say that I didn’t quite follow the middle section of your comment. I do find GWP an odd concept to use for policy decisions but it is embodied in international treaties. I see the choice of a time frame for GWP as what economists call revealed preference. You didn’t reveal yours. Might I guess your preference is nearer to 100 years rather than 20 years?

    I understand that greenhouse gasses and particulates we are emitting change the Earth’s radiation balance and this perturbs our climate in a dangerous way. We (the human race?) are grappling with strategies to avert the disasters that climate scientists such as yourself predict and other climate scientists may already be measuring.

    I also understand that in discussing “attribution” – the measure of how emissions should be judged – depends both on “science” and “strategy”: the strategy that we (or following generations) might follow. For me the key question is the balance between short-term and long-term forcing.

    I have come across two trains of thought.

    The first says the effect of long term forcing over many decades is the most important because we are building up to a situation that cannot be retrieved.

    The second thinks that because we are so near the danger zone we have to reduce short term forcing very quickly because the climate system is already too dangerous. This second view thinks we must hold the fort waiting for the cavalry to arrive.

    I am sure you know just what I am talking about and I expect you could express this better.

    My impression is that you are in the first train. Do you believe that

    1. That the “missing feedbacks” in the underpowered climate models are not large enough to affect their message – that we must concentrate on reducing our emissions of long-term forcing agents (mostly CO2)? (We cannot afford to worry too much about shorter term forcing agents, which dissipate.)

    2. That it will be practically impossible (for scientific and political reasons) to have geo-engineering solutions e.g. extraction of CO2 from the atmosphere.

    My gut feel is that we are in imminent danger – at least the poor in the world are. We should slow warming by all means possible in the short term, while we wait for the biochar, olivine or other cavalry.

    I believe reducing forcing this year is much more important than a projected reduction in 50 years time.

    Do you?

  43. 93
    Martin Manning says:

    Comparing methane with CO2 often gets oversimplified and so I would like to make some comments.

    After only small changes for about 7 years, methane started increasing around September 2006 and we still do not know why! When I showed my summary of the ESRL/CMDL methane data at the “Greenhouse Gases and Related Measurement Techniques” meeting in Wellington last October, Ed Dlugokencky, who leads that programme, agreed with me that this recent methane increase seems to have started in the southern hemisphere. A running 12-month mean shows a high degree of consistency for a large number of different flask sampling stations, so this is not just some local effect – and it does not seem to have started in the Arctic.

    We do not know nearly as much about the methane budget as we do about the CO2 one. For the last IPCC assessment there was no simple way of producing a break down into the different sources and sinks that was consistent with all the data and model analyses. For example, most of the atmospheric chemistry models ignore removal of methane by reaction with chlorine, despite this being the only way of explaining the seasonal cycle in isotopic data in the southern hemisphere. So the budget for methane is complex and still raising some significant questions.

    Next, methane is predominantly removed by the hydroxyl radical and that removal rate is now more than twice what it was during the preindustrial period – whereas for CO2 the gross removal rate is only ~3% higher. Because the Montreal Protocol has caused a switch to more use of HCFCs and HFCs that now means we are becoming increasingly dependent on this tropospheric chemistry. So it should be recognised that it does more to reduce climate forcing than all of the combined ocean and biospheric uptake of CO2 – see Manning & Reisinger, Phil Trans Roy Soc 369:1891-1905, 2011.

    Recent work led by Markus Rex from the Alfred Wegener Institute is now showing evidence for a tropospheric “ozone hole” in the equatorial Western Pacific, but we don’t know if it was always there or is some recent development. So the argument that CO2 emissions will make long lasting changes in our environment is absolutely right – but it also has to be recognised that further perturbation of highly non-linear atmospheric chemistry could trigger some significant transition like the Antarctic Ozone hole.

    Global Warming Potentials are not the right way to compare methane with CO2 because they just raise major issues about the time horizon and the range of processes and feedbacks that should be included. Even more seriously, they are based on a simplified linear perturbation approach to cover what are becoming significant changes in a complex system. We don’t require the medical profession to come up with a single number to compare heart attacks and lung cancer, so climate science should start adopting a much broader perspective when comparing quite different types of global environmental stress.

  44. 94
    MMM says:

    “The Intergovernmental Panel on Climate Change supports using a 20-year timeframe for methane.”

    Moreover, that sentence is self-inconsistent. It doesn’t make sense to use one timeframe for one gas, and another timeframe for another gas, and then claim that the two calculations are comparable. Either use 20 year GWPs for all gases, or 100 year for all gases (personally, I’d prefer the latter as coming closer to a reasonable balance between short-term and long-term effects), but using a 20 year GWP for methane and a 100 year GWP for, for example, N2O, and then trading them is just not a supportable approach – though some people keep suggesting it.

  45. 95
    Anonymous Coward says:

    #93 Martin Manning,
    Thanks for your insightful comment.
    Would you have a reference for the analysis of “a large number of different flask sampling stations” attributing a recent global change in methane concentrations to the southern hemisphere? Even if it’s only your slides, I think it could be helpful.

  46. 96

    #76 Tenney, impressive data, can you display a full year? like does 2011.1 mean version 1 or January?

  47. 97
    WhiteBeard says:

    # 20, Hank Roberts, 4 Jan, 6:57 PM

    Curious to know the details on the model and observations differences in lower latitudes discussed behind the pay-wall. The authors noting discrepancies in Southeast Asia and central Africa with the term “such as” leaves the Amazon Basin hanging? These seem to be the prime non anthropogenic methane emitting areas. The available observation network is absent there, with that absence being a part of the orbiting instrument’s rational.

    Also wonder if anyone plans to “proof” the bird aginst the far northern TCCON observatories Spitzbergen at 79º N and Eureka on Ellesmere Island at 80º N. (Strange there’s no barrow – and per Canadian PM Harper, soon no Eureka?)

    Hank Roberts and # 21, John Reisman, 4 Jan, 7:24 PM

    And ’yall might extend thanks to the TCCON observation net run out of CalTech with sponsorship from NASA, and stuff like

    scheduled for launch by Feb 2013. That might please Gavin for one.

  48. 98

    @ Wayne, comment #96.

    Sorry, those numbers will appear in full if you click on the images. All the images are from November data from the 3 years presented. Links to the originals are provided. They are from Yurganov’s ftp files.

    If anyone can give help on deciphering the colors on these images from the Arctic, I would be forever grateful:

    I think the colors relate to the type of ice. That black spot near the Laptev Sea is growing.

  49. 99
    Hank Roberts says:

    > 20
    That GOSAT link is all I know, I’m not one of the scientists.
    Just saying, glad there’s an instrument in orbit to look into this.

  50. 100
    Killian says:

    D Goin says:
    6 Jan 2012 at 3:52 PM

    Maybe I missed it, but how is bio-activity accounted for; whereby melting of permafrost initiates biological activity, heating the surrounding permafrost, causing deeper melting and composting, etc.? Intuition (which is not the best way to analyze things) makes me thing that these types of runaways would not have such a long lag.

    [Response:Interesting question. I tend to think of soils in the active (seasonally melted) zone of permafrost or around Arctic lakes as just plain cold, but I’ve never actually been to the Arctic, what do I know? David]

    If I recall correctly, there was a recent paper claiming 50% of methane would convert to CO2 via biogenesis in permafrost. I found that optimistic, but hoped it was true.

    Might be this one:

    This one does not inspire hope:

    And another paper on topics discussed above:

    “To answer this question, the researchers looked at the proportions of different forms of oxygen in bubbles of air trapped in ice during these time periods.

    “There are different forms of oxygen, and as that oxygen in the carbon dioxide molecules is being moved around between different sources, you get different proportions of those different forms,” Harrison says. “You can use that change to tell you where the carbon dioxide is coming from.”

    Combining this information with climate models, the researchers concluded that the extra carbon dioxide was being released from vegetation, particularly tundra and cold steppes, which are very rich in carbon.

    “These plants were stocking carbon in the soil, and when the climate started warming at the end of the glacial period, that carbon was released into the atmosphere,” Harrison says.

    Scientists know that there is carbon locked up in permafrost and permafrost soils at high northern latitudes today. They also expect that as the climate warms in the future, that carbon is going to be released and increase the amount of carbon dioxide in the atmosphere.

    But without being able to explain exactly the natural carbon dioxide changes in the past, they have been hesitant about projecting exactly what the impact might be. “You do wonder if there are things you don’t understand about the system,” Harrison says.

    “Essentially what this paper is saying is that we now have a much better understanding of what was happening in the past through the use of these modelling tools and these measurements.”

    The new findings will help scientists develop more accurate models of what will happen to atmospheric carbon levels as the permafrost melts.”