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The story of methane in our climate, in five pie charts

Filed under: — david @ 23 September 2014

106 Responses to “The story of methane in our climate, in five pie charts”

  1. 1
    Joe Wiseman says:

    As a species I sometimes wonder if we most resemble the ostrich. If we duck our heads, ignore the problem for long enough, it will just, maybe, hopefully, please, go away. Or perhaps our approach is more like Bill Clinton’s solution to gays in the military – don’t ask, don’t tell! After all, if nobody talks about it, it isn’t there, is it?
    My brother-in-law, a house painter and his friend, who is working in the Alberta oil patch sum it up this way: “it’s been about 150 years since the Industrial Revolution and we’ve done this much damage to the environment. We might get another 100 years out of it all.”
    At a church luncheon, a fellow parishioner relates to me his experience of reading about the poisoning of the St Clare River at Sarnia. “I was there the night the company put that stuff in the ground and supposedly sealed it off.” There was pain in his eyes and no doubt, in his heart and in his soul. I stated that it was amazing how many people I speak with, ordinary people, blue collar workers, who understand that we are gradually destroying the planet. He casually observed, “there will be a revolution.”
    It’s hardly unlikely that for some inexplicable reason, I am the only guy who has these conversations. It is more likely that most of us see the truth for what it is. We are gradually, speeding up, speeding up, speeding up, destroying the very planet that gives us life. Suicide or madness? Take your pick, I can’t figure it out.
    I wonder who our political leaders talk to? Do they have these conversations or are they shielded for their own protection? They don’t appear to be losing much sleep about it all as the oil companies drill away, as the auto manufacturers continue to turn out the gas combustion engine, as poisons are released into our rivers, lakes, oceans, landfills – anywhere the millions upon millions of barrels of poisonous waste can be hidden for awhile. Long enough, they hope, to finish making the money, packing up and leaving the deadly stuff behind. Perhaps, like Chernoble, the animals will have another paradise, free of humans, in a future that may be as inevitable as the prediction of my house painter friend – a hundred years or so.
    Is it possible to change a future that is rushing towards us virtually unhindered except for sporadic demonstrations and vocal minorities who are often perceived as “radical”, “inhibiting progress”, “tree-huggers”, “terrorists”, “trouble – makers”, etc? Most days are like today – I simply have no idea whether we have the rational or empathetic ability to slow down, stop and possibly reverse the race to the “end of the human race.”
    Joe Wiseman

  2. 2
    Salamano says:

    Simple. Informative.

    This would also work in cake, yes?

  3. 3
    wili says:

    Thanks for these excellent pie charts and notes.

    It would be nice to have another one (or two…) that reflects an intermediate time period between the very near future (20 years) and some ultimate time when all sequestered carbon may be released, say the next hundred to two hundred years.

    This is the time period that most of us can imagine, since we hope that living children and their children’s children will be living during it. And this is exactly the time period that many of us worry about when it comes to impacts from permafrost and perhaps Arctic methane hydrates.

    Thanks again.

    [Response: The fifth chart is meant to speak to this question, by depicting the feedback-CO2 that could be released from various sources. My own modeling work [cite ref="Archer and Buffett (2005)"]10.1029/2004GC000854[/cite] finds that the radiative impact of the accumulating CO2 is comparable to that of the transient methane during a long, slow release. But then the CO2 effect persists after the release stops. ]

  4. 4
    Chris says:

    Does 4* refer to GT?

    [Response: The fourth chart, like the third, shows methane emissions. I compared numbers in Tg/yr, but since the plot only shows proportions, they could be in any units. ]

    The long term impact may be an underestimation, also it is unclear what long term refers to (1000 years?).

    [Response: For hydrates in the ocean, 1000 years is just getting started. For permafrost, the time scale is one or a few centuries. ]

    Since there have been discussions about a “sudden” 50 GT release of methane, originating from hydrates, im unsure where such an event would fit in.

    [Response: Not too clear where that comes from myself, but where it would fit in would be a huge explosion of that tiny Ocean (hydrates) sliver on the fourth chart.]

    On the bottom line, we face a chronic deglaciation – which is on course to thaw the entire northern hemispheric carbon budget. It appears valid to assume that there will be isolated or pattern of larger carbpn spikes in between, which would dent any linear projections.

  5. 5
    MM says:

    So, I agree that people have been placing too much importance on short-lived climate pollutants these days (see the recent “super pollutant” bill introduced in the Senate today). Having said that, I find your first charts a little misleading.

    Left Side of Figure 1:
    1) The 20 year change is not, I think, the most relevant metric of importance for today’s emissions. It is a result of a combination of factors, some involving reductions in natural emissions, others involving methane abatement efforts, and others yet possibly relating to changes in atmospheric chemistry. This period included a decade-long “pause” in the increase in methane concentrations which may not be repeated.

    [Response: It includes a period of fast concentration growth, a period of stagnation, and a period of slower growth. It’s true though that extending the calculation back 30 years gives a bigger proportion of forcing from methane, so I made that change in the updated figure I’m uploading. However, if we consider 30 years in the past to be “our time”, then for symmetry I pushed the second chart to 30 years in our future.]

    2) Total radiative forcing contribution today from historical emissions of anthropogenic methane is a standard metric that would be useful to present, in my opinion.

    [Response: But there is nothing wrong with focusing our attention on shorter time intervals. 20 or 30 years is a long time.]

    3) The ozone and stratospheric water vapor effects of methane should be included. Additionally, if you are trying to make implications about the effects of methane emissions, then you should also account for the fact that our NOx emissions have led to reductions in methane concentrations.

    [Response: You are correct that I forgot the factor of 1.4 “efficacy” for methane. I made that change also.]

    Right Side of Figure 1:
    This pie chart assumes a 300 year lifetime for today’s CO2 emissions, but the usual Bern carbon cycle approximation used in the IPCC is composed of 4 exponentials, 3 of which are shorter than the 300 year lifetime. According to the approximation, 50% of today’s emissions should be modeled as having a lifetime of less than 20 years.

    [Response: I was thinking of the drawdown of our cumulative emissions, rather than the response to an impulse release, based on my own results with the Hamburg model HAMOCC, which is at least as mechanistic as the Bern model. The land is a wild card I didn’t deal with, but ocean uptake today is 2 Gt / yr, pulling down an atmospheric excess of about 200 Gt C, which would lead one to predict a drawdown time of 100 years. But if the atmospheric concentration stopped growing, the ocean invasion would slow down, and the time scale get longer. ]

    Also, the perturbation lifetime of methane has most recently been estimated to be 12.4 years (AR5).

    [Response: OK, I changed that too. ]

    Also, I’m guessing you didn’t account for ozone or stratospheric water vapor here, either.

    [Response: Now I have. ]

    While Chart 3 is informative, it doesn’t address two important points: 1) how likely is it for the different reservoirs to release their carbon,

    [Response: None of those reservoirs are completely out of play, or I wouldn’t include them. ]

    and 2) are there potential short-term impacts from the release of that carbon as methane rather than immediately as CO2.

    [Response: Yes, as I responded above, but the CO2 effects are about as strong through the time period of release, then persist after the release stops. ]

    I do believe, strongly, that CO2 should remain our first priority, and I am concerned that the SLCF community might distract from CO2 reductions, but I found this set of charts to be more propaganda than real scientific analysis.

    [Response: I do appreciate your suggestions. Propaganda? I think my main point (which you seem to understand and agree with) stands. cheers, David]


  6. 6
    MMM says:

    ps. Now that I realize that “david” is David Archer, I’m even more disappointed – I often cite Archer et al. 2009, found “The Long Thaw” to be a great read and very insightful, and think that “The Warming Papers” were a very useful contribution to pulling together the historical foundations of climate science.

    There are all sorts of ways to dice the onion that is the contribution of different gases to climate change, and I think that the ones presented in this post were not representative of relevant impacts on human timescales.

  7. 7
    John Finn says:

    Do we have direct measurements which enable us to calculate the TOA energy imbalance. I was under the impression that CERES was supposed to provide this data.

  8. 8
    Ed Davies says:

    Sorry, bit off topic but any comments on the comments by Dr Grant Allen here?:

    It seems to me that both rates and cumulative emissions matter but that his comments could easily lead to people putting far too much emphasis on rates.

  9. 9
    Climate Scientist says:

    Why are the tropical oceans still cold in the depths? Why don’t they become isothermal like you think the troposphere would have been without that most-prolific of all greenhouse pollutants, water vapour sending all that warming back radiation back to the surface to warm it to a higher temperature than it was when it sent the original radiation and cooled in doing so.

    Well the tropical oceans are colder in the depths because the poles act as a heat sink. Isothermals (such as 4 degrees C) are deep down in the tropics, but break out at the surface in the polar regions.

    So too would the atmosphere be colder at the base for the same reason. If the whole globe were paved in black asphalt the surface would be about 235K – nearly 40 degrees below freezing. You can work it out yourself with an on-line Stefan Boltzmann calculator using solar radiative flux of 161W/m^2 and emissivity 0.93.

    So there is a lot of thermal energy entering the ocean surface in non-polar regions, moving downwards through the thermocline and exiting in the polar regions.

    But why is the thin transparent ocean surface so hot? Before you say it’s the back radiation, I have to tell you that radiation from colder regions does not penetrate the warmer ocean surface more than a few nanometres. It is “pseudo scattered” because it merely raises electrons to higher energy states and then those electrons immediately drop back and emit an identical photon. The electro-magnetic energy is not converted to thermal energy, and so it does not raise the temperature.

    In fact there is a gravitationally induced temperature gradient (aka lapse rate) in any planetary troposphere, and thermal energy absorbed from solar radiation in the upper troposphere can flow up that sloping thermal profile restoring thermodynamic equilibrium as it does so, and even entering the oceans. Water vapour reduces the temperature gradient (fortunately) making the surface about 10 to 12 degrees cooler. Carbon dioxide makes it another 0.1 degree cooler for the same reason.

  10. 10
    Dan Miller says:

    I’ve heard that the permafrost holds about twice as much carbon as the entire atmosphere . What happens if we continue BAU and it warms 10ºC+ in the Arctic later this century? Is that assumed in the “long term” chart?

    [Response: Yes, permafrost carbon can be released either as methane or CO2. Time scale of centuries. ]

    Also, in the first “today” charts, it shows the impact of methane dropping greatly over 20 years. But I assume the right chart does not include the impact of methane released 20 years from now. Correct?

    [Response: Correct. The question is, do we care about methane emissions so far. For me, the answer is, not so much as I care about CO2, because the methane will just peter out in a few decades. ]

    What would the “today” chart look like 20 years from now if Arctic hydrates and permafrost emissions accelerate under reasonable scenarios and then-current and then-recent emissions are included?

    [Response: You can take the Arctic slabs in the fourth chart and make them bigger. It looks like we could compensate for even a doubling of land (permafrost) sources, by cleaning up the Arctic fossil fuel industry. ]

  11. 11
    DrewKeeling says:

    By my count there are three, not five, pie charts here. I’d be curious to see two more (if there are two more).

  12. 12
    Tony Weddle says:

    I’m not sure of the usefulness of the second pie chart, given that methane will likely continue to be released for the next 20 years, with the proportion in the atmosphere increasing. But an interesting post, nonetheless.

    [Response: Trying to balance carbon emission today vs. methane emission today, which is worse? Methane emitted today will be gone soon. Methane emitted 20 years from now is a different question. David]

  13. 13
  14. 14

    #9–(‘Climate Scientist)–I call BS–as nearly as I can parse several pretty undecipherable sentences, at least.

    John Daly lives again, apparently, and absorption of energy is now (and once again) functionally equivalent to complete reflection of said energy.

  15. 15
    Chris says:


    Nazarenko et al. 2013, submitted

    The interactive aerosols and chemistry atmospheric models, TCAD and TCADI, include interactive calculations of methane concentrations in all future RCP simulations. As shown in Fig. 2, the calculated methane mixing ratios are larger in both TCAD and TCADI models than in the NINT models. Methane is prescribed according the corresponding RCP scenario in the NINT models. As noted in the paper by Shindell et al. [2013b], the radiative forcing from methane is from 0.05 to 0.18 W m2 higher in the TCAD and TCADI models than in the prescribed RCP methane radiative forcing estimates. This leads to larger warming in the TCAD and TCADI models compared to the NINT simulations. The high mitigation scenario RCP2.6 is the only one that shows the global warming below 1°C by 2100. This scenario with low forcing level simulates the surface warming below the 2°C threshold at the end of the twenty-first century relative to the pre-industrial surface temperature.


    The North Atlantic overturning collapses in the RCP8.5 scenarios around the year 2200 in all coupled models.

  16. 16
    Susan Anderson says:

    3 to 5: Do you see 5 circles? Manner of speaking (chuckle).

  17. 17
    Chris says:

    With Few Data, Arctic Carbon Models Lack Consensus

    As climate change grips the Arctic, how much carbon is leaving its thawing soil and adding to Earth’s greenhouse effect? The question has long been debated by scientists. A new study conducted as part of NASA’s Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) shows just how much work still needs to be done to reach a conclusion on this and other basic questions about the region where global warming is hitting hardest.

  18. 18
    Hank Roberts says:

    Tony Weddle says: “…given that methane will likely continue to be released for the next 20 years”

    Most of that methane released from “human sources (mostly fuel industry)” — so it’s only a given assuming the industry continues to pollute.

  19. 19
    DocMartyn says:

    Do we have the 14C age of the methane in the various reservoirs believed to be mobilized by a warming of, say, two degrees?
    Do we have good estimates of arctic methane hydrate ages and of CH4 being released in US and Russian permafrosts?

  20. 20
    Carbomontanus says:

    Dear Real Climate & al

    I was able to enlight you on how to ruin the Svensmark CLOUD in CERN project by classic chemical means, John Willam Herschels Cyanotypie without getting ethnically rinsed out.

    For that I am very thankful.

    But I have a failing detail in my private climate Kabbala or puzzle.

    To check up on the time- scale of CO2 remaining in the atmosphere, I found the Nuclear bomb effect of C14 that shows typical exponential growth and then a halving- time of about 11-12 years,…….

    ……. that is way off from “Hundreds of years” and I never found an explaination for those hundreds of years, that are obviously very important to our possible understanding and eventual opinions. I can only guess that a next and natural, different process is being caused by artificial exhalation of CO2 to the atmosphere, that together will be an auto- catalytic effect of CO2. That next and natural process must also have a much longer halving time than for instance the sinking and assimilation of C14

    Thus not the the material presence of what was exausted, that can be traced by isotopes, but rather the amplitude or concentration level of the specific substance as such and from a much larger source and by a much longer decay or halving time.

    I never found rational and plausible litterature on this, which is quite essencial in order to take it for serious..

    Thus can you show us to that.

    [Response: There is a difference between carbon exchange fluxes (say growth and decay of plants, or invasion / evasion of CO2 from the ocean), and net fluxes (any imbalance between the two). The former will affect the isotopic composition of the atmosphere but not the CO2 concentration. ]

    As for CH4, it is relevant and interesting from many other points of wiew. For instance Methane- hydrate in the continental shelves to discuss the very fameous Storegga Avalanche and Tsunami that seems to be world record, for recent mysterious holes in Siberia, even for the Bermuda triangle….

    …….and perhaps best of all in order to explain necessary water for the nocti- lucent clouds. By CH4 passing the tropopause and then being oxidized by UV and air and maybe ozone higher up. H2SO4 is also necessary for it, but that is easy by SO2 and ozone + UV and even “NOx”.

    (You see, I do not believe in the experts unless I can see it for myself in Nature and in the lab because, the experts are often cheating us…)

    But I need an explaination for that longtime durability of the CO2- level in the atmosphere. Where the fameous Sawtooth form of the keeling curve shows us that it goes rather fast up and down by rotting organic material and summer photosynthesis on the northern hemisphere. That curve is valid, making also the Eurasian continent, Norway and Canada quite more important as a proof and reference..

    Then I can follow it in my own garden and can tell it to my grandchildren, and do not have to believe in the experts.

    I have been discussing the Bicarbonate- buffer, the fameous Ramløsa soda water and the fameous low affinity between CO2 and water in the light of very classical chemistery for (Upstairs at the University of Uppsala) when they came to Fred Singer and Roger Revelle.

    Revelle scores quite much higher in classical chemistery, which is how we like it.

  21. 21

    Thanks for the link on CARVE, Chris. Not reassuring, really, but good to know what is going on nonetheless.

  22. 22

    Somewhat OT, but interesting: I stumbled across this 2007 presentation on atmospheric observation using IR interferometry to measure downwelling IR, water vapor and temperature profiles, and even airborne dust from the Sahel. Dr. David Turner presents more detail than I, or most here, will ever need, but creates a nice window into the ‘nuts and bolts’ of an observational campaign.

  23. 23

    Ah, yes, now I remember this post on DWIR and the oceanic surface:


  24. 24

    #9, #14, etc, etc–

    Ah. I think our “climate scientist” has been sighted (“Sited?” “Cited?” No, probably not!) before:

  25. 25
    jef says:

    This article at Arctic News states;

    “There are fractures here that give mantel methane a route to the surface that have been safely sealed by ice. The hydrates and seals are thawing.”

    If true is that something that has been factored in to your analysis?


    [Response: We have a good estimate of the time scales for melting permafrost, on land (century) and in the ocean (millennia). If you really want methane-driven climate drama you gotta move much faster than that. David]

  26. 26
    Leland Palmer says:

    Nice charts, based on calculations, based on assumptions.

    There are a couple missing, though, maybe.

    One that might be missing would show the roughly 5 gtons of carbon from methane in the atmosphere, versus the estimated 5000 to 20000 gtons of carbon in the methane hydrates. That wouldn’t make much of a pie chart, though, since the amount of methane in the atmosphere right now is a thousand times or so less than the amount in the hydrates. So, the relative amount of methane in the atmosphere would be exaggerated by a thin line on the pie chart. Should the relative enormity of the methane hydrate reservoir make us a little less certain about predictions 30 years in the future?

    [Response: I considered exactly that chart, but consider it to be deceptive because I don’t believe in any mechanism to get that much methane into the atmosphere on time scales where a significant fraction of it could be in the atmosphere at once. David]

    Another missing chart might compare the amount of carbon released by our modern man made triggering event compared to past flood basalt triggering events for past probable methane catastrophes such as the End Permian, the End Triassic, and the PETM. That might not make much of a pie chart, either, because pie charts aren’t very good at showing very uncertain and fuzzy numbers. But it might give us some idea of how close we are to a methane catastrophe ourselves, based on actual past events, not based on calculations based on assumptions.

    [Response: I don’t actually believe in methane for the PETM, either. The isotopes don’t add up, in that if methane were the source of the 13-C, it wouldn’t be enough carbon to warm things up as much as the 18-O indicates. The end Triassic is less well-constrained. David]

    Another pie chart might try to capture the effect of methane hydrate dissociation on ocean acidification and hypoxia. Modeling by Reagan and his associates at the national labs shows an anoxic and acidic plume of deep water stretching from the sea of Okhotsk, across the North Pacific, down the coast of Alaska, down the coast of Canada, down the coast of California, wandering out into the Pacific around Baja California, wandering back close to the western shores of South America, and continuing down the coast of South America, after 30 years of hydrate dissociation according to their conservative modeling. But, that might not make a very good pie chart, either.

    [Response: There’s enough hydrate in the ocean to bring it to the brink of anoxia, but it would have to be oxidized in the ocean on a time scale of the ocean turnover, of about 1000 years. ]

    It’s the assumptions and the lack of three dimensional modeling that those of us who fear a methane catastrophe question, though, not the form of presentation. What we are looking for is a realistic three dimensional multi-physics calculation of the rate of methane hydrate dissociation, taking into account difficult to predict and model processes such as mass flow, gas driven pumping of seawater through the hydrates, the contribution of high salt hydrates at equilibrium with ocean temperatures, and so on. Even then, because of the enormous risks to humanity, past apparent methane catastrophes in the fossil record, and the enormity of the methane hydrate reservoir, many of us worried about a methane catastrophe will be skeptical of the results.

    [Response: You don’t need 3-D to model the diffusion of heat into the sediment column, to discover the slow time scale on which this takes place. ]

  27. 27
    Hank Roberts says:

    > “climate scientist” and “visiting physicist” aka Cotton et al.

    sighted over at Stoat’s, thanks for the pointer, Kevin.
    As Eli wrote there: “Oh goody, new pinatas. The Weasel has all the luck.”

  28. 28
    Leland Palmer says:

    OK, pie chart #1-
    Methane is being released at a constant or increasing rate. Methane lost to oxidation will be more than made up for by new methane, released over that 30 year period. The pie chart is misleading, because it tells us only what we already knew – that methane lifetime is less than CO2 lifetime. The pie chart says nothing about the relative contributions of methane caused warming to CO2 caused warming 30 years from now, because it neglects methane released during that interval.

    [Response: It tells the impact that have already had, on radiative forcing in 30 years’ time. You’re asking for a different plot. ]

    Pie chart #2-

    This chart also tells us something we already knew. Current contributions from Arctic methane hydrates are small. It’s the huge size of the enormous hydrate reservoir combined with its potential for spontaneous dissociation under continued global heating that concerns many of us. So, it’s future emissions from the hydrates that concern many of us, not the current emissions.

    [Response: Glad you already knew that Arctic emissions are small, not everybody gets it. Tried to capture the future emissions by comparing to CO2, because I don’t believe it can come out so quickly that comparing the methane in the ground to that in the atmosphere would be relevant. It would be apples and oranges, that is my point. ]

    Pie chart #3-

    This pie chart is misleading because it draws a false equivalence between CO2 and methane – methane has a much greater short term greenhouse potency, added to its long term greenhouse impact after it is oxidized into CO2. Draw the same chart with reasonable assumptions for methane GWP, in terms of total cumulative radiative forcing, and the methane hydrate and Arctic permafrost methane slices could take up 95 percent of the pie.

    [Response: I do not understand your point. There is no CO2 in that plot, I’m only comparing the relative sources of methane to the atmosphere. 95 of what pie? ]

    This chart also neglects the different volatility of the carbon in the different reservoirs. It’s not likely that a worldwide coal fire will release all of the carbon in coal without human intervention, for example. But the Arctic methane hydrates could spontaneously dissociate under the impact of global heating without direct human intervention. The Arctic is warming the fastest of all regions on the earth, so the impact of the Arctic hydrates could be the greatest. Also, the size of the methane hydrate reservoir is not well known, and it could in fact be several times as large as is shown.

    [Response: I think the coal is much more threatened, in the coming century, than the hydrates. Hydrates can’t spontaneously dissociate; they need to pay the latent heat bill. Carbon-rich permafrost soils can catalyze their own decomposition, but not hydrates. ]

    Draw the chart in terms of total cumulative radiative forcing, and take into account worst case scenarios about the global methane hydrate inventory, and the methane hydrate total cumulative radiative forcing could take up as much as 99% of the area of the pie.

  29. 29

    #26–Good points, in some ways. But consider the inverse: those charts also show that we have a very big ‘non-methane’ (or, a bit better, ‘partially methane’) catastrophe ongoing now. It’s really not speculative.

    For me, this is all really about mitigation and adaptation, ultimately, even if the former is, for the moment, OT here. So, would mitigating the methane threat imply different measures? (Hank’s ‘drill and burn,’ maybe?) And if so, what would the rational prioritization look like? I’m suspecting that the best chance would still be to cut emissions as fast & hard as practically possible.

  30. 30
    Hank Roberts says:

    Nature Geoscience | News and Views
    Seafloor methane: Atlantic bubble bath
    John Kessler
    Nature Geoscience 7, 625–626 (2014)
    Published online 24 August 2014

    The release of large quantities of methane from ocean sediments might affect global climate change. The discovery of expansive methane seeps along the US Atlantic margin provides an ideal test bed for such a marine methane–climate connection.

    Paywalled, of course. That’s all I know.
    What kind of test does he suggest, anyone know? Anyone trying to do that?

  31. 31
    Sean says:

    I would very much like to hear what Peter Ward’s opinion is about this article, it’s rationale, and it’s conclusions.

    So I will go an ask him myself. thx

  32. 32
    Tony Weddle says:


    Yes, it’s an assumption that fossil fuel industry will continue to pollute, but most people (and I feel sure that includes David) seem to think that is a given. Natural sources will also continue. Consequently, the second pie chart on the top line, doesn’t seem very useful, since there will be more methane appearing in the atmosphere, in 30 years. I understand what the chart is trying to convey but it would only be useful if all emissions (natural or otherwise) stopped today.

    [Response: That would be a different chart, not “our (today) impact in 30 years”. I don’t think it’s a given that fossil fuels will continue to be used. I think that most of the apocalypto-carbon is still in the ground, and we’ll dig it up only if we continue to decide to. Social systems (like environmental restrictions) are very tippy — they seem like they will persist forever, then they surprise everybody by tipping over. Written as a non-social scientist (some would say anti-social!). David]

  33. 33
    Chris Colose says:

    David (#26 re PETM)

    But if a methane release did occur at the PETM, presumably it would have been a feedback to some initial ocean warming, and thus a large forcing for the C13 excursion but not the trigger for the event. So do you not believe in methane playing a role at all, or is there a a self-consistent way to tie the d18, C13, and dissolution evidence together with a sizable methane feedback?

    [Response: The problem is that if the carbon came from methane (to become CO2, then warm the planet for 100,000 years), there wasn’t enough of it to generate the warming observed. So maybe the climate sensitivity was much higher then, or maybe the warming as you suggest could have come from some other reason. Or maybe it was some less isotopically labeled source, like soil or permafrost carbon, released in greater quantity. David]

  34. 34
    Dan Miller says:

    These charts seem to be answering a question that is not being asked (by most people concerned about climate change). If the question is “Should we be worried about the current amount of methane in the atmosphere?”, then the charts are clear that CO2 is much more dangerous. But if the question is “Does methane pose a very significant potential threat to civilization?”, these charts do not address that issue (and I think that is the question that more people are concerned about). With 10ºC+ of warming predicted in the Arctic later this century and impact this will have on permafrost and Arctic sea hydrates, that certainly raises concerns. And while the release of the rest of the oceans’ hydrates may take a long time, it may become an unstoppable civilization ending event (if the CO2 doesn’t do us in on its own).

    [Response: The question is, which gas should we expend more effort on curbing, methane or CO2? My answer to your second question is in the fifth pie chart. I don’t think all that methane can get out fast enough to affect climate much as methane, so I didn’t include a chart showing atmospheric methane vs. hydrate or permafrost methane. That chart would be apples and oranges in my opinion. But as CO2, in the long term, that’s relevant, and in chart #5. David]

  35. 35
    Lawrence Coleman says:

    1: Joe Wiseman. Very well put. My god/ inspiration and source of wonderment is all the dynamic living interactions and entities that constitute our biosphere. My wife is a catholic but I have opened her eyes to the scientific nature of life. I have explained evolution is such a way that she completely understands the concept and now willingly accepts it as fact. I think we were mislead over the millennia by the old testament concept that we humans have ‘control’ over the natural world, that we could do to her as we wished..and then came capitalism which thrived on this mindset and became the insatiable monster it is today. We now know that thanks to scientific knowledge it is actually nature and the biosphere that has complete control over us. Case in point, humans are a helpful host for populations of trillions of bacteria, for without such useful micro-organisms we would surely die. It is rather that we are actually the fleas on a dogs coat arguing as to which family of fleas owns the dog. Science has finally put human’s ego into perspective. It will unfortunately take religions and capitalism too long to come up to speed for to save us from the unspeakable consequences of the unstoppable juggernaut of a radically destabilised global climatic system.

  36. 36
    Leland Palmer says:

    Hi David, thanks for the responses, to post #26.

    “I don’t actually believe in methane for the PETM, either. The isotopes don’t add up, in that if methane were the source of the 13-C, it wouldn’t be enough carbon to warm things up as much as the 18-O indicates. The end Triassic is less well-constrained. David]”

    Well, perhaps the atmospheric chemistry effects of methane increased its greenhouse potency during the PETM, as modeled by Isaksen and collaborators:
    Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions

    ” It is shown that if global methane emissions were to increase by factors of 2.5 and 5.2 above current emissions, the indirect contributions to RF would be about 250% and 400%, respectively, of the RF that can be attributed to directly emitted methane alone”

    Certainly, large scale release of methane would start to exhaust the hydroxyl radical oxidation mechanism of the atmosphere and increase methane lifetime before oxidation and so increase radiative forcing (RF).

    Your calculation could be interpreted to mean that this sort of atmospheric chemistry effect was significant during the PETM. Certainly, taking atmospheric chemistry into account would seem necessary, in the real world, to make a realistic model of the PETM event.

    [Response: The warming, as indicated by the oxygen-18, persisted for long after the time period of the carbon release stopped (when the 13-C stopped rising). This is why I conclude that CO2 was the warming agent, not methane itself (which goes away in 10 years after the emission stops). David]

  37. 37
    Hank Roberts says:

    > more methane appearing in the atmosphere, in 30 years

    But not the same methane; what’s in the air now will be CO2 in 30 years.
    That’s the point.

  38. 38

    “…unstoppable juggernaut…”

    Interesting perspective generally in the comment, but can we leave the cheap despair at home, please? No-one can actually know at this point that it’s ‘too late’ or that we have an ‘unstoppable juggernaut’. And it certainly isn’t helpful, providing as it does an attractively nihilistic rationale for comfortable inaction–indulgence masquerading as tough-mindedness.

  39. 39
    Zeke Hausfather says:

    Here are two figures that might be interesting for folks, and help illuminate the point David is making.

    The first shows typical pulse-response functions for CO2 and CH4; both decay similarly for the first few years, but almost all of the CH4 is eliminated rapidly while nearly 40% of the CO2 still remains after 100 years.

    The second shows the integration of pulse response functions for each gas over a century, assuming a constant emission rate of 1 ton per year. The CH4 atmospheric concentration equilibrates with the emission rate after a few decades, such that the rate of decay matches the rate of emissions and atmospheric concentrations stay roughly constant at ~12 tons. CO2, on the other hand, continues to accumulate, reaching ~50 tons (of the total 100 emitted) by 2100.

    [Response: Nice plots. Of course, human emission rates of CO2 are about 100x that of methane, not one-to-one. No pies, which will be pleasing to some. David]

  40. 40
    Aaron Lewis says:

    The five pies are neat and clean, depicting the current situation. However they say very little about the uncertainty of tomorrow. Let us remember that circa 2007, this forum was still offering its readers reassurance that the Arctic Sea Ice was good for another 80 years. In that case, this forum was late to catch the power of the trend. I expect clathrates are another case where RealClimate misses the power of a trend.

    While diffusion of heat, pressure, and gases through ocean sediments are generally rather slow, sometimes faster mechanisms appear. Ten years ago, moulins were generally dismissed as a large scale water and heat transport mechanism through ice sheets. Now, moulins are accepted. Today, there are areas at the north edge of the Greenland Ice sheet that have been subjected to 100 melt days this year. Ten years ago, the idea that north Greenland would be melting on more days than southern Greenland was dismissed with, “It does not work that way.” I think that recent discoveries about clathrates along the California coast suggest that methane is moving vertically faster than is plausible in the context of Dr. Archer’s models. The history of climate models is that they have failed to estimate first occurrence of exceptional weather forced by AGW. (And, a large methane release is exceptional weather.)

    [Response: I am not reassuring anybody about the stability of ice sheets! And I agree with you about uncertainties in what happens to gas after it forms. It should freeze in the hydrate stability zone but bubbles do make it (although mostly near the horizontal edge of the stability zone), and there are huge explosion marks called pockmarks indicating some pretty nasty methane weather. But the diffusion of heat into soils and sediments is so well understood that it’s used to back out past changes in surface temperature (borehole temperature records). I don’t doubt eventual positive carbon cycle feedbacks from permafrosts and hydrates, I just don’t think they can happen fast enough to make much difference to climate on the short term, relative to the huge radiative forcing from the accumulating CO2. David]

    I suggest that exceptional weather forced by AGW is the primary risk as we plan infrastructure and buy insurance. It is the exceptional weather events, the like of which we have never seen before, that cause the most damage. People say, “That is a once in 10,000 year event.” Then, such events occur twice in a decade, and such events become our “climate”. Prior to first occurrence, these are the weather events that are hardest to model, and harder still to get peers to consider as plausible. Large scale methane releases are one of those weather events that we have not seen recently, and thus is hard to model, and hard to get peers to accept as plausible.

    [Response: Not seen recently, or ever, in my opinion, in the geologic record (I don’t favor methane as a culprit in the PETM). David]

  41. 41
    Mal Adapted says:

    Lawrence Coleman:

    I think we were mislead over the millennia by the old testament concept that we humans have ‘control’ over the natural world, that we could do to her as we wished..and then came capitalism which thrived on this mindset and became the insatiable monster it is today.

    Regarding that old testament concept, a famous paper published in Science 37 years ago supports you: The Historical Roots of Oour Ecological Crisis. It can be considered one of modern Environmentalism’s foundational documents.

  42. 42
    Hank Roberts says:

    DOI: 10.1038/NGEO1955

    Three decades of global methane sources and sinks
    Stefanie Kirschke et al.

    Brief excerpt from the Abstract:

    … We build three contrasting emission scenarios — which difer in fossil fuel and microbial emissions — to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985.

    Although uncertainties in emission trends do not allow deinitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions.

    We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain.

    (para. breaks added for online readability — hr

    [Response: Natural wetlands that are mostly in the tropics. David]

  43. 43
    wili says:

    Thanks to COBob for this link:

    With few data, Arctic carbon models lack consensus

    “As climate change grips the Arctic, how much carbon is leaving its thawing soil and adding to Earth’s greenhouse effect? The question has long been debated by scientists. A new study conducted as part of NASA’s Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) shows just how much work still needs to be done to reach a conclusion on this and other basic questions about the region where global warming is hitting hardest.

    Lead author Josh Fisher of NASA’s Jet Propulsion Laboratory, Pasadena, California, analyzed 40 computer models of the amounts and flows of carbon in the Alaskan Arctic and boreal ecosystems. His team found wide disagreement among the models, highlighting the urgent need for more measurements from the region.

    Models represent scientists’ integrated understanding of Earth processes and systems. They are used both to test that understanding, by comparing their results with real-world observations, and to gain insight into how current trends may affect our planet’s future.

    ‘We all knew there were big uncertainties in our understanding, and we wanted to quantify their extent,” said Fisher. That extent proved to be greater than almost anyone expected. “The results were shocking to most people,’ he said.”

    [Response: It’s true that there are lots of uncertainties on the rate of Arctic or oceanic hydrate methane emission. But there isn’t much uncertainty on whether or not these sources are globally significant. They are small, relative to other sources. That’s well known. David]

  44. 44
    Leland Palmer says:

    Re the reply to post # 26 –
    “Response: You don’t need 3-D to model the diffusion of heat into the sediment column, to discover the slow time scale on which this takes place. ]”

    Yes, assuming that diffusion of heat is the primary process at work in methane hydrate dissociation. What if the primary process at work is mass flow or gas driven pumping of sea water through the hydrates? That’s where 2D or better 3D modeling might be useful, I think. Similar calculations for ice sheet stability turned out to be greatly in error, compared to the dynamic real world behavior of ice sheets.

    [Response: I agree with you about ice sheets, but that’s a different story. The agreement of the geothermal heat flux in sediments far from spreading centers and in soils with the temperature gradient times a conduction coefficient sort of pins diffusion of heat as the primary process. What happens to the gas after it is liberated is not so well understood. David]

  45. 45
    Jan says:

    Kaiser Fung, a blogger, author, and self-proclaimed expert on data visualization, has picked this blog entry as an example for ill-used pie charts. Despite his silly headline, I feel he raises some serious issues, given that this blog’s aim is to inform the interested public and journalists.

    Any responses?

    [Response: 1: Neglecting the other greenhouse gases makes methane seem more important than it would be. Since I am arguing that methane is not very important, this was a conservative choice. Really. 2: The critic (who didn’t use my name either; I don’t see his/hers) didn’t seem to get that, indeed, my point is that methane is as worrisome to me as CO2. This is a person with strong opinions about pie charts but who has not been following the actual dialog on methane in realclimate. I regard this post as synonymous with a long series of posts on the topic, told another way. 3: The decrease in the radiative forcing from our excess CO2 in the air is very small, so the use of the pie chart instead of bar graphs is not deceptive in the way that the pie-critic guesses it might be. The situation corresponds to his possibility number 2, as might have been determined by the words “drawdown time scale”. 4: “If the data are to be believed, then the scale of the impact of Methane is expected to become much smaller relative to that of CO2 in the next 30 years.” I would change his wording to “the scale of the impact of the methane that we have already caused to be released is expected …” 5: “I don’t know what the story of methane is. I doubt that the intention of the author was to tell us that methane is extremely unimportant relative to CO2.” My point exactly! The criticism is that these plots are not very effective at conveying my message to an intelligent but uninformed reader, but he/she actually got my point, just refused to believe it. David]

  46. 46
    Hank Roberts says:

    Another story with interview quotes on the North Carolina coast bubbles; ignore the “climate bomb” headline, that’s not what the story says; these are deep sources at an interesting depth, though.

  47. 47
    Hank Roberts says:

    Quotes from the above-linked NBC News story follow.

    The paper cited is Skarke, Ruppel and colleagues … published Sunday
    Nature Geoscience.

    While researchers have long suspected gas hydrates are ubiquitous in the world’s ocean, until now few seeps were known outside of the Arctic. The new research confirms the hunch and suggests that “tens of thousands of seeps could be discoverable,” Skarke, Ruppel and colleagues write in their study published Sunday in the journal Nature Geoscience.

    “There is a sense that the upper ocean is absorbing a lot of the heat from global warming and a lot of these seeps are sitting right at the water depth where they are going to be affected by that warming,” Ruppel told NBC News, adding that “those warmer waters impinging on the upper slope could be triggering maybe a more active phase of methane emissions.”

    Whether or not that is actually happening, for now, is unknown, noted Gerald Dickens, an earth scientist at Rice University in Houston, Texas, who has studied gas hydrates for more than 20 years and long suspected seeps existed in continental shelf sediments. He was not a part of this study.

    “Certainly, the first question is, is this normal,” he told NBC News. “In other words, is this just a steady state and we just haven’t looked at it?”
    ‘Prolonged seepage’

    Skarke, Ruppel and colleagues used sonar instruments to identify the seeps and subsequently revisited a few of them with a remotely operated vehicle. Images of the seafloor indicate the presence of carbonate rock, which forms over timescales measured in centuries via a series of chemical reactions starting with methane and sulfate.

    “The fact that it is there in the quantities that it is and it is exposed suggests that indeed the processes at these locations have been going on, in a very general sense, on the order of at least 1,000 years,” Skarke said. While more seeps need to be visited to see if there is similar evidence elsewhere, “the ones we visited suggest a very prolonged seepage,” he added.

    [Response: The paper never claimed that these sources are large in the global picture. David]

  48. 48
    wili says:


    [Response: It’s true that there are lots of uncertainties on the rate of Arctic or oceanic hydrate methane emission. But there isn’t much uncertainty on whether or not these sources are globally significant. They are small, relative to other sources. That’s well known. David]

  49. 49
    Sean says:

    @31 Sean

    email reply from Prof Peter Ward, working in the field at a fossil dig site.

    Quote: “Staring at the five methane pies not getting it.”

    More info:–peter

    [ also RE David: ” methane will just peter out in a few decades” – well since when was methane not an issue given it has a GWP of 25 times greater than CO2? And is transformed into higher amounts of CO2ppm than any other direct CO2 per unit forcing itself? This RC article looks far more like it was motivated by scientific politics than valid scientific output, but that’s just my uneducated opinion. ]

    How bad can climate change be?

    How concerned should we be? Maybe don’t do anything if it will ruin the economy?

    Does deep time inform the near future? We can look at what has happened with carbon dioxide levels in the deep past.

    5 major mass extinctions of animal life on earth; 65 million years ago earth was hit by a meteorite, comet or asteroid. to 10mins.

    The Cretaceous-Tertiary mass extinction event was sudden and may have happened in less than a year, or even in a week.

    The huge Yucatan Mexico impact crater, Nautilus and the Allonautilus.

    By the 1990s many assumed impacts caused all the other mass extinctions, but they didn’t, only the last extinction event was caused by asteroid impact; a close look at the Permian Mass Extinction 250 million years ago.

    Huge quantities of Hydrogen Sulphide Gas, aka Rotten egg gas, comes out of the ocean. ( can be used for suspended animation. More reptiles survive the Permian extinction. to 21m30s

    What caused the other extinctions was sudden volcanism (flood basalt flows) extruding CO2 and the world warmed by 10 degrees centigrade over 50,000 years and this warming produced hydrogen sulphide. Cold poles causes ocean and atmosphere circulation (a biological pump) but ice free poles in a 10C world stops this and the oceans die.

    Summary of extinction records, global circulation and CO2.

    Every time we hit high CO2 (1000ppm) we lost the ice caps. Now CO2 402ppm rising 2-3ppm per year. (Business as Usual carbon energy use projects CO2 @ 450 by 2040, 560ppm by 2060 to ~950ppm by 2100) Effects of sea level rise.

    Ocean Heat Content, sea level rise, sea level delta crops, Greenland and Antarctic Ice loss. Sea level airports, ship terminals docks with ~1 metre rise by 2100.

    Sea level changes higher in different locations

    The ‘Global warming is false’ arguments, science literacy, academic scientist public outreach, what would 1m sea level rise do in the SW USA? Culture change needed to inform the public. Best to get the worst of the bad news out on climate change.

    Remembering of course that every single molecule of CH4 that is relocated from storage into the oceans and atmosphere WILL Add to the total Carbon Budget being spent, and adds to the accumulated CO2 in the atmosphere and the oceans on a never ending upward spiral.

    People must learn to walk, talk and chew gum at the same time.

    You don’t have the luxury of saying X is more important that Y if your intention is to avoid another major mass extinction of animal life on Earth.

    If it’s politics, winning debates, or being impressive and looking good and BEING RIGHT (no matter what), which is the unconscious motivation then it really doesn’t matter what you do or say, nor what your “scientific credentials” state that they are.

    Highly recommended lecture for Communicators of Science
    – How Brains Think (2014)


  50. 50
    Hank Roberts says:

    > what-we-dont-know-really-could-kill-us

    Reality will be what it is, as it works out.
    Many models, but one actual planet and climate evolving.

    Regardless of the details, we know the answer: stop burning fossil carbon.

    Seven billion people will die this century.
    Details to follow, as we arrange them.