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Unforced variations: August 2013

Filed under: — group @ 1 August 2013

This month’s open thread.

Since there are two main topics (Advocacy and Methane bombs) buzzing around the blogo-twitter-sphere this week, perhaps those are our starters for ten… (Feel free to populate the comments with links to various commentaries – we will chime in as we find time).


450 Responses to “Unforced variations: August 2013”

  1. 251
    Hank Roberts says:

    This seems to be reason for suggesting that near-surface hydrates might be found close under the shallow seabed separate from areas where they’re drilling for fossil fuels. Anyone know more?

    “… previously unknown species of methane hydrates, located outside oil and gas producing areas, have been found within the pores of near-surface continuous permafrost in northeastern Siberia (Chuvilin et al., 2000; Rivkina et al., 2004) …”
    http://ic.ucsc.edu/~acr/BeringResources/Articles%20of%20interest/Eurasian%20Basin/Shakova%20and%20Semiletov%202007.pdf

  2. 252
    prokaryotes says:

    Hank Roberts #249 “But what they describe is bubbles coming up that don’t reach the surface, they dissolve into the ocean.”

    Seems you did not read the study paper(which i can highly recommend), since it describes pathway mechanism like ebullition. Heck, they even state “gas-water” fountain in the case Hank was referring to.

    Apparently this paper should be read before anyone starts to comment on ESAS hydrates, let alone criticize the science.

  3. 253
    Kevin O'Neill says:

    # 249 Hank, they describe a gas-water fountain that originated from beneath the sub-sea permafrost. At 50m beneath the sediment surface and at 64m water depth and rose 10m above the ship. That’s not bubbles rising to the surface.

    10 days later the fountain was 10m wide and still rose nearly to the surface. I don’t know what kind of pressure it was under, but to throw the initial fountain 10m above the ship from a depth of 114m took a bit of pressure. It’s unclear whether this methane originated from clathrates.

    I doubt there are many drillers in the arctic. Most of the research seems to be in Russian with no English translations available.

  4. 254
    prokaryotes says:

    We believe that a few additional points concerning mechanisms of methane ventilation to the atmosphere should be taken into consideration.

    First, the estimate assumes a diffusion mechanism for methane transport to the sea surface, but the most powerful mechanism for methane transport in shallow shelf areas is bubbling or ebullition (Chanton et al., 1989). Ebullition transports methane directly to the atmosphere, bypassing the mediating effects of an oxygenated sediment–water interface and water column. A common misunderstanding is that dissolved methane must exceed the solubility of the gas in water (roughly 1 mM at 20 °C and P CH4 = 1 atm) for bubbles to form. In fact, bubbles can form at methane concentrations well below saturation (Chanton et al., 1989).
    The proportion of methane bubbles that survives passing through the water column to reach the atmosphere generally depends on water depth and bubble size. It was shown by Semiletov et al. (1996)that from a depth of 10 m, bubbles with radius of 0.1 cm reach the air–water interface in 62 s losing only 15.1% of their methane. As mean depth within the study area was 123 m in 2003 and 13.1 m in 2004, we can assume that ignoring ebullition is a major gap in our estimates.

    Second, the Arctic Ocean has a natural trap for the gas bubbles — sea ice. During the freeze-up period gas bubbles are accumulated within ice structures in direct proportion to surface water saturation, and in inverse proportion to the speed of freeze-up (Zubov, 1938). Bubbles observed within the fast ice can reach up to 10 cm in diameter, and can completely deform the bottom of the fast ice. It is documented in the literature that after ice within Dmitri Laptev Strait was demolished using explosives (for the purpose of improving navigation) a flame of burning methane was seen (Zhigarev, 1997). We measured concentrations of methane beneath the ice (November, 1994) equal to 20,000 nM (Semiletov et al., 2004). When the ice begins to break up, methane accumulated beneath the ice may be abruptly released into the atmosphere.

    [Response: If this was a major mechanism then maximum atmospheric concentrations would be in September. It is not, it is in June - before the major retreat of the sea ice. - gavin]

    Third, ventilation of methane through the annual ice is possible because of its brine content. It was shown that methane was enriched in the air 2 m above the ice up to 4 ppm (Kelley and Gosink, 1979). In summer time (June) during the ice break period they measured concentration of methane in surface seawater increased up to 107 nM. A number of recent studies have shown that sea ice is highly permeable to gases through numerous tiny channels (Gosink et al., 1976; Semiletov et al., 2004). In addition, more than 1% of shelf area consists of open polynyas (Kulakov et al., 2003) providing a pathway for methane to escape during the winter period.

    [Response: Either the ice is a cap (point 3) or it isn't (point 4). Which is it? - gavin]

    Fourth, for the shallow ESAS, fall convection is particularly important in late September to early October (freeze-up period) when the probability of convection penetrating down to the seafloor can reach 40–50% (Kulakov et al., 2003). During the summer period the surface layer warmed up to 8.5 °C (Fig. 2); subsequent cooling during ice formation leads to vertical convection. Therefore, convective mixing may homogenize the concentration of dissolved methane in a body of water and increase super-saturation in the surface water following the significant release of methane into the atmosphere before ice formation is complete.

    [Response: Is the issue transport of methane from the sediments or release of dissolved methane (a tiny amount)? This is not relevant. - gavin]

    Fifth, it was mentioned above that the late summer period was much windier in 2004 than in 2003. Since the rate of gas exchange between the ocean surface and the atmosphere is a function of wind speed, this perturbation might have affected methane release substantially. Moreover, the changing of the relatively stable summer situation on the Arctic shelf to fall storm conditions appears to be a possible triggering mechanism for increasing the methane flux (Wanninkhof, 1992). In our estimates using long-term mean wind speed (6 m/s) instead of actual measured wind speed alters the resulting flux up to + 9 times.

    [Response: But this only affects the time to vent a particular mixed layer. It doesn't draw more methane out of the sediments. Thus the total flux doesn't change. - gavin]

    http://ic.ucsc.edu/~acr/BeringResources/Articles%20of%20interest/Eurasian%20Basin/Shakova%20and%20Semiletov%202007.pdf

    [Response: There is still no evidence of actual (thermodynamically unstable) shallow hydrates on ESAS. Sorry, but I'm not buying it. - gavin]

  5. 255
    prokaryotes says:

    Re Steve Fish #220 “Moderators: Have you or your colleagues been intimidated into altering your published projections of sea level rise for the last 30 years, as suggested by Prokaryotes above?

    Steve

    [Response: Not in the slightest. - gavin]”

    In the end of segment 2 of the following video James Hansen talks about intimidation and SLR

    Bush’s Climate Of Fear (2006)
    http://climatestate.com/2013/05/13/bushs-climate-of-fear-2006/

    [Response: You can read all about this in the Inspector General's report on the incident(s). Everyone associated with that intimidation lost their jobs. However, this is no longer an issue and hasn't been (at NASA at least) since Michael Griffin's statement on scientific openness (in 2006). Using this to imply that everyone is currently being intimidated because they don't agree with you is neither logical nor true. - gavin]

  6. 256
    Hank Roberts says:

    Look, it’s pointless to have a proxy argument. I’m not a researcher. Nor is prokaryotes or any of the others posting the methane emergency stuff. I’m a citation-checking skeptic. If there’s any actual reason to support the notion that there are methane hydrates that can exist outside the stability region — that’s big news for the chemists and physicists and someone will document it.

    If not, it’s scary big round numbers.

    [Response: Hear, hear. - gavin]

  7. 257
  8. 258
    Hank Roberts says:

    > gas discharge erupted from a well

    That happens all the time with drilling — it’s a recognized, routine hazard, coming up a drill pipe — not a fountain out in the open ocean. When they looked at the seabed, later, they found methane dissolving. It’s not clear if they plugged or capped the drill pipe either.

    > If there’s any actual reason to support the notion that there are methane
    > hydrates that can exist outside the stability region — that’s big news …
    (me)

    Such a molecule would be getting competitive in energy density with gasoline, wouldn’t it? A clathrate molecule stable at a few atmospheres’ pressure and above the freezing point of water — controllable — would be magic, transportable fuel. But has anyone got such a structure in mind?

    That would have to exist, for what they’re describing to be from shallow hydrates — but what unknown new form would that be?

    Seems like a great rumor hinting at a speculative opportunity, doesn’t it?

  9. 259
    prokaryotes says:

    [Response: But this only affects the time to vent a particular mixed layer. It doesn't draw more methane out of the sediments. Thus the total flux doesn't change. - gavin]

    With less sea ice insulation this could very well be the case. This could be especially the case when the Jet Stream stuck over northern parts of Siberia or more frequent Arctic cyclone activity in the Arctic Circle.

    The Arctic Ocean traditionally has been described as an ocean with low variability and weak turbulence levels. Many years of observations from ice camps and ice-based instruments have shown that the sea ice cover effectively isolates the water column from direct wind forcing and damps existing motions, resulting in relatively small upper-ocean variability and an internal wave field that is much weaker than at lower latitudes. Under the ice, direct and indirect estimates across the Arctic basins suggest that turbulent mixing does not play a significant role in the general distribution of oceanic properties and the evolution of Arctic water masses. However, during ice-free periods, the wind generates inertial motions and internal waves, and contributes to deepening of the mixed layer both on the shelves and over the deep basins—as at lower latitudes. Through their associated vertical mixing, these motions can alter the distribution of properties in the water column. With an increasing fraction of the Arctic Ocean becoming ice-free in summer and in fall, there is a crucial need for a better understanding of the impact of direct wind forcing on the Arctic Ocean. http://www.tos.org/oceanography/archive/24-3_rainville.html

    [Response: Sure. But how is this supportive of your previous point? Methane emissions are not driven by the ocean/sediment gradient in dissolved methane, therefore changes in turbulence or mixing are not going to affect total flux, just the residence time (and saturation level) in the column. - gavin]

  10. 260
    prokaryotes says:

    [Using this to imply that everyone is currently being intimidated because they don't agree with you is neither logical nor true. - gavin]
    Apparently i did not imply that. Instead i link to a quote, see my comment #216.

  11. 261
    prokaryotes says:

    [Response: Sure. But how is this supportive of your previous point? Methane emissions are not driven by the ocean/sediment gradient in dissolved methane, therefore changes in turbulence or mixing are not going to affect total flux, just the residence time (and saturation level) in the column. - gavin]

    Can you link to that “previous point”? I’m unaware of making such point.

    The above cited Shakhova paper is very rich with gradient analysis.

    Quote
    The vertical water density gradients are the strongest in the central area of the eastern ESS (between Lopatka Peninsula and Novaya Sibir Island) and in the zone influenced by the drifting ice edge (Kulakov et al., 2003). Within all these areas the high concentrations of dissolved methane were measured (Fig. 4a, spot 1; Fig. 4c, spot 6; Fig. 5b, all the area adjacent to the fast ice boundary), suggesting a subsurface methane source. Link (page 239)

    [Response: Well, if you are just posting random clips from papers without actually trying to make a point, forgive me if I get confused. If you are trying to argue that shallow hydrates are both currently an important source of methane to the atmosphere and that they are poised to become increasingly so, please provide evidence that such shallow hydrates actually exist. Note that the presence of methane does not imply the presence of hydrates, nor do fluctuations of surface fluxes, wind changes, or column amounts. If however you are simply trying to inform people about the fascinating details regarding methanogenesis in the Arctic, feel free to carry on. Either way, try and be a little clearer about the point you are trying to make. - gavin]

  12. 262
    prokaryotes says:

    Thanks for this clarification gavin. Well, i have to admit i do not try to make a case or point (at least not yet). Though from time to time i ask some question or collect “clips” and combine them because i think they are related, which i share here in the comments. I do not endorse any kind of emergency or a particular scenario at all (at least not yet). If i post a particular scenario, it is only because i like to share the science and often hope to get some valuable input, that’s all :) I will try to make this more clear in the future, cheers!

    Though, but i feel overall we should be more cautious about the climate system and should reduce our emissions and introduce a carbon fee, as Hansen has suggested. (I guess that’s my endorsement)

  13. 263
    Tony Weddle says:

    JHC, I find it odd that any climate scientist would not know about or cite the recent research done showing the the oceans are soaking up much of the heat, suppressing surface warming, or the work done by Foster and Rhamstorf showing a continuation of the underlying warming, when temporary factors are corrected for. However, the name of the lead author seems familiar ….

  14. 264
    Tony Weddle says:

    I get that there is no evidence of shallow hydrates, despite what Peter Wadhams implies. However, I’ve read a number of comments elsewhere that what Shakhova is (also) talking about is free methane trapped under an undersea permafrost cap which is now degrading, offering pathways for the methane to escape. Someone commented on this in the SkepticalScience article but I’m still not sure if this represents the main threat that Shakhova, et al, are talking about. Comments?

    [Response: There is evidence for free gas and hydrates below the permafrost layers (around 200m below sea floor), and tectonic activity/faults can cause that to be released (and does), however to create new pathways via warming on anything like the scale being discussed would take hundreds of years because of the diffusion time from heat anomalies. Remember that this permafrost is a relic from the last ice age and so has been (slowly) thawing for thousands of years. - gavin]

  15. 265
    Hank Roberts says:

    prokaryotes, on your website you list these Contributing
    Writers — quite a respectable list, if these are endorsements.
    They could help draft these self-links you post to be clearer.

    Contributing Writers

    Dana Nuccitelli / Skeptical Science
    Rasmus Benestad / RealClimate
    Ted Scambos / NSIDC
    Carl Franzen / The Verge
    Bill McGuire / UCL
    Clive Hamilton / CAPPE

  16. 266
    Kevin O'Neill says:

    #254 Gavin inline, regarding ice cover as a methane-trapping ‘lid’ “If this was a major mechanism then maximum atmospheric concentrations would be in September. It is not, it is in June – before the major retreat of the sea ice. – gavin”

    I’m not sure I follow your logic here. The ice cover in the East Siberian Sea typically begins melting out in June and has virtually disappeared by the end of July. Depending on the geography of the melt and the location of any trapped gases, I would expect maximum concentrations in June or July – not September.

    [Response: I think it highly unlikely that the pan-Arctic methane level is determined solely by emissions from the ESAS. - gavin]

  17. 267

    “…we should be more cautious about the climate system and should reduce our emissions and introduce a carbon fee, as Hansen has suggested…”

    I’d certainly re-endorse that notion (if that’s an allowable verb formation.)

  18. 268
    Grady Cash says:

    A previous poster asked about reclaiming the world’s deserts and the potential impact on CO2. The YouTube video by Allan Savory can be seen here. His before and after photos make a strong visual case for his recommendations. http://www.youtube.com/watch?v=vpTHi7O66pI

  19. 269
    JCH says:

    263
    Tony Weddle says:

    Tony, people appear to think he’s properly accounted for that.

  20. 270
    prokaryotes says:

    Again Hank, if you do not provide a “link” or a quote and ask me a question about what was not clear to you, i can not help you. I asked you on page 5, but you did not respond.

  21. 271
  22. 272
    Mal Adapted says:

    Grady Cash:

    A previous poster asked about reclaiming the world’s deserts and the potential impact on CO2. The YouTube video by Allan Savory can be seen here. His before and after photos make a strong visual case for his recommendations. http://www.youtube.com/watch?v=vpTHi7O66pI

    His case may be strong for natural grassland ecosystems that developed under heavy grazing by native herbivores, and that have been desertified by overgrazing or other human activities. A strong case against his recommendations can be made for natural desert ecosystems like the Sonoran desert, and for that matter most of the Intermountain West of North America, which never had large herds of native grazing animals, and where the native flora is not adapted to heavy grazing.

    AGW is having a huge impact on ecosystems, adding to historic degradation due to human exploitation, but I’m against deliberately sacrificing the last remnants of wild nature to atone for our sins against climate.

  23. 273
  24. 274
    Hank Roberts says:

    > prokaryotes … not clear
    See Gavin’s inline responses to you.

  25. 275
  26. 276
    prokaryotes says:

    Hank Roberts, these have nothing to do with your random claims and he is responding and able to communicate, something you always avoid.

  27. 277
  28. 278
    Jim Larsen says:

    276 Prok said, “Hank Roberts, these have nothing to do with your random claims and he is responding and able to communicate, something you always avoid.”

    Speaking of communicating, what are “these”? And I haven’t seen any “random claims”. Hank’s been spot on topic. Degrading the conversation to baseless insults is counterproductive.

  29. 279
    prokaryotes says:

    Changing Sea level budget and Semi-Empirical models http://www.glaciology.net/Home/Miscellaneous-Debris/changingbalanceofthebudgetandsemi-empiricalmodels

    How long will it stay linear?

  30. 280
    Susan Anderson says:

    Prokaryotes, please calm down and read all Gavin’s responses (including the one to me) with a dispassionate eye, if you can. He is taking a lot of pains to make it clear this particular methane problem is only one of many, and the science does not support the clathrates bomb stuff just yet. He seems to be keeping an open mind; please do the same. Also please note that you are not in the borehole but front and center. I also suggest you emulate Neven who keeps an open mind.

    Nobody is saying we shouldn’t be very very worried. They just saying the hype on this one needs a mite more evidence before history is rewritten. There are a lot of different methane sources, and I find some of the others more worrying.

    Also, on your website/blog it is important to properly acknowledge your sources and your connection with them.

    Hank Roberts is a straight arrow. I too ran across him on this issue, but his objection caused me to back off a bit. The AMEG people are worthy of attention because they are trying to do something, but some of them have been known to exaggerate too.

  31. 281
    prokaryotes says:

    Jim, you can read about baseless content from Hank here. Quote = I think you do know what people are talking about: the lack of evidence problem, for those doing the promotion of the methane emergency idea.

    I was asking him what he meant but he ignored my question. And now he is posting (265) Quote = They could help draft these self-links you post to be clearer.

    I have no idea what is not clear to Hank Roberts. Maybe he can shine some light to it? Otherwise it appears as he tries to muzzle the discussion around methane, i certainly do not promote any emergency idea.

  32. 282
    Hank Roberts says:

    > … diffusion time from heat anomalies

    Gavin, let me put on the tinfoil hat for a moment and speculate.
    What worst case — if diffusion isn’t the limiting process — is imaginable?

    Supposing: say there’s this cap of permafrost with gas under it (not ‘shallow hydrates’ but what’s actually known). Suppose that layer gets a lot of drill holes punched through it, along with natural faulting, down to the depth where hydrates can exist.

    Suppose in one location there’s gas rising up through drill holes or faults, carrying cold water with it — water that has to be replaced from the surrounding sediment, if it’s too cold/deep for hydrates to dissociate there to fill the volume.

    Suppose down in the sediment there’s some horizontal layer of gravel, like an aquifer, connecting to another drill hole or fault that connects to the seabed vertically — so it’s available for replacement water from the seabed to travel down into the deep stratum and move laterally.

    That’s how an under-gravel-filter works in aquaria — air bubbles up in one spot carrying water with it; water moves down through the gravel, as long as the bubbles keep carrying water up: http://www.newaquariuminformation.com/pictures/under-gravel-aquarium-filter.jpg

    So, worst imaginable case, an active circulation carrying relatively warmer water down to where it’s potentially transferring heat to known deep hydrates.

    With a tip of the tinfoil hat to the methane emergency people — this is one scenario I can imagine where any drilling into the area where gas extraction is now being planned could, maybe, cause problems rather larger than gas coming up single drill pipes, if warm water could get sucked down to where (real, known) hydrates could get warmed up.

    Whether such horizontal conduits exist, I dunno. I recall speculating along the same lines years ago about whether diffusion is the limit on how heat propagates through glacial icecaps, or whether fluid flow might carry enough heat to make a difference. As far as I know that was pure science fiction on my part, the magnitude is trivial, so this notion probably is too.

    I’m doing an exercise of “what could these people be seeing or imagining, to be saying what they’re saying” — trying to come up with some notion.

  33. 283
    Radge Havers says:

    @ grist
    Advocacy

    http://grist.org/politics/conservative-hostility-to-science-predates-climate-science/

    The core of Edwards’ argument is that “advocacy by climate scientists has damaged trust in the science.” Unfortunately, she offers no evidence to support that proposition. Instead her post links to a series of Twitter and blog conversations taking place among the comparatively tiny group of professionals who are involved with climate change and care about these kinds of things. (Note to Edwards: Drawing on blog comments to make one’s argument is not a sign of confidence.)

    …In fact, polls show that the broad public trusts scientists more than anyone else on climate change.

    …What has happened over the past 40 years is a steady erosion in the trust conservatives hold in science and scientists.

    …The process was accelerated in recent decades by the rise of a conservative alternative media,

    …So scientists can be as studiously neutral as they want. It will make no substantial difference. The battle is over cultural identity; it will be long, and messy, and the outcome is unlikely to have much to do with how scientists behave.

    OTOH, I’m not seeing anyone else sorting it out very well.

  34. 284
    prokaryotes says:

    Susan Anderson #280,”on this one needs a mite more evidence before history is rewritten.”

    “This one” (i guess you refer to the recent nature study on economic lose.)
    However i do not endorse this study anywhere.

    Susan Anderson #280, “Also, on your website/blog it is important to properly acknowledge your sources and your connection with them.”

    All sources are properly cited, if you find a particular source not correct cited you can inform me by using the contact form or in the comments.

  35. 285
    Kevin O'Neill says:

    #266 [Response: I think it highly unlikely that the pan-Arctic methane level is determined solely by emissions from the ESAS. - gavin]

    Gavin, I merely remarked on the logic of your statement in #255 that ice-cover as a lid would not show until September. I made no statement whatsoever regarding pan-arctic methane levels. I don’t know anyone claiming that emissions from the ESAS are the determinant factor in pan-arctic methane levels. These would, I believe, be mainly land sources. The ESAS would be the dominant ocean source.

    I do find it interesting that, per N.Shakhova, “…the amount of methane annually escaping from the ESAS is equal to that escaping from the entire World Ocean…” If my recollection is correct, this fact wasn’t known just 10 or 12 years ago. If we went back 10 years ago would it have been a well-received hypothesis that the ESAS releases as much methane as the entire World Ocean?

  36. 286
    Hank Roberts says:

    Mention of seabed structure promised here (abstract only at the link; no other copy and no DOI in Scholar at the moment, sorry to say)

    Determining the response of hydrate offshore Svalbard to ocean warming during the next century
    http://adsabs.harvard.edu/abs/2013EGUGA..15.3300M
    (the “fulltext article” link above goes to the abstract):
    http://meetingorganizer.copernicus.org/EGU2013/EGU2013-3300-1.pdf

    Geophysical Research Abstracts
    Vol. 15, EGU2013-3300-1, 2013
    EGU General Assembly 2013
    Héctor Marín Moreno (1), Tim Minshull (1), Graham Westbrook (1), Bablu Sinha (2), and Sudipta Sarkar (1)

    (1) National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom, (2) National Oceanography Centre, Southampton, United Kingdom

    Anyone have access to the full text?
    Do they have pictures/figures?
    Depth info, at least, must be there.

    Quoting a bit from the abstract:

    … Based on a recently published modelling study, offshore of Svalbard the methane release is occurring predominantly in a region where hydrate is likely to have been destabilised by ocean warming over the past 30 years. However, the future significance of this methane release remains uncertain.

    … Here, we use the TOUGH+Hydrate code to model hydrate growth and dissociation in response to a range of possible future ocean temperature scenarios in the Svalbard region obtained from climate models…. Below the seabed the structure and stratigraphy of the sediments and their gas and hydrate contents are constrained using high-resolution and very-high-resolution seismic data acquired in 2008, 2011 and 2012 and wide-angle seismic data acquired in 2008 and 2011.

    Seismic data, yea.

  37. 287
    prokaryotes says:

    Depth is not necessarily a good indicator for Methane Hydrate stability, since according to some studies.

    Fresh water is less dense than salty water, so the fresh water pulses from glaciers and melting ice bergs will act as a wedge, driving the denser, warmer, saltier water toward the bottom

    With all the changes in ocean currents and freshwater runoff from increased melt rates in the Arctic region and with all the extra heat from loss of sea ice it is possible that the added energy goes to the bottom.

  38. 288
    Tony Weddle says:

    Gavin, this confused me (from this post):

    [Response: If this was a major mechanism then maximum atmospheric concentrations would be in September. It is not, it is in June - before the major retreat of the sea ice. - gavin]

    Looking at the data from ESRL stations in and around the Arctic (e.g. Alert, Nunavut) the maximum concentrations seem to be around Feb/March time, with minimums around July/August. Of course, this still doesn’t jive with the theory you were answering but I just wondered why you’re stating something different from what it seems the data are showing? Am I misinterpreting something?

  39. 289
    Doug says:

    # 265 Hank,
    I asked a question on real climate and found out later that remarkably, Prokaryotes had copy pasted it to his blog, as if I had asked it there. I was even given credit for having asked it there. So, I guess I am in good company with all the contributing writers listed on his site. (:

  40. 290
    Chuck Hughes says:

    I’ve been following the conversation closely about possible “methane bombs” and I’m convinced as per Gavin Schmidt, Hank Roberts et al that we probably should refocus our attention on more pressing issues such as mitigation and public awareness. Speaking for myself as a non scientist and listening to the concerns of other readers around the internet, I’m down to just asking basic questions about the coming decades and the future of the next several generations of young people.

    One thing I would like to know is the likelihood of global temperature averages surpassing the 2C mark and possibly hitting 4 degrees Celsius by the end of this century. Is that a habitable temperature?

    I know time doesn’t stop at 2100 as others on here have pointed out but I figure if we’re sitting at 4 degrees celsius increase by 2100, it will be pretty tough going for humans. This is of course assuming we don’t see drastic cuts in CO2 emissions within the next ten years or so. I’m also assuming we will easily surpass the two degree increase no matter what we do, so if we hit 500ppm, what will that mean for global average temperature and is that pretty easy to calculate? Thanks.

  41. 291

    “Fresh water is less dense than salty water, so the fresh water pulses from glaciers and melting ice bergs will act as a wedge, driving the denser, warmer, saltier water toward the bottom…”

    That–as written–seems as implausible a statement as I’ve read in quite a while. I mean, what’s at the bottom already? So there’s increasing stratification at the top of (by implication in this context) at least 270 meters of ocean water. Is that going to affect the bottom conditions greatly? Surely the *cold* salty water that’s down there already won’t be destabilized. And I’d think there would be a hell of a lot more of it than the surface freshwater.

    Now, maybe given more context, this idea could actually make sense. (Maybe in connection with other constraints, like horizontal spatial structure?) But as stated here, I have a reaction of incredulity, I’m afraid.

    Is this from a paper, and, if so, which? I find it a bit hard to tell from the website.

  42. 292
    prokaryotes says:

    Apparently Hank’s comments in #265 created more confusion. I thought it is pretty obvious that the author’s mentioned contributed content to the 1st issue of ClimateState, a magazine issue which was released in June 2013. Skeptical Science reported it here.

    The article “Doug” mentions in #289 can be found here, a very interesting read i hope, and i welcome any feedback in the comments – under that article.

  43. 293
    prokaryotes says:

    Kevin, all quotes and content is cited. Just click those links called “Source” at the end of each text part. However, here is the link to the quote you was referring to

    Even more ominously, a wedge of cold water at the surface spreading out from the poles would push hotter, saltier water toward the ocean bottom. Fresh water is less dense than salty water, so the fresh water pulses from glaciers and melting ice bergs will act as a wedge, driving the denser, warmer, saltier water toward the bottom The net effect of such changes would be a shallower and weaker ocean circulation system as more warm water is averted toward the ocean bottom near the equator and then spreads northward and as warmer surface waters toward the poles and temperature regions are driven toward the sea-bed.

    Link

  44. 294
    Edward Greisch says:

    How flammable or explosive is the air above those methane bubble-ups in the Arctic ocean? Researchers could get burned. They should stand a few miles away and fire an incendiary bullet across it before sailing close. If it burns, they can measure the fire from space.

    [Response: To burn, CH4 needs to be above ~5% per volume of air. That is 5 orders of magnitude higher than observed concentrations. - gavin]

  45. 295
    Hank Roberts says:

    > from a paper, and, if so, which?

    That post has a period and paragraph break following the words “according to some studies” — probably should be a colon and blockquote, if it’s a quote from some study. The attribution link points to his climatestate blog.

    Citation’s not easy to do well.

    Gavin asked for DOI links, which are stable and permanent references.
    Providing those links to studies is a good practice.

  46. 296
    flxible says:

    Apparently Hank’s comments in #265 created more confusion. I thought it is pretty obvious that the author’s mentioned contributed content to the 1st issue of ClimateState …

    I think it’s yourself who creates the confusion. My read is that nobody has “contributed content”, rather you are collating ‘stuff’ [you think important] by pasting content from all over the place. As for Dougs comment above, your use of barely noticeable light blue for links makes it less than obvious that you had lifted his question from here at RC. What Hank is saying is you should be making it very explicit where your content is actually from.

  47. 297
    Hank Roberts says:

    > flammable or explosive
    Only where a concentrated puff of gas is channeled into the air, as you see in those pictures of flames above holes in ice, or on drilling rigs. See the table on this page: https://en.wikipedia.org/wiki/Flammability_limit

    But remember, bubbles rising from the seabed may contain CO2 as well as or instead of methane.

    Bubbles rising through seawater exchange gases with the surrounding water — the methane is very soluble in water, so a bubble reaching the surface isn’t the same gas that escaped from the seabed — gas is exchanged across the surface of the bubble with the surrounding water as the bubble rises.

    Modeling of methane bubbles released from large sea-floor area: Condition required for methane emission to the atmosphere
    21 June 2009, http://dx.doi.org/10.1016/j.epsl.2009.05.026

    Enhanced lifetime of methane bubble streams within the deep ocean
    7 AUG 2002, DOI: 10.1029/2001GL013966

    Serious work’s being done identifying what’s actually coming out, e.g.
    http://pubs.acs.org/doi/abs/10.1021/es401698p

    Simultaneous Analysis of Noble Gases, Sulfur Hexafluoride, and Other Dissolved Gases in Water
    Environ. Sci. Technol., 2013, 47 (15), pp 8599–8608
    DOI: 10.1021/es401698p
    (where, interestingly, supersaturation of gases was observed due to circulation of warm water through the gravel bed – small artificial lake)

    ————
    I’m an amateur poking at what I find; I hope the conversation here will sound interested enough and respectful enough of the actual work being done that the thread will attract thoughtful responses, eventually, from more of the scientists working in the area.

  48. 298
    Jim Larsen says:

    Edward G,

    The risk is minimal. Something dense enough to ignite fiercely would be quite small in area. And scientists measuring methane surely know when to back off. If you look, you can find photos of scientists deliberately venting methane on a lake and setting it on fire.

    Prok,

    Sorry, your quote of Hank’s seemed crystal clear to me.

    It isn’t a methane bomb, but a methane fizzle. As Gavin pointed out, this has been going on through the entire holocene. Different bits of methane in different states at different depths in different climates on land and sea don’t all come out at once. But then again, time doesn’t end in 2100.

  49. 299

    #287, 293–Thanks for elaborating. But I’m still a bit bemused: the context for #287 was methane hydrates; the context for the ‘source’ was possible future Heinrich events consequent to a rapid and near-total melt of Greenland. (Well, OK, that would certainly supply *lots* of fresh water, and would help supply the context that I wrote of in my comment.)

    But the speculative chronology here seems a tad jumbled, if I’m following all this correctly.

  50. 300
    prokaryotes says:

    flxible #296, Nope, all authors were informed, all sources are correct cited. Though i feel we addressed enough chatter now about ClimateState. For further “concerns” regarding content at ClimateState you are welcome to voice your constructive feedback over at that site.


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