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Climate Science: Got Doom Today? (Part 2)

by Nomad Mon Mar 6th, 2006 at 08:22:35 AM EST

Once more, I bring you some good news on the earth.

In this and the previous session on climate science, I report on remarkable discoveries in climate research which (so I suspect) are not broadly reported by the daily press. In a sea of press clippings spelling out the doom of humankind on nearly weekly basis, this news is actually somewhat comforting. But, as these findings do not have the proper "impact" factor, it won't get massively printed. To reiterate my catch phrase of last time: if it ain't doom, it won't boom.

In my previous diary, I described how a team of biologists from Colorado discovered a potential negative feedback loop on global warming, which could theoretically aid in slowing global warming. The protagonists in that story were microbial communities living in forest soil. In today's diary, microbes again play a part, but we've to go much, much deeper this time. This time, they're linked to one of the most fascinating features of our world's oceans: methane ice, or methane clathrates.


The existence of methane clathrates itself has been fruitful writer's material, witnessed in such books as "Mother of Storms" by John Barnes, or used with similar catastrophic effects in "The Swarm" by Frank Schätzing. (Both are good reads, BTW.)

And true enough, methane clathrates are in potential the stuff of nightmares. As always, the Wikipedia entry on Methane clathrates is a welcome starting point (but should never be the end point of one's curiosity). I will suffice here with the cliffs notes: The major component (up to 99%) of the clathrates is methane (CH4), a greenhouse gas with a ten times higher capacity to capture heat compared to the nefarious CO2. The compression of methane gas in clathrates is enormous: 1 cubical meter of clathrates brought to the ocean's surface releases up to 164 cubical meters of CH4. And lower (but inaccurate) estimates on size of the methane clathrates in the oceans are simply gargantuan, making them hands down the largest concentration of methane found on earth. Possibly there is 10 times more methane present in the oceans than in the gas reservoirs we now tap.

Today, methane is a word freighted with concerns on climate change. There is no doubt that free methane, methane in gaseous form in the atmosphere, enhances global warming. Logically, when the enormity of the methane clathrates was discovered, immediately there were worries what would happen if this reservoir would be released in its entirety into the atmosphere. And interestingly, there is strong evidence that this indeed once happened in our earth's history: during the Paleocene - Eocene extinction. Eocene was possibly the warmest periods in the Cenozoic (the time after the dinosaurs) and global temperatures has since that period dropped dramatically, eventually culminating in the Pleistocene ice ages.

But there have been found indicators that even during the Pleistocene the methane clathrates can become instable and degas, influencing the climate. This scenario of violent degassing is coined the clathrate gun hypothesis. Some of these degassing events are triggered by natural instability, perhaps occurring on a cyclic frequency, as speculated in a 2000 paper in Science. There is even a theory afloat on the Internet that mammoths are extinct because of a dramatic clathrate burst, triggered by an oceanic landslide. The most dramatic report that I know of a clathrate gun was presented in a paper published in Geology (among others), and suggests that ocean's bottom waters can warm up to 8 degrees C, setting off massive clathrate destabilisation, as recently as the late Pleistocene (85.000 years ago). All in all, this has led to frightful scenarios where global warming makes the methane clathrates a ticking time bomb. In a nut shell: Doom.

The violent degassing of clathrates is used to explain the historic spikes visible in the historic CH4 record, which shows a fair number of CH4 spikes. There is, however, an opposite view, which explains those spikes by the increased release of methane from wetlands and bogs, under the influence of changes in the hydrologic cycle, the water household of the earth.

Phrased differently, these two theories approach both sides of the chicken and the egg. The first theory is saying: massive CH4 degassing caused increased global temperatures. The second theory is saying: increased global temperatures caused increased CH4 degassing. Both have something to say for.


Now geoscientist Todd Sowers connected to Pennsylvania State University enters the fray. In his article, published in Science on 10 February, Sowers describes his analysis on ice samples from the GISP II ice-core, drilled out of the Greenland ice sheet. Particularly novel in Sower's study is the choice of his stable isotopes, his "tool" to make his assessment.

First, the basics. To form the methane captured in the clathrates both CO2 and hydrogen (H2) are needed. The source of the CO2 used in the methane clathrates is, through a long process, organic in nature and involves our beloved microbes. Carbon (C) comes in several isotopes (14C, 13C, 12C, where the number correspond with the atomic "weight" of the element.) Organisms prefer lighter atoms above heavier atoms, and this causes a natural selection for the 12C atom above 13C. For that reason, methane clathrates have a fingerprint of increased 12C. Expressed as a ratio, the 13C/12C ratio of methane is smaller compared to a standard 13C/12C ratio.

The methane produced in the wetlands also has an organic (microbes!) source, similarly resulting in a smaller 13C/12 ratio compared to the standard. This makes interpreting the ice core data and determining which CH4 comes from where pretty hard. The two opposing theories sketched out above were largely based on measurements on the carbon isotopes from the CO2, by attaining the 13C/12C ratio from ice samples.

The critical new point in Sowers' work is that he leaves the carbon alone and moves toward that other component of CH4: hydrogen. Like carbon, hydrogen also comes in stable isotopes. The most abundant isotope is hydrogen (H), with one proton, and the second isotope is deuterium (D), with one proton and one neutron in its atomic core. This makes deuterium almost twice as heavy, so even although there is not much deuterium around in natural form, its heaviness can still produce a traceable mark.

What the deuterium/hydrogen ratio sets apart from the carbon isotopes is that there is a clear distinction between deuterium in clathrates methane and deuterium in wetlands methane. The problem, however, was in measuring the ratio because of the low detection levels. A new measuring technique was developed to work around that and Sowers is one of the firsts to pick the fruits of it.

In wetlands, part of the hydrogen to form methane comes from the groundwater, precipitated in rain. Sowers used the estimation that about a quarter of the hydrogen is originally from precipitated rain water, the rest is from an acetate substrate. Yet rain water heavily samples light hydrogen (which, being lighter, evaporates quicker), and very little deuterium. This creates methane with a very small D/H ratio and hence, a large negative deviation from the standard D/H ratio. This negative deviation from the standard is expressed in per thousand, or per mil. See in this introduction to stable isotopes for those who can't stop reading. For wetlands the D/H deviation from the standard ranges from -250 to -380 per mil.

The hydrogen used for methane clathrates, after passing through a biological process, also has a negative deviation from the standard. But that negative deviation, in contrast to the wetlands CH4, is smaller: -189 per mil. This difference is significant enough to make a distinction between the two D/H signals in the CH4 stored in the ice.

In today's atmosphere, CH4 has a D/H deviation of about -100 per mil. Most contributing CH4 sources are far, far more depleted in deuterium. Methane clathrates, with a -189 per mil deviation is one of the least depleted CH4 sources. Now for the tricky but important part: if clathrates would heavily contribute to CH4 in the atmosphere, the D/H deviation becomes less negative (increases) .

Back to Sowers. He took an ice core going back up to 30.000 years, measured the oxygen isotopes (as global temperature indicator), the CH4 concentrations and determined the D/H deviations in the CH4. That's easy to put within one sentence, but a lot of work in total. The resulting graphs, however, are immediately telling and show two important things:

Firstly, the graphs show that there is an increasing CH4 concentration with time, together with a progressive decrease in the D/H deviation (mind the scale bars!!). Meaning, the D/H deviation becomes more and more negative. As stressed above, this is the exact opposite what we would expect if clathrates would heavily contribute to the increasing CH4 concentration: that would cause an increase in its deviation.

Sowers attempted to explain this increase of CH4 by the increased contribution of different CH4 sources (none of which methane clathrates), which I will not go into at this point.

To fully make sure that methane clathrates are not the source, Sowers focussed on a number of already identified warming events and sampled specifically around these time periods.

Here, even more clearly, it shows that with an increasing temperature there is an increasing amount of CH4 in the atmosphere. But in one case the D/H deviation does not change at all, or in the posted graph, it lags behind the CH4 increase and when it does change, the deviation decreases. In a final devastating blow to the clathrate gun, Sowers made a model that simulated what would happen if all the CH4 released in the atmosphere would be from the clathrates with a -189 per mil D/H signature. This gives the black line in the graph and shows that the simulation resulted in an increase (less negative) of the D/H deviation, the precise opposite of what the record is showing.

In one stroke, Sowers delivers damning evidence that the clathrate gun hypothesis in the earth's most recent history is not even smoking. In fact, it provides the question whether it was loaded in the first place. And this is good news, since it indicates that the methane stored in the oceans is a LOT more stable than what many people were speculating. It shows that even with abrupt warming events in our recent history, the clathrates contribute insignificantly to increasing global CH4 concentrations. For the greater part, they remain undisturbed on the bottom. With his findings, Sowers gives us a reason to sleep a little more comfortably - at least on this issue. And the theory that mammoths were knocked off this sphere by a catastrophic clathrate degassing can be carried for certain to the grave.

A final note. Of course, the results of Sowers' work does not rule out cataclysmic clathrate degassing from happening. Yet one conclusion that I draw from his work is that on a warming Earth there should be more attention directed to other methane sources, which are quicker to degas than clathrates. In that respect, I find reports of degassing marshes and bogs in Siberia releasing their CH4 of far greater concern. But in a diary on the good news, that subject is clearly out of place.

More internet articles on Sowers' paper:
http://www.bioedonline.org/news/news.cfm?art=2334
http://live.psu.edu/story/16054

Poll
Before you read this diary, were you familiar with this story? In others words: Am I bringing you old news?
. Yes! 11%
. No! 88%

Votes: 9
Results | Other Polls
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Slight disclaimer: the figures I used are scanned renderings from the Science article and in that form I never know where copyrights end. Of course, this diary is not meant for commercial goals, so my first guess is that it's safe. However, if the ET Gnomes do not agree with that view, I'd appreciate a call and will take proper action asap.
by Nomad on Mon Mar 6th, 2006 at 08:36:12 AM EST
It would have been news had it not been for your first diary on the topic.

Very well documented and easy to read for neophytes like me, congratulations.

There does not seem to be many "ET Gnomes" around this afternoon in any case <s>

When through hell, just keep going. W. Churchill
by Agnes a Paris on Mon Mar 6th, 2006 at 10:12:22 AM EST
Thanks Nomad. I more or less followed the argument though it's a challenge to get some of it into my head.

I appreciate the time it took to put this together and, as always, your analysis.

by gradinski chai on Mon Mar 6th, 2006 at 02:42:01 PM EST
It was the entire goal of this string of diaries to make  these discoveries understandable for those not in the field. And this one sure was a challenge. The ones with formulas always are.

Thanks for reading! As long as I can make clear that there is more going on in climate science than just daily doom, I'm more than satisfied.

by Nomad on Tue Mar 7th, 2006 at 09:39:23 AM EST
[ Parent ]
jesus Nomad.. jesus.. you know how much effort you put on this....you really know it? I guess so... but oh man.. I am speechless.. what I can say? Great, wonderful...fantastic... you explain an article in Science better than what any can do.. you basically review a paper.. it could be a paper of its own...

It is just great...really...

Regarding the poll... part I knew part is new to me...so I am really hapy about the discovery.. in any case the positive feedbacks because of diminishing ice in the poles and the impact on ocean currents has been always more worrisome...

I hope good news about the ocean current too... regarding the ice.. I just hope that the feedback does not obliviate us completely from the Earth...

As they say, the earth has virus and it needs to get some fever to get rid of it...

I always add .. even better...reduce the virus to the standard healthy dosis...as we all have in us...a standard healthy dosis of virus and bacteria....reduce the number of humans to a healthy dosis...please....

A healthy entitiy is not something without virus or bacteria taht can kill you.. a healthy body has the right amount of virus and bacteria that may kill you.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude

by kcurie on Mon Mar 6th, 2006 at 04:54:18 PM EST
I'm humbled by your praise, kcurie. All I can say is that doing this is a lot more satisfying than constantly calling out to people to calm down and tell that there's more going on.

I always add .. even better...reduce the virus to the standard healthy dosis...as we all have in us...a standard healthy dosis of virus and bacteria....reduce the number of humans to a healthy dosis...please....

I agree, but how? The rise of mankind was one of unfathomable success, linked to the end of the last ice age. The turning point in global population growth will come, but I think that only changing boundary conditions (climate) will make it happen. The other option is the Easter Island scenario: continuous growth, full destruction of the planet's habitat and then... starvation of the surplus the Earth no longer can feed.

by Nomad on Tue Mar 7th, 2006 at 09:49:05 AM EST
[ Parent ]
Luckily it seems the Earth  will recover...and new species will inhabit the earth..after all this is the bacteria planet... bacteria and algae.. in our blue or brown surface.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude

by kcurie on Tue Mar 7th, 2006 at 10:19:43 AM EST
[ Parent ]
Thanks for another fascinating diary! But as usual, I will roast you with lots of questions:

  1. Nomad, would you please explain the key argument here? I don't understand how a -189 per mil D/H ratio-reduced cathrate could, if released, move the atmosphere above the -100 per mil deviation, especially given that evaporation would favor further decrease in the ratio.

  2. In connection to the previous, how do methane releases from bogs and cathrates relate in relative intensity of effect on the H/D ratio? Could it not be that a smaller amount of highly depleted bog methane completely masks a greater amount of methane releases from the seabed? (I suspect Sowers dealt with these questions, but I thought I ask the expert to explain it before digging into the article :-))

  3. How sound are Sowers' assumptions regarding typical methane concentrations (in bogs, in cathrate, in releases, in evaporation, in the air)? I mean, what are the standard deviations and the theoretical extrapolations in this?

  4. There is one line of evidence missing from your diary: seabed evidence, before Norway and the North Sea, of large landslides and circular depressions from the last 15,000 years. I even read of one depression before England that has a 100-year-old missing trawler in the middle - apparently sunk as the bubbling-up methane reduced the displaced water's specific weight and eliminated the ship's buoyance (I'll dig up a reference when I get home). Has this evidence been dismissed lately?


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Tue Mar 7th, 2006 at 09:55:14 AM EST
Forgot one point and my consequent speculation:

5) Could there be any significant processes that counter-act the methane releases? E.g. say an isotope-differentiating washing-out of the atmosphere? To connect to the previous diary, a negative feedback process could exist at some level or timescale.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Mar 7th, 2006 at 10:07:28 AM EST
[ Parent ]
Sorry for the silence; I've been taking off-line time to get myself shaped up for a presentation on a congress in 1.5 weeks. Not something I've grown used to yet.

All of your questions are excellent and deserve a thorough answer. I hope to do so in say, 12 hours, from now. I need some sleep first.

by Nomad on Wed Mar 8th, 2006 at 08:38:43 PM EST
[ Parent ]

1) That's the entire crux of the article isn't it? And it was exactly this point that had me puzzling for a while - which is why it took me a while to write it down properly. The best advice I can give you: try it yourself. Doing a sum is far more insightful than what I can muster on education skills. But I'll try.

The key point is that the other CH4 sources (wetlands, but also rice paddles and burning biomass) that also heavily contribute to the atmospheric CH4 all have a far more negative D/H deviation. (The one exception being coal mining.) So, all of these are the sources to atmospheric CH4. All lumped together, you'd expect an atmospheric D/H ratio between -150 and -350, probably between -200 and -250 (I don't have the exact number).

But the atmospheric D/H is between -90 to -100. The reasons is that there are also CH4 sinks at work in which CH4 fractionate differently. And this fractionation is an enrichment which balances back the negative D/H deviation.

If, however, all the CH4 released is from the clathrates with a -189 deviation in an atmosphere with an enrichment fractionation of 100 to 150: -189 +100 = -89. In an atmosphere with where the D/H deviation is -100, this means an enrichment, resulting in a move above -100.

At this point, you've to forget about the evaporation, I've swept it up in the total of sinks.

2) If I get your thrift, you're talking about the lever rule. If we put little methane in the atmosphere with this (heavier weight) and put lots of methane in the atmosphere with (lighter weight), the total balance we observed is tilted toward the heavier weight. Correct?

Actually, Sowers does not specifically deals with that question. And I've pondered on it for the morning. In fact, it makes explaining why the D/H deviation flatlines in the second figure easier. I think the best way to puzzle about this is to make some more sums; I don't have the answer for you right now.

  1. He doesn't do that math, but he refers to lots of studies which estimate the methane concentrations in the CH4 sources. As shown, he gives a number for what's in the atmosphere. And he fixes on that one: he suggests, based on other models, that the observed atmospheric CH4 variations is not by a change in the removal from the atmosphere, but by a change in the sources contributing to it. It's a common approach to focus on the ins and outs of one reservoir, than make assumptions for all the contributing reservoirs.

  2. This is the factor time: is CH4 release gradual or is it sudden, instantaneous? Clathrate gun hypothesis applies instantaneous increase. The evidence you quote is not dismissed, but Sowers' work sure makes it irrelevant. Look at the second figure: the CH4 increase is gradual with time. The precision of the sampling is phenomenal: the sampling is roughly every 20 years. A clathrate gun would release tonnes of CH4 in the atmosphere in mere moments: you would expect the entire increase within one sampling. It doesn't show. So, even if the clathrate gun works, it doesn't make obvious dents in the record - rendering it insignificant.

  3. There are a number of negative feedbacks, some temperature related. But to be honest, I've not found much time to study them - so in that subject I'm still indebted to you.

Thanks for keeping up with these good questions; it's a delight to have an attentive audience. Keeps you on edge.
by Nomad on Thu Mar 9th, 2006 at 10:35:36 AM EST
[ Parent ]
...Clathrate gun works in two ways:
  1. Temperature instability
  2. Pressure instability.

The North Sea scars are most likely examples of landslides and catastrophic, rapid pressure changes - release part of the methane clathrates. Sowers work shows that pressure triggered clathrate release are likely irrelevant for climate CH4. The temperature induced clathrate release, which I suspect was the bigger worry, is shown to be fairly well reduced. They certainly do not dominate the CH4 signal.
by Nomad on Thu Mar 9th, 2006 at 03:22:34 PM EST
[ Parent ]
  1. I still don't get it, though now I understand more of it. So the -100 in the atmosphere is the result of a balance between sources and sinks. The release part in turn is a balance between various kinds of sources. So if, all other factors being equal, the latter balance shifts in favour of the clathrates, the overall balance with the sinks will shift too?

    My problem with this is that "all other factors being equal" is not true. If there is a jump in releases, it's not just the ratio of the sources that changes, but the overall (H+D) sources-sinks balance too.

    Cowers surely covered the above issue, and I hope you can explain. But, one has to contemplate change in the absorbtion rates of the sinks, too. At first sight, this seems to involve vague untested assumptions like the hockeystick graphs.

  2. Yes. From the second graph, it seems what Sowers thinks he closed out is merely that clathrates were the only souce of methane increase, not that they were significant part of it (i.e. you seem to be going beyond his conclusions).

  3. Yes there is focus on one reservoir, but the standard deviation of concentrations in the sources are important for the reliability of the model - and comparison with the latter is what we drew conclusions from.

  4. You are assuming that the different sudden clathrate release events (there must have been hundreds of them) were simultaneous. Why? (BTW sorry for forgetting about digging up the source for the 'recently' sunk trawler, will do so today evening, promise!)

Supplementary note: observing the second graph more, what I notice is that the D/H ratio seems constant during the methane releases (e.g. the atmospeheric methane concentration jump), and rises sharply after it is over. To me this suggests some balancing process that kicks in just after the releases start, and continues to act after the releases are over and CH4 concentration has started sinking again - my bet would be on some change in the sinks, in particular the artic bogs and seas.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Mar 10th, 2006 at 07:19:58 AM EST
[ Parent ]
1. My problem with this is that "all other factors being equal" is not true. If there is a jump in releases, it's not just the ratio of the sources that changes, but the overall (H+D) sources-sinks balance too.

I don't follow the argument. How is it not true; in what way do the sinks change? Of course, you do have a good point: Sowers builds his case on the argument that during the last glaciation period were in the changes in sources, opposed to the changes in the rate of removal. A model study (uh-oh..), published in Geophyiscal Research Letters (P. Martinerie et al., 1995) is used to build the case.

2.Sowers phrases it a lot more decisive than I do. I made the significant claim, Sowers write in his concluding paragraphs:
"The general trend of decreasing (delta)D(CH4) throughout the termination, combined with relatively stable (delta)D(CH4) values during periods of rapidly increasing CH4, suggests that marine clathrates are stable during during this period and specifically during abrupt warming events."

Bold mine. I interpret from that that Sowers concludes there were zero clathrate methane releases from the oceans whatsoever. Then again, this is a Science article, which generally need to have a bold and crisp approach...

3.Hang on, perhaps I understood you wrong. When you write concentrations in the sources, do you imply with that CH4 concentrations in the sources or the range of D/H deviations present in the CH4 for each source? If it's the latter, I've to re-answer your first question differently, as I took the first interpretation.

4.Again, I need to ask first whether we're talking about the same thing. Are you talking about those ocean scars of the last 15.000 years, or do you specifically mean the warming event projected in the Sowers' figure?

If you mean the first, I've given you the wrong impression. There's no evidence that I know which suggests that there were simultaneous releases; in fact, all I know are cases separated by chunks of time. The Storegga landslide is the best well known case and has been used in publications (such as this one) to claim that catastrophic land slides trigger massive clathrate methanes which then boost global methane levels... And well, they're not showing in the D/H record of Sowers.

In an aside, I noticed that the atmospheric CH4 increase is nicely parallel with the temperature increase. This always makes me wonder about CH4 release (and also CO2 releases) who's the most important chicken: temperature or CH4. If these sort of findings are right, they suggest that temperature is forced on the earth and that CH4 just trails behind. The alternative is that temperatures rapidly respond to CH4 increases.

by Nomad on Fri Mar 10th, 2006 at 11:08:39 AM EST
[ Parent ]
BTW, I couldn't vote: I haven't read of Sowers' article, but the methane issue (and the applied isotope depletions) are known to me.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Tue Mar 7th, 2006 at 09:56:37 AM EST
We are dooooooooooooooooooooooooooooooooooomed I tell you!
by Metatone (metatone [a|t] gmail (dot) com) on Tue Mar 7th, 2006 at 11:37:52 AM EST
And, pray tell, what site was that, Metatone?
by Nomad on Tue Mar 7th, 2006 at 04:32:46 PM EST
[ Parent ]
Stop worrying, technology will save us. We'll have windmills (or photovoltaics) providing bountiful pollution-free electricity for all purposes. What's the problem?
by asdf on Tue Mar 7th, 2006 at 11:45:14 PM EST
[ Parent ]
Low speed of buildup?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Wed Mar 8th, 2006 at 05:56:03 AM EST
[ Parent ]
The problem is the lags of years, decades and even centuries in the global climate system. We have been injecting greenhouse gases into the atmosphere at an increasing pace for 200 years, with the peak in recent times. Even if instantly stopped carbon emissions altogether climate change would continue for years, maybe decades.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman
by Migeru (migeru at eurotrib dot com) on Wed Mar 8th, 2006 at 05:58:44 AM EST
[ Parent ]
I should have put the snark flag on that one...
by asdf on Wed Mar 8th, 2006 at 09:46:04 PM EST
[ Parent ]
Well, I understood you were being snarky... Otherwise I'd have reminded you we were fiddling while Rome burned...
by afew (afew(a in a circle)eurotrib_dot_com) on Thu Mar 9th, 2006 at 10:48:02 AM EST
[ Parent ]
This is a great series, Nomad, and necessary. Thanks.

I'd read about methane being released from the ocean bed, though I hadn't tried to get further information about it. Your diary makes things look less worrisome, though there remains the considerable problem of melting Siberian permafrost.

I'd be interested in reading your response to DoDo's questions (1) and (5) particularly. (Because (1) might help me understand the negative ratio thing better, no reflection on your excellent powers of exposition, only on my scientific dimness, and (5) seems a useful query).

by afew (afew(a in a circle)eurotrib_dot_com) on Wed Mar 8th, 2006 at 05:28:26 AM EST


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