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ChrisReynolds

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Re: Possibly important paper regarding CH4
« Reply #50 on: October 16, 2013, 07:40:16 AM »
I'm not sure exactly how you came up with that assessment of their time scale or how they did, but I can't imagine how accurately dating something 55.8 million years ago so accurately in years is done. It falls into a category of things that aren't impossible, but are highly unlikely.

Read the bloody paper!

wili

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Re: Possibly important paper regarding CH4
« Reply #51 on: October 16, 2013, 05:42:34 PM »
"Read the bloody paper!"

Good idea.

In case anyone missed it, here is the link again that idunno graciously provided up thread (but still hasn't read? Hence his handle?? '-)):

http://thingsbreak.files.wordpress.com/2013/10/evidence-for-a-rapid-release-of-carbon-at-the-paleocene-eocene-thermal-maximum.pdf

Much of the paper is exactly devoted to how they came up with the time scale. There are regular rhythmic deposits in the cores they are looking at. The authors rule out regular changes in orbital cycles that would alter insolation patterns as being too long. The only other possibility would seem to be annual cycles.

If someone can come up with cycles likely to occur between these extremes that could possibly result in the layering they describe, that could go a long way toward explaining the apparent instantaneousness of the changes they describe and would be most welcome. But just saying one doesn't like the time scales and pontificating about the scientific method is not much help to the discussion, imho.
« Last Edit: October 16, 2013, 06:09:22 PM by wili »
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #52 on: October 16, 2013, 07:14:13 PM »
Ccgwebmaster - you get it.

A 1200Gt (biogenic methane) or 3000Gt (thermogenic methane) pulse in a few years (up to 4 by my reckoning) is verging on the inherently improbable. And as you've calculated, an asteroid/comet sufficient to deliver that much carbon would have caused a mass extinction at least as great as the KT impact.

And I'm sorry to those who are still clinging on to methane hydrates, you need to have a mechanism that can deliver all the methane in a large region of ocean clathrates (100s of metres deep) into the atmosphere within a few years. It's not feasible, it really isn't.

If there is something wrong with this paper it's most likely in the timing part, IMO.

Out of interest, and just for fun, David Archer has a page of models, they're set up for now, not the PETM.
http://climatemodels.uchicago.edu/
The slugulator allows you to see what happens with a 1200Gt slug of methane.
http://climatemodels.uchicago.edu/slugulator/

The authors note that if released as CO2 this would result in 5degC GW, with slugulator (3000Gt CO2 we get around 5degC GW after 20 years (5degC is what the paleo data indicates happened). If released as 1200Gt CH4 we get 7 degC GW after 20 years, which falls off rapidly. to be replaced by warming from CO2.

Try quoting the paper!

Quote
Therefore, we interpret the 13 observed
layers through the onset of the CIE at Millville as 13 annual
cycles, and the 750 layers within the Marlboro clay at Millville as
representing 750 annual cycles.

Source: http://thingsbreak.files.wordpress.com/2013/10/evidence-for-a-rapid-release-of-carbon-at-the-paleocene-eocene-thermal-maximum.pdf

Does it match what you posted?

Quote
A 1200Gt (biogenic methane) or 3000Gt (thermogenic methane) pulse in a few years (up to 4 by my reckoning) is verging on the inherently improbable.

ccgwebmaster

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Re: Possibly important paper regarding CH4
« Reply #53 on: October 16, 2013, 07:23:19 PM »
Much of the paper is exactly devoted to how they came up with the time scale. There are regular rhythmic deposits in the cores they are looking at. The authors rule out regular changes in orbital cycles that would alter insolation patterns as being too long. The only other possibility would seem to be annual cycles.

As - as far as my limiting understanding permits - it seems fairly robust to me. That doesn't alter the fact that it's logical to look for the weakest link here? Once you've ruled out the impossible, whatever is left - however improbable... and all that?

If someone can come up with cycles likely to occur between these extremes that could possibly result in the layering they describe, that could go a long way toward explaining the apparent instantaneousness of the changes they describe and would be most welcome. But just saying one doesn't like the time scales and pontificating about the scientific method is not much help to the discussion, imho.

I don't like the timescales simply because it's so tremendously difficult to comprehend mechanisms that can make them work - and I'm not sure if they fit other information about the PETM extinction (that is much harder to quantify of course, and I can't even do an adequate job on the mechanisms).

Incidentally, another objection I can think of about the cometary carbon idea - to counter anyone who thinks you can conveniently park something that big in an ocean:

http://en.wikipedia.org/wiki/Impact_depth

The question really is - does something that big moving at that speed act as a Newtonian impactor - or do other factors come into play?

If it does, the implication is clear - the object was minimum 13km in diameter (if pure carbon, and not impacting on land where you'd expect a big signature) - and I'm not sure where there's enough water to park it without still leaving a crater (or at least a mark)? One can play with the angle of incidence - but the more you decrease that the lower probability the event becomes.

I'd also be extremely skeptical of something that large blowing up into little pieces in the atmosphere (eg Tunguska) - the Wikipedia article above suggests the atmosphere is good for around 10m of water - against 13,000m+ of impactor?

If it arrived as lots of little pieces, it's hard to see how they'd all have been small enough to hide and still densely packed enough (in time and space) to have that level of effect.

Likewise if those few million years were characterised by multiple hyperthermals - I would've thought release of methane via volcanic activity rather fluky and likely to be a one off?

With respect to submarine clathrates - am I right to think the planet was already pretty warm and ice free at the start of this process? If so - that further undermines that argument (at least taking my view that only shallow water clathrates are likely to respond especially abruptly) as shallow water clathrates are necessarily stabilised by temperature and not pressure - and hence you require areas with the Arctic climate to retain them. While I still think shallow clathrates in the Arctic are a real threat for us today, I'm currently less and less convinced they fit the scenario described by the paper.

The challenge for anyone is to find a way to justify and explain their position - whichever possibility you favour. Personally though, it feels like something way beyond my knowledge/understanding to think of a good answer - even though it keeps nagging me as I hate unsolved problems.

Still, I've learned quite a bit trying - I stumbled over something interesting about the formation of coal that suggested so much was formed during a particular period in earth history as the organisms to digest it hadn't got going (more on the coal thread).

So there are certainly plenty of things about the earth system most of us don't know, and plenty more that nobody at all knows.

Maybe we're looking for some other unexpected quirk that could explain the hyperthermals and the speed of change - something unique to those few millions of years of earth history?

ccgwebmaster

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Re: Possibly important paper regarding CH4
« Reply #54 on: October 16, 2013, 09:47:59 PM »
Another thought just struck me - could large scale volcanic activity in conjunction with a very large coal bed (or maybe even oil field) produce this sort of signature so rapidly? Is there any reason thermogenic methane is favoured over other sequestered carbon?

ChrisReynolds

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Re: Possibly important paper regarding CH4
« Reply #55 on: October 16, 2013, 10:24:05 PM »
Ggelsrinc,

Your quote of the paper seems to have no bearing on what I think you're getting at. If you are trying to say the initiating release of depleted carbon took more than a few years, you don't get the CaCO3 excursion and argument about physical diffusion vs equilibrium impact of the depleted carbon injection.

Yes, with regards thermo/biogenic carbon, the paper does match what I've said, in the final para of the paper they state: "If released as CO2, this would be consistent with observations of an ∼5 °C global warming" having previously stated this is non-biogenic (i.e 3000Gt C)! Therefore I was fine to use 3000Gt carbon as CO2 not methane.

ChrisReynolds

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Re: Possibly important paper regarding CH4
« Reply #56 on: October 16, 2013, 10:32:33 PM »
Another thought just struck me - could large scale volcanic activity in conjunction with a very large coal bed (or maybe even oil field) produce this sort of signature so rapidly? Is there any reason thermogenic methane is favoured over other sequestered carbon?

I seriously doubt it would be that fast, from what I've read such events 'cook' the coal over centuries/millenia.

I'm as clueless as you are as to what could release so much depleted carbon so fast. And I suspect it's causing a lot of head-scratching amongst real scientists.

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #57 on: October 17, 2013, 12:20:27 AM »
http://www.largeigneousprovinces.org/

The evidence of a large volcanic event should still be around and the only event I know about is that large kimberlite field in Canada. Anything that can change the carbon isotope ratio is a possible cause. Both volcanic activity and bolide impact provide multiple sources of carbon and seem to be the most likely causes. About 20 million years later there were bolide impacts in the Chesapeake Bay, another off the coast of New Jersey and another in Russia that all date to the same period of time. Comets are known to break apart and cause multiple impacts, so they aren't easy to dismiss. Could a pressure wave cause a methane clathrates release? 

The paper cites footnotes 19 and 20 for dating. If they can really determine the onset of the CIE event to 13 years, getting an accurate date of those samples would be very helpful. It would assist in eliminating the possibility that the samples show the results of local fires, for example, like in the Amazon. Periodic droughts and monsoons need to be considered. Finding a proxy demonstrating seasonal changes within the layers would confirm their annual hypothesis and there should be something in that tropical rainforest near there that leaves (no pun intended) a seasonal signature in ocean sediments. 

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #58 on: October 17, 2013, 12:50:29 AM »
Ggelsrinc,

Your quote of the paper seems to have no bearing on what I think you're getting at. If you are trying to say the initiating release of depleted carbon took more than a few years, you don't get the CaCO3 excursion and argument about physical diffusion vs equilibrium impact of the depleted carbon injection.

Yes, with regards thermo/biogenic carbon, the paper does match what I've said, in the final para of the paper they state: "If released as CO2, this would be consistent with observations of an ∼5 °C global warming" having previously stated this is non-biogenic (i.e 3000Gt C)! Therefore I was fine to use 3000Gt carbon as CO2 not methane.

How did you come up with a few years (up to 4 by my reckoning) when they said 13 years?

ChrisReynolds

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Re: Possibly important paper regarding CH4
« Reply #59 on: October 17, 2013, 07:57:56 AM »
The CaCO3 drop is extremely rapid (fig 3) - as they say, this is due to rapid effect of increased atmospheric concentration of CO2 taking weeks to effect the ocean column. Note that it is also present as a steep drop in all the sediment columns considered (fig 4a), and it happens just as the 13C drop starts.

The longer term decline of 13C is due to the physical infiltration of 13C atoms (in molecules) into the sea water column, as Revell/Suess find this takes about ten years.

Therefore the process was intiated by a massive increase of atmospheric carbon, taking no more than a few years, and sustained by continued high levels of atmospheric carbon. By my reading of those two graphs it looks like a period of no more than 4 years (8cm - assuming the bands in the clay are annual).

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Re: Possibly important paper regarding CH4
« Reply #60 on: October 17, 2013, 11:47:47 AM »
My guess as to the possible origin of such a large release would be the disturbance of a massive natural gas field by tectonic movement. Either India or Australia colliding with Asia would suffice. 

idunno

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Re: Possibly important paper regarding CH4
« Reply #61 on: October 17, 2013, 07:11:31 PM »
Or  disturbance of a large gasfield by meteor impact? Like liquor, that'd be quicker. The meteor can then be much smaller.

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #62 on: October 18, 2013, 02:33:03 AM »
The CaCO3 drop is extremely rapid (fig 3) - as they say, this is due to rapid effect of increased atmospheric concentration of CO2 taking weeks to effect the ocean column. Note that it is also present as a steep drop in all the sediment columns considered (fig 4a), and it happens just as the 13C drop starts.

The longer term decline of 13C is due to the physical infiltration of 13C atoms (in molecules) into the sea water column, as Revell/Suess find this takes about ten years.

Therefore the process was intiated by a massive increase of atmospheric carbon, taking no more than a few years, and sustained by continued high levels of atmospheric carbon. By my reading of those two graphs it looks like a period of no more than 4 years (8cm - assuming the bands in the clay are annual).

Quote
The longer term decline of 13C is due to the physical infiltration of 13C atoms (in molecules) into the sea water column, as Revell/Suess find this takes about ten years.

I see it this way.

Quote
Deep sea carbon isotope and CaCO3 records across the Paleocene/
Eocene thermal maximum (PETM) and associated
carbon isotope excursion (CIE) (55.8 Mya) require a massive
addition of 13C-depleted carbon to the ocean–atmosphere system
in a geologically short interval of time (1–3).

Source: http://thingsbreak.files.wordpress.com/2013/10/evidence-for-a-rapid-release-of-carbon-at-the-paleocene-eocene-thermal-maximum.pdf

bold is my addition.

Quote
Isotopes of carbon are atomic nuclei that contain six protons plus a number of neutrons (varying from 2 to 16). Carbon has two stable, naturally occurring isotopes.[11] The isotope carbon-12 (12C) forms 98.93% of the carbon on Earth, while carbon-13 (13C) forms the remaining 1.07%.[11] The concentration of 12C is further increased in biological materials because biochemical reactions discriminate against 13C.

Source: http://en.wikipedia.org/wiki/Carbon

In simple English, they are looking for a source of carbon that is 12C richer than what is normally found on the Earth's surface to explain the changes in isotope ratios discovered in a carbon isotope excursion (CIE) event. Think of it this way! Life on Earth prefers 12C over 13C and life sequesters carbon. It therefore removes more 12C than 13C producing a richer 13C environment than the substance originally making up the proto-Earth. Changing that ratio points to carbon sequestered by life or incoming carbon from outer space.

With today's technology, measurements of isotopic ratios isn't hard to do. Accurately dating the past is very hard to do. The title of this thread is misleading, but still correct in a way. The carbon isotope excursion could be the result of adding CH4 or any carbon sequestered by life, which is 13C-depleted. All fossil fuels have different carbon isotope ratios than the normal carbon we live with on the surface of the Earth. It could be the addition of extra-terrestrial carbon or done in a way to add more biologically sequestered carbon. That's why methane hydrates and bolide impact are suspected.

I can totally understand the need to spend grant money getting the most scientific evidence it will produce. The potentials for advancements in chronology are not dependent on the couplets being annual, any periodicity serves the same purpose for an event that happened around 55.8 million years ago. With my limited knowledge of clays and sedimentary rocks, I think the couplets are annual and capture nearly the moment of the CIE, as far as a shallow water column can show.

The evidence I see in the clays is consistent with weathering from the Delaware and Susquehanna rivers of today. I believe such weathered materials separate on the ocean floor and produce those layered sedimentary rocks we see so often and some do reflect seasonal changes. The chemistry between kaolinitic clay and (smectite clays and micaceous silts) should allow the ocean to separate them in distinct annual layers under the right conditions of deposit. If such deposits aren't weathered away, they can reveal details of Earth's past history.

Personally, I believe it's a mistake to go too far trying to tie the past to our present global warming problems. If someone doesn't believe adding or subtracting CO2 will change the environment, then they don't know the history of the Earth, because it certainly does. I also think the doomsday message is a mistake. Harping on a message of fear just shows a lack of understanding of human nature. People don't respond to fear unless it's attacking them at the moment. Our children were born that way and even as adults we will behave that way. It's in our very nature. There is nothing wrong with using a little creativity and putting a spoon full of sugar to make the medicine go down in our message. You have to provide people with hope.

The last paragraph wasn't anything personal to you. I have a hard time reading your blog, because it is white on black background and I don't know what your position is on that issue, based on what I've read elsewhere. I can understand how someone thinks they are doing a service by saying such things, but I know it's a mistake. If it doesn't work, so try another approach! My interests aren't in my vanity of being right, but making sure the future is brighter for humanity.

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #63 on: October 18, 2013, 03:42:37 AM »
My guess as to the possible origin of such a large release would be the disturbance of a massive natural gas field by tectonic movement. Either India or Australia colliding with Asia would suffice.

The problem with that hypothesis is India was only getting close to Asia and Australia was still near our present Antarctica. Another problem is we have never discovered a natural gas field nearly of the size needed to supply the amount of carbon needed to produce the CIE PETM event and to do so as rapidly as indicated by many studies. Our ability to date the past is very limited, because much of it depends on particular fossils existing widespread throughout the Earth and dying off at a particular moment. They are called index fossils. They can give us a black on white picture of approximately what happened in the past, but can't provide a full color version. 

Scotese is a good site for Paleogeography, but here is another useful site with both links:

http://www.scotese.com/

http://www.palaeogeography.net/palaeogeography/cenozoic_maps/pg_eocene1/pjmg1eoc1.html

When talking about the past, you have to look at the world as it once was.

ChrisReynolds

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Re: Possibly important paper regarding CH4
« Reply #64 on: October 20, 2013, 08:38:41 AM »
Ggelsrinc,

Sorry for not getting back, I've been busy. I've had a few complaints about the white on black format at my blog, following your complaint I've decided to change it to a black on white template.

I agree that dating is problematic with regards the PETM, but I suspect you'll agree that this paper doesn't attempt to date as it's key message, it just assigns a timescale based on an argument about the timescale of the banding of the clay cores. Whether or not the timing of that banding is correct determines how fast the event happened. I do think the timescale is based on sound argument, but I'm still having massive problems accepting a minimum 1200Gt addition of 13C depleted carbon in such a small period of time.

I agree that this means little for current GW, losing an analogue doesn't change observations such as Semiletov/Shakhova. In any case with the PETM 13C excursion being driven by marine clathrates the analogue would still be flawed due to the Azolla event.

This paper still leaves me very puzzled.

ggelsrinc

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Re: Possibly important paper regarding CH4
« Reply #65 on: October 20, 2013, 08:21:25 PM »
Ggelsrinc,

Sorry for not getting back, I've been busy. I've had a few complaints about the white on black format at my blog, following your complaint I've decided to change it to a black on white template.

I agree that dating is problematic with regards the PETM, but I suspect you'll agree that this paper doesn't attempt to date as it's key message, it just assigns a timescale based on an argument about the timescale of the banding of the clay cores. Whether or not the timing of that banding is correct determines how fast the event happened. I do think the timescale is based on sound argument, but I'm still having massive problems accepting a minimum 1200Gt addition of 13C depleted carbon in such a small period of time.

I agree that this means little for current GW, losing an analogue doesn't change observations such as Semiletov/Shakhova. In any case with the PETM 13C excursion being driven by marine clathrates the analogue would still be flawed due to the Azolla event.

This paper still leaves me very puzzled.

I have no dispute that quickly adding CO2 to our atmosphere is a very dangerous thing to do and understand why people look and find examples from the past to try to prove their global warming case, such as PETM.

I hope the annual hypothesis is correct, whether it involves the moment of PETM or any event that occurred, because accurately finding any event of the past around 55.8 million years ago offers the potential to calibrate other dating methods, which aren't very good.

Their consideration that the CIE event during PETM was nearly spontaneous is reasonable, based on all the studies I have read. Their proof is lacking, because it needs solid evidence beyond a footnote linking their clay samples to that exact period of the past. Finding an index microfossil in the specific samples they took that dates to the PETM period is much more convincing than claiming the carbon isotope change they found has to come from the PETM period, because so and so dated the Marlboro Clay to that period, which is the reason they looked. Their samples should contain something like a foraminifera that became extinct during PETM and other contemporary microfossils of that period.

Everything about PETM is a puzzle to me. The amount of methane clathrates in the oceans are believed to be less then than exist today. The only volcanic event during that time I've ever heard about is that kimberlite field in Canada. That material is believed to originate deep within the Earth and is carbon rich. Could the Earth burp up that much carbon, as some scientists believe? Evidence of shocked quartz points to a bolide event, but linking that evidence to a particular event isn't an easy task.

If the paper's findings hold up, I would be thinking the area isn't that unique and try to find similar areas dating back to that time containing similar records. I'm sure it wasn't the only area on Earth with a river flowing to the ocean and leaving evidence of it's sediments.       

Steven

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Re: Possibly important paper regarding CH4
« Reply #66 on: September 23, 2014, 07:27:07 PM »
From Skeptical Science:

http://www.skepticalscience.com/the-perplexing-PETM.html


" One paper last fall suggested that the onset of the PETM occurred in as little as 13 years, based on seemingly annually-layered clays in New Jersey. Those authors concluded the PETM was likely caused by a comet exploding in the atmosphere, and was too fast to be a useful analog for modern global warming. "

" But that paper’s conclusions were demolished in a series of responses, which pointed out that the heat capacity of the oceans required centuries to warm to the PETM extent, that an instant release of carbon in the atmosphere would produce a carbon isotopic shift far larger than observed, and that microfossils ruled out the sedimentary rates claimed. "

" Currently the PETM emissions are estimated to have been spread over between 1,000 and 6,000 years, based on their effects on ocean chemistry and the carbon isotope excursion."

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Re: Possibly important paper regarding CH4
« Reply #67 on: December 21, 2014, 03:09:44 PM »
This paper still leaves me very puzzled.

I think it was worth linking to this in the context of this thread. It appears to suggest there were two seperate isotopic shifts, which would tend to undermine the cometary idea further.

http://arstechnica.com/science/2014/12/record-of-past-warming-event-shows-carbon-was-emitted-fast-and-twice/

I haven't looked into this much, just stumbled over it and thought it worth adding into this discussion. I think I'm leaning towards the timescale must be wrong with the original paper that prompted all this - but either way - I think clathrates win the day when it comes down to the potential for multiple events.