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Deep-sea heat: now there's the rub

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Shanta Barley | 17:23 UK time, Thursday, 16 July 2009

About 55 million years ago and over a period of less than 10,000 years, the Earth warmed up by 5 to 9 degrees C. It was so hot, in fact, that crocodiles frolicked in Canada.

But at the same time, the most severe extinction of deep-sea foraminifera recorded in the last 65 million years took place. Why? A new study published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology sheds light on the mystery.

Dr Laia Alegret and colleagues at the University of Saragossa in Spain pored over ancient marine sediments containing the remains of foraminifera, tiny creatures which build shells from calcium carbonate.

Previous studies had tentatively put the unfortunate fate of forams 55 million years ago down to ocean 'acidification': perhaps rising levels of carbon dioxide reduced the amount of calcium carbonate available to shell-builders?

But according to Alegret's experiments, foraminifera did not fall foul of a drop in the ocean's pH. Nor did they die from a lack of oxygen. What killed 'em, scientists now say, was the heat.

Indeed, the team thinks that deep-sea heat (the ocean bottom reached 15 degrees C, compared with 4 degrees C today) directly affected the metabolism of these coolth-loving creatures, impairing their ability to feed, reproduce and convert carbon into shells.

'The exact causes of the extinctions are not clear, yet', notes Dr Alegret, 'but they are likely to be related to paleoecological and paleoenvironmental instability triggered by global warming.'

Many scientists believe the past is the key to the future: could the impact which climate change had on life 55 million years ago act as a guide to the future, given that the Earth could warm by up to 4 degrees C by 2100?

Not necessarily, warns Dr William Hay, a geologist. 'The past climates of the earth cannot be used as a direct guide to what may occur in the future'.

Comments

  • 1. At 8:07pm on 16 Jul 2009, SheffTim wrote:

    It's a little unfair to expect people new to the PETM to make sense of this paper (one of hundreds of papers on the PETM) so I'll try and set the scene. (I hope it makes some sense as I'm rushing off to a dinner-date later.)

    The paper Shanta cites is establishing a sequence for that area of an initial extinction event caused by the 'intense warming', this was then followed by the negative carbon isotope excursion (CIE) and increased acidity of the seas with a few foram species from deep waters that could inhabit such conditions. The usual foram species returned when the acidity (and temperature) levels dropped.

    Some explanation first as to what the evidence so far tells us, and of the processes that produces the changes that provide the evidence.

    Though microscopic, single-celled animals called Foraminifera form their shells from calcium ions and carbon dioxide in the ocean, their remains are the basis of much of the world's limestone rocks.
    The chalk cliffs of Dover in England are 98% pure calcium carbonate, formed in the Cretaceous period from the remains of blooms of marine algae called coccospheres. (The term 'Cretaceous' derives from the Latin for chalk.)

    Many sea creatures such as foraminifera, coccoliths (algae), corals, diatoms and shellfish rely on secreting calcite taken from seawater molecules to form their shells and any internal structures.

    Where these foraminifera are abundant, when they dies they fall to the sea floor and their gradually their shells decay and form thick layers of calcite ooze on the seafloor, this is generally a pale white in colour. (As limestone and chalk rocks are also white, and formed from the same material in the same way.) Where there is an extinction event this shows up by pronounced calcite free reddish layers. There's a change in the strata, in both rocks and seabed cores.

    Although insoluble in ordinary water the calcium carbonate mineral - CaCO3 - dissolves in acidic carbonic solutions.

    Increasing the acidity of the oceans leads to fewer carbonate ions. By reducing the quantity of these raw materials, it slows the speed at which these creatures produce their calcite shells, making them less healthy, prone to dissolution and predators.

    When these organisms die their calcareous shells fall to the bottom of the ocean, there they mix with silts to form sediments. Increased acidity dissolves their shells, the greater the acidity the less calcite reaches the sediment. The point at which the dissolution rate exceeds the supply rate of calcite produces the calcite-free red clays that clearly mark the PTEM, found by geologists across the world and recovered from dozens of deep sea drilling cores.

    The PETM also shows clearly in the strata by a drop in the levels of the heavy carbon-13 (C-13) isotope compared with the lighter carbon-12 (C-12) isotope.
    Stable isotope results from carbonate and organic materials from many different sites at sea and on land, from the tropics to the poles, all show a marked decrease in the ratio of C-13 / C-12, indicating the initiation of the PETM and increases in CO2 concentrations.
    Geologists call this drop in the amount of heavy carbon isotopes a carbon isotopic excursion or CIE.

    The PETM's carbon isotopic excursion (CIE) - the increase in the ratio of light to heavy carbon isotopes found in rocks and fossils - is so distinctive it is now used across the world by geologists and oceanographers to date the origin of rocks and fossils.

    Examination of the remains of these shells (and those from other creatures) from the sediment layers below, in and above the acidic layer of 55 mya shows that the acidic layer marked a period of mass extinction for (or lack of recovery by) Phytoplankton, with dire consequences throughout the food chain.

    At the time of the PETM the Betic Cordillera, Southern Spain was part of a shallow sea, now its part of mainland Spain.
    (At the time of the Paleocene the shapes of the continents were similar to those of today, but they were in different positions on the globe due to the movements of tectonic plates. During the Cretaceous period North America, Greenland and Eurasia had together formed a northern super-continent called Laurasia, but at the end of the Paleocone North America and Greenland began to separate from Eurasia due to the action of tectonic plates and seabed rifting. Volcanically it was a very active period; the Atlantic was forming.)

    So onto the paper Shanta brings to our attention.

    "The beginning of the BEE coincides with the onset of the CIE [carbon isotopic excursion] (+ 0 ky) and with an interval with abundant calcite, and it has been recorded under oxic conditions at the seafloor (as inferred from the benthic foraminiferal assemblages and the reddish colour of the sediments). We conclude that dissolution and dysoxia were not the cause of the extinctions, which were probably related to intense warming that occurred before the onset of the CIE."

    It looks as if they're saying that the initial 'intense warming' caused the initial mass extinction of existing forams (probably most, not all of a species) this was immediately followed by the negative carbon isotope excursion (CIE) ' as inferred from the benthic foraminiferal assemblages and the reddish colour of the sediments.'
    The seas had become acidic, this also prevented any usual forams from living in it in great numbers during 'the survival interval'; apart from Glomospira Acme - that usually lived in the deep sea and were used to less oxygenated waters and survival on meagre food sources. As the seas cooled so the original foram species recovered.

    The reference to 'interaction between dilution of the carbonate compounds by silicate minerals' refers to the known reaction between the two in which carbonate breaks down into bicarbonates. This also means less calcite reaches the seafloor, hence the reddish clay layer. (CCD = calcite compensation depth.)

    PS: I'm pulling together material for a website on the PETM, so thanks for this Shanta. I'll let you know as and when I get it live.

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  • 2. At 9:03pm on 16 Jul 2009, Shanta_Barley wrote:

    Thanks Tim - you've obviously got a soft spot for the Eocene, so I wonder if you can enlighten on a few outstanding puzzles the article poses. For example, what triggered the initial warming which led to a 5-9 degree C rise? And how much of a scientific consensus is there around the idea that the temperature rise led to a 'massive dissociation of marine methane hydrates', as the report suggests?

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  • 3. At 9:05pm on 16 Jul 2009, Jack Hughes wrote:

    Hi Tim !

    Looking forward to seeing the new site. Hope you allow comments so you can get feedback and improve the site as you go.

    One useful tip is to clearly distinguish between facts and theories:

    "Professor X found Y and measured it" is a fact

    "Professor X suggests that Y is caused by Z" is a theory

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  • 4. At 9:36pm on 16 Jul 2009, U13900240 wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 5. At 07:49am on 17 Jul 2009, Jack Hughes wrote:

    Fron the 'New Scientist' piece:

    The new Intergovernmental Panel on Climate Change report says there is 90% certainty that the burning of fossil fuels and other human activities are driving climate change.

    What does this '90% certainty' mean ? How do you measure certainty ? What would move it on to 95% or down to 85% ?

    I'm calling Bravo Sierra on this.

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  • 6. At 08:07am on 17 Jul 2009, MangoChutney wrote:

    90% certainty means even the IPCC have some doubts that AGW is real

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  • 7. At 08:56am on 17 Jul 2009, Jack Hughes wrote:

    I read the IPCC report that Timbo linked us to yesterday. They drift effortlessly between facts, opinions, projections, and meaningless babble:

    "There is medium confidence that other effects of regional
    climate change on natural and human environments
    are emerging, although many are difficult to discern
    due to adaptation and non-climatic drivers. {1.2}
    They include effects of temperature increases on: {1.2}
    * agricultural and forestry management at Northern Hemisphere
    higher latitudes, such as earlier spring planting of
    crops, and alterations in disturbance regimes of forests
    due to fires and pests

    * some aspects of human health, such as heat-related mortality
    in Europe, changes in infectious disease vectors in
    some areas, and allergenic pollen in Northern Hemisphere
    high and mid-latitudes
    * some human activities in the Arctic (e.g. hunting and travel
    over snow and ice) and in lower-elevation alpine areas
    (such as mountain sports).


    What does "alterations in disturbance regimes of forests due to fires and pests" actually mean ?

    More forest fires ? Fewer forest fires ? More squirrels ? Secret squirrels ?

    It's tosh.

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  • 8. At 10:26am on 17 Jul 2009, U13900240 wrote:

    And falling to your death because gravity makes you fall DOWN is a theory too.

    Funnily you don't seem willing to test this theory.

    But you're pretty OK if someone else takes the "fall" as it were for your hypothesis that AGW isn't a problem turns out to be wrong.

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  • 9. At 10:27am on 17 Jul 2009, U13900240 wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 10. At 10:28am on 17 Jul 2009, U13900240 wrote:

    "90% certainty means even the IPCC have some doubts that AGW is real"

    And what is your certainty level that the IPCC is wrong?

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  • 11. At 10:37am on 17 Jul 2009, U13900240 wrote:

    "They drift effortlessly between facts, opinions, projections, and meaningless babble:"

    Well, you should be used to that. You're doing that all the time.

    Is there a reason why a statement cannot include facts, opinions (that would be based on those facts), projections (based on the facts again, with some opinions being what should and could be done)?

    I.e.

    My carpet is on fire. (fact)

    I think it was because the cigarette was alight when I fell asleep and it set fire to the carpet (opinion)

    The fire is too big for me to tackle (opinion)

    Therefore if I stay here to try I'll die (projection)

    So I will leave the house (opinion)

    And my house may well be burnt down (projection)


    Or do you just like complaining all the time, adding nothing useful yourself?

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  • 12. At 10:47am on 17 Jul 2009, U13900240 wrote:

    "For example, what triggered the initial warming which led to a 5-9 degree C rise?"

    Try staring here:

    http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum

    MEthane and CO2 (since Methane decays to CO2 in such long past scenarios it would be difficult to define which). But both will come from Volcanoes.

    You DO remember "Volcanoes produce more than humans have in their lifetime" hacked meme? Well, its people who deny AGW listening to some factoid and forgetting anything that doesn't allow it to be used to peddle their mythology.

    PETM was one event where volcanoes DID do more than humans have ever done.

    Denialists forget that the PETM was long ago (and assume that this event means volcanoes NOW produce more) and that it caused widespread extinction (so therefore it doesn't really help their case that our production is safe).

    http://news.mongabay.com/2006/1207-petm.html

    "And how much of a scientific consensus is there around the idea that the temperature rise led to a 'massive dissociation of marine methane hydrates', as the report suggests?"

    Do a google scholar search on hydrate and petm.

    http://scholar.google.co.uk/scholar?q=hydrate+petm&hl=en&btnG=Search

    Doesn't seem to be a single paper in the first page against the idea.

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  • 13. At 10:48am on 17 Jul 2009, U13900240 wrote:

    And this paper
    http://geology.geoscienceworld.org/cgi/content/abstract/25/3/259
    seems to be highly cited.

    Journalist much?

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  • 14. At 11:18am on 17 Jul 2009, Jack Hughes wrote:

    @EWE

    Maybe you can explain the meaning of:

    "alterations in disturbance regimes of forests due to fires and pests"

    from the IPCC bible

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  • 15. At 11:34am on 17 Jul 2009, U13900240 wrote:


    "alterations in disturbance regimes of forests due to fires and pests"

    It means there will be alterations in the disturbance regimes of forests. And this alteration will be due to fires and pests.

    You don't read much of posts you write to, do you:

    http://www.bbc.co.uk/blogs/climatechange/2009/06/british_columbias_forest_trans.html

    And proof you were on that thread (though apparently you didn't notice):

    http://www.bbc.co.uk/blogs/climatechange/2009/06/british_columbias_forest_trans.html#P81938980

    Then again, expecting intelligence from a denialist would be a bit optimistic.

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  • 16. At 1:26pm on 17 Jul 2009, MangoChutney wrote:

    @yeah_whatever

    #10

    My certainty level is irrelevant to my statement. My statement is the IPCC by default are a little sceptical of AGW and yet you, in all your wisdom, are 100% sure. What do you know that the IPCC doesn't? Perhaps you think your crystal ball is bigger than the IPCC's?

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  • 17. At 1:48pm on 17 Jul 2009, U13900240 wrote:

    "My certainty level is irrelevant to my statement. "

    Why?

    "My statement is the IPCC by default are a little sceptical of AGW and yet you, "

    Your statement isn't a 10% chance that AGW is wrong.

    You believe it wrong, so you misread anything available to bolster your case.

    "What do you know that the IPCC doesn't?"

    Me: "My certainty level is irrelevant to my statement. "

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  • 18. At 2:00pm on 17 Jul 2009, MangoChutney wrote:

    What do you think 90% certainty actually means?

    What happens with the other 10%?

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  • 19. At 2:26pm on 17 Jul 2009, U13900240 wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 20. At 2:29pm on 17 Jul 2009, U13900240 wrote:

    Oh, and it's "90-95%" anyway.

    And that was because the politicians (who you all seem to think are in cahoots to up the taxes) didn't want what the scientists said "95-100%" printed down.

    So

    1) It's not 90%
    2) The only reason for not 100% is because the politicians didn't want them to state the certainty the science had on the results.

    #1 shows you're lying again

    #2 shows that your idiotic screed that this is all a political scam is wrong

    Then again truth was never your strong point.

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  • 21. At 2:52pm on 17 Jul 2009, U13900240 wrote:

    "What do you think 90% certainty actually means?"

    It means you have a certain level of certainty of your answer.

    But the IPCC talk of confidence. Not certainty.

    Check your dictionary.

    (and it looks like Chutney doesn't like advice on reading... Awww,)

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  • 22. At 2:54pm on 17 Jul 2009, U13900240 wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 23. At 2:58pm on 17 Jul 2009, MangoChutney wrote:

    @yeah_whatever # 20

    Oh, and it's "90-95%" anyway.

    And that was because the politicians (who you all seem to think are in cahoots to up the taxes) didn't want what the scientists said "95-100%" printed down.


    From the above you seem to be agreeing ehe IPCC report was a political report not a scientific report

    And saying you have evidence to show the scientists wanted to say 100% not 90% and this was watered down by the IPCC. Please present your evidence.

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  • 24. At 2:59pm on 17 Jul 2009, MangoChutney wrote:

    #21 semantics;

    What do you think 90% confidence actually means?

    What happens with the other 10%?



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  • 25. At 3:00pm on 17 Jul 2009, U13900240 wrote:

    And 21 was removed, though it only contained
    "Shanta, can you sort this out too like you did for Bishop. Post 19 killed probably for this line:

    [a line that just gave advice but obviously someone wants to silence]"

    There's a lot of pointless killing of posts going on. Again.

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  • 26. At 3:13pm on 17 Jul 2009, U13900240 wrote:

    "From the above you seem to be agreeing ehe IPCC report was a political report not a scientific report"

    Only if you skip the comprehension part of reading.

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  • 27. At 3:14pm on 17 Jul 2009, U13900240 wrote:

    "What happens with the other 10%?"

    It is less than 10%.

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  • 28. At 3:25pm on 17 Jul 2009, SheffTim wrote:

    #14. (?) "alterations in disturbance regimes of forests due to fires and pests." (?)

    You may have noticed on TV news there's been an increase in the frequency of brush and forest fires in California and elsewhere in western USA. That's an alteration to the disturbance regime.
    http://www.innovations-report.de/html/berichte/umwelt_naturschutz/bericht-67420.html

    In Colorado (and elsewhere in the USA and Canada) milder winters, earlier springs and droughts in the recent past have encouraged the spread of Beetles that infest trees to such a great extent they kill them in great numbers. Thats another example of an alteration to the disturbance regime.
    http://coloradoindependent.com/21349/tea-time-for-bark-beetles-would-only-slow-inevitable-demise-of-colorado-forests

    Droughts can also take a toll on forests, another alteration to the disturbance regime. e.g.
    http://news.nationalgeographic.com/news/2005/12/1205_051205_drought_forest.html

    I'll respond to Shanta (#2) later. I'm just on a coffee break at the mo.

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  • 29. At 3:38pm on 17 Jul 2009, MangoChutney wrote:

    #25 not me, I have only ever asked for the term denier to be removed, because it is offensive to holocaust survivors. I do know I had a lot of posts removed by somebody recently

    #26 please explain what you mean by 2) The only reason for not 100% is because the politicians didn't want them to state the certainty the science had on the results. in #20, if you do not mean the IPCC report was political not scientific, because with my poor comprehension this seems to suggest you do not think the IPCC report was scientific

    #27 ok, what happens with the other less than 10% or whatever figure you believe this should be

    By the way, Im still waiting for an apology or confirmation that you were lying in the other thread.

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  • 30. At 3:50pm on 17 Jul 2009, U13900240 wrote:

    "#27 ok, what happens with the other less than 10% or whatever figure you believe this should be"

    0% is less than 10%.

    And maybe whatever % it is, the answer is "worse than we thought".

    "please explain what you mean by 2) The only reason for not 100% is because the politicians didn't want them to state the certainty the science had on the results."

    That doesn't make the IPCC report political any more than saying it has to be in three languages for the EU records makes it political.

    Heck, it could be that the politicians don't know the science and like you, overestimate the uncertainties.

    But let's say it's 95%.

    There's a 5% chance that things could be WORSE than the IPCC report says.

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  • 31. At 3:54pm on 17 Jul 2009, U13900240 wrote:

    By the way, I'm still waiting for you to show you've learned something.

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  • 32. At 4:20pm on 17 Jul 2009, MangoChutney wrote:

    @yeah_whatever

    Clearly from the dodge giving real answers and the fact that you refuse to apologise for lying when you accuse me of saying something I didnt say (it was boringusername that said the quote you gave, not me), you are clearly unfit to hold a conversation with.

    Consider yourself sent to Coventry.

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  • 33. At 4:21pm on 17 Jul 2009, MangoChutney wrote:

    see, i've learned something ;)

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  • 34. At 4:31pm on 17 Jul 2009, U13900240 wrote:

    You haven't answered mine:

    "So a newer case where you use one months' average to define whether AGW is real or not somehow disproves that you use one months' average to define whether AGW is real or not.

    How does that work?"

    Are you saying that you haven't said it because you said it more recently? Or are you avoiding it? Like you did the effect of CO2 increases increasing the width of absorption to the log of the density increase AND increasing the optical depth proportionally to it?

    You've never said you were wrong there.

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  • 35. At 4:32pm on 17 Jul 2009, U13900240 wrote:

    And I'm not avoiding it, I have a newer and better example. One you said whilst saying you never said it, even!

    I mean, in the VERY SAME POST you say that you never use monthly figures to establish trends, you use a monthly figure to establish a trend!!!

    Why bother digging up that old example when you dropped one five times better!!?!?!?

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  • 36. At 10:23pm on 17 Jul 2009, SheffTim wrote:

    #2. Hi Shanta:
    I think it probably was a multi-causal event; that the PETM was caused by a combination (or a sequence) of different mechanisms. In particular resulting from magma meeting methane (below).
    There is consensus amongst those that research the PETM that the warming was caused by an increase in CO2. There are various hypotheses as to what caused that increase - hydrates and volcanism are the two most supported - and there is a convergence of the two.

    The methane hydrates hypothesis has been the leading contender to explain both the rise of atmospheric CO2, as shown by the ratios of C-13 / C-12 isotopes discovered by geologists and oceanographers, [CH4 degrades in the atmosphere, producing CO2 - to put it in simply] and the rise in temperature (as revealed by ratios of oxygen O-16 and O-18 isotopes - see footnote); but there are other hypothesise. There are also doubts whether methane alone explains the amount of CO2 found in the record.

    Volcanism is the other leading hypothesis; the PETM onset was a very volcanically active period; the rifting of the Atlantic started at that time; there were major volcanic episodes elsewhere too.

    There were almost certainly eruptions much as we see today on TV, but the rifting also took the form of large outpourings of magma being disgorged onto land or the seafloor. The products of these magma outpourings are known to geologists as Large Igneous Provinces.

    The North Atlantic Igneous Province is one of the largest such on earth and extends from Baffin Island and Greenland northwards into the Arctic, east across to Norway and southwards down to Denmark, Scotland and Northern Ireland. Outpourings of this magma created the Scottish islands of Skye, Rhum, Eigg, Canna, the basalt columns of the Giant's Causeway and Fingle's Cave and some of the granite mountain ranges in Scotland and Ireland - and date to 55 mya.

    Norwegian geologists (as part of oil exploration surveys) have discovered, from 2D & 3D seismic imaging of the seabed in the north-east Atlantic, the presence of thousands of large craters (vents) ranging in diameter from 500 to 3,500 metres rising from deep under the seafloor to the PETM sediment layer of 55 mya. At the base of these craters is basaltic rock that had been squeezed up through the earth's crust.

    These craters are accompanied by extensive, thick sheets (sills) of basaltic magma covering tens of thousands of square kilometres of the surrounding seabed. It's thought these must have been extruded over a short time period (days to a few years), as solidification didn't occur around the vent. (One of the vents has now been drilled to produce more data.)

    Argon isotopes dating using the known decay rates of potassium to argon (Ar-40 / Ar-39) from a volcanic ash layer found overlying sequences of basaltic lava in Greenland, the Faeroes and also in ocean floor sediments from the seabed north of Scotland also shows the ash dates to 55 mya, also indicating massive volcanic activity at the time of the onset of the PETM.

    It's also been found that much of the seabed of the Norwegian sea of this time consisted of layers of organic rich Cretaceous and Paleocene mudstone. Organic carbon in sedimentary rocks is converted into methane when heated beyond approx. 100 degrees C 200 degrees C.
    Temperatures of most magmas are in the range of 700 degrees C to 1300 degrees C.

    A leading hypothesis has seabed volcanism in the NE Atlantic releasing CO2 and also causing the release of methane from hydrates and mudstones from under the seabed.

    Other hypotheses have been put forward to account for the PTEM: emission of CO2 from wide-spread peat fires, a large shallow sea drying and its seabed material decaying, drying wetlands etc. There are pros and cons to each. There is little support for them as the main cause of the PETM - they may have been its consequences. A large comet strike on an area of carbonate rock has also been suggested, but with little evidence.

    It's also thought that feedbacks (I think any drying of shallow seas, peat fires would probably have been a result of the initial warming, and then contributed feedbacks) must have also played a major role in forcing temperatures to rise so high. Increased amounts of atmospheric water vapour, a greenhouse gas, in a warmer atmosphere would also have amplified the warming.

    Alegret's paper (and there are others in a similar vein) is interesting, indicating that the initial period of warming was both steep and relatively rapid.
    Because it takes time for the oceans to absorb large quantities of CO2 from the atmosphere (much longer than it takes to increase CO2 concentrations in the atmosphere), the oceans only later began to become acidic (so acidic they caused the PETM's distinctive signature, the CIE [carbon isotopic excursion]). The oceans' response rate lagged behind that of the atmosphere.

    Algret's work is also showing similar results from other areas of Spain. (At the time this was part of the bed of a large shallow sea called the Tethys sea - ancestor of the modern Mediterranean, Black, Caspian and Aral Seas.)
    Extinctions began when the seas warmed, but accelerated after the onset of the CIE.
    e.g.: The PaleoceneEocene Thermal Maximum: New Data on Microfossil Turnover at The Zumaia Section, Spain. L. Alegret et al. Palaios (Society for Sedimentary Geology). 2009. [PDF]
    You can download this from the publications list on Dr Alegret's web-pages:
    http://wzar.unizar.es/perso/alegret/publicaciones.html

    Investigating the PETM, like much of science, is much like building a jigsaw puzzle picture out of thousands of pieces of research. (The work of archaeologists is an example that many people will have some familiarity with from TV programmes.)

    Algret's (and others) work is adding pieces that extend the picture's resolution and detail; in particular by adding to, buttressing and developing earlier key research papers: e.g. 'Rapid Acidification of the Ocean during the Paleocene Eocene Thermal Maximum'. J. Zachos et al. Science. 2005. and other research.

    I think we're starting to see a good broad-brush picture of the PETM, but there's still a lot of detail yet to be added.

    I tried to keep it short(ish), but hope that answers your questions Shanta; if not ask away.
    ------------------------------------------------------------------------
    NB: Oxygen has two stable isotopes, O-16 and O-18; most of oxygen is O-16. The O-18 isotope is two neutrons heavier than O-16 and less susceptible to evaporation than O-16. (O-18 molecules require more energy than O-16 molecules to change from its liquid state to a gas state.)
    When the oceans warm, much more O-16 evaporates leaving behind greater ratios of O-18. These help identify changes in the temperature of the oceans. Oxygen isotopes from carbonate samples, from seabed cores taken from widely separate locations across earth, all show that the oceans became much warmer at the time of the PETM, by as much as 4 degrees C (7 degrees F) in deep ocean and 8 degrees C (14 degrees F) in waters at high latitudes.
    ------------------------------------------------------------------------

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  • 37. At 11:48pm on 17 Jul 2009, SheffTim wrote:

    Re the above:
    I've just added a photograph of a deep-sea sediment core cross-section to a webpage that clearly shows the abrupt change in sediments that is the result of increased ocean acidification; this is the signature of the PETM. This change in sediment layers also shows up in strata in rock formations now above sea level, across the world.

    This change in sediment is due to the die-off of the many minute foraminifera species (which make their shells from [white] calcite) and is found in seabed cores taken from dozens of locations around the world.
    The upper red/grey sediment layer is formed by clay materials that come from soils washed into the oceans from the land. Usually the clays are mixed with the greater numbers of foraminifera shells to produce white sediments.

    The remains of the shells from billions of the foraminifera make up much of the seabed material, and have done so for millions of years. Modern day chalk and limestone rocks are the result.

    The ending of the PTEM in cores is shown by the return of white sediments as acidification levels drop and foraminifers' numbers increased.

    The sediment layers can also be examined by microscope for shells of individual forams (so telling their species) and their numbers counted, giving an indication of the health of their species for particular periods.

    http://sites.google.com/site/thepaleoceneeocenethermalmaxim/home/carbon-isotopic-excursion

    Foraminifera (microfossils)
    http://www.ucmp.berkeley.edu/foram/foramintro.html

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  • 38. At 01:13am on 18 Jul 2009, ManmadeupGW wrote:

    @ Shefftim

    Thank you for the lesson and thank you Mr Barley for allowing such and erudite by Mr tim Sheff.

    Apologies in advance for me next post.

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  • 39. At 01:15am on 18 Jul 2009, ManmadeupGW wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 40. At 8:15pm on 18 Jul 2009, SheffTim wrote:

    If people are interested I've added a photograph, of Polecat Bench in the (badlands) hills of Wyoming, USA, that demonstrates the distinctive change in the colour and type of rock strata found in rocks above sea level, that marks the start of the Paleocene Eocene Thermal Maximum. (PETM)
    Analysis of carbon and oxygen isotopic ratios identified the PETMs signature carbon isotope excursion.
    http://sites.google.com/site/thepaleoceneeocenethermalmaxim/home/strata-marking-petm

    The PETM was a period of major changes to mammalian life, the major focus of paleo-archaeological research at Polecat Bench. It is a fossil rich location.
    The remains of the earliest horses and primates found in North America are from here and date from this period.
    The increased in warmth allowed the spread of habitat across land bridges that allowed them to migrate from the (proto) Eurasia to N. America. (South America only joined onto N. America 3.5 mya at the Isthmus of Pamama.)
    I've added some more detail on mammalian changes onto the webpage. (Above.)

    Below is the page of one of the main researchers into this area. It gives an overview and his publications list.
    http://www-personal.umich.edu/~gingeric/PDGwyoming/PEmammals.htm

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  • 41. At 10:36pm on 18 Jul 2009, Jack Hughes wrote:

    Hi Tim !

    If the IPPC meant to say there would be more forest fires then why did they not just use those words instead of pseudo-scientific babble ?

    The quote was from the summary for policy makers.

    If they meant to say there would be more pests in the forest then why not use those words ?

    And what's your take on the 90% certainty bit ? It looks like a pretence at science.

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  • 42. At 08:52am on 19 Jul 2009, U13900240 wrote:

    "If the IPPC meant to say there would be more forest fires"

    Then maybe they meant MORE than forest fires.

    Things like this:


    http://www.bbc.co.uk/blogs/climatechange/2009/06/british_columbias_forest_trans.html

    which isn't a forest fire, so wouldn't be covered by that.

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  • 43. At 08:54am on 19 Jul 2009, U13900240 wrote:

    "And what's your take on the 90% certainty bit ? It looks like a pretence at science."

    You mean "greater than 90%" certainty, don't you? Seems like you're using PRETEND QUOTING...

    And I take it you agree that it's greater than 90% chance then? If not, what % chance do you think it is of being real?

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  • 44. At 12:42pm on 19 Jul 2009, SheffTim wrote:

    Hi Jack,
    Use of language. I'm afraid every profession/field/discipline has its own terminology and jargon, which tends to confuse outsiders. (Computing is notorious for it. 'Reboot' for example - why not just say 'restart'?).
    Some phrases can also cover a multitude of eventualities, spelling them all out individually could produce some long lists.

    Personally, I am in favour of trying to put things simply and clearly - perhaps they should hand the final report to the Plain English Campaign to produce a summary for the public.
    http://www.plainenglish.co.uk/

    Certainty levels: Nothing in science can be said to be known with 100% certainty, one rarely gets absolute certainty.
    Absolute certainty is the lack of any doubt at all; short of that, there are various levels of relative certainty.

    We can't prove that apples will always (until the end of time, everywhere in the entire universe) fall to the ground when they fall from a tree, because of gravity (as described by Newton's theory of gravitation), though they always have done so and we see no reason for that to not to continue. But100% certainty? We can't see into the future and we haven't visited every planet in the universe, so no.

    The IPCC used to just use terms such as 'Highly Likely', 'Likely' and so on. This prompted discussion as to what those terms actually meant. Certainty levels, expressed as a percentage, are attempting to convey those terms more precisely - and consistently across various topics.

    Certainty levels are used also by professions that have to assess risk - the insurance industry, betting industry, Intelligence agencies and so on.

    Does it mean they're infallible? No, but it's the best judgement that can be made at that time.

    The IPCC guidance to report authors on ascribing certainty levels is here:
    http://tiny.cc/J3DVr
    Guidance for journalists on how certainty levels should be interpreted is here:
    http://www.sejarchive.org/resource/IPCC_terminology.htm

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  • 45. At 3:20pm on 19 Jul 2009, MangoChutney wrote:

    @sheftim

    Nothing in science can be said to be known with 100% certainty, one rarely gets absolute certainty.

    I agree. Some posters on these blogs refuse to accept that there are doubts about AGW (true denial in my humble opinion), even within the IPCC and AGW believers. 90% or higher certainty, means there are doubts.

    My own personal view is AGW isn't proven beyond reasonable doubt, but I do accept some AGW does occur - e.g deforestation must cause some climate change (even if just locally) and since deforestation is man made, this must be man made climate change. There are other examples such as land usage, which is without doubt man made.

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  • 46. At 4:21pm on 19 Jul 2009, U13900240 wrote:

    "My own personal view is AGW isn't proven beyond reasonable doubt"

    But you can find out if your doubt is reasonable only by finding out the science. Not repeating what you've been told proves AGW wrong.

    If it isn't CO2, what makes 2008 warmer than even the warmest years before 1998? Everything was set to make it cold globally: sunspot minimum, El Nino. Yet it was warmer than the warmest years before 1998.

    So what is the cause?

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  • 47. At 4:24pm on 19 Jul 2009, U13900240 wrote:

    And you doubt that a doubt means that it could mean it's happening.

    Are you refusing that the IPCC could be wrong and UNDER-estimating GW?

    How about this?

    1) CO2 is a warming agent 100% certainty
    2) It is responsible for more than 60% of the warming since 1850, 100% certainty
    3) It is responsible for more than 80% of the warming since 1850, 10% certainty
    4) It will raise more than 2C if we go over 500ppm, 100% certainty
    5) It will raise more than 4C if we go over 500ppm, 60% certainty

    Overall there is a 90% certainty on the facts there.

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  • 48. At 4:26pm on 19 Jul 2009, U13900240 wrote:

    And I take it Chutney that you don't have insurance. After all there's a 90% chance you won't lose or break something worth collecting insurance on in a year.

    I take it you don't have a pension since there's a better than 10% chance you won't live to collect it.

    Or do these chances of misfortune change when its your life at risk and not when it's someone else's?

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  • 49. At 4:26pm on 19 Jul 2009, U13900240 wrote:

    And Chutney avoids the questions.

    Again.

    "And I take it you agree that it's greater than 90% chance then? If not, what % chance do you think it is of being real?"

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  • 50. At 12:25pm on 20 Jul 2009, Jack Hughes wrote:

    This comment has been referred for further consideration. Explain

  • 51. At 12:37pm on 20 Jul 2009, MangoChutney wrote:

    @Jack_Hughes_NZ

    As difficult as it is, Jack, just try to ignore him

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  • 52. At 12:39pm on 20 Jul 2009, U13900240 wrote:

    Jack says "Please stop someone disagreeing with me! Defend to the death my right to ignore uncomfortable questions!!!".

    Can't answer questions, can't give proof, can't come up with anything that stands up to anything other than credulous adoration.

    Try the science, not the ad-hom.

    Answer the questions.

    You've said it's cooling but it has been proven from the very data you used to say this that it isn't cooling.

    "Oh, he's trolling me!!"

    You've said that 9 errors make An Inconvenient Truth wrong. Yet 350+ errors in a paper that says AGW is wrong goes unmentioned.

    "Stop asking me questions!!!"

    You continually get weather and climate wrong.

    "You're just closed-minded!!!"

    You say of engineering that you have TOTAL UNDERSTANDING of the physics. Yet when a bridge is built to take 100 tons, it is built to withstand 200 or more. Seems like engineers do not take their total understanding as actually total understanding.

    "He's trolling!!!".

    So you jump back to the silencing of your critics.

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  • 53. At 12:46pm on 20 Jul 2009, U13900240 wrote:

    That's it Chutney! Keep an Open Mind!!!

    That way you won't have to answer any questions.

    Like what is the chance that AGW is right in YOUR estimation.

    Better avoid that one, eh?

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  • 54. At 1:02pm on 20 Jul 2009, Jack Hughes wrote:

    Hi Tim and thanks for the answer.

    I don't agree with the 90% idea. It's pretending to be scientific. It suggests that if we ran world history 10 times then we would get global warming on 9 occasions and not on the tenth.

    Your analogy with the betting industry is incorrect - they do not say there is an X% chance of a horse winning. They just set the odds and you can take it or leave it. In fact they change the odds as people bet to make sure that those betting on the losers will more than pay for the winners. Also the betting industry don't keep squealing that each race is "worse than our last predictions".

    They are more grounded in reality: they use real horses, not computer models.

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  • 55. At 1:48pm on 20 Jul 2009, eumenydes wrote:

    "I don't agree with the 90% idea. It's pretending to be scientific."

    I can see how it might appear that way to the lay public, but that is how *all science* is phrased. Mechanics, gravity, particle physics, astronomy, space physics, biology, medicine... You name it - that's just the way science works, because as explained aptly by Tim above you hardly ever have 100% certainty about anything. That's why statistics, uncertainty analysis and confidence levels are key undergraduate course components of any scientific discipline.

    Anyone waiting for a "100% certain" conclusion will have to throw out the majority of modern scientific knowledge. And if that's the level of confidence you require, then definitely don't bother visiting the doctor if you get sick, most of the available treatments will have much lower values than 90% attached to them ;)

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  • 56. At 2:32pm on 20 Jul 2009, U13900240 wrote:

    And notice how they don't need any confidence in the denialist papers when considering AGW wrong.

    Heck, they don't even need confidence in how right AGW is. It's 100% wrong according to them and impossible to be true.

    Yet they complain that AGW proponents say it's 100% true that AGW is right.

    Demands for "balance" seems not to be required in many denialists minds (of reasonable facsimile thereof).

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  • 57. At 2:34pm on 20 Jul 2009, U13900240 wrote:

    "It suggests that if we ran world history 10 times then we would get global warming on 9 occasions and not on the tenth. "

    No it doesn't.

    It says that if you want it to mean that, but check up on what the meaning of "confidence" is.

    After all, there's a 50% chance you're taller than 5' 8" Jack.

    That doesn't mean there's a 50% chance you have no height at all.

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  • 58. At 3:08pm on 20 Jul 2009, eumenydes wrote:

    Interesting post, Shanta and many thanks to SheffTim for some expert background info! I've always found paleoclimate fascinating although it's not my field... I have a question though about the timeline:

    "About 55 million years ago and over a period of less than 10,000 years, the Earth warmed up by 5 to 9 degrees C. "

    I thought the PETM warming occurred over 20,000 years? Or did I get it mixed up and it was actually 10,000 years warming followed by 10,000 years cooling back to the initial state? (If the latter, I'm kinda surprised by such a symettrical warming-cooling curve...) Perhaps Shanta or Tim could clear it up for me? Thanks!

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  • 59. At 5:33pm on 20 Jul 2009, U13900240 wrote:

    Just from the Wiki on the PETM:

    "Importantly, they both detect two steps in the drop of 13C, each lasting about 1000 years, and separated by about 20,000 years. The models diverge most in their estimate of the recovery time, which ranges from 150,000[11] to 30,000[12] years. There is other evidence to suggest that warming predated the 13C excursion by some 3,000 years.[13]"

    and

    "Average global temperatures increased by ~6 °C in the space of 20,000 years. "

    Looks likely that the uptick was in two drops.

    One may be the original vulcanism which then caused enough warming to get stored methane exhausted.

    Add in the ~3000 year float in the timeline, 12.000 - 18.000 would and could easily get shortened to 10.000 or 20.000 depending on what paper you read.

    In much the same way as solar photosphere temperatures are given as 6000K AND 6000C interchangeably. The ~300 difference doesn't make much difference and that figures rounded anyway.

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  • 60. At 7:35pm on 20 Jul 2009, eumenydes wrote:

    "Add in the ~3000 year float in the timeline, 12.000 - 18.000 would and could easily get shortened to 10.000 or 20.000 depending on what paper you read."

    OK, thanks - that makes sense...

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  • 61. At 7:39pm on 20 Jul 2009, U13900240 wrote:

    I didn't say it was the answer, though. It DOES fit what I've read though. The word picture is pretty consistent. It's the imprecision of the english: "start" from when? "end" happened when?

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  • 62. At 9:18pm on 20 Jul 2009, SheffTim wrote:

    eumenydes #58.
    WikiP' gives 20,000 years for the onset, but doesn't give a reference for where it got that figure from.

    Figures of approx. 10,000 ky for the onset and approx. 100,000 ky (k = thousand) for the recovery period are widely accepted. (See below.)

    There have been many attempts to determine the duration of the PETM, based on several different lines of evidence. Needless to say (given it occurred 55 my ago) it's not an easy exercise. The longest I've seen gave around 200,000 ky; getting agreement on how best to define the end-point is the first hurdle.

    Estimates based on stable-isotope records of the carbon isotope excursion, together with estimates for sediment deposition rates from several deep sea cores gives:
    "The sections, from between 2.7 and 4.8 kilometres water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (10,000 years) by more than 2 kilometres and recovered gradually (100,000 years)."
    Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum. Zachos et al. Science. 2005.
    http://www.sciencemag.org/cgi/content/abstract/308/5728/1611

    Related:
    "The time lag before the carbonates start to reappear is about 40 to 50 thousand years, and then it's another 40 thousand years before you see the normal carbonate-rich ooze again."
    http://www.ucsc.edu/news_events/press_releases/text.asp?pid=706

    "During the most prominent and best-studied hyperthermal, the Palaeocene Eocene Thermal Maximum (PETM); about 55 million years ago), the global temperature increased by more than 5 °C in less than 10,000 years."
    "An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics" Zachos et al. Nature. 2008
    [Unsuitable/Broken URL removed by Moderator]

    More on the N. Atlantic magma out-pouring here:
    http://www.sciencedaily.com/releases/2008/03/080327172238.htm
    http://tinyurl.com/m44jsc


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  • 63. At 9:47pm on 20 Jul 2009, SheffTim wrote:

    Hmm. Anyone like to explain why I've been sent to the naughty-step?

    The short version of my post above reads:
    Figures of approx. 10,000 yrs for the onset and approx. 100,000 yrs for the recovery period are widely accepted.

    I also give citations etc.
    That's all. *Sniff*.

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  • 64. At 10:10pm on 20 Jul 2009, U13900240 wrote:

    Tim, I think someone is playing silly buggers again.

    Probably a denialist who wants to "get back" at the propaganda as he sees it.

    Maybe even one of the ones who used to post here. Maybe Pog. Maybe CT. Maybe Bish himself.

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  • 65. At 05:10am on 21 Jul 2009, Jack Hughes wrote:

    Hi bloggers and statisticians !

    Maybe someone can tell me which statistical test the IPCC used to establish their 90% certainty ?

    I've used a lot of different statistical tests over the years and maybe they used one that's new to me. I'd love to find out more.

    You get extra points if you link to the data they used. Then I can run the test for myself and check their maths.

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  • 66. At 08:02am on 21 Jul 2009, SheffTim wrote:

    Hi Jack
    I gave a link to the guidance notes for IPCC authors etc above.
    There's also this:
    http://www.ucsusa.org/global_warming/science_and_impacts/science/findings-of-the-ipcc-fourth-2.html

    Those that argue for inaction often demand an impossible level of 'certainty'. Creationists do the same with the case for evolution. (They go quiet if the same demand is made back.)

    I'd be interested to see you as a juror in a court case Jack; how would you run a statistical test of the evidence to arrive at a conclusion of beyond a reasonable doubt?

    If two doctors (you asked for a second opinion) told you that they were 90% certain that your heart would fail over the course of the next year, unless they operated - how would you respond?

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  • 67. At 08:21am on 21 Jul 2009, MangoChutney wrote:

    @sheftim

    #62

    check your email, the mods will tell you why it's been removed

    having read most of your posts, i don't think you are the sort of person to deliberately post something that would break the rules - was there a link to a pdf?

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  • 68. At 08:49am on 21 Jul 2009, U13900240 wrote:

    It's a bit late for you to start worrying about statistics now.

    You've never used them to "prove" your assertions.

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  • 69. At 08:49am on 21 Jul 2009, U13900240 wrote:

    "I've used a lot of different statistical tests over the years"

    Not on these blogs you haven't.

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  • 70. At 09:18am on 21 Jul 2009, Jack Hughes wrote:

    Tim,

    Thanks for the link. It says that when they say "90%" they mean "very likely".

    Are you saying that the certainty of 90% is not the result of a statistical test ?


    Looks like some backtracking here.

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  • 71. At 09:58am on 21 Jul 2009, eumenydes wrote:

    SheffTim wrote:

    "The short version of my post above reads:
    Figures of approx. 10,000 yrs for the onset and approx. 100,000 yrs for the recovery period are widely accepted."

    Thanks, Tim - I wish I'd checked back here before your post was removed, but will read the citations with interest if it's brought back from the naughy-step :)


    Jack_Hughes_NZ wrote:

    "It says that when they say "90%" they mean "very likely".

    Are you saying that the certainty of 90% is not the result of a statistical test ?"

    Er, no offense but I think you need to re-read it because it actually says the opposite of what you quote: when they say "very likely" they mean ">90%". In other words, they use phrases like "very likely" / "very unlikely" etc to make the report more readable rather than having to say "with a likelihood of greater than 90% / less than 10%" all the time, which is a bit of a mouthful.

    The exact statement being: "When the IPCC ascribes a likelihood to a scientific finding, the term used reflects a specific range of certainty as defined by the chart below."

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  • 72. At 10:21am on 21 Jul 2009, U13900240 wrote:

    "Looks like some backtracking here. "

    Only in your delusion.

    You too have never read the IPCC report of which you're so skeptical. Just like Laz.

    So how can you be skeptical of something you didn't read?

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  • 73. At 10:46am on 21 Jul 2009, Jack Hughes wrote:

    Hi eumenydes !

    Do you know which statistical test they used to arrive at 90% ?

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  • 74. At 11:06am on 21 Jul 2009, Jack Hughes wrote:

    If they say very likely it's obviously subjective: the feelings of the writers.

    But saying 90% certain sounds so very scientific.

    It sounds objective - it sounds like they've run some formula and it's told them what will happen.

    But if they have not run any statistical test to arrive at the number 90% then its just a crock.

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  • 75. At 11:27am on 21 Jul 2009, SheffTim wrote:

    The mods have adjudicated in my favor. The full post (62) plus links are now there. My thanks to them.

    #70. Jack, go back and read what I put on both posts.
    And you are avoiding my questions.
    I doubt this discussion can be resolved. Jack how would you statistically prove the IPCC is wrong (as you seem to have no doubts that they are), or that you are right?

    #67. Mango: Posted links to 2 PDFs wrapped in tinyurls. They seem to go through most times. PDFs are used more and more nowadays and it is useful to post links to them.
    One was a link to a full photocopy of a paper published in Nature on the N. Atlantic vents/magma discovery. That has been allowed, the other hasn't. (62 above.) The other magma link's also interesting,.

    Ignore the 'ky' at the end of the numbers. Should just be just 'y'. (I was shuttling between cooking in the kitchen and the keyboard is my only excuse.)

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  • 76. At 11:45am on 21 Jul 2009, Jack Hughes wrote:

    Tim,

    I'm not making any claims about 90% or any other %. It's their expression and I'm calling B.S.

    They are trying to create a false sense of objectivity about their feelings. They should have stuck to "very likely". But they couldn't stop themselves.

    Making a more general point I think bloggers on here are maybe talking about different branches of science or even non-science.

    When I studied thermodynamics we learned the laws. Nobody introduced the 2nd law as "we are 90% certain that this law is true".

    At school it was Ohm's Law - V=IR. The teacher never said "V=IR to 90% certainty".

    When astronomers forecast an eclipse they know it's going to happen - they don't waffle around and hedge their bets.

    Are some people talking about "soft science" like sociology or even scientology ?

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  • 77. At 11:59am on 21 Jul 2009, U13900240 wrote:

    "At school it was Ohm's Law - V=IR. The teacher never said "V=IR to 90% certainty"."

    What about superconductors? R=0. Infinite current?

    So it was "wrong". For 90% of your needs for V=IR it is right.

    Or are you going to deny superconductors now?

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  • 78. At 12:14pm on 21 Jul 2009, U13900240 wrote:

    "When astronomers forecast an eclipse they know it's going to happen - they don't waffle around and hedge their bets."

    Ask an astronomer which side of the sun Pluto will be in 10 billion years.

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  • 79. At 12:30pm on 21 Jul 2009, eumenydes wrote:

    Jack_Hughes_NZ wrote:

    "Do you know which statistical test they used to arrive at 90% ?"

    Hi Jack - sorry for the delay, I'm at work so technically I should be researching the climate not chatting about it! ;)

    A complete answer to your question would require several pages plus further reading... It's not as simple as churning out some numbers and applying a t-test - this isn't GCSE maths after all!

    First there's an analysis of observational uncertainty, which combines the error margins of the instrumentation and the uncertainties of the assimilation methods and data coverage. This gives the confidence level in the global temperature measurments.

    Then there's the determination of the forcing agents and the temperature changes they would cause (eg anthropogenic greenhouse gases, volcanic aerosols, solar radiation, natural internal variability etc), each of which has an associated confidence level calculated from a combination of direct observation of these forcings and modelled climate response.

    This is then backed up by stochastic significance tests, based on thousands of random simulations of each of the above components of the calculation, to see what the probability is that that the observation or modelled response could have occurred by chance.

    These tests and uncertainties are all combined to arrive at a final confidence level for each statement.

    And this explanation doesn't even really scratch the surface of the enormous amount of painstaking work and calculation, checking and re-checking that goes on.

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  • 80. At 12:40pm on 21 Jul 2009, eumenydes wrote:

    Jack_Hughes_NZ wrote:

    "They are trying to create a false sense of objectivity about their feelings. They should have stuck to "very likely". But they couldn't stop themselves."

    I know you probably don't mean it the way it sounds, but this kind of statement is why many of my colleagues get too frustrated to try explaining their work to non-scientists. The idea that we write reports based on our "feelings" is hilarious - any scientist who did that would be out of their job within a week :)


    "At school it was Ohm's Law - V=IR. The teacher never said "V=IR to 90% certainty". "

    Then you evidently were never taught experimental science - otherwise known as "real world" science. It might say V=IR on your teacher's blackboard, but in the lab V would never exactly equal IxR, because you would never be able to measure V, I or R with 0% error. One of the first rules students are taught in any undergraduate (or even A-level) physics lab is that any measurement, statement or conclusion that doesn't have an uncertainty attached is worthless.


    "Are some people talking about "soft science" like sociology or even scientology ?"

    No, I'm a physicist by training and profession. The IPCC scientists that deal with detection and attribution of climate change are physicists, chemist, biologists, mathematicians and statisticians.

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  • 81. At 12:52pm on 21 Jul 2009, SheffTim wrote:

    #78. Ask an astronomer which side of the sun Pluto will be in 10 billion years.

    Not even that is 100% certain Jack.
    They may answer that Pluto and Earth may not exist at that time. http://physicsworld.com/cws/article/news/33056

    Other estimates give 7.5 billion yrs.

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  • 82. At 1:07pm on 21 Jul 2009, MangoChutney wrote:

    @sheftim #75

    the pdf links within your links shouldn't really bother the mods and i agree that many articles on the web are pdf's these days - perhaps the house rules should be updated?

    anyway, glad your post is back, although haven't read it yet

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  • 83. At 1:08pm on 21 Jul 2009, U13900240 wrote:

    I know, Sheff.

    Though Pluto may well exist, earth may have been kicked out of orbit well before such an event, though there are suns that are older than they "should" be so the sun may not have pushed into full-nova mode. And as the sun grows, it will eject mass. And since the orbit of the earth depends on that mass to keep it in so close without flying away, it will extend out to a further orbit and so may not be swallowed by the sun in its giant phase.

    I did astrophysics.

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  • 84. At 1:13pm on 21 Jul 2009, MangoChutney wrote:

    @Jack_Hughes_NZ #76

    I can't remember where i read it but i understand the IPCC wanted to include 95% certainty, but the Chinese and Saudi representatives refused to agree to 95%, so a compromise was reached.

    To me, this would suggest there was no statistical analysis

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  • 85. At 1:17pm on 21 Jul 2009, MangoChutney wrote:

    @sheftim #81

    that question statement was made by YW - i would guess Jack knows the answer or at least where to find it

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  • 86. At 1:27pm on 21 Jul 2009, U13900240 wrote:

    "To me, this would suggest there was no statistical analysis"

    Why?

    If someone says "This bridge will stand up to 100T loading" and have done the maths to prove this statement, yet the city official says "stick a 80T Max Load on it", this somehow proves the engineer didn't do any proving???

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  • 87. At 1:29pm on 21 Jul 2009, U13900240 wrote:

    The question for #82 is will you really read it? You didn't read

    [Unsuitable/Broken URL removed by Moderator]

    You didn't read a link to what optical depth was.

    You haven't read the IPCC reports (which answered several of your questions posed on this board).

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  • 88. At 1:31pm on 21 Jul 2009, U13900240 wrote:

    "i would guess Jack knows the answer or at least where to find it"

    You would have guessed wrong, since if he'd known about it, he wouldn't have said:

    "When astronomers forecast an eclipse they know it's going to happen - they don't waffle around and hedge their bets."

    Would he?

    Especially since that information shows that they would do just that.

    Also, strange that Jack says that V=IR is proven, 100% accurate and true.

    Yet neither you nor Laz have taken him to task and told him that science can only be disproven, not proven.

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  • 89. At 1:33pm on 21 Jul 2009, eumenydes wrote:

    SheffTim wrote:
    "The mods have adjudicated in my favor. The full post (62) plus links are now there. My thanks to them."

    Hi Tim - thanks for a very informative explanation! Haven't read the links yet but will when I get a chance.

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  • 90. At 1:38pm on 21 Jul 2009, U13900240 wrote:

    How can the URL be unsuitable?

    It has been posted many times and links to no pdf.

    http://www.bbc.co.uk/blogs/climatechange/2009/07/bbc_stifles_climate_change_deb.html#P82861547

    See it?

    and ends in .htm.

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  • 91. At 00:33am on 22 Jul 2009, SheffTim wrote:

    #85. Thanks Mango. When a thread begins to reach it's 'end-phase' it 'kind of falls apart'. I'm sure someone, somewhere will write a paper on the dynamics of blog comments and start a new field.
    Apologies to Jack; thought he was arguing (along the lines of) Newtonian gravitational theory meant certainty in long-term predictions was possible.

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  • 92. At 08:44am on 22 Jul 2009, U13900240 wrote:

    "thought he was arguing (along the lines of) Newtonian gravitational theory meant certainty in long-term predictions was possible."

    He was arguing that.

    I used the query "where would Pluto be in 10 billion years time" to show that his theory that the solar system was predictable.

    Go read his post again.

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  • 93. At 09:24am on 22 Jul 2009, SheffTim wrote:

    So what was his point? That some things are (he thought) 100% predictable and he wants that certainty? Even if the timescale was of one million years Pluto could still be deflected from its orbit by an asteroid strike etc. Few things come with 100% certainty (apart from death and taxes :-) ).

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  • 94. At 09:53am on 22 Jul 2009, U13900240 wrote:

    IIR in a few million years, they don't know which side of the Sun Pluto would be. They know it would be in the same orbit (absent collision), but don't know WHERE in that orbit it would be.

    PS the denialists would merely say "Where's your evidence that I will die?" And when you point to every other person who died, would say "that isn't evidence *I* will die".

    "So what was his point?" That some things are (he thought) 100% predictable and he wants that certainty?"

    Yes, he was trying to show up climate science as not science since they put error bars on their predictions and he doesn't know any science beyond Junior School, so he thinks that astronomy and Ohms Law are "real science", despite the fourth (?) bar on a resistor being the *error* of its resistance and that the occurrence leap second cannot be usefully predicted, just observed it will be needed.

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  • 95. At 11:22am on 22 Jul 2009, Jack Hughes wrote:

    Hi Tim and fellow bloggers !

    Lets get to the point. The 90% certainty bit in the IPCC report.

    Can we all agree now that this was a "figure of speech" and not the result of a statistical test.

    Let's not get carried away with extreme examples about millions of years into the future or temperatures near absolute zero or speeds near the speed of light.

    We are talking about the weather over the next 40 years.

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  • 96. At 11:42am on 22 Jul 2009, U13900240 wrote:

    " The 90% certainty bit in the IPCC report. "

    There is no 90% certainty.

    "Let's not get carried away with extreme examples about millions of years into the future or temperatures near absolute zero or speeds near the speed of light."

    Hey, YOU brought up how V=IR has no shilly-shallying about with uncertainties.

    YOU were wrong.

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  • 97. At 12:43pm on 22 Jul 2009, SheffTim wrote:

    Jack #95: It's offering an expert opinion as to likelihood. To quote the intro to the IPCC report:
    "On the basis of a comprehensive reading of the literature and their expert judgement, authors have assigned a confidence level to the major statements in the Report on the basis of their assessment of current knowledge, as follows:

    Terminology Degree of confidence in being correct
    Very high confidence = At least 9 out of 10 chance of being correct
    High confidence = about 8 out of 10 chance.
    Medium confidence = about 5 out of 10 chance.
    Low confidence = about 2 out of 10 chance.
    Very low confidence = less than a 1 out of 10 chance.

    Likelihood refers to a probabilistic assessment of some well defined outcome having occurred or occurring in the future, and may be based on quantitative analysis or an elicitation of expert views.

    In the Report, when authors evaluate the likelihood of certain outcomes, the associated meanings are:

    Terminology - Likelihood of the occurrence/ outcome
    Virtually certain = 99% probability of occurrence
    Very likely = 90 to 99% probability
    Likely = 66 to 90% probability
    About as likely as not 33 to 66% probability
    Unlikely = 10 to 33% probability
    Very unlikely = 1 to 10% probability
    Exceptionally unlikely = less than 1% probability."

    No-one claimed that it was based on a 'statistical test', that is a straw man of your making.
    Still, we have a real-time, real-life experiment running, so we'll have to see where we are in a few decades time and by the end of the century. (No I won't see it either, I'll be lucky to still be around in 2050.)

    I'll ask again, if two doctors (you asked for a second opinion) told you that they were 90% certain that your heart would fail over the course of the next year, unless they operated - how would you respond?
    (Confidence/certainty levels are used in medicine too.)

    I'll let you have the last word on this Jack, if you want one, as I have work to do.
    To quote from Mark Kemode on his movie blog; 'Everyone's entitled to an opinion, so feel free to be as wrong as you wish.'

    'We are talking about the weather over the next 40 years.'

    Hmm, do you realise there's a difference between weather and climate?
    http://sites.google.com/site/weatherandclimate/

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  • 98. At 12:46pm on 22 Jul 2009, U13900240 wrote:

    And what are the certainties of the Lindzen's or Monkton's view?

    What, Jack, do you think the likelihood of AGW being real is?

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  • 99. At 04:33am on 23 Jul 2009, Jack Hughes wrote:

    Hi Tim !

    So can we agree that the 90% idea is a way of turning an opinion into a number ?

    input = opinion
    output = integer in range 0 to 100 (often a multiple of 10)

    I must admit that science is going in a new direction nowadays.


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  • 100. At 08:00am on 23 Jul 2009, Jack Hughes wrote:

    Thanks for your help - I think I'm starting to understand it now.

    When the IPCC say "90% certain" the "%" bit has a special meaning that is different from the usual everyday meaning.

    It's just a rating. Like hotels with a 5 star rating - or the Michelin Restaurant Rating system.

    A 4-star hotel is posher than a 2-star hotel. But not twice as posh because poshness is subjective.

    90 is more certain than 45 - but not twice as certain.

    The 90% certain expression is straight from the IPCC - not from me.

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  • 101. At 08:11am on 23 Jul 2009, MangoChutney wrote:

    90% certain means 10% doubt

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  • 102. At 10:36am on 23 Jul 2009, U13900240 wrote:

    "90% certain means 10% doubt"

    No it doesn't.

    A grown male is 5'8". There is a 90% chance they are that height within 2 inches.

    This doesn't mean there's doubt that he has any height at all.

    You do not know anything, do you.

    Physics? No. Statistics? No.

    All you "know" is that AGW is wrong.

    Yet you are unable to explain why.

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  • 103. At 10:40am on 23 Jul 2009, U13900240 wrote:

    "Hi Tim !

    So can we agree that the 90% idea is a way of turning an opinion into a number ? "

    And so we see the denialists "brain" at work again.

    He read Tim's message and got this far:

    "Very likely = 90 to 99% probability"

    And stops without reading the 99.

    Ignoring YET AGAIN, 99% is there and just as likely as the 90% they want to concentrate on.

    And ignoring the rest of the post, since it doesn't give him anything to mislead and tell you thinks that are not the truth nor the facts:

    "Likelihood refers to a probabilistic assessment of some well defined outcome having occurred or occurring in the future, and may be based on quantitative analysis or an elicitation of expert views."

    And jumps straight to "it's all made up".

    And ignores a question (but what's new with that with denialists: big on ASKING question, complete pants at answering them):

    "I'll ask again, if two doctors (you asked for a second opinion) told you that they were 90% certain that your heart would fail over the course of the next year, unless they operated - how would you respond?
    (Confidence/certainty levels are used in medicine too.)"

    So, Jack, what would you do? Ignore them until they were 100% certain?

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  • 104. At 11:00am on 23 Jul 2009, U13900240 wrote:

    "The 90% certain expression is straight from the IPCC - not from me. "

    It is?

    Here?

    "Now, the panel concluded that it was at least 90% certain that human emissions of greenhouse gases rather than natural variations are warming the planet's surface".

    If that's where you say it is 90% from then you're lying.

    It's at least 90%.

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  • 105. At 11:04am on 23 Jul 2009, U13900240 wrote:

    Mind you it seems like the denialists have answered the question. They think that AGW is real with a confidence of 90% in that assessment.

    Now, according to the Stern Report, it will cost much more to leave things get worse than to fix them. Let's say it's 10 trillion cost to fix, 100 trillion damage will be done if AGW is right and nothing it done.

    Expected loss for doing something: 10 Trillion.
    Expected loss for doing nothing: 90 Trillion. (there's a 10% chance doing nothing is right)

    So we should do something.

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  • 106. At 00:54am on 24 Jul 2009, Jack Hughes wrote:

    Real science involves numbers.

    The IPCC are turning their opinion into a number so it looks more scientific. They should have stuck with "very likely".

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  • 107. At 07:08am on 24 Jul 2009, MangoChutney wrote:

    and i would reiterate an early comment - the rest of the world wanted to say something like "in excess of 95% certainty", but the Chinese and Saudi's refused to co-operate. The compromise was 90%. How can that result be from a scientific analysis?

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