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PETM Weirdness

Filed under: — gavin @ 10 August 2009

The Paleocene-Eocene Thermal Maximum (PETM) was a very weird period around 55 million years ago. However, the press coverage and discussion of a recent paper on the subject was weirder still.

For those of you not familiar with this period in Earth’s history, the PETM is a very singular event in the Cenozoic (last 65 million years). It was the largest and most abrupt perturbation to the carbon cycle over that whole period, defined by an absolutely huge negative isotope spike (> 3 permil in 13C). Although there are smaller analogs later in the Eocene, the size of the carbon flux that must have been brought into the ocean/atmosphere carbon cycle in that one event, is on a par with the entire reserve of conventional fossil fuels at present. A really big number – but exactly how big?

The story starts off innocently enough with a new paper by Richard Zeebe and colleagues in Nature Geoscience to tackle exactly this question. They use a carbon cycle model, tuned to conditions in the Paleocene, to constrain the amount of carbon that must have come into the system to cause both the sharp isotopic spike and a very clear change in the “carbonate compensation depth” (CCD) – this is the depth at which carbonates dissolve in sea water (a function of the pH, pressure, total carbon amount etc.). There is strong evidence that the the CCD rose hundreds of meters over the PETM – causing clear dissolution events in shallower ocean sediment cores. What Zeebe et al. come up with is that around 3000 Gt carbon must have been added to the system – a significant increase on the original estimates of about half that much made a decade or so ago, though less than some high end speculations.

Temperature changes at the same time as this huge carbon spike were large too. Note that this is happening on a Paleocene background climate that we don’t fully understand either – the polar amplification in very warm paleo-climates is much larger than we’ve been able to explain using standard models. Estimates range from 5 to 9 deg C warming (with some additional uncertainty due to potential problems with the proxy data) – smaller in the tropics than at higher latitudes.

Putting these two bits of evidence together is where it starts to get tricky.

First of all, how much does atmospheric CO2 rise if you add 3000 GtC to the system in a (geologically) short period of time? Zeebe et al. did this calculation and the answer is about 700 ppmv – quite a lot eh? However, that is a perturbation to the Paleocene carbon cycle – which they assume has a base CO2 level of 1000 ppm, and so you only get a 70% increase – i.e. not even a doubling of CO2. And since the forcing that goes along with an increase in CO2 is logarithmic, it is the percent change in CO2 that matters rather than the absolute increase. The radiative forcing associated with that is about 2.6 W/m2. Unfortunately, we don’t (yet) have very good estimates of background CO2 levels in Paleocene. The proxies we do have suggest significantly higher values than today, but they aren’t precise. Levels could have been less than 1000 ppm, or even significantly more.

If (and this is a key assumption that we’ll get to later) this was the only forcing associated with the PETM event, how much warmer would we expect the planet to get? One might be tempted to use the standard ‘Charney’ climate sensitivity (2-4.5ºC per doubling of CO2) that is discussed so much in the IPCC reports. That would give you a mere 1.5-3ºC warming which appears inadequate. However, this is inappropriate for at least two reasons. First, the Charney sensitivity is a quite carefully defined metric that is used to compare a certain class of atmospheric models. It assumes that there are no other changes in atmospheric composition (aerosols, methane, ozone) and no changes in vegetation, ice sheets or ocean circulation. It is not the warming we expect if we just increase CO2 and let everything else adjust.

In fact, the concept we should be looking at is the Earth System Sensitivity (a usage I am trying to get more widely adopted) as we mentioned last year in our discussion of ‘Target CO2‘. The point is that all of those factors left out of the Charney sensitivity are going to change, and we are interested in the response of the whole Earth System – not just an idealised little piece of it that happens to fit with what was included in GCMs in 1979.

Now for the Paleocene, it is unlikely that changes in ice sheets were very relevant (there weren’t any to speak of). But changes in vegetation, ozone, methane and aerosols (of various sorts) would certainly be expected. Estimates of the ESS taken from the Pliocene, or from the changes over the whole Cenozoic imply that the ESS is likely to be larger than the Charney sensitivity since vegetation, ozone and methane feedbacks are all amplifying. I’m on an upcoming paper that suggests a value about 50% bigger, while Jim Hansen has suggested a value about twice as big as Charney. That would give you an expected range of temperature increases of 2-5ºC (our estimate) or 3-6ºC (Hansen) (note that uncertainty bands are increasing here but the ranges are starting to overlap with the observations). ALl of this assumes that there are no huge non-linearities in climate sensitivity in radically different climates – something we aren’t at all sure about either.

But let’s go back to the first key assumption – that CO2 forcing is the only direct impact of the PETM event. The source of all this carbon has to satisfy two key constraints – it must be from a very depleted biogenic source and it needs to be relatively accessible. The leading candidate for this is methane hydrate – a kind of methane ice that is found in cold conditions and under pressure on continental margins – often capping large deposits of methane gas itself. Our information about such deposits in the Paleocene is sketchy to say the least, but there are plenty of ideas as to why a large outgassing of these deposits might have occurred (tectonic uplift in the proto-Indian ocean, volcanic activity in the North Atlantic, switches in deep ocean temperature due to the closure of key gateways into the Arctic etc.).

Putting aside the issue of the trigger though, we have the fascinating question of what happens to the methane that would be released in such a scenario. The standard assumption (used in the Zeebe et al paper) is that the methane would oxidise (to CO2) relatively quickly and so you don’t need to worry about the details. But work that Drew Shindell and I did a few years ago suggested that this might not quite be true. We found that atmospheric chemistry feedbacks in such a circumstance could increase the impact of methane releases by a factor of 4 or so. While this isn’t enough to sustain a high methane concentration for tens of thousands of years following an initial pulse, it might be enough to enhance the peak radiative forcing if the methane was being released continuously over a few thousand years. The increase in the case of a 3000 GtC pulse would be on the order of a couple of W/m2 – for as long as the methane was being released. That would be a significant boost to the CO2-only forcing given above – and enough (at least for relatively short parts of the PETM) to bring the temperature and forcing estimates into line.

Of course, much of this is speculative given the difficulty in working out what actually happened 55 million years ago. The press response to the Zeebe et al paper was, however, very predictable.

The problems probably started with the title of the paper “Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming” which on it’s own might have been unproblematic. However, it was paired with a press release from Rice University that was titled “Global warming: Our best guess is likely wrong”, containing the statement from Jerry Dickens that “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models”.

Since the know-nothings agree one hundred per cent with these two last statements, it took no time at all for the press release to get passed along by Marc Morano, posted on Drudge, and declared the final nail in the coffin for ‘alarmist’ global warming science on WUWT (Andrew Freedman at WaPo has a good discussion of this). The fact that what was really being said was that climate sensitivity is probably larger than produced in standard climate models seemed to pass almost all of these people by (though a few of their more astute commenters did pick up on it). Regardless, the message went out that ‘climate models are wrong’ with the implicit sub-text that current global warming is nothing to worry about. Almost the exact opposite point that the authors wanted to make (another press release from U. Hawaii was much better in that respect).

What might have been done differently?

First off, headlines and titles that simply confirm someone’s prior belief (even if that belief is completely at odds with the substance of the paper) are a really bad idea. Many people do not go beyond the headline – they read it, they agree with it, they move on. Also one should avoid truisms. All ‘models’ are indeed wrong – they are models, not perfect representations of the real world. The real question is whether they are useful – what do they underestimate? overestimate? and are they sufficiently complete? Thus a much better title for the press release would have been more specific “”Global warming: Our best guess is likely too small” – and much less misinterpretable!

Secondly, a lot of the confusion is related to the use of the word ‘model’ itself. When people hear ‘climate model’, they generally think of the big ocean-atmosphere models run by GISS, NCAR or Hadley Centre etc. for the 20th Century climate and for future scenarios. The model used in Zeebe et al was not one of these, instead it was a relatively sophisticated carbon cycle model that tracks the different elements of the carbon cycle, but not the changes in climate. The conclusions of the study related to the sensitivity of the climate used the standard range of sensitivities from IPCC TAR (1.5 to 4.5ºC for a doubling of CO2), which have been constrained – not by climate models – but by observed climate changes. Thus nothing in the paper related to the commonly accepted ‘climate models’ at all, yet most of the commentary made the incorrect association.

To summarise, there is still a great deal of mystery about the PETM – the trigger, where the carbon came from and what happened to it – and the latest research hasn’t tied up all the many loose ends. Whether the solution lies in something ‘fundamental’ as Dickens surmises (possibly related to our basic inability to explain the latitudinal gradients in any of the very warm climates) , or whether it’s a combination of a different forcing function combined with more inclusive ideas about climate sensitivity, is yet to be determined. However, we can all agree that it remains a tantalisingly relevant episode of Earth history.

203 Responses to “PETM Weirdness”

  1. 101
    counters says:

    Doctor K,

    I’m not sure it’s clear what you’re asking. It’s a bit ironic asking how models allow for “fact[s] of physics” seeing as a GCM is – in a terribly simplified way – just a giant physics equation solver. The thermodynamics I think you’re referencing are pretty straightforward (they’re treated in the book that Jim linked for you, and they’re not difficult to understand and derive) and most definitely considered in the core of the model.

    Now, what sort of investigative work do you think the media should do this end? Is it a journalists job to dig through a model’s source code and analyze it? Of course not. Now, we can argue all day about whether or not the media accurately characterizes papers in the scientific press or whether they fairly represent the basic science behind global warming, but it’s not their place to do the actual science. On a similar note, how does UN politics come in to play here? The IPCC merely summarizes the existing literature on the atmosphere and climate change, and then based on projections (informed by presumed, clearly described economic/greenhouse emissions scenarios) makes conservative policy suggestions on how to best avert catastrophic global warming. It’s not like they’re political bosses sitting in the smoke-filled back room of Tammany Hall fabricating scientific figures!

    Finally, I hope you do go back and read through the textbook Jim linked you. That will explain CO2’s role in the atmosphere and global warming far better than a mere comment on a blog can.

  2. 102
    wili says:

    Doctor K, your question about physics and global warming is so ill informed, it is hard to know where to start. Read some basic non-denialist works on GW. In short, no one is saying that warming is from increased pressure of GHGs add to the atmosphere.

    Yes, politics doubtless played a role in IPCC–the findings and especially the recommendations were watered down because of pressure from governments including our own. The decision not to consider the most recent data also ended up creating a report that understated the pace at which the negative effects of global warming would unfold, particularly in the Arctic.

    Why would you think “the contribution of CO2 to atmospheric warming is overstated drastically”? You have to explain your position before anyone can address it intelligently. Since models have turned out to underestimate the amount of warming and other effects, it is more likely that the contribution of CO2 to warming is drastically understated than overstated.

  3. 103
    J. Bob says:

    #88 What simple analysis?

  4. 104
  5. 105
    Hank Roberts says:

    > IPCC …. politics

    “… virtually all of the world’s governments belong to it. Thus, governments that don’t want to do anything about climate change have just as much input to the report as countries that do.

    This tension between the ideological factions of the IPCC actually gives the reports credibility. Only statements that everyone agrees to make it into the report. A few countries that object to some result can keep it out of the report. This is, in fact, why the IPCC process was designed this way.”

  6. 106
    glen says:

    Rod B (85)
    glen (56), does Lovelock hold that belief because he scientifically thinks it’s inevitable, or because his tack requires less work, as in ‘might as well lie back and enjoy it?’

    not sure which “belief” you are pointing to?

  7. 107
    Jerry Steffens says:


    In what sense is the ideal gas law (pV = nRT) a relationship between elevation and temperature? If it were, how can it be that the law holds in both the troposphere and stratosphere, yet air temperature decreases with height in the troposphere (on average), but increases with height in the stratosphere?

    [Response: The ideal gas law is for a circumstance in which there are no phase changes or external energy sources (and for ideal gases of course). So it works well for dry air that is compressed or expanded. In the atmosphere, the pressure is basically just the weight of air above you, and so if you move a dry air parcel up, the pressure will decrease, and the temperature will fall (at about 9 C/km – the dry adiabat). In moist air, you can make a correction assuming that the water vapour will be saturated and the resulting latent heat release when water condenses can be included as a correction to T. This makes the effective cooling rate less (about 6 deg C/km – the moist adiabat). However, if you have significant amounts of radiative transfer (i.e. internal heating from absorption by ozone, water vapour, clouds or aerosols), then the approximations start to break down. So in the stratosphere, where ozone is very important, it doesn’t work at all. It should also be noted that it breaks down as well if there is no convective instability – the atmosphere is perfectly happy to have temperature gradients that are larger than the adiabat (i.e. very cold air near the bottom is stable). – gavin]

  8. 108

    Are we not in a very perilous place already?

    In the paleoclimate record the rate of change was of the order of +0.1K per century, possibly less. And the temporal lag between temperature rise and the observed GHG increase is something in the range between as little as 200 years to maybe 800.

    So the temperature rise that triggered the GHG increase (if it is initiated by temperature rise) is somewhere in the range of 0.2 to 0.8K.

    Which is roughly where we are now, isn’t it?

  9. 109

    Re #85 where Rod B questions Lovelock’s motives.

    About 5 years ago, Jame Lovelock visited the Hadley Centre, and discovered that all the scientists were sitting in different rooms in despair at the way the environment, ocean acidification, depletion of fisheries, loss of top soil, desertification , loss of biodiversity, increase in wildfires, melting of glaciers, warming ocean, loss of Arctic sea, and the collapse of the Antarctic Peninsula ice shelves. They could not speak out for fear of being labeled alarmist by the scientists in the other rooms.

    Lovelock wrote his book, “the Revenge of Gaia” to warn about this and proposed nuclear power as the answer to solving the problem of global warming. He believed that when the US came to its senses, they would deal with the problem in their characteristic robust fashion.

    But nothing has happened. He has now written another book:

    The Vanishing Face of Gaia A Final Warning by James Lovelock Allen Lane, London, 2009. 199 pp. £20, C$34. ISBN 9781846141850. Basic Books, New York, 2009. 288 pp. $25. ISBN 9780465015498.

    which Lee Kump reviewed along with a biography of Lovelock by the Gribbens in Science.. It was that article that glen cut and pasted into comment #56.

    I share Lovelock’s despair. The US cannot even sort out the health of their own citizens, far less that of our planet :-(

    Cheers, Alastair.

  10. 110

    #78 Nagraj Adve

    re. Gavins comment and information about methane hydrate clathrates

    Euan Nisbet has been working in that area and last I heard from him the general assessment Gavin made still stands as far as I can tell. It is being looked at and while there are indicators, we don’t know a lot yet. But this is a very interesting area.

    Euan gives a general talk about it. Don’t mind the drop out in the front, it does not last long… and download the slide show to follow along.

  11. 111

    Re #109

    I apologise for misspelling John and Mary Gribbin’s surname. I have seen John post here, so I hope he is not offended when he sees my mistake.

    As a further penance I am reposting details of their book [moderators permitting]. Its UK title is He Knew He Was Right: The Irrepressible Life of James Lovelock and Gaia and the US title is James Lovelock In Search of Gaia by John Gribbin and Mary Gribbin Allen Lane, London, 2009. 262 pp. £20, C$42. ISBN 9781846140167. Princeton University Press, Princeton, NJ, 2009. 286 pp. $24.95, £16.95. ISBN 9780691137506.

  12. 112
    Rod B says:

    glen (106), the following (sorry for the confusion). “…He calls for an immediate shift of focus to adaptation to a hothouse world, expecting that in the coming decades humanity will be forced to migrate to the few habitable refugia that remain (including the British Isles). The world population will be reduced from billions to millions, Gaia selecting those humans with the traits to live sustainably (her revenge)…”

  13. 113
    Rod B says:

    Alastair (109). Interesting. Thanks.

  14. 114

    112 Rod B.

    “…migrate to the few habitable refugia that remain (including the British Isles)”

    That idea has its limitations too, as it will be standing-room only on the British Isles by the time Gaia has settled down again.

    80m sea level rise gives:

  15. 115
    Jim Galasyn says:

    Re refugia, I trust we’ve all seen Children of Men? There’s your Lovelockian near-future.

  16. 116

    Re #113

    James Lovelock outlined the ideas from “The Revenge of Gaia” in a lecture to the Royal Society which can be seen here:
    Professor James Lovelock CH CBE FRS “Climate change on the living Earth”

  17. 117
    Ray Ladbury says:

    CM @98


    Ooh! I like it. Ladies and germs, I think we have a winner!

    Dr. K @ 96 Oh dear! You poor man. No wonder you are so confused.

  18. 118
    Bryan S says:

    You make all the right caveats in your above essay, but the fault lies in how you stress them to your audience. Please indulge me some scientific liberty to make a point.
    Allow us first to surmise that the forcing changes needed to accomplish the PETM temperature spike indeed involve a sustained contribution of CH4 from methane hydrates, as you propose in your 2003 paper. One could imagine that this might hypothetically be triggered by a change of gateways controlling ocean circulation, but it also might be simply be a highly non-linear feedback response to an initially modest CO2 out-gassing from a pulse of volcanic activity. Next, we note that the base climate during the Paleocene was already much warmer than today, and may have already been near a critical threshold that tripped the sustained liberation of methane stored in the gas hydrates. The modern background earth system however may be very far away from such a tipping point so that a modern doubling of C02 triggers much more moderate positive feedbacks. In such a case, the full earth system sensitivity inferred from a doubling of CO2 (after the full geochemical response to the methane release) during the PETM might yield a grossly different sensitivity than for a doubling scenario over the modern background climate. Depending on the location, geometry, and volume of methane hydrates at any given time in the earth system (and we have no idea about the variability of these hydrates over geologic time), there may be no linear scaling of climate sensitivity whatsoever.
    This is just one example of many other potential pitfalls relating a deep time climate to modern analogs. I can think of more factors which might suggest that the earth system response to changing atmospheric gas forcing is non-linear across many different scales, especially across long spans of geologic time.
    Finally, you say in conclusion: “we can all agree that it remains a tantalisingly relevant episode of Earth history.” Relevant to what? If you are subtly inferring that there is any evidence from the PETM that in some way can be used to infer a climate sensitivity of 6-8C to the modern CO2 forcing changes, I’m afraid I will need to call BS on that (as I have done before on this same subject).

  19. 119
    glen says:

    Rod B (112)

    inevitable — Lovelock’s “beliefs” turns everyone on this blog into a climate optimist! He has a pretty gloomy outlook.

  20. 120
    J. Bob says:

    #104 – If it’s so simple, you should be able to explain it, in say 1 or 2 paragraphs, not give a bunch of ref.

  21. 121
    glen says:

    In my first post(56) — what I really wanted to highlight is Lovelock’s reasoning for decrying American Science(maybe I was too subtle). Is American Science emphasizing the wrong science?

    “We seem to have forgotten that science is not wholly based on theory and models: more tiresome and prosaic confirmation by experiment and observation plays just as important a part. Perhaps for social reasons, science has in recent years changed its way of working. Observation in the real world and small-scale experiments on the Earth now take second place to expensive and ever-expanding theoretical models. It may be administratively and politically convenient to work this way, but the consequences could be disastrous. Our tank is near empty of data, and we are running on theoretical vapor: this is especially true of data about the oceans that make up more than 70 percent of the Earth’s surface, and about the responses of ecosystems to climate change — and, just as importantly, the effect of change in the oceans and ecosystems on the climate.
    The ideas that stem from Gaia theory put us in our proper place as part of the Earth system — not the owners, managers, commissars, or people in charge. The Earth has not evolved solely for our benefit, and any changes we make to it are at our own risk. This way of thinking makes dear that we have no special human rights; we are merely one of the partner species in the great enterprise of Gaia. We are creatures of Darwinian evolution, a transient species with a limited lifespan, as were all our numerous distant ancestors. But, unlike almost everything before we emerged on the planet, we are also intelligent, social animals with the possibility of evolving to become a wiser and more intelligent animal, one that might have a greater potential as a partner for the rest of life on Earth. Our goal now is to survive and to live in a way that gives evolution beyond us the best chance. The philosopher John Gray has discussed the extent to which we are still an emerging intelligence and still have far to go to match even our own estimation of ourselves. Do we really believe that we humans, wholly untrained as we are, have the intelligence or capacity to manage the Earth?
    We have become good at burying bad news, and maybe this is why we do not like the reports brought back by those brave and true scientists who go out into the world — like Charles David Keeling and his son Ralph, who for so long and so accurately monitored carbon dioxide on the peak of Mauna Loa, or Andrew Watson who took wintertime measurements from a ship that bounced on the cold and stormy seas off Greenland. There are a few scientists like them who now make observations of temperature and sea-level rise, and their measurements were reported by Stefan Rahmstorf and his colleagues in May 2007 in Science. They found the sea level was rising 1.6 times as fast and the temperature 1.3 times as fast as the IPCC had predicted in 2007. In September 2007 we were devastated to discover that all but 40 percent of the ice floating on the Arctic Ocean had melted. It is true that the visible loss in 2008 was slightly less, but the remaining ice had thinned by a record 1.5 feet. These changes are far more rapid than the gloomiest of model forecasts and, as we shall see, could have serious consequences.
    Through Gaia theory I offer a view of our and the Earth’s possible future as climate change develops. It differs from that of most climate scientists. The differences come from procedure, not from a different factual basis. Most of the climate-change models, for example, do not yet include the physiological response of the ecosystems of the land or oceans. In no way is this the consequence of a battle between theories; it is that climate models stretch our mental and computing capacities so much that it takes a long time before new procedures can be included reliably — it is somewhat like changing the transport system of a city from buses to trams. In an ideal world all-inclusive climate models might lessen or even remove the disagreement, but we cannot afford to wait for perfected models: we have to act now, so I offer predictions based on simple models from Gaia theory and evidence from the Earth now and in the past.
    Professional climatology is based mainly on geophysics and geochemistry and often assumes that the Earth is inert and incapable of a physiological response to climate change. What makes the ideas in this book different is that they are based on a consistent theory of the Earth — Gaia — which has proven itself by successful predictions and is beginning to be accepted as the conventional wisdom of Earth and life science. Do not suppose that conventional wisdom among scientists is similar to consensus among politicians or lawyers. Science is about the truth and should be wholly indifferent to fairness or political expediency.
    When I criticize the IPCC consensus, I am most of all criticizing the lack of wisdom among managers and politicians who forced (I suspect unwilling) scientists to present the conclusions of different national and regional climate centers this way. Just before completing this book, I read Steve Schneider’s deeply moving recent work, A Patient from Hell, about his long and painful but successful battle with cancer. Schneider is one of the world’s leading climate scientists, and he recalls in the book his part in a session at the UN in Geneva during the development of the IPCC Working Group II report of 2001, describing how the good science presented at the session was manipulated until it satisfied all of the national representatives present. The book makes clear that the words used to express the consequences of global heating were blurred until they were acceptable to representatives from the oil-producing nations, who saw their national interests threatened by the scientific truth. If this is what the UN means by consensus, scientific truth cannot be expected to come from its deliberations, and we are misled about the dangers of global heating. This may also be why national governments and international agencies are reluctant to fund observation and measurement but ready to fund models. Measurements by scientists are much harder to contest. It is said that truth is the first casualty of war, and it seems that this is also true of climate change. If I am more right than the consensus, it alters profoundly the best course of individual and political action.”

    Excerpt from J Lovelock’s book The Vanishing Face of Gaia, 2009

  22. 122
    dhogaza says:

    I’m afraid I will need to call BS on that (as I have done before on this same subject).

    Well, yes B[ryan] S, but why do your initials carry any weight whatsover?

    The world wonders.


    This is just one example of many other potential pitfalls relating a deep time climate to modern analogs.

    I’m heartened to see that you reject the “climate has changed drastically over geologic time therefore anthropomorphic change is impossible” crap.

    Thank you.

    I can think of more factors which might suggest that the earth system response to changing atmospheric gas forcing is non-linear across many different scales, especially across long spans of geologic time

    So perhaps the earth isn’t entering an ice age today, after all, as is so widely touted by your denialist cohorts?

    I do presume you’ve informed them of your wisdom, too, and don’t restrict yourself to “correcting” working scientists …

  23. 123
    ross glory says:

    Doctor K,
    I look forward to the result of your investigations. Personally, the few models I’ve looked at make a point of ‘substantiating’ their asumptions, it’s a key part of building an Earth Systems model. However the fact that they’re assumptions (i.e. parameters) means they are often based on measured values not built from first principles.

    From where I sit it appears that someone that knows nothing about GCMs is claiming GCMs know nothing…not sound foundations for an argument imho.

    Similarly claiming the scientific method will weed out the facts from theories show little understanding as well….it can only weed out theories. And again from my perspective, it seems to be doing a prety good job judging by the lack of substantiated theories telling me there’s nothing to worry about.

  24. 124
    pete best says:

    Re #109, Joe Romm over at climate progress would not agree with you. He knows the score in the USA with regard to its energy politics and what needs to be done. He also knows that the USA burns 1/4 of the worlds fossil fuels and it needs to start to do something about it. Its wind power is growing nicely but its a slow process that needs a lot of incentives to get going and really make a difference.

    Not relying on middle eastern oil sounds good. Self sufficient in energy provision is another good sound bite and the arguments about the USA new found natural gas reserves can make a big difference in getting rid of coal. Its all up in the air though and as yet not strategy exists.

  25. 125

    #118 Bryan S (BS)

    dhogaza – you nailed it well.

    Re. BS’s “Relevant to what?” statement:

    Learning more and understanding mechanisms regarding earths climate I imagine.

    And I’m suggesting before you start calling something BS without relevant context you have at least the courage to post your real name… unless of course you are under threat of being fired for calling something BS that you don’t even have context for?

    Nail down the context first, then call BS.

    However, since there is so much yet to learn in this area, I think it is a bit premature to attack what Gavin is saying: “we can all agree that it remains a tantalisingly relevant episode of Earth history.”.

    What I read in Gavin’s inference is that it is a very interesting event and we can learn a lot from it. You’re inferred reading of his inference in my opinion is readily seen as well… BS.

  26. 126

    Dr. K,

    PV = nRT only gives lower temperature for a gas due to volume if the gas has expanded. The air at upper altitudes has not expanded; it has been at its present “volume” for a long time. The lapse rate with altitude is due to other factors.

    I recommend checking out a book like Houghton’s “The Physics of Atmospheres” (2002). If you don’t like all the math, an explanation of just this phenomenon (why higher altitudes are colder) is found in an appendix to S. George Philander’s “Is the Temperature Rising?” (1998).

  27. 127

    J. Bob writes:

    If it’s so simple, you should be able to explain it, in say 1 or 2 paragraphs, not give a bunch of ref.

    Okay, here it is in two paragraphs.

    The greenhouse effect works like this: sunlight gets through air without much being absorbed, but is absorbed by the ground and heats it. The ground radiates infrared light. Greenhouse gases (GHGs) in the air absorb the IR and this heats the atmosphere. The GHGs in the warmer air radiate infrared, and some of this goes back to the ground, heating it further. You’ve got both sunshine and “atmosphere shine” heating the ground, so a planet with GHGs in its air is warmer than one without.

    Add more GHGs to the air and the ground will get warmer, all else being equal. In the past 150 years, “all else has been equal”–there has been very little variation in sunlight, ENSO, cloud cover, surface albedo, etc., etc. But GHGs have gone way up, and the surface has warmed accordingly. The correlation between NASA GISS temperature anomaly and ln CO2 for 1880-2007 is r = 0.87, which is confirmation of the theory.

  28. 128
    Ellen Thomas says:


    A. Climate change during Cenozoic – the last 65 million years of Earth
    history, i.e. the time after the etxinction of the dinosaurs.

    1. in response to several posts: most paleoceanographers indeed think
    that permanent ice sheets on Antarctica REACHED SEA LEVEL at about
    33.7 Ma (in the earliest Oligocene); e.g. Zachos, J., Pagani, M.,
    Sloan, L., Thomas, E., and Billups, K., 2001, Trends, Rhythms, and
    Aberrations in Global Climate Change 65 Ma to Present. Science, 292:
    686-693. That paper shows development of a significant Arctic ice
    sheet much later, although earlier than 3 Ma ago, i.e. somewhere in
    the late Miocene, about 8-9Ma.
    2. Many scientists would argue that smaller Antarctic ice sheets (and
    present at higher altitudes) developed earlier, with cooling of high
    latitude oceans starting at the end of the early Eocene, i.e. at about
    49 Ma.
    3. Since the publication of Zachos et al 2001 much evidence has been
    published documenting at least possible ice sheet formation on
    Greenland and sea ice in the Arctic somewhere at the same time as on
    Antarctica, i.e., in the middle-late Eocene (45-35 Ma ago). See
    Eldrett, J., Harding, I. C., Wilson, P. A., Butler, E., and Roberts,
    A. P., 2007. Continental ice in Greenland during the Eocene and
    Oligocene. Nature, 446, 176-179, and the special volume of the Journal
    Paleoceanography (vol. 23, 2008; Introduction has doi:
    10.1029/2007PA001516; references in see various references in Thomas,
    E., 2008. Research Focus: Descent into the Icehouse, Geology, 36:
    4. This evidence for global rather than Antarctic cooling reinforces
    the argument that the ice sheet formation at both poles reflects
    falling atmospheric CO2-levels (De Conto, R.M., Pollard, D., 2003:
    Rapid Cenozoic glaciation of Antarctica induced by declining
    atmospheric CO2. Nature, 42,: 245-249; Liu, Z., Pagani, M., Zinniker,
    D., DeConto, R., Huber, M., Brinkhuis, H., Shah, S. R., Lackie, M. R.,
    and Pearson, A., 2009. Global Cooling during the Eocene-Oligocene
    Transition. Science 323, 1187-1190)
    4. There is indeed ample evidence for warm (even very warm Arctic)
    during the PETM; see e.g. Pagani et al., 2006, Arctic hydrology during
    global warming at the Palaeocene/Eocene thermal maximum, Nature 442,
    671-675, and references therein; many papers in the special volume of
    the Journal Paleoceanography mentioned above (vol. 23, 2008;
    Introduction has doi:10.1029/2007PA001516)
    5. Antarctica as a separate continent formed during the split-up of
    the southern continent of Gondwanaland during the Early Cretaceous, so
    any Antarctic climates during the Triassic (much earlier than the
    Cretaceous) can not really be used to arguments on the most recent
    Antarctic ice sheet.
    5. Yes, such a warm world would have a very different ocean, biosphere
    and climate system than what we know today – see for reviews e.g.
    Thomas E., Brinkhuis, H., Huber, M., and Röhl, U., 2006. An ocean view
    of the early Cenozoic Greenhouse World. Oceanography (Special Volume
    on Ocean Drilling), 19: 63-72 or Huber, M., and Thomas, E., 2008.
    Paleoceanography: Greenhouse Climates. Encyclopedia of Ocean Sciences,
    J. H. Steele, S. A. Thorpe and K. K. Turekian, eds. , 2nd edition,
    (Elsevier), p. 4229-4239; doi: 10.1016/B978-012374473-9.00701.3; and
    references therein.

    B. Extinctions during the PETM: in fact, there was NOT a lot of
    extinction during the PETM, even if I have in many instances argued
    for serious extinction. Robert Kunzig said in Discover magazine in
    March 2004: ‘Not much that “WE” care about died then; the most
    prominent victims were deep-ocean microscopic foraminifera that live
    on the sea floor’. Since I have been studying these microscopic
    organisms for many years I do not think that I am included in the ‘we’
    above. However, oceanic surface dwellers did show evolutionary
    turnover and changes in their assemblages but no great extinctions;
    many organisms on land and in the sea show exactly what we expect
    during global warming, i.e. migration from low to higher latitudes.
    Mammals show high rates of evolution, not so much of extinction (see
    review by Gingerich, P. D., 2006, Environment and Evolution through
    the Paleocene-Eocene Thermal Maximum; Trends in Ecology and Evolution,
    21 (5). In my opinion we can still not explain the extinction of deep-
    sea bottom dwelling foraminifera; they live in the largest habitat on
    Earth, and many species are cosmopolitan, so than can easily re-
    migrate in if they go extinct locally. We have no evidence that all
    the world deep oceans became anoxic or highly corrosive to carbonate.
    They did not suffer significant extinction during the mass extinction
    at the end of the Cretaceous. Animals (i.e., metazoan organisms) in
    the same environment did not go extinct to such a large degree (paper
    in press, September volume of the journal Geology, Webb, A. E.,
    Leighton, L. R., Schellenberg, S. A., Landau, E. A., and Thomas, E.,
    2009, in press. Impact of Paleocene-Eocene global warming on
    microbenthic community structure: using rank-abundance curves to
    quantify ecological response. They have short lifespans months to a
    few years at the maximum). So I do think it is important to undertsand
    what happened to them at the PETM: was it the warmth itself and
    changes in metabolic rates and effects on ecosystems? was it
    sensitivity to environmental pCO2 in the oceans, which supposedly is
    higher for unicellular organisms than for animals (e.g., Melzner et
    al., 2009, Physiological basis for high CO2 tolerance in marine
    ectothermic animals: pre-adaptation through lifestyle and ontogeny?
    Biogeosciences Discuss. 6, 4693-4738)?

    Reviews of biotic reactions to the PETM are: Bowen, G. J., Bralower,
    T. J., Dickens, G. R., Delaney, M., Kelly, D. C., Koch, P. L., Kump,
    L. R., Meng, J., Sloan, L. C., Thomas, E., Wing, S. L., Zachos, J. C.,
    2006. Disciplinary and cross-disciplinary study of the Paleocene-
    Eocene Thermal Maximum gives new insight into greenhouse gas-induced
    environmental and biotic change. EOS Transactions AGU, v. 87 (17), p.
    165, 169, and Sluijs, A., Bowen, G. J., Brinkhuis, H., Lourens, L. J.,
    and Thomas, E., 2007. The Palaeocene-Eocene Thermal maximum super
    greenhouse: biotic and geochemical signatures, age models and
    mechanisms of climate change. ‘Deep Time Perspectives on Climate
    Change: Marrying the Signal from Computer Models and Biological
    Proxies’, eds. M. Williams, A. M. Haywood, F. J. Gregory, and D. N.
    Schmidt, The Micropalaeontological Society, Special Publications, The
    Geological Society, London, 323-351

  29. 129
    pete best says:

    Re #128, If we have evidence of ice sheets on Greenland and Antartica as far back as 49 mya then does that mean that we will not threaten them until we reach much higher levels of GHG than we might be thinking now. Those foraminifera appear to be the method that is used to reconstruct past ocean temperatures and indeed indicate when they started to form.

    If summer Arctic sea ice is disappearing but Greenland and WAIS are safe for now although they are losing mass then at what point did the great ice sheets stabalise I wonder in terms of mass balance?

  30. 130
    Hank Roberts says:

    Dr. Thomas, thank you.
    > what happened to them at the PETM
    Your post helps make the puzzle easier to appreciate

    All — That’s a wonderful compilation. Paste those cites given as text directly into Google Scholar, to get links to papers or abstracts.

  31. 131
    J. Bob says:

    #127 Barton, I assume you are using the “homogenized”, or “corrected” temperatures, that seems to change, or “re-homogenized” over time. Have you looked at other sources, closer to the original data, to correlate against CO2? Try correlating CO2 against the 1659-2008 English data or go to:

    and look for long term temperatures without being “homogenized”. Here’s a hint:
    Stockholm-GML 1755-2005
    Stuttgart Ger 1792-2005

    At least the English and Stuttgart data, being in the heart of the early industrial revolution, would show some influence on AGW. The oldest US data
    Mpls-St. Paul USA 1819-2006
    Is fairly flat except for a dip in the 1880’s.

    Use the Rimfrost option to sort on length of data to get the oldest sets of the original data (wo GISS homogenization). It’s not the best, but gives a idea where some of the oldest data is.

    When you start using more of the long term, 150+ years, more original data, then we can talk. Establishing significant correlation C02 and “global temperature” is NOT a simple statistics exercise.

    P.S. Having had graduate & post grad work in radiation heat transfer, as well as working in that area, I’m well aware of the Far to Near IR region of the atmosphere.

  32. 132
    Hank Roberts says:

    Pete Best, you’re asking questions based on assumptions Greenland quit melting? What basis do you have for this belief? Where are you reading it? The IPY news is pretty well covered:

  33. 133
    Hank Roberts says:

    JBob’s having a laff isn’t he?
    First says he can’t be troubled to read even the Start Here link for the basics, then a day later asserts he has gone past a graduate degree in, and now has a job involving, radiation physics.

    Claim authority based on a graduate degree?
    Say where and when obtained and who you are.
    Else nobody can verify that you’re not a dog …

  34. 134
    Adam says:

    Re: post 93

    >Oh, wait — where’d this come from?
    >Adam, what’s your source for saying this?

    >>outgassing from the mantle does not change
    >>the carbon composition of the atmosphere

    Delta-13 C of atmosphere over geologic time (+2 to -7 per mil) is near mantle carbon values(0 to -10 per mil)…Which makes sense since that’s where our atmosphere came from! Massive degassing of primordial carbon would be nearly invisible to the Delta-13 C of our atmosphere. Check any isotope book or carbon cycle paper.

    >Well, where is the missing carbon?
    >Where did it come from, and where did it go?

    The relationship between flood basalts and catastrophe is undeniable (e.g., Siberian Traps, CAMP Volcanism and for the PETM, North Atlantic Igenous Province). The paper we are discussing in this post suggests that methane release may not explain the extreme warming or ~2km rise in CCD. Therefore, missing carbon, not missing feedbacks, can explain this discprepency…see post 92

  35. 135
    Hank Roberts says:

    PS for Pete, did you read to the end of the Newsweek piece?
    It’s being quoted quite a bit. Google as of today:

    Results … about 428 for “A consensus has developed during IPY that the Greenland ice sheet will disappear”

  36. 136
    Hank Roberts says:

    Adam, what would have happened to the carbon you’re talking about? Is there a spike in accumulation of some carbon-containing material (sedimentary rock, presumably?) associated with the end of the PETM? I haven’t found mention of such, and as I read the original post, that’s part of the puzzle — if there were such a spike in carbon what became of it, how did it leave the atmosphere, where did it move to?

  37. 137
    Paul K in Seattle says:

    Re: Two paragraphs… I wrote the following textual passage to explain and discuss measured data supporting global heating by GHGs to friends who may not be knowledgeable or patient enough to understand more complicated descriptions. The passage reads better broken into smaller paragraphs, but it still is fairly short. If anyone could suggest some editing to improve it, thanks in advance.

    Lets discuss the key data supporting global warming… the effect can be summarized fairly briefly:

    First look at the heat balance on Earth:
    1. Energy from the sun strikes the Earth, and some of the energy is absorbed in the atmosphere and at the surface.
    2. The only way that energy can leave the Earth is as long wave radiation (similar to the infrared radiation a human emits, that can be seen in IR detectors, such as those used by the military). This is because the Earth is surrounded by the vacuum of space, which prevents heat loss except by LW radiation.
    3. LW radiation increases as the temperature of the upper troposphere increases, and decreases as the temperature drops. LW radiation from lower levels of the atmosphere are mostly absorbed, then re-radiated. In the upper troposphere, and in the even higher stratosphere, most of the outward LW radiation escapes into space.
    4. If the energy coming in from the sun is higher than the LW radiation emitted outward, the Earth gets hotter. And the heat must build up somewhere. The bulk of the excess heat will end up in the oceans, with lesser amounts melting icecaps and glaciers, and even lesser amounts heating up the air and water vapor in the atmosphere, thus raising global temperatures.

    Now lets look at the data; satellite measurements show that the temperatures of the upper troposphere and stratosphere are cooling globally, so the net LW radiation going out is dropping. This is incontrovertible… a lower temperature in the atmosphere at that level must result in less outgoing LW radiation and hence less heat loss.

    So where is the heat building up? In the oceans! Sea levels have been steadily rising, and although a portion of sea level increase is due to the melting of ice sheets, the bulk is due to thermal expansion of sea water. This is also incontrovertible… rising sea levels clearly show increased heating of our planet.

    In addition, NASA’s GRACE satellite project (which uses changes in measured gravitational pull) clearly show that the ice sheets in Greenland and Antarctic are losing ice mass. Furthermore,the long term global temperature record for the planet surface shows that the ten hottest years have been in the period from 1998 until 2008. So all three major components of our planet are showing heat buildup; the lower atmosphere and surface is heating, the ice sheets are absorbing more heat, and most importantly, the oceans are heating.

    Meanwhile, other possible sources of heat, such as total solar irradiance (TSI) remain remarkably constant. Although there is an eleven year cycle in TSI, the net energy from changes in solar are almost insignificant in explaining the heat buldup on Earth. A major volcanic eruption can slow down the heating for several years, but the planet has heated over time in spite of the cooling effect of these eruptions.

    Notice, all this data clearly shows global heating. These key datasets showing global warming are actual measured data, and don’t rely on the complex computer models attempting to analyze the impacts of increased GHGs on the planet. The facts point overwhelmingly to global warming, and the heat buildup will impact and severely change our planet’s existing biosphere.

  38. 138
    Hank Roberts says:

    One for Gavin —

    noticing “Earth Systems” turn up here
    via a link I followed from the International Polar Year page; does what they’re doing have any relation to the Earth System Sensitivity term you talked about in the original post?

    The page includes links for

    “Earth system research online consultation … deadline … extended to 1 September.”
    “World Climate Conference-3 (WCC-3) … in Geneva, Switzerland, 31 August – 4 September. WCC-3, co-sponsored by ICSU, will identify the essential elements of a global framework for meeting the future climate information needs of the United Nations …”

  39. 139
    Hank Roberts says:

    Adam, I’m working on this but not clear why a large volcanic CO2 spike wouldn’t show up. Is this the sort of discussion and analysis you’re talking about when you say there’s no difference expected?
    Interpreting carbon-isotope excursions: carbonates and organic matter
    Lee R. Kump* and Michael A. Arthur

    “… . The counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in δ13Corg. In addition, we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50% increase in volcanic CO2 outgassing ….”

    Cited By in Scopus (164)

  40. 140
    J. Bob says:

    #133 Hank – If it’s so easy, how about your 1-2 paragraph proof of CO2 warming? One shouldn’t need a link to more links.

  41. 141
    Hank Roberts says:

    You’re now chasing your own imagination, J.Bob, and deluding yourself I offered you the impossible you dream of.

    Mathematics has proofs.

    “For the physics with equations there is no shortcut: you must study the full, complex story as described in textbooks for science students.”

    Anyone who claims a graduate degree and a job in radiation physics but still imagines a 2-page proof in words is badly wrong about something. Try to track your the error.

  42. 142
    Hank Roberts says:

    Oh, and the updated version:

    “… it would do little good to present a copy of the Manabe-Wetherald paper to a technically trained person who demands proof that global warming is a problem. The paper gives only a sketch of complex and lengthy computations that take place, so to speak, offstage….”

    “I’m not saying we don’t understand the greenhouse effect. We understand the basic physics just fine, and can explain it in a minute to a curious non-scientist. (Like this: greenhouse gases let sunlight through to the Earth’s surface, which gets warm; the surface sends infrared radiation back up, which is absorbed by the gases at various levels and warms up the air; the air radiates some of this energy back to the surface, keeping it warmer than it would be without the gases.) For a scientist, you can give a technical explanation in a few paragraphs. But if you want to get reliable numbers—if you want to know whether raising the level of greenhouse gases will bring a trivial warming or a catastrophe—you have to figure in humidity, convection, aerosol pollution, and a pile of other features of the climate system, all fitted together in lengthy computer runs.”

  43. 143
    Jerry Dickens says:

    No clue what to call this bizarre saga of science and media — it’s a first for me.

    Gavin and I have had a few emails over the last few weeks, and he kindly told me ahead of time about the idea of posting a “PETM weirdness” article on RealClimate. Of course, we have had a few interesting back and forth discussions. So, with Gavin’s blessing, I post parts of these (with some editorial modifications).

    Well, first off, there was no deliberate attempt on my part to hype the story. A press guy at Rice contacted me about the paper (after seeing a release by Nature). After about 45 minutes of chatting and all, he asked me for a basic summary of why the paper is interesting, whereby I gave the quote: *In a nutshell, there appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.* Okay, think here — I’m an oceanographer not a politician nor a movie star — I had no idea that the story and the quote would take off through the media like a rocket. So, yes, in retrospect, I agree the quote might have been cut, reworded, stressed differently, etc., given its over-saturation and public consumption. (Though please note the crucial word *appears*, and thankfully this came through in most references to the quote). I disagree with Gavin, though, that the title of the paper should be worded differently – this hits right at the main message (more below).

    There have been two diametrically opposed responses, which I find fascinating.

    One response, with hindsight, was fairly obvious. Skeptics of global climate took the quote as true but completely out of context. This led to suggestions that climate models are intrinsically wrong, that future global warming is unlikely, and other such commentary. This response is probably not worth dwelling upon at RealClimate; as pointed out by the Washington Post and several blogs above, neither the original article nor the press release lead to such inferences. In fact, as correctly noted by the Washington Post, one might take from the original paper or the press release that, if anything, climate sensitivity as often modeled is too low for a given carbon input.

    The other response was somewhat surprising. Several of my colleagues from the climate modeling community reacted as if the statement was entirely false (i.e., Jerry – how could you possibly have said that ….)

    For a truly meaningful discussion, we probably need to qualify the quote with some definitions, in particular like what does *fundamentally wrong* mean. (This is where, I think, Gavin and I both agree and disagree). In any case, and to bypass the semantics for now, to date:

    1/ No climate model has been able to explain temperature distributions, especially at
    high-latitudes, during past *Greenhouse intervals* (e.g., the early Paleogene – nominally 60 to 48 million years ago). We can argue ad infinitum about the merits and demerits of individual proxies for past temperature, but the sum total of evidence for extreme high latitude warmth during past time intervals is overwhelming and unexplained. My favorite example, because it’s across the street where I can show kindergarten kids, is the beautiful early Eocene fossil palm frond from Wyoming at the Houston Museum of Natural Science. Does a current model exist which can explain early Paleogene temperatures – well maybe – but this has not been demonstrated.

    2/ No sophisticated model has been able to adequately explain changes in late Quaternary climate (or other intervals) with CO2 as an internal parameter (i.e., as a coupled feedback that responds to external forcing). Instead, CO2 (and usually methane) are prescribed as external parameters.

    3/ Our interpretations for the PETM (aka the Nature Geoscience article), assuming they are correct, suggest another problem. This is one regarding sensitivity to carbon input. Specifically, that the sensitivity is too low.

    [Here, it is worth responding to Gavin’s blog on two issues. If CO2 was much lower than 1000 ppmv in the early Paleogene (which is inconsistent with most proxy data, especially and interestingly the presence of the mineral nacohlite in lake deposits), then the temperature discrepancies between models and data pointed (item 1) are worse than suggested. If elevated atmospheric methane is the correct answer for enhanced sensitivity (which is inconsistent with the extended >30,000 yr of warmth following the carbon injection at the start of the PETM), where is this source or feedback of methane in climate models?]

    These are, in my opinion as a scientist, pretty fundamental problems with current climate models. Does this mean that the models are wrong or that the idea of AGW is incorrect – absolutely not. But, the *paleo-evidence* definitely suggests that some component linking atmospheric carbon and global temperature is missing, at least on the 1000 year time-scale. I (and other colleagues) strongly suspect there is a major positive feedback involving methane, the terrestrial biosphere, or both. Does the unknown *it* need to be included the short term predictions for global climate … well that’s an interesting question indeed!

    I guess the one bright side to the PETM weirdness saga is that probably thousands of new people now know about this truly amazing event in Earth’s history. Ellen’s references are great ones for reading. If anyone is really interested, I also attempted to write a short article for the public earlier this year at:


  44. 144
    J. Bob says:

    #137 Paul, there has been a gradual rise (trend line) in temperature, according to the East English data, since 1659. So how is that related to man or CO2? The earth has probably been warming since the last glacial period. Again, looking at long term temperatures (~200 years, what correlation to C02 can you show?

  45. 145
    Adam says:

    Re post 92,93,139…


    Perhaps I shouldn’t have suggested any ‘carbon cycle paper’…In the paper you cite, he actually relates global temperature to photosynthetic fractionation, which is interesting, but confuses my point that volcanic degassing would go unnoticed in the atmos. delta-13 C. Kump often uses functions relating global temperature to something, for example,increased organic matter burial. Burial of very light carbon (delta-13 C -25 per mil), would cause the atmos. delta-13 C to be strongly positive. Therefore, you can see how a Kump model of volcanic degassing of CO2 (again, delta-13 C of ~-5 per mil) would have purely indirect effects on delta-13 C of atmos.

    If you look closely in the paper you cite, it should say that volcanic CO2 is ~-5 per mil. In Payne and Kump, 2007,

    “To investigate the potential effects of these eruptions, we modeled the
    release of 3×1018 mol of volcanogenic CO2 (δ13C=−5%) over periods of 100, 300, and 600 ky.”

    Now, volcanic degassing would have gone unnoticed to atmos. delta-13 C, but wouldn’t have gone unnoticed to the CCD…which rose more than can be explained by estimates of methane release during PETM…hence, volcanoes.

  46. 146
    Hank Roberts says:

    > probably been warming since the last glacial

    Way, way off topic. I sure wish you guys who want to prevent the discussion of the PETM would get a blog somewhere else. But as long as you’re here:

    Says who? Why do you think so? Got a source? Got any logic or facts?

    It’s sort of true, not quite the way you spin it.

    And that’s odd, because the normal pattern is that the planet would have been cooling — as it did after each previous interglacial peak. You can look it up.

    For any youngster who needs the help, here it is.
    Note today is at the left side of the timeline:

    This last interglacial peak was different — the cooling barely began and then — agriculture and the human activity began, this last time around.

  47. 147
  48. 148
    dhogaza says:

    Jerry Dickens, thanks for posting.

    I have to wonder, though, how can models be “fundamentally wrong” if, as you say here:

    Does this mean that the models are wrong or that the idea of AGW is incorrect – absolutely not.

    They’re not wrong?

    I think “fundamental problems”, which you also say, is a better phrasing, though still subject to deliberate misrepresentation (lies) from denialists.

    But even better would be to state that the models “are imperfect”, or something else milder.

    Because the denialsphere can be *guaranteed* to pick up on the word “fundamental”, and then to scream repeatedly that you’re saying “CO2 does not cause warming”.

    It’s a shame that as a scientist you have to be the least bit concerned about political operatives intentionally lying about your work by quote mining or otherwise misrepresenting things you’ve said in all innocence and honesty.

    But, I’m sorry, you’ve got to worry about it. These people can be relied upon to ignore what a paper actually concludes and to twist your words to say the opposite if you give them the least opportunity.

    You’ve got to be on your toes, I’m afraid, and actively guard against dishonest misrepresentations of your work and words if you want to avoid a repeat experience.

  49. 149
    Hank Roberts says:

    Dr. Dickens’s post slipped in as I was writing.
    THANK YOU, and thank you for commenting on Dr. Thomas’s references and adding your article, and — please — more from you all who are actually doing the science.

    Dr. Thomas gave us one such – the personal really helps:

    “the most prominent victims were deep-ocean microscopic foraminifera that live on the sea floor’ …. I have been studying these microscopic organisms for many years …”

    How does an event like this do the most harm to the best protected organisms? Something odd fell through the depth of the ocean and landed on them?? (grin) Maybe a toxic bloom… argh. I’ll quit speculating. But … more please.

    Mention the obvious that interests you. What was alive on Earth where (or, where should we ordinary readers look to all get on the same page about what we should know to be able to follow your conversations).

  50. 150
    tamino says:

    Re: #144 (J. Bob)

    Your characterization of central England temperature is both wrong and misleading.