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‘The Discovery of Global Warming’ update

Filed under: — group @ 14 July 2006

If you haven’t already seen the American Institute of Physics website by Spencer Weart on the ‘The Discovery of Global Warming’, we heartily recommend it. It provides both a summary of science, and more importantly, a history of how an obscure speculation from over one hundred years ago has become the scientific consensus of today. It has recently been updated with many more references from 1873 to the present, and so is even more worth reading. Spencer is very keen on getting feedback on the project, so don’t hesitate to let him know what you think.

78 Responses to “‘The Discovery of Global Warming’ update”

  1. 1
    Peter Larkin says:

    Great link, which is sort of deep in the AIP website. Would not have found it otherwise, thanks for that!

  2. 2
    Stephan Harrison says:

    I know it’s off-topic, but what are RC’s views on the newly-published Wegman, Scott and Said report (highlighted on Climate Audit, not surprisingly)?

    [Response: This is probably an unavoidable off-topic, so I’ll paste in the text of Mann’s released comment on the issue, but I’m actually pretty bored of this subject by now, and I think most everyone else is too. – gavin]

    The un-peer reviewed report commissioned by Rep. Barton released today adds nothing new to the scientific discourse on climate change and is a poor attempt to further personalize and politicize what should be a matter of scientific debate not politics.

    The impartial and independent National Academy of Sciences convened a panel of experts in climate science and statistics and performed a far more extensive review of the science, confirming the key conclusions of our earlier work, as well as numerous more recent supporting studies. Namely that late 20th century warmth is likely anomalous in the context of the past 1000 years and cannot be explained by natural variability. The scientific evidence for human influence on current climate comes from a large body of independent lines of evidence of which paleoclimate data is but a small part.

    Barton’s report, written by statisticians with no apparent background at all in the relevant areas, simply uncritically parrots claims by two Canadians (an economist and an oil industry consultant) that have already been refuted by several papers in the peer-reviewed literature inexplicably neglected by Barton’s “panel”. These claims were specifically dismissed by the National Academy in their report just weeks ago. Barton’s report also reveals that his panel collaborated closely with the two Canadians, yet made no attempt to contact me or my collaborators at any point.

    The panel makes the odd claim that there is “too much reliance on peer-review” which goes against every principle of current scientific practice. Barton in his ‘factsheet’ goes further and suggests that the anonymous peer reviewers themselves are in some way biased, a claim that he cannot possibly support since peer reviewers are in fact anonymous and this was not studied in the report.

    Climate science, like many multidisciplinary fields, requires broad collaboration with researchers across many areas. Any well published scientist would show a wide-ranging pattern of connection with other researchers in the field. While I am flattered that the committee seems to think that I am at the center of the field, the same analysis would have shown a very similar pattern for any researcher engaged in widespread interdisciplinary research.

    My colleagues and I continue to work on reducing the uncertainties in past climate reconstructions and understanding the mechanisms of past and current climate change. Policy-makers should more constructively focus their attention on the consensus findings on climate change as presented by the Intergovernmental Panel on Climate Change (IPCC) and the National Academies of all G8 countries, rather than on pursuing politically-motivated attacks against individual scientists.

  3. 3
    Steve Holmes says:

    Best advice is: when you’re in hole, stop digging.

  4. 4
    lars says:

    Are we giving up on orbital variations then? Is CO2 the main culprit as this appears to say? Then what has caused these many cyclical and periodic rizes and declines in CO2 gas then? Are there any answers put forward? Not just the current one but the past dozens of cycles.

    Among these feedbacks, the most obvious and momentous was the close connection between global temperature and greenhouse gas levels through the ice age cycles. Relatively straightforward analysis of the data showed that a doubled level of CO2 had always gone along with a rise of a few degrees in global temperature. It was a striking verification, with entirely independent methods and data, of what computer models had been predicting for the planetâ??s greenhouse future

  5. 5
    Roger Smith says:

    Lars, did you fully read that section of the book? Nobody’s giving up on orbital changes which may have led to increases in CO2 in the past.

    Why do you assume that the causes of the present warming and previous warmings are identical when humans have only been burning massive amounts of fossil fuels for the last century and a bit?

  6. 6
    John A says:

    With reference to Dr Mann’s dismissive reply to a careful report composed of real statisticians (of which he is not one, having said so to the NAS Panel), I’ll bring up just one misrepresentation out of the many: What Wegman et al actually said was

    “In this case we judge that there was too much reliance on peer review, which was not necessarily independent

    So far from complaining about too much reliance on peer review, Wegman was pointing out that the peer review was done between a small coterie of the author’s friends who had also staked their scientific reputations on similar results in studies that had lots of the same non-independent proxies.

    [Response: Hmmm… So Wegman had access to all the peer reviews and who did them for all of the relevant studies then did he? I don’t think so. He just looked at co-authorship – which is not the same thing at all. Statements about who the peer reviewers were are just speculative with no actual facts to back them up. – gavin]

  7. 7
    Hank Roberts says:

    Lars, did you happen to read these pages?
    Try the button on Weart’s main page labeled “Search”

    I used that Search for words from your question; try searching, you ought to be led among others to these:

  8. 8
    John A says:

    So Gavin, are you confirming that neither you, nor the 41 others mentioned in the “mutual admiration society” mentioned by Wegman performed peer review on each others key studies that backed AGW?

    [Response: What is your point? First, how can I (or Wegman) possibly know who any paper’s anonymous reviewers are if I didn’t review it? Second, what part of ‘anonymous’ don’t you understand? and finally, where can I join this ‘mutual admiration society’? Wegman doesn’t mention it all, and certainly doesn’t give a contact number…- gavin]

  9. 9
    Hank Roberts says:

    Why are people not just naive, but badly mistaken about how science is done?

    Because much about global warming is being written by PR firms. This PR expert got sick of it:

    “… it is infuriating – as a public relations professional – to watch my colleagues use their skills, their training and their considerable intellect to poison the international debate on climate change.

    “… On one hand, you have the report of the Intergovernmental Panel on Climate Change, the largest and most rigorously peer-reviewed scientific consensus in history….

    “On the other hand, you have an ongoing public debate – not about how to respond, but about whether we should bother, about whether climate change is even a scientific certainty.

    “Few PR offences have been so obvious, so successful and so despicable as the attack on the scientific certainty of climate change.

    “This is a triumph of disinformation.”

  10. 10
    Rhett says:

    What will your response be? The statement by Mann doesn’t address any of the issues raised in the Wegman Report. Unfortunately the battle has now moved to the statisticians’ turf and you guys are going to have to fight on their terms. Are your methods valid? If they aren’t, we have big problems.

    [Response: I don’t see how the ‘battle’ has moved at all. There is nothing original in the Wegman report except the neat, but basically meangingless, social network stuff (I’m in a clique!), and so the scientific discussion hasn’t moved on one iota. In particular, Wegman completely fails to address the issue of whether any of these critiques ‘matter’ – which was the point of the earliest responses on this topic, here or in Rutherford et al, 2005, Wahl and Ammann (2006), or the NAS report etc. The answer was, and remains, no they don’t. They could have, but they didn’t. Them’s the breaks….- gavin]

  11. 11
    Mark A. York says:

    As if top climate scientists aren’t trained in statistics as much as a couple of “social scientists.” What a foolish assertion on its face.

  12. 12
    Armand MacMurray says:

    Re: response to #10
    Gavin, you say “There is nothing original in the Wegman report except the neat, but basically meangingless, social network stuff… ”

    Isn’t the important issue whether the report is *correct*, not whether or not it is “original”?

    [Response: If there is nothing new, how can it take the debate forward? If Wegman, ‘with [McIntyre’s] assistance’, can get McIntyre’s code to work, but doesn’t then bother to see what difference it makes to the final reconstruction (which we know is tiny – Wahl and Ammann (2006)), what has been added? – gavin]

  13. 13
    Rhett says:


    I’ve read the Wegman report. The social network stuff is padding.

    I’m printing out the “Dummies Guide” now to see if it addresses the issues that Wegman raised.

    It will be vacation reading along with the Wegman report.

    I’ll get back to you in about ten days.

    Thank you for your patience.


  14. 14
    Hank Roberts says:

    They’re trying to attack that work the way the creationists attack “Darwinism” — the fundie notion that if you can dethrone the Founding Father you devalue all that follows.

    They’re treating early scientific work as though it were a foundation document on which everything that follows has to be based.

    Reading Spencer Weart’s history should disabuse the ‘skeptics’ of the notion — would y’all please read the first link, and come talk about the origins of the study of global warming?

    In science early work gets attention into an area — but what people do when they study science in the area depends scarcely at all on the original work having been precise or even properly interpreted. It’s the next work and the work after that that matter.

    Each new study looks at the underlying natural world and corrects what came earlier.

    There’s no founding father here to overthrow.

    Look up “Darwinist” to see the foolishness that comes from thinking that attacking early work is a sane way to evaluate later work, eh?

  15. 15
    Dano says:

    RE 9 (Roberts):

    Hank, here is a film clip of Luntz repudiating his prior stance on his AGW campaign.

    Hopefully back OT, the AIP website is indeed a treasure and IMHO there should be a link on the homepage or FAQ or somewhere like that.



  16. 16
    Hank Roberts says:

    Long term time series measurements like this one deserve a place in the AIP document (if you have them, I didn’t find them searching).

    “Smoothed monthly mean temperatures for the 3 deepest standard depths (1200m, 1500m, 2000m) are shown in Figure 4 for the period 1948-1995. Notice that a recent warming has occurred, starting at 2000m in 1985, then gradually penetrating upwards through 1500m in 1987 and reaching the 1200m level in 1990. The temperature increase is about 0.07°C, and nearly constant with depth.”

    The main page is:

    It begins:
    “Having performed daily oceanographic measurements in the deep Norwegian Sea since 1 October 1948, Ocean Weather Ship Station (OWS) Mike, at 66N,02E, can present the longest existing homogeneous time series from the deep ocean. …”

    Note this is not a statistical model; this is temperature.

  17. 17
    jayster says:

    I have already know that the reason why china is poor in the science field.
    In china,there are few of science blogs,few of science magzines and few of science chairs.Our science education is not universal.
    we can’t combine the science research with the common people.
    your country,has done very well.

  18. 18
    Mark Shapiro says:

    The social network analysis section of the WSS report is absolutely fascinating.

    I would love to see such an analysis for a typical congressman, for example, Barton.

  19. 19
    Steve Bloom says:

    Re #10 response: Gavin, you forgot to mention the other sort-of original part of the Wegman recommendations, which is to employ a lot more statisticians in climate science research.

    [Response:I have yet to see any evidence for the implicit assertion that statistitians bring forth the true answers whereas other scientists don’t. My guess is that there are clever statisticians as well as poor statisticians – probably as in other disciplines. There are as far as I know a number of statisticians involved in climate research already, and they bring in benefitial new aspects to the analysis, but physicists are just as important (if not more) for advancing the climate science. I sounds as if Wegman has some naive idea are some kind of magicians who can bring out the right numbers (?). -rasmus]

  20. 20

    It’s possible I’ve missed it — in which case please ignore this comment — but I don’t see a reference to “the other CO2 problem”, ocean acidification, in Spencer Weart’s very useful study. If there is none, then I suggest you consider including one in a future revision. Further references can be found in the wikipedia entry – including to The Royal Society report last summer, and the NSF NOAA USGS workshop report by J A Kleypas et al published at the beginning of this month.

  21. 21
    Terry says:


    “[Response: If there is nothing new, how can it take the debate forward? If Wegman, ‘with [McIntyre’s] assistance’, can get McIntyre’s code to work, but doesn’t then bother to see what difference it makes to the final reconstruction (which we know is tiny – Wahl and Ammann (2006)), what has been added? – gavin]”

    The Wegman Report (page 49) says:

    “As mentioned earlier in our background section, tree ring proxies are typically calibrated to remove low frequency variations. The cycle of Medieval Warm Period and Little Ice Age that was widely recognized in 1990 has disappeared from the MBH98/99 analyses, thus making possible the hottest decade/hottest year claim. However, the methodology of MBH98/99 suppresses this low frequency information. The paucity of data in the more remote past makes the hottest-in-a-millenium claims essentially unverifiable.”

    On page 14, the Report elaborates on this point:

    “Wider rings are frequently produced during the early life of a tree. Thus the tree rings frequently contain a low frequency signal that is unrelated to climate or, at least, confounded with climatic effects such as temparature. In order to use tree rings as a temperature signal successfully, this low frequency component must be removed. … Because the early history of tree rings confounds climatic signal with low frequency specimen specific signal, tree rings are not usually effective for accurately determining low frequecny, longer-term effect. … Thus tree ring proxy data alone is not sufficient to determine past climate variables.”

    This sounds like an important issue. Did Wahl and Ammann (2006) address this issue? Has anyone?


    [Response: Yes. The whole point of Esper et al was to demonstrate that tree ring composites can have low frequency variability. The whole point of the MBH approach was to use multiple proxies that would bring together information from different archives and hopefully compensate for the different weakness in each separate archive. However, the first paragraph you quote is very poor in its understanding – the IPCC 1990 graphic was a schematic, not a reconstruction, and the understanding that the medieval climate anomaly was not as coherent in time or space than the 20th Century change had begun well before MBH – and was most recently demonstrated in D’Arrigo et al and Osborne and Briffa. – gavin]

  22. 22

    Re #17,


    How do you explain the cooling trend 1955/1960 until 1985/1990(!) in the deeper North Atlantic (or worldwide in all oceans down to 700 m for 1980-1990 according to fig. 1 in Levitus e.a.) in a world with increasing GHGs and stabilising aerosols (SO2 emissions are stable since 1975, be it with a huge shift from North America and Europe to SE Asia). IMHO there is something like natural variability at work (changes in cloud cover – not directly linked to any forcing – come into mind)…

  23. 23
    Leonard Evens says:

    To compound the paranoia, I wonder if it would be fruitful to do a cohort analysis of the people who keep harping on Mann, et. al.

    I am sure lots can be said about the details of climate reconstruction for the past millenium or two. And any statistician who is willing to learn enough about climate science to contribute should try his or her hand by the usual methods, submitting work to established scientific journals. I think it is clear that scientists sometimes get the statistics wrong, but it is also true that statisticians sometimes get the science wrong and misinterpret what they think the statistics are saying. But I find it very hard to believe that the NAS is unreliable in such matters. While not accepting everything that Mann, et. al. concluded, the NAS committee did accept their main conclusions and also pointed out that these conclusions have been confirmed by multiple other studies. They are also consistent with other independent threads of evidence.

    Conservatives, in particular, who often object to sociallly constructed definitions of truth, should be wary of those who think they can and should skew the debate by choosing their authorities with a desired end in mind.

    I haven’t yet read everything in Spencer Weart’s compendium, but the history makes clear how science in an area like climatology progresses. It is a long complex process with many false starts, but at a certain point, a general consensus on certain basics becomes established. Later, details of this consensus may be modified, but the basic conclusions remain the same. I think the preponderance of evidence shows that the late 20th century warming is unprecedented and human contribution through greenhouse gas emissions is a primary cause. If you set the entire American Statitistical Association to work on the subject, you wouldn’t change that.

  24. 24

    I am quite reluctant to weigh in into the HS debate, as I am interested in the science, not the politics around it (I was heavily involved in politics, and had my fair share of beaten by police sticks, water guns and tear gas, but that is not relevant here).

    I must admit that I was shocked the first time that I saw the HS, as that was against all knowledge that I had about a MWP and a LIA at that time. Of course, if there is new scientific evidence, that should be used, but there was little explanation about what that evidence might have been. So I was quite skeptic about the HS from the first moment on (not about (A)GW, be it that the (A) IMHO has less influence than said in many horror stories). Thus that makes that I have some bias against HS curves…

    After the NAS report and now the Wegman report, it is clear that neither the choice of some tree series, nor the statistical methods used in MBH98/99 were appropriate. That has nothing to do with personal attacks, but with using only proxies which show a real correlation with temperature and using the right statistical methods.

    Are the more recent reconstructions (using RegEM) better? I don’t know, but I like to see the comments by a statistician outside the field to give his/hers opinion. Anyway, many of the more recent reconstructions still use the tree series, in one form or another, which are rejected by the NAS panel.

    Is this all relevant? Yes and no. It is not relevant for the reality of (A)GW. But it is highly relevant for knowing how large natural variability in the pre-industrial past was, as that gives a clue to what the future may bring. Past variability makes the difference between a disaster (if MBH98/99 was right) and a benign warming (if Moberg is right. Although Moberg also used the tree series in question, his method downplayed their influence).

    So let the climate community admit that the HS has problems, that the recent reconstructions are not much better, and move on to look for better methods and better proxies to find out what really happened in the past thousand(s) years…

  25. 25
    Tom Fiddaman says:

    Re 18,22 etc. (social networks)

    You can do your own analysis using Touchgraph Googlebrowser. I posted some static analyses here a while back.

  26. 26
    Hank Roberts says:

    Ha! New Hope (whois still shows their old name and owner) now also shows up in the Internet FAQ on the very short list of Internet “Weather Services” providers.

    Now this exemplifies a lobbying firm at its best, eh? — the Western Coal Association’s advocacy PR firm listed in the Internet FAQ along with NOAA, and wunderground as a reliable source for weather-related information.

    Here’s the entire category – Weather Services:

    telnet 3000 or [Freese-Notis Weather Page] offers: InterRAD/RainRAD + Commodities trade reports with weather [Storm Prediciton] [WWW Weather Map] [WeatherNet] [World Climate Report] < =======(!) [Weather Underground, Inc] offers: Live access to climate data >(Note this FAQ does include ‘WWW weather’ as weather, and misspell ‘prediction’ — so as usual with the Internet, not all’s clear.

  27. 27
    Hank Roberts says:

    >17, 21
    You ask how I explain the results in Levitus et al. Why ask me? Their conclusions appear at the end of the paper you link to.

    “In terms of the causes of the increase in ocean heat content we believe that the long-term trend as seen in these records is due to the increase of greenhouse gases in the Earthâ��s atmosphere [Levitus et al., 2001]. In fact, estimates of the net radiative forcing of the Earth system [Hansen et al., 1997] suggest the possibility that we may be underestimating ocean warming. This is possible since we do not have complete data coverage for the world ocean. However, the large decrease in ocean heat content starting around 1980 suggests that internal variability of the Earth system significantly affects Earthâ��s heat balance on decadal time-scales.”

  28. 28
    Steve Bloom says:

    Re #21: Broadly speaking, why would one expect ocean warming to be even? That it is uneven is no surprise since warming occurs near the surface and ocean water is moved around via currents that are themselves uneven. Regarding the North Atlantic, why wouldn’t we expect the relatively slow movement of the deeper currents to result in a significant lag between surface warming (or the relative lack thereof due to aerosols) and warming at depth? Your cloud ideas remain highly speculative.

  29. 29
    John Althauser says:

    Spencer –
    I read and enjoyed your book as the first in a series of personal updates on AGw. I also visit the AIP site on occasion. Thanks for the continuing effort. The search feature is very useful, as here. I notice there is a category called ‘events since 1998’ on the menu. Is there also one summarizing major findings or papers since the book’s publication?
    John Althauser
    Urbana, IL

  30. 30
    Steve Bloom says:

    Re my #28: The reference was to what is now #22 (FE). Speaking of clouds, it appears that a major part of the prior uncertainty (is that what you mean by “natural variability”?) has now been resolved: .

    Re #24 (FE): “Past variability makes the difference between a disaster (if MBH98/99 was right) and a benign warming (if Moberg is right. Although Moberg also used the tree series in question, his method downplayed their influence).” Ferdinand, you know that this is wrong and why it’s wrong. It’s become an article of faith among denialists because without it they are left with nothing to argue from. If you want to prove it’s right, point me to where differences in paleo reconstructions have been used to adjust climate sensitivity. (As an aside, there’s nothing in MBH 98/99 that implies a “disaster,” whatever that means.)

  31. 31

    Re #27, 28

    Hank, while the overall heating of the oceans in the full period 1955-2000 is reproduced by climate models, any cyclic (internal, natural) variation in the order of 10-100 years is significantly not captured by the models. Thus the fast increase in ocean heat content 1990-2000 is likely a composite of forced warming and natural variability. Which leads to the question of what is the weigth of the different forcings and natural variability…

    Steve, the Levitus figures give a cooling in the period 1980-1990 for all oceans (except the Indian) for both hemispheres, and globally for a depth until 700 m. The figures that Hank quoted are from a particular (deeper) part of the North Atlantic, but fit in the general trends. But both show huge variations around an upgoing trend.

    That changes in cloud cover may have something to do with this can be read in the works of Wielicki and Chen, and further by Pinker e.a.. The change in insolation in the tropics (~ 3 W/m2, caused by a reduction of low cloud cover) over the past 15 years is an order of magnitude larger than calculated from the increase in GHGs…

  32. 32
    Roger Smith says:

    The ExxonSecrets website has some mapping of organizations and individuals funded by Exxon to work on global warming.

  33. 33
    Eli Rabett says:

    a. The whole networking thing is a strange. Said )the third author( was a PhD student of Wegman, Scott and Wegman serve on all sorts of committees together. George Mason is a hotbed of right wing think tankers. usw

    b. The basis of ocean acidification can be found at

  34. 34
    Stephen Berg says:

    Spencer, I’ve only taken a brief look at the site but I think you have done a great job! Keep up the good work and I hope to have a detailed read of it in the next month or so.

  35. 35
    Lloyd Flack says:

    I’ve looked at the Wegman report. I have not gone over it in detail. These are my impressions from a brief reading.

    I am a statistician who has mostly worked on environmental problems. I also have a biological background. I have mostly worked on ecological, physiological, hydrological, chemical and sedimentological data.

    Briefly I agree with most of their criticism of the paleoclimate reconstructions. I have not looked at their social network analysis in sufficient detail to make an informed comment. They seem to have misunderstood the attribution of recent warming to greenhouse gas forcing.

    Wegman et al. claim that the principal component analysis was incorrectly centered and that this could create a hockey stick even if there wasn’t one there. On the data that they have presented I would have to agree with them. I think they are also right when they suggest that different types of time series models be tried.

    They seem to be under the impression that Mann et al. are claiming that because both temperature and CO2 are increasing that there is a causal relationship. This looks like a misunderstanding to me. As I understand it the attribution of recent temperature increases to greenhouse gas forcing depends on three main arguments.

    The first is the claim that the warming over the past century is far faster than any warming period on record thus implying that a different mechanism is involved.

    The second is is the claim that the pattern of temperature changes over the past century can be replicated by models including greenhouse gas forcing but not otherwise.

    The third is the claim that the pattern of changes is what would have been expected from greenhouse gas forcing not that which would have been expected from other causes.

    The hockey stick supported the first argument. However this was always the least important argument. As has been pointed out before on this blog it doesn’t matter what the cause of previous warmings was. It just matters what the cause of the current one is.

    The hockey stick is irrelevant to the second and third arguments. The third one about the pattern of changes always seemed to me to be the strongest one.

    What follows are some of my observations on why people are talking past each other. As I understand it the general circulation models are deterministic. People in climate modeling develop a lot of expertise in creating deterministic models but not necessarily enough in creating stochastic models. There seems to be a shortage of people who have both a good feel for climatic processes and a good feel for random processes. The way into climate modeling may discourage people from developing both. And both are needed in paleoclimate reconstructions.

    There is a quotation by George Box that is well known among statisticians. “All models are wrong. Some models are useful.” Most phenomena can be modeled in many ways. There is a danger of a statistician unfamiliar with the subject matter of a study choosing a model for it mathematical tractability or familiarity rather than because it aids understanding. A statistician working on paleoclimate data needs to have an understanding of climate processes in order to create truly useful models. I’m not sure Wegman et al. realize this.

  36. 36
    Alex Brown says:

    Re: “The Discovery of Global Warming” update — Excellent treatment of both science and history – many thanks to Spencer Weart. I wonder about the cutoff at May 2001 however – are there any plans to continue the timeline?

  37. 37
    jhm says:

    Does this report from the BBC on a possible new history of molecular oxygen (O2) levels have reprocussions in the GW debate?

  38. 38
    Leonard Evens says:

    Re Gavin’s response in 21:

    “the understanding that the medieval climate anomaly was not as coherent in time or space than the 20th Century change had begun well before MBH”

    Even I knews that. I long ago learned that, no matter how expert you might be in your own field, it takes at least two years of study of a new subject—about the time of pre-thesis graduate work—to get to the point where you can start saying sensible things, and even then many of them are wrong. It takes longer to be able to comment usefully. The only way a statistician is going to be able to advance the subject is by taking the time to familiarize himself with it at a professional level, not by jumping in to debate one narrow point.

  39. 39
    Eric says:

    Lloyd, thanks for your perspective. The danger in a purely statistical analysis comes when you use the word “cause” since statistics won’t tell you anything about cause and effect. Another danger with a purely statistical analysis is not understanding the physical processes behind the measurements. How, for example, does a particular temperature proxy like a tree ring reflect the climate conditions for that year? Or for a CO2 measurement in an ice core, how does a layer of ice get physically created, compacted and sampled? It seems that that requires a broad understanding of biology and physics.

  40. 40
    Hank Roberts says:

    >37 Jhm
    The new model confirms the older models, according to the story about the charcoal study. See the chart there of two
    “… models describing oxygen (O2) level changes in the atmosphere – a new model (A) and a popular, older one (B) …” — the new information about timing and type of plant involved in the fires fits the atmosphere models.

  41. 41
    rasmus says:

    I am currently reading a book by Richard Hamblyn: The invention of Clouds ( which also provides a fascinating account an important part of the history of meteorology/science, for those who find science history or meteorology history interesting.


  42. 42
    BG says:

    I know this is a bit off topic, but I could not help my self to share:

    I hope no one runs and buys one…

  43. 43

    Models gone wild! Re: Lloyd no. 35, the second pillar of attribution is model based. Model based evidence is dependent on the quality of the models (not profound). Climate modelers also have a practice of assuming that ensembles of models “tackle model uncertainty”. Keep in mind also, that the third pillar of attribution, the pattern of changes, is also at least partially informed by insight from models.

    Pillar number one is the weakest pillar. Pillars three is partially dependent on pillar two. Recent evidence now shows, that all the AR4 models, yes “all”, show a systematic bias against solar forcing, the leading competing theory to anthro GHG warming. They all have a positive albedo bias. For references, see the Roesch (2006) and Bender (2006) in my comments here:

    [Response: First off, the ‘positive’ bias in the albedo is on the order of 1%, leading to a potential bias against solar irradiance forcing of ~1.4% which compared to the uncertainty in the solar forcing itself is negligible. Secondly, the actual mean albedo is still not that well known – true, recent estimates are lower than the earlier numbers which most GCMs were tuned against, but I would be hesitiant in assuming that a 1% change in global albedo will suddenly make a big difference in response. That is not our experience at all. – gavin]

  44. 44
    Stephen Berg says:

    Re: #42,

    There must be something wrong with that article. Given the crisis in the Middle East, economists are predicting $4 per gallon prices in the coming months, even weeks ahead. If this occurs, this is certainly no time to buy an SUV. (Is there ever a good time to buy one?)

  45. 45
    Armand MacMurray says:

    Re: response to #19
    Rasmus, the implicit assertion is actually somewhat different from what you wrote. Rather than being “that statistitians bring forth the true answers whereas other scientists don’t,” the assertion is that statisticians are much less likely to make errors in statistical analyses. This seems like common sense to me. In my field of biology, we commonly consult and/or collaborate with statisticians in order to help ensure the analysis is done correctly; I can’t imagine that such a practice would harm climate research.

  46. 46
    Hank Roberts says:

    Lloyd, your #35 made things clearer.

    Can you say or point to more elsewhere about deterministic and stochastic modeling?

    It sounds like it’d be an educational conversation for people like me to watch, if it’s going on elsewhere.

  47. 47
    Wayne says:

    Statement from a “denialist”(who shall remain unnamed):
    “Earth has warmed from about 287 K to about 287.6 K during the Twentieth Century. At most, increased radiative forcing from added atmospheric carbon dioxide can account for ~0.17 K (an increase in Earth’s estimated mean surface temperature of <0.06%). The IR absorbency bandwidths where atmospheric carbon dioxide is active are either saturated or approaching that state. This means the trivial warming attributable to increased atmospheric carbon dioxide is almost complete.”


    [Response: Steve Milloy again. Complete cr*p again. Neither CO2 nor water vapour nor CH4 nor O3 nor N2O spectra are saturated. – gavin]

  48. 48
    Grant says:

    Re: #46

    At most, increased radiative forcing from added atmospheric carbon dioxide can account for ~0.17 K.

    This statement is false. Did the unnamed denialist provide any context (reference, calculation, logical argument) to support this? It’s a very common tactic of denialists simply to make a false claim, confident that their listeners/readers don’t know enough about the subject either to see through it, or to check references. You, however, came to the right place.

    (an increase in Earth’s estimated mean surface temperature of <0.06%)

    Even *if* this were true, it’s irrelevant. If I’m standing in 5 feet of water, unable to swim, I’m still safe. If sea level rises two feet (a mere 0.005% compared to the depth of the Marianas trench), I drown. It’s another very common (and totally misleading) tactic of denialists to make modern warming *seem* insignificant by comparing it to the largest number they can plausibly suggest.

    The IR absorbency bandwidths where atmospheric carbon dioxide is active are either saturated or approaching that state

    The center of the absorption band is saturated, but not the wings. Also, even when saturated, increasing CO2 can warm the surface. Doing so decreases the “optical depth” of the atmosphere, raising the altitude at which the atmosphere glows at the pure-blackbody temperature. Raising the “skin height” warms the surface due to the increase of temperature with greater depth in the atmosphere.

  49. 49
    Hank Roberts says:

    Google: I found that in only one place, at the junkscience site — unsigned — as of today.
    Don’t rely much on people who don’t footnote or even sign their work.

  50. 50
    Mark Shapiro says:

    1) Thanks for this “Discovery of Global Warming” update. I had seen the book before and glanced at the website. This gave me the impetus to read some major pieces, all informative, and bearing amazingly well on many issues at hand here. The cycles of questioning, observation, speculation, measurement, debate, and even forgetting, are all part of the process.

    2) Gavin and Michael – I saw the transcript of your discussion with Lou Dobbs 7/13/6 courtesy of! All to the good, though I can only imagine that it’s tough to switch gears when he cuts you off by agreeing with you! Asking you to offer solutions was quite a challenge – taking you out of your comfort zone. How will you bone up on solutions for the next discussion? I recommend efficiency, renewables, and conservation (as always). Nuclear? That’s the big government solution, with big bureaucracy, regulation, and subsidies. The free-market, high-tech approach of Amory Lovins (at ) would be to his liking. Dobbs’ key phrase: “this is a can-do country”. You bet.

    3) About that OT Wegman report – there are some good responses to it floating about. Please choose wisely. (More free advice later.)