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Climategate: There Is Normal Scientific Discourse Too (revisiting the millennial temperature ‘trick’)

By Chip Knappenberger -- December 12, 2009

[see bottom of post for an update]

Steve McIntyre, chief blogger and workhorse at the blog ClimateAudit, has a recent post which is grabbing a lot of attention across the web and being trumpeted by some as a triumphant unmasking of the fraudulent behavior in the preparation of the IPCC Third Assessment Report (TAR).

Science/science policy blogger Roger Pielke Jr. covers Steve’s post, with a post of his own, under the title The “Trick” in Context. However, I think the post should more accurately have been titled The “Trick” in “Context.” For the “context” is one supplied by Steve McIntyre. My read of the relevant emails surrounding the incident in question doesn’t lead me to the same conclusions as Steve.

Context must be supplied in this case. For as anyone who has looked through any of the leaked/stolen Climategate emails (available here) quickly realizes, most of the email threads are not complete from start to finish, and, as is typical of most conversations, they assume the participants already know a lot of what is being discussed, including the context. To outside parties peering in, often the context must be derived, inferred, or guessed at.

The topic in question has to do with development of the discussion and graphics to be included in the paleoclimate section of Chapter 2 of the IPCC’s TAR. (The IPCC has since published its Fourth Assessment Report [AR4], which dedicates an entire chapter to paleoclimate rather than a brief section of a single chapter.) The discussion taking place in the emails highlighted by McIntyre is about what the best scientific understanding (at the time) of what the earth’s temperature behavior was during periods that pre-date the widespread direct temperature measurements made by thermometers (in this case, the past 1,000 years or so).

This is relevant to the issue of anthropogenic climate change because quantifying the degree of “natural” variability of the earth’s temperature helps to understand how unusual our current warmth might be. To some people, it is also important because they want to use it to try to argue that the earth’s temperature has gotten to be as high as it is now solely because of natural process. But this view is almost certainly wrong.

The Temperature ‘Trick’ Revisited

McIntyre has dedicated a phenomenal amount of time and energy into trying to decipher just how paleoclimate researchers have come to assemble their millennial temperature reconstructions—which are necessarily built upon uncertain data, relationships, and interactions—and then trying to determine whether the methods (and thus the ultimate results) are robust. By and large, he has had to do this without the assistance and/or blessing of the paleoclimate community (to put things nicely—look through the Climategate emails to see opinions of Steve in less nice terms). Steve’s effort has basically introduced the idea of research “audits” to the climate community, as well as forwarding the idea that all data and methodologies in the peer-review literature should be archived and open. This alone is a praiseworthy and significant contribution that will (hopefully) have lasting positive influence on how climate science is documented.

But, in this particular case, I think that he is trying too hard to attach something nefarious to actions that occurred nearly a decade ago.

To understand the scenario that Steve is putting forth, you have to visit his site and read through his line-of-reasoning. Basically, he thinks the authors responsible for the relevant portion of the IPCC TAR Chapter 2 were being “tricky” to an extent unjustified by the scientific knowledge at the time, in order to try to show that the earth’s temperatures during the latter part of the 20th century were unprecedentedly high (furthering the evidence that human greenhouse gas emissions were driving the climate warmer).

However, when I look through the emails and try to follow Steve’s thread, I don’t arrive at the same conclusions (nor do some other folks). Steve imparts a context to snippets of emails that I believe does not accurately reflect the true context. Steve sees the authors trying to “hide the decline” (i.e., trying to conceal one particular reconstruction: the one published by Briffa et al. in 2000 that shows temperatures in the latter half of the 20th century declining), while other reconstructions–and the observations themselves–show that temperatures were rising. But I see them trying to understand why the available temperature reconstructions are different from one another. Steve sees actions that are highly questionable; I see fairly normal scientific discourse.

I can agree with Steve on one thing: the IPCC presented some data in a way that was different from how the data was originally presented in the peer-reviewed literature. Primarily, the reconstructed temperature as described by Briffa et al. (2000), which originally extended from the years 1402 to 1994, was truncated to end in 1960. However, this truncated version of the Briffa et al. (2000) reconstruction was supplied to the IPCC by one of the co-authors of original research, with the explanation that they did not have very much faith in the accuracy of the reconstruction past that date (because the reconstructed temperatures diverged from the observed temperatures) (see email 951763817.txt).

That the IPCC authors choose to accept and use this version of the Briffa dataset doesn’t seem to me to be much of a “trick.” If I were going to use some data, and the researchers who had derived the data informed me that some of it was quite possibly wrong, I probably would try to avoid using it—or at least the questionable portions.

Perhaps the only thing vaguely “tricky” was that Briffa was also a contributing author to this IPCC chapter. So perhaps it could be argued that he was allowing his dataset to be used in a way other than how he originally published it in order to further the IPCC’s desire to show that the recent temperatures were unprecedented (and humans were the cause).

However, three things argue against that proposition: 1) that in Briffa’s peer-reviewed publications (prior to the IPCC review) describing his reconstructions, he openly recognized the post-1960 divergence problems between his data and the observations and admitted it needed further explanation; 2) in one of the emails he stated that he did not believe that there was sufficient evidence to conclude that the temperatures in the recent decades were unprecedented in the past 1,000 years (see email 938031546.txt); and 3) based on the personality that Briffa displays throughout the Climategate emails, he certainly doesn’t act like one who rolls over under pressure. So it seems unlikely that Briffa volunteered to truncate his dataset in order to satisfy the IPCC’s desire (or at least the desire of the other authors of that particular Chapter) to show that recent temperature were unprecedented. The only person who knows for sure is probably Keith Briffa.

Now perhaps, you may argue that if Briffa was uncomfortable about any parts of his analysis the prudent thing would have been for him to have requested that it not be included at all. And maybe that would have been the correct thing to do and then there would have been no apparent “trick” at all. But that is not what Briffa decided—and that decision 10 years ago has led to this discussion.


I totally agree that several (or many) IPCC/TAR authors wanted to push the idea that the warmth of our most recent decades was unprecedented in the history of earth’s temperatures during the past 1,000 years. And those authors who wanted to do so were incredibly successful in actually doing so (look no further than Figure 1b on page 3 of the Summary for Policymakers [SPM]). And perhaps the science at the time did not justify this. But, SPM Figure 1b (and its creation) is not the figure under discussion by McIntyre.

Don’t get me wrong: I think that there is a lot of scientific misbehavior evident in the email collection, some of which I commented on in an earlier post. But I also think there is a lot of normal scientific discourse. I want to be careful not to confuse the latter for the former. In this specific case, I come down on the side of the latter.

[update 12/14/2009: Upon further reflection and consultation of the (at the time) extant Briffa peer-reviewed publications, I think the best course of action would have been not to include the Briffa series in IPCC TAR Figure 2.21. The problems with it were not fully resolved and it was not an apples-to-apples comparison with the other data series in Figure 2.21 anyway. The IPCC TAR authors acted outside the peer-review literature when they decided not to include the Briffa series post-1960. If they were intent on doing so, their decision should have been clearly justified in the text. There was a brief description in Section (TAR p. 135) of a problem with tree-ring temperature reconstructions in recent decades, but in no indication that the TAR authors took this into account in the preparation of Figure 2.21. In fact, a reader would have been confused if they had turned to Figure 2.21 in order to confirm the description in Section that the “tree-ring density variations have changed in their response to temperature in recent decades.” There was no evidence whatsoever of this in Figure 2.21.

The TAR authors should have included a direct acknowledgement in the caption of Figure 2.21 that the Briffa series had been modified. But they did not. Whether or not this was done in a coordinated IPCC effort to “hide the decline,” or whether it was a decision that rested only with Briffa being uncomfortable with the that portion of his reconstruction, cannot be determined from the associated email content (in my opinion). -Chip]


  1. Major Mike  

    I’m surprised you don’t see that if there is divergence since 1960, the validity of tree-ring and other proxies for temperature comes under question for the entire period of the study. If some current conditions cause divergence, would not similar conditions, perhaps a thousand years ago, result in the same divergence? If the tree-ring proxies don’t reflect current warming, they may not have during the Medieval Warm Period either. It’s obvious that they diverged with the record showing warming during that period evidenced by vineyards in England and farming and pasuturing livestock in Viking Greenland that can’t exist today. The evidence where certain crops have grown and lands were habitable is much clearer and incontrovertible than attempts to torture climate trends from unwilling proxies.


  2. stan  

    I don’t know if you have spent as much time analyzing the work of the hockey team as M & M have, but they absolutely bend over backward to avoid assigning fraudulent intent to Mann et al, even when the evidence establishes that such a conclusion is warranted. There is a whole lot more than simply the file of Jones” e-mails from which McIntyre derives the context.

    Let’s look at all the clues of fraud in Mann’s original work. Why did he ignore the variety of commercially available statistical software packages to do his standard principal components analysis and write his own from scratch? Makes no sense at all from a quality perspective. Except that using quality, debugged software didn’t get him his hockey stick and his “innovative” home-cooked software did.

    Why did Mann ignore standard statistical measures of significance and resort to making up his own home-cooked measures? Doesn’t make any sense from a quality perspective. Until one realizes that the study doesn’t pass standard measures of statistical significance. It only passes his newly created, home cooked measure. Oh wait, did we mention that M & M found the files which show that Mann actually computed those standard statistical measures, yet somehow forgot to publish the results as he should have?

    Why did Mann knowingly use datasets from bristlecones which were known to be improper proxies? Maybe because he couldn’t get a hockey stick without them?

    There is a long history of dodgy choices and curious behavior involving Mann and his friends that really put those e-mails in context.


  3. Joel McDade  

    Yes, the ‘hide the decline’ refers to a decline in the proxies, not temperature.

    No, the trick is not merely grafting on instrumental temperatures to the proxy charts to put the proxies in context. It as to do with their use of a centered smoother. If done correctly the smooth points downward in the late 20th century, and this could not be allowed. What Mann originally did (in his 1999 GRL paper, not Nature) and Jones subsequently did was documented by UC, Jean S, and Steve at Climataudit. As the smoother needed future data approaching the end of the series they padded the data with instrumental temperatures. This of course created an uptrend in the smooth that was so desired. This is “the Trick.” In Mann’s case it was completely undocumented and to this day has not admitted to doing it. (Why?… because it is an act of F&@&D, IMO.)


  4. cknappenberger  

    Commentors 1, 2, and 3,

    Thanks for starting off the discussion.

    However, this is not a discussion of those topics.

    My article is about whether the IPCC authors of the paleoclimate section of Chapter 2 of the IPCC TAR acted in a scientifically improper way in constructing Figure 2.21 (especially in regard to the handling of the Briffa reconstruction).

    Comments veering too far off that topic will be removed.

    There are plenty of other places for general venting about paleoclimate methodologies.

    Thanks for everyone’s cooperation!



  5. stan  

    Oops. I’m sorry. You wrote: “Context must be supplied in this case.” And “To outside parties peering in, often the context must be derived, inferred, or guessed at.” Your post was then about supplying the context.

    I sought to add more information which adds to an understanding of the context relating to McIntyre and his evaluation of Mann.


  6. cknappenberger  


    Granted. But the issue at hand is not any of Mann’s reconstructions. It has to do with the how Briffa’s reconstruction was handled in the TAR.




  7. Andrew  

    Regarding the relevance of reconstructions on attribution of climate change-while the MWP being warmer than now would not prove that natural forces dominated recent warming. It would prove that nature could create such a warming. More importantly it would prove that something is missing from models which do not predict such a thing, and therefore the argument that recent warming is mostly anthropogenic because the known natural processes don’t explain the warming would be invalidated.

    Of course I agree that anthropogenic forcings are having an effect, but I also think that if we don’t have accurate estimates of natural variability, then we won’t have accurate estimates of the uncertainty in the amount we attribute to AGW.


  8. AMac  

    CK wrote:

    Steve sees the authors trying to [conceal the decline in the late 20th century portion of the Briffa et al reconstruction], while other reconstructions–and the observations themselves–show that temperatures were rising. But I see them trying to understand why the available temperature reconstructions are different from one another.

    In general, when considering a document like an IPCC report, there are a two important questions that those of us outside the field would like to have addressed. As far as paleoclimate reconstructions:

    * What do the models show, as far as variations in the earth’s climate over the past centuries?

    * How robust are the models? In particular, are different models consistent with each other? How much confidence do working scientists have in them? What are the (statistical) confidence boundaries on them? How well do the models’ values agree with the 1850-on instrumental record?

    Knowledge of the post-1960 decline in temperature anomalies computed by Briffa’s model is very important, as far as lay people developing an informed understanding of the paleoclimate reconstructions and their limits.

    In my opinion, this episode illustrates that substandard data handling and data presentation techniques are routinely practiced in paleoclimatology. More exactly, in an often-painful process, standards in most or all other areas of science or engineering have steadily risen over the past few decades, while practitioners of paleoclimate science have remained comfortable with the accepted practices of the 1950s or 1960s.

    Imagine the hue and cry if pharma scientists hid the unfavorable parts of the data when presenting the results of a Phase 3 clinical trial of a promising new drug.

    Or if the report of a new pedagogical technique presented high-performance test scores of second, third, fourth, and sixth graders, while omitting mention of the poor results of fifth and seventh graders.

    It seems to me that the consensus climate community has become accustomed to the “easy living” offered by debased methodologies. Its members repeadedly show themselves as unwilling or perhaps unable to respond properly to criticisms.

    Until this paradigm changes, I’m unwilling to accord climatologists and climate models “the benefit of the doubt.”


  9. C3H Editor  

    Good review/posting as usual. But I would differ with your conclusion – I lean more to the “former” explanation based on years of “context” that this group of individuals did not want their work challenged and went to great lengths in attempt to accomplish that objective. (Maybe Briffa is cleaner than others on this and belongs in the “latter” camp conclusion, though.)

    Also, you inserted the following statement in your post, which has me puzzled based on some of your previous postings (have not read all of your postings): “To some people, it is also important because they want to use it to try to argue that the earth’s temperature has gotten to be as high as it is now solely because of natural process. But this view is almost certainly wrong.”

    Chip, could you point me to which of your previous postings (or published articles elsewhere) where you elaborate on your view of that the last sentence of above statement?(I have no doubt you’ve written about that view and want to learn more how you came to it, but I just don’t want to go through the large haystack looking for the needle.) Thanks for any pointers that would help explain your view.


  10. Robert Bradley Jr.  

    This comment is from Marlo Lewis who is remote:

    If the IPPC wants to reconstruct global temperatures going back 1000 years, they should finish the dance with the data they started with. Switching horses would be appropriate only if there were no divergence — but then switching would not be necessary. Briffa admits he can’t explain the divergence, so why assume the proxies after 1960 are too cool rather than that the instruments are too hot? Tree rings from remote forests or sediments from lake beds or the sea floor are not subject to multiple false warming biases that distort the instrumental record — land use changes, improper placement of temperature sensing equipment near artificial heat sources, data recalibrations that always seem to increase the warming rate. Using a “trick” to “hide the decline” in proxy data you are using to show unprecedented in a thousand years warming rather screams of fraud. What am I missing?

    Marlo Lewis


  11. cknappenberger  

    C3H Editor,

    Well, formally laying out the facts in one place, as I see them concerning CO2 and global warming was going to be Part II of my ultra-skeptics series, which I have not gotten around to writing yet.

    But in a nutshell:

    CO2 is a greenhouse gas which acts to raise the average temperature of the earth.
    CO2 has increased from roughly 270 to 390 ppm over the past 100-150 years.
    Since the greenhouse effect from CO2 was not saturated at 270ppm, the additional CO2 imparts a “warming pressure” on the earth. Natural variability acts on top of this.
    There is no mechanism for which natural variability has led to a century-long warming of the magnitude observed.

    But, this is not the place to pursue this topic.

    Perhaps later.



  12. cknappenberger  


    You say “Tree rings from remote forests or sediments from lake beds or the sea floor are not subject to multiple false warming biases that distort the instrumental record.”

    Nor are there particularly accurate thermometers. What’s worse, their accuracy most certainly varies over time.

    So, you do the best you can with what you have.

    But, I am willing to bet the Keith Briffa is more qualified to assess the performance of his tree-ring proxies than I am. Whether he does so perfectly, I can’t say. But others (for instance, some folks over at ClimateAudit) clearly have their own opinions about this.
    But the bottom line here, is that I have seen no evidence in the emails (or anywhere else) that leads me to think anything other than, at that time, in September/October of 1999, that Keith Briffa was acting to put forth the temperature reconstruction for which he had the most faith in.



  13. Robert Bradley Jr.  


    I bet you get challenged for your statement:
    “There is no mechanism for which natural variability has led to a century-long warming of the magnitude observed.”

    I think that natural variability is something that all scientists have more respect for today than maybe ten years ago.

    Isn’t the argument for anthropogenic forcing related to the different characteristics of warming we have seen more recently? Is the nighttime/winter warming still disproportionately high looking at the last decade? (I know you and Pat Michaels did a lot of work on this a while back.)


  14. Marlo Lewis  

    Chip, the issue, as you say, is whether the IPCC handled Briffa’s data properly and what the Climategate emails do or do not reveal about that. If I read Steve’s analysis correctly, Briffa, responding to the IPCC’s (especially Mann’s) concern that his reconstruction would “dilute” the message of unprecedented warming, recalculated his chronology, and came up with an even steeper decline! So in the hockey stick graph and discussion thereof, the IPCC TAR simply deleted Briffa’s post-1960 data, hiding the decline. That surely goes beyond “normal scientific discourse,” if in fact it is what the IPCC did. I do hope that Steve reads your column and the various comments, and posts one of his own. Best, Marlo


  15. cknappenberger  


    Nowhere in the relevant string of emails do I see evidence that Briffa produced a new analysis and truncated it in 1960 under pressure by the other IPCC TAR authors in order to tell a particular story.

    He did produce a new series and he did truncate it in 1960. But it’s the pressure part that has not been proven.

    Since Briffa was a co-author of the TAR Chapter in question, I guess you could assign him the moniker “IPCC” if you wanted to, and yes, he did truncate his own dataset post-1960 because he was uncomfortable that it accurately reflected the true temperature during that period of his reconstruction.

    Like I said in my post, perhaps the most prudent thing would have been for Keith to pull down his entire reconstruction until he was compeltely happy with it instead of only providing part of it to the IPCC process. Then, presumabley this would not be an issue.

    Here are some particularly relevant emails to start with if you want to investigate for yourself (rather than having to accept my or Steve’s story as presented).

    September 22, 1999
    September 22, 1999
    September 23, 1999
    September 23, 1999
    October 5, 1999
    October 5, 1999
    February 28, 2000



  16. cknappenberger  


    Let me make sure that I am clear that I mean a century-long warming during the most recent 100 years of the magnitude observed.

    If you think my assertion is challengeable, go ahead and give it a shot…name as many natural influences during the past 100 years that in combination explain all the warming. Hint, your best approach would be to go with the “something we have yet to realize.”

    Actually, I think it is best to save your thoughts for another place and time as this discussion is off-topic on this thread (sorry to have to such a stickler on this, but the topic at hand tends to veer off uncontrollably).



  17. stan  


    “There is no mechanism for which natural variability has led to a century-long warming of the magnitude observed.”

    If only we had some competently managed databases from which we could observe how much warming has supposedly happened. Whether hubris or incompetence, the statistical work is very poor. See e.g. http://wmbriggs.com/blog/

    “there are three facts which must be remembered: (1) the uncertainty with picking an arbitrary starting point; (2) any method will result in attaching uncertainty bounds to the missing values, these must remain attached to the values; and (3) the resulting trend estimate, itself the output from a model which takes as input those missing values, will have uncertainty bounds—these will necessarily be larger than if there were no missing data at A. Both uncertainty bounds must be of the predictive and not parameteric kind, as we discussed before.

    Again, near as I can tell, carrying the uncertainty forward was not done in any of the major series. What that means is described in our old refrain: everybody is too certain of themselves. ”

    Let’s highlight that last part –” everybody is too certain of themselves. ”
    If only Professor Wegman’s advice had been embraced.


  18. JD Will  

    I agree with your central point that this was a case of over-glossing the presentation. But there is an underlying theme of stifling other points of view that is dangerous.

    Let’s say for argument that earlier reconstructions show a MWP 1,000 years that was warmer than now and a Holocene 8,000 years ago that was even warmer and more sustained.
    And the reconstructions are messy, so cherry pickers can have a field day:

    Further, let’s say that the slope we are on now started about 1900 and that manmade GHG was not that significant until 1940 (both camps are pointing to the same curve and declaring victory).

    My take is the current warming is probably both natural and manmade. The 64 trillion dollar question is how much is due to manmade GHG? And will it take us past some climatic tipping point?

    The media have been obsessing on a CO2 centric answer and calculations based on GCM models with data controlled by a relatively small group. This group has not been open or collegial with other scientists that presented diverging hypotheses. Yet, their own AR4 reporting shows great uncertainty in areas, especially aerosol or clouds.

    If we do have a problem with CO2, we need to put our scientific house in order ASAP and focus on:

    1. Open sourced data and methods.
    2. More certainty in separating the C02 signal – which leads to the next point.
    3. Some other method than GCM parameters to ascertain climate sensitivity (we need to know a lot more about cloud formation and cloud feedback to solar radiance).

    None of this will be well served by politicizing science or economically castrating our economies and generating public revolt against both environmental activism and the scientific method.


  19. Marlo Lewis  


    I think you’re looking at these emails as would a court and deciding that there is reasonable doubt. Granted, nobody in the emails says, “Hey, let’s rig the results to fool the public and don’t tell anybody,” and no one threatens to “beat the cr*p” out of Briffa if he doesn’t come along quietly. Nonetheless, Steve’s interpretation of the “context” is quite plausible. The IPCC used part of Briffa’s reconstruction when that fit into their “tidy story,” deleted the part that didn’t, and then didn’t bother to tell anyone about the deletion. This in spite of Briffa’s privately expressed opinion that “the recent warmth was probably matched about 1000 years ago,” and privately expressed doubt “that global mean annual temperatures have simply cooled progressively over thousands of years as Mike appears to [believe].” I find the IPCC’s handling of the Briffa reconstruction hard to interpret as anything but cherry picking and slight of hand. Steve’s conclusion therefore seems spot on:

    “Contrary to claims by various climate scientists, the IPCC Third Assessment Report did not disclose the deletion of the post-1960 values. Nor did it discuss the ‘divergence problem’. Yes, there had been previous discussion of the problem in the peer-reviewed literature (Briffa et al 1998) – a point made over and over by Gavin Schmidt and others. But not in the IPCC Third Assessment Report. Nor was the deletion of the declining values reported or disclosed in the IPCC Third Assessment Report. [Dec 11.- IPCC TAR does contain a sly allusion to the problem; it mentions ‘evidence’ that tree ring density variations had ‘changed in their response in recent decades’. Contrary to claims of realclimate commenters, this does not constitute disclosure of the deletion of the post-1960 values in the controversial figure or even of the decline itself.]”

    As to Briffa producing a new chronology with an even steeper decline, which was then deleted from the IPCC presentation, I am at a loss as to why you and Steve see things so differently. Either Briffa did a recalculation — what the IPCC accepted, minus the post-1960 data, even though not previously published in the peer reviewed literature — or he did not. Here’s Steve’s take:

    “After the Arusha meeting, Briffa hurriedly re-did his chronology and the new version was delivered to Mann on Oct 5, 1999 – it was this version that had the big decline. In the First Order Draft of Oct 27, 1999, IPCC author Mann deleted the post-1960 portion of the Briffa reconstruction plus other things that I don’t yet quite understand. Jones’ trick, as observed in the post, is a little different. (The post-1960 portion of the Briffa reconstruction was also deleted from the NCDC archive and the Climategate Letters, as previously noted, was the first digital ‘archive’ of the post-1960 Briffa reconstruction used in TAR.)”

    This seems a purely factual matter. I hope you and Steve will sort it out for us laymen. Best, Marlo


  20. cknappenberger  


    Lacking evidence that the other IPCC authors were threatening to proverbially hit Briffa across the knees with a baseball bat, I am left to go by what is in the emails. Briffa supplies his new reconstruction and recommends not using it post-1960.

    The latter is pretty straight from the horse’s mouth.

    The only question, I guess, is whether Briffa had his independent researcher’s hat on, or his IPCC co-author hat on when he provided the data and instructions on how to use it.

    We are all realizing that this distinction is very blurry.

    Which potentially points to a problem with the IPCC process in place 10 years ago in preparation of the TAR.

    If enough people think this type of thing is a problem, then hopefully the IPCC will act to enact a better process next time around (if they haven’t already). But, then again, perhaps the IPCC thinks the way they have it is fine. But that leaves the door open to criticism—which may or may not lead to the IPCC’s undoing.



  21. kgreen  

    Chip –

    I largely agree with you. Having read a lot of the archive myself, I’m less convinced that this was intentional scientific fraud, and have focused my criticisms on the with-holding of data, and the apparent corruption of the peer-review process, which I see as more troubling.

    However, as a few others have asked, I would like some support for this sentence: “To some people, it is also important because they want to use it to try to argue that the earth’s temperature has gotten to be as high as it is now solely because of natural process. But this view is almost certainly wrong.”

    I agree that recent warming is almost certainly not *entirely* free of some human causality, whether it’s greenhouse gas emissions, or land-use changes (or both of the above), but I would like some clarification about what evidence you think gives the best estimate of how much human GHG emissions have contributed to the recent temperature rise. Is it, as the IPCC says, the cause of “most” of the warming of the last 50 years? Or is it some undefined contributor to the observed warming, along with emergence from an ice age, oscillations in ocean currents we don’t understand, changes in solar activity, or some combination of all of the above?

    Best, and thanks for the great posts,

    Ken Green


  22. John Droz  


    It seems to me that there is a major assumption in your statement “There is no mechanism for which natural variability has led to a century-long warming of the magnitude observed.”

    The assumption is that “mechanism” is singular.

    We live in a complex natural environment, and there are significant feedbacks, inter-relationships, etc.

    Further, from a a science viewpoint we do not accept a hypothesis just because we can’t currently formulate a “better” one. That is NOT the Scientific Method.


  23. cknappenberger  

    John ( #22),

    See my Comment #16.



  24. George Walton  


    “There is no mechanism for which natural variability has led to a century-long warming of the magnitude observed.”

    Looking at the “Historical Video Perspective” at WUWT I see several periods in the last 10,000 years with similar warming periods vased on the Greenland ice core data. See the graphs http://wattsupwiththat.files.wordpress.com/2009/12/noaa_gisp2_icecore_anim3.gif

    I cannot speak for the accuracy of the ice core science, but the graphs suggest we should continue looking for naturals reasons for the temperature variations (up & down) since the last ice age. I do not question the existance of “Climate Change.”



  25. cknappenberger  


    For one, people like to say “recovery from the Little Ice Age” but there needs to be a mechanism attached to that—perhaps your solar or ocean currents, of perhaps a dearth of volcanoes. But, by and large, you need a lot of forcing to get the temperature to rise as much as observed (even accounting for uncertainties in the temperature record from urbanization, et al.). And if you believe the low sensitivity estimates, then you even need more forcing.

    Thus far, “natural variability” even from all sources, doesn’t come close to producing what we need.

    I would agree that most of the rise in global temperatures in the past 50 years is from human activities (primarily greenhouse gas emissions)—even if we are still uncertain as to what the true amount of warming has been.

    When it comes down to it, there are two processes that lead to global warming…more sunlight or the greenhouse effect is enhanced. The reasons for each are myriad. But we know quite well that the latter is occurring and why.



  26. cknappenberger  

    George (#24),

    Greenland temeratures do not well-represent global temperatures.

    Certainly there are loads of examples where local temperatures vary much greater than the global average.



  27. per  

    majormike and amac make exactly the same on-topic point; that the hiding of the decline hides the data that proves that tree-ring measurements are unreliable. This goes to the heart of whether it is appropriate to use tree-rings for reconstructing temperature histories. At the very least, there is an unquantifiable uncertainty in reconstructing temperatures from tree-ring measurements.

    The divergence problem was well-known at the time- yet IPCC TAR allegedly fails to mention it. Isn’t this precisely on-point ?

    Why isn’t this on-topic ?


  28. Noblesse Oblige  

    I guess the key points have to be drilled home again and again. Regardless of the conversations, contexts, and apologies. Regardless of endless columns of obfuscations, keeping the blogs busy and the media scurrying. This remains:

    1. The post 1960 proxy data were deleted because they didn’t make a blade. That is cheating, pure and simple.

    2. If you can’t trust the proxies post 1960, you can’t trust them before 1850.

    if the data don’t fit, you gotta aquit.”t


  29. Marlo Lewis  


    I agree – the main problem revealed by the emails is that the Jones gang was prepared to go great lengths — including destroying files — to prevent outside researchers from reproducing/invalidating their results. Skeptics have been accused of waging a “war on science,” because we often question the IPCC interpretation of the rapidly expanding field of climate research. But real science is not a body of dogmas certified by government-funded experts. Nor is peer review the gold standard of real science, as Climategate apologists keep insisting. As Chip noted in an earlier post, peer review is not an audit. And as a recent expose of PNAS in Science magazine shows, collusion among peers to accept each others’ papers can become standard practice. The real audit occurs post peer-review and publication, when independent researchers attempt to “find something wrong” (as Phil Jones put it). Real science is an adversarial process, and it only works when scientists — especially big name influential scientists — play by the rules and allow competing researchers to examine their data and methods. As Willis Eschenbach said, the Jones gang attacked the “heart of science” by hiding their data and code to prevent outside scrutiny. Doing so in defiance of FOIA makes this unethical behavior also illegal.

    Although hiding data and code in defiance of FOIA is the most important part of Climategate, it does of course raise the question of why the Jones gang didn’t want anyone checking their results and their math. Presumably, if they had nothing to hide, then they would not have hidden anything. I will be very, very surprised if people with such low regard for scientific practice and FOIA are later shown to have been totally scrupulous in the way they got their results. Best, Marlo


  30. George Walton  

    Chip (#26)

    “Greenland temeratures do not well-represent global temperatures.”

    True. But what does? Certainly not Mann’s Hockey Stick with its bogus methods, and trees are very uncertain thermometers. The record using real thermometers does not go back very far (mid to late 1800s), for many parts of the world not far at all, and it is questionable what is being measured – temperatures representative of wide areas or of local land use, land covers, and local human activities. Right now I do not trust the handling of the measured temperatures, GHCN, etc. based on net reports on the handling of some data stations and some comparisons of rural and urban sites, etc.

    Climatology is a new science. It is also a difficult science because we cannot create experiments to test our theories. A show about the Little Ice Age (in Europe) on the History Channel mentioned that it started with several years of excessive rains. Consistent changes in cloud cover could have large impacts on temperature, but what would cause such changes? The cosmic ray – solar activity theory has not been proven, but there may be an experiment underway that will tell. Let’s see what happens with the next couple solar cycles. I will check back with you in 20 years. 🙂



  31. jae  


    “My article is about whether the IPCC authors of the paleoclimate section of Chapter 2 of the IPCC TAR acted in a scientifically improper way in constructing Figure 2.21 (especially in regard to the handling of the Briffa reconstruction).”

    As you noted in your update, the authors should have documented their procedure. They did not do so, and I look at that failure as “hiding” something.


  32. jae  


    “My article is about whether the IPCC authors of the paleoclimate section of Chapter 2 of the IPCC TAR acted in a scientifically improper way in constructing Figure 2.21 (especially in regard to the handling of the Briffa reconstruction).”

    As you noted in your update, the authors should have documented their procedure. They did not do so, and I look at that failure as “hiding” something. Which is not a proper thing to do in science, to be kind.


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