In the Northern Hemisphere, the late 20th / early 21st century has been the hottest time period in the last 400 years at very high confidence, and likely in the last 1000 – 2000 years (or more). It has been unclear whether this is also true in the Southern Hemisphere. Three studies out this week shed considerable new light on this question. This post provides just brief summaries; we’ll have more to say about these studies in the coming weeks.
First, a study by Gergis et al., in the Journal of Climate uses a proxy network from the Australasian region to reconstruct temperature over the last millennium, and finds what can only be described as an Australian hockey stick. They use an ensemble of 3000 different reconstructions, using different methods and different subsets of the proxy network. Worth noting is that while some tree rings are used (which can’t be avoided, as there simply aren’t any other data for some time periods), the reconstruction relies equally on coral records, which are not subject to the same potential (though often-overstated) issues at low frequencies. The conclusion reached is that summer temperatures in the post-1950 period were warmer than anything else in the last 1000 years at high confidence, and in the last ~400 years at very high confidence.
Gergis et al. Figure 4, showing Australian mean temperatures over the last millennium, with 95% confidence levels.
Second, Orsi et al., writing in Geophysical Research Letters, use borehole temperature measurements from the WAIS Divide site in central West Antarctica, a region where the magnitude of recent temperature trends has been subject of considerable controversy. The results show that the mean warming of the last 50 years has been 0.23°C/decade. This result is in essentially perfect agreement with that of Steig et al. (2009) and reasonable agreement with Monaghan (whose reconstruction for nearby Byrd Station was used in Schneider et al., 2012). The result is totally incompatible (at >
95% confidence) with that of O'Donnell et al. (2010).
Probability histograms of temperature trends for central West Antarctica (Byrd Station [80°S, 120°W; Monaghan] and WAIS Divide [79.5°S, 112°W; Orsi, Steig, O’Donnell]), using published means and uncertainties. Note that the histograms are normalized to have equal areas; hence the greater height where the published uncertainties are smaller.
This result shouldn’t really surprise anyone: we have previously noted the incompatibility of O’Donnell et al. with independent data. What is surprising, however, is that Orsi et al. find that warming in central West Antarctica has actually accelerated in the last 20 years, to about 0.8°C/decade. This is considerably greater than reported in most previous work (though it does agree well with the reconstruction for Byrd, which is based entirely on weather station data). Although twenty years is a short time period, the 1987-2007 trend is statistically significant (at p<.1), putting West Antarctica definitively among the fastest-warming areas of the Southern Hemisphere -- more rapid than the Antarctic Peninsula over the same time period. We and others have shown (e.g. [cite ref = "Ding et al., 2011"]10.1038/ngeo1129[/cite]), that the rapid warming of West Antarctica is intimately tied to the remarkable changes that have also occurred in the tropics in the last two decades. Note that the Orsi et al. paper actually focuses very little on the recent temperature rise; it is mostly about the "Little-ice-age-like" signal of temperature in West Antarctica. Also, these results cannot address the question of whether the recent warming is exceptional over the long term -- borehole temperatures are highly smoothed by diffusion, and the farther back in time, the greater the diffusion. We'll discuss both these aspects of the Orsi et al. study at greater length in a future post. Last but not least, a new paper by [cite ref = "Zagorodnov et al."]10.5194/tcd-5-3053-2011[/cite] in The Cryosphere, uses temperature measurements from two new boreholes on the Antarctic Peninsula to show that the decade of the 1990s (the paper state “1995+/-5 years”) was the warmest of at least the last 70 years. This is not at all a surprising result from the Peninsula — it was already well known the Peninsula has been warming rapidly, but these new results add considerable confidence to the assumption that that warming is not just a recent event. Note that the “last 70 years” conclusion reflects the relatively shallow depth of the boreholes, and the fact that diffusive damping of the temperature signal means that one cannot say anything about high frequency variability prior to that. The inference cannot be made that it was warmer than present, >70 years ago. In the one and only century-long meteorological record from the region — on the Island of Orcadas, just north of the Antarctica Peninsula — warming has been pretty much monotonic since the 1950s, and the period from 1903 to 1950 was cooler than anything after about 1970 (see e.g. Zazulie et al., 2010). Whether recent warming on the Peninsula is exceptional over a longer time frame will have to await new data from ice cores.
- J. Gergis, R. Neukom, S.J. Phipps, A.J.E. Gallant, D.J. Karoly, and . , "Evidence of unusual late 20th century warming from an Australasian temperature reconstruction spanning the last millennium", Journal of Climate, pp. 120518103842003, 2012. http://dx.doi.org/10.1175/JCLI-D-11-00649.1
- A.J. Orsi, B.D. Cornuelle, and J.P. Severinghaus, "Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide", Geophysical Research Letters, vol. 39, pp. n/a-n/a, 2012. http://dx.doi.org/10.1029/2012GL051260
- E.J. Steig, D.P. Schneider, S.D. Rutherford, M.E. Mann, J.C. Comiso, and D.T. Shindell, "Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year", Nature, vol. 457, pp. 459-462, 2009. http://dx.doi.org/10.1038/nature07669
- D.P. Schneider, C. Deser, and Y. Okumura, "An assessment and interpretation of the observed warming of West Antarctica in the austral spring", Climate Dynamics, vol. 38, pp. 323-347, 2011. http://dx.doi.org/10.1007/s00382-010-0985-x
- R. O’Donnell, N. Lewis, S. McIntyre, and J. Condon, "Improved Methods for PCA-Based Reconstructions: Case Study Using the Steig et al. (2009) Antarctic Temperature Reconstruction", Journal of Climate, vol. 24, pp. 2099-2115, 2011. http://dx.doi.org/10.1175/2010JCLI3656.1
- N. Zazulie, M. Rusticucci, and S. Solomon, "Changes in Climate at High Southern Latitudes: A Unique Daily Record at Orcadas Spanning 1903–2008", Journal of Climate, vol. 23, pp. 189-196, 2010. http://dx.doi.org/10.1175/2009JCLI3074.1
192 Responses to "Fresh hockey sticks from the Southern Hemisphere"
Ray Ladbury says
Actually I think this episode illustrates beautifully the difference between the scientists and the “auditors”. The auditors are crowing over a victory and suggesting that the changes will favor their position. The scientists just want to know the new result.
The described methodology was passed by review but it’s now been discovered it wasn’t followed so the paper has been withdrawn. The obvious response now is to redo the analysis with the original methodology correctly applied to the same data and publish whatever the result is. Of course “unprecedented warming” wasn’t being sought so it doesn’t matter whether it is there or not. Even without climate change a historical temperature reconstruction of this sort provides a useful addition to our scientific knowledge. The only possible hiccup is if insufficient correlating proxies can be found in which case the paper should be shelved and a retraction of the reported claims tendered (this paper made news headlines).
Unsettled Scientist says
@Armand MacMurray, thanks for that info. I haven’t followed this issue closely. As Roger pointed out, Climate Audit is full of innuendo, and that’s just not my cup of tea when it comes to science. I tried reading through McIntyre’s posting, but even while admitting that this may not impact the results much he puts words like get in quotes and phrases as, “They might still claim to “get” a Stick using the reduced population of proxies that pass their professed test.” Using that kind of language isn’t exactly a gracious way to accept thanks, privately or publicly.
I’m still not sure it was a public thanks. In my line-of-work I’ve recently seen some individuals publishing on their website the details of a private correspondence from a colleague from another institution, and that is just scummy. So that kind of thing just leaves a bad taste in my mouth.
[Response:Yes, I agree. This is exactly the kind of behavior by which he repeatedly shoots himself in the foot, weakens his cause and creates unnecessary bad blood.–Jim]
I’d consider it a public thanks if it was made public by the author, not but the recipient. This way is a private thanks, a classy way to handle a public thanks is simply to link to it.
To Ray’s point, I agree. Give credit where credit is due. I just don’t know the full details and I find McIntyre’s innuendo off-putting. I’ll definitely give credit to the journal and the authors for being good scientists, acknowledging the problems in their own work, and moving forward to address them.
simon abingdon says
#51 Ray Ladbury
You say “Actually I think this episode illustrates beautifully the difference between the scientists and the “auditors”. The auditors are crowing over a victory and suggesting that the changes will favor their position. The scientists just want to know the new result”.
Ray, you could equally well have said “Actually I think this episode illustrates beautifully the difference between scientists A and scientists B. Scientists B are crowing [shame on them] over a victory and suggesting that the changes will favor their position. Scientists A just want to know the new result” (their enthusiasm unabated).
Ray Ladbury says
Simon@55…except scientists publish. Auditors don’t.
@ Comment by Unsettled Scientist — 9 Jun 2012
Paragraph 1: “Climate Audit is full of innuendo, and that’s just not my cup of tea when it comes to science.”
Paragraph 2 (referencing Climate Audit): “I’m still not sure it was a public thanks. In my line-of-work I’ve recently seen some individuals publishing on their website the details of a private correspondence from a colleague from another institution, and that is just scummy. So that kind of thing just leaves a bad taste in my mouth.”
McIntyre has been “auditing” climate-science for something like a decade now. And it looks like this will be the first time that he has actually unearthed significant errors in a published paper. Science will never be error-free, but the fact that it has taken McIntyre (someone who is obsessed with uncovering scientific malfeasance/wrongdoing and who has had nearly unlimited spare time to pursue his obsession) on the order of a decade to find nontrivial errors in a paper really is a testament to the robustness of climate-science as a whole.
This whole thing seems reminiscent of the IPCC Himalayan glacier brouhaha. A real error uncovered, and an embarrassing one at that — but nonetheless an isolated one that did not have any impact on the science as a whole.
And has McIntyre ever acknowledged that he erred when he used tree-ring data to train his “hockey-stick” red-noise noise generator without de-trending the tree-ring data first (to remove the long-term climate signal)? Because he failed to de-trend the tree-ring data before using it as a noise model, the “random noise” that he claimed would produce “hockey sticks” was itself contaminated with “hockey stick” signal statistics. That was definitely a major screwup/oversight on his part. It seems to me that when it comes to acknowledging errors, there’s more than a bit of a double-standard here.
[Response:He didn’t unearth them, one of his readers did. But it is not at all clear that this mistake by Gergis et al is in fact even a real problem–not nearly enough is known about exactly what the error was, much less what kind of impact on their study it will have. It has to do with how they did their calibrations. I’ve made several points over there since he raised this issue; the latest one is here: http://climateaudit.org/2012/06/08/gergis-et-al-put-on-hold/#comment-337241 Until Steve McIntyre addresses this “Screening Fallacy” issue (as he calls it), with conclusive, detailed analysis, he just doesn’t have a case, period. As for the detrending, I think you’re mixing up two different detending steps. The detrending of the tree cores to remove the age/size effect is not the issue, it’s rather the detrending, during the instrumental data period of the (1) climate data and (2) site-level chronologies (mean ring value for each year, after removing the age/size effect).–Jim]
Radge Havers says
simon abington @ 55
You could say it. You could say anything you want rhetorically and pretend it’s meaningful.
You could say that when I fly a kite that I’m just like a commercial airline pilot.
oakwood @ 57
So you’re making innuendo about supposed innuendo about Climate Audit’s innuendo? Is this supposed to be clever?
L. Hamilton says
“This whole thing seems reminiscent of the IPCC Himalayan glacier brouhaha. A real error uncovered, and an embarrassing one at that — but nonetheless an isolated one that did not have any impact on the science as a whole.”
A while back, out of curiousity I looked up the *physical* IPCC AR4, that is the books themselves, in a library. Took a few photos of exactly what glaciergate amounts to. Feel free to link these if they’re useful.
Here are the AR4 Working Groups I, II and III reports, close to 3,000 pages. The orange tab marks the page containing glaciergate.
Here is glaciergate itself, which happens on page 493 of the Working Group II (impacts) report. The orange tab marks the paragraph containing glaciergate.
Here’s a closer look at glaciergate . It consists of two sentences out of that one paragraph.
These are the two sentences, grammatically incoherent, mutually contradictory, and obviously written or copied carelessly while looking at something else.
There you have it, the scandal.
simon abingdon says
#56 Ray Ladbury
What defines science is its ability to make correct predictions: eclipses, Trinity, Apollo, for example. (That something happens to be published doesn’t necessarily confer scientific credibility, far from it).
For those who study climate to arrogate to themselves the title “climate scientist” is in my view sadly hubristic and premature. Radiative physics is one thing but understanding the actual behaviour of clouds quite another. For me a field of study needs observable and verifiable results to qualify as science. In climatology there just aren’t any. Not any.
Sorry Ray, until the climate community can make some convincing predictions about climate development and evolution they’re just wannabe climate scientists. Maybe one day, but not nearly yet.
[Response: Utter nonsense. There have been skillful predictions of all sorts – for future events: the impact of Pinatubo, the impact of ozone depletion, long term trends in temperature, etc. – for resolutions of apparent inconsistencies in the observed data – CLIMAP LGM SST, MSU temperatures, etc. – out-of-sample hindcasts for paleoclimate – the LGM, 8.2kyr event, the mid-holocene etc. That you choose not to acknowledge any of this is far more a commentary on your perception than it is the reality. – gavin]
Considering that the Gergis et al paper has been “put on hold,” would it not be proper to indicate the same under the chart prominently displayed at the beginning of this section, or remove the chart in its entirety?
[Response: I’ve put in a note. – gavin]
Regardless of ones views/opinions on the overall subject global warming, this episode does highlight one aspect that frustrates sceptics.
They make the charge, speaking in the generality here, that the MSM blindly and unquestioningly report stories, with lots of coverage, where a summary might fall under the headings ” it’s worse than we thought”, “it’s worse than it’s ever been”, etc. – and that this is the nature of the MSM. Their frustration is inflated then because no matter what happens afterwards, those headlines stick and any rereporting as a result of other evidence, retractions, etc – never get the same degree of coverage.
’twas ever thus.
[Response: The media does have biases of course, but the biases are towards things that are ‘news’ – controversy, sensation, man-bites-dog etc. But this is not bias towards any particular side in the climate issue – indeed, anyone of us can list dozens of high profile stories that got things horribly mangled or where marginal issues and people are erroneously elevated to the central stage. Generic paranoia about media coverage is not useful, one is better off trying to understand the fault lines in the whole enterprise and trying to avoid them. – gavin]
What writers of and posters to, Real Climate do not acknowledge is that the MSM seizes on papers such as that of Gergis et al to promulgate the position of the proponents of anthropogenic climate change/global warming but do not run subsequent stories announcing that the results may not be entirely as initially presented. Consequently although scientists and possibly even auditors, may be aware that there could be a modification of the results, this is not made clear to the general public and could generate a bias in public opinion. That said, I agree entirely with Gavin that “giving different sides ammunition” is not the way forward and I wish it were possible for both sides to discus their differences without rancour which, unfortunately, stems more from posters to rather than writers of blogs addressing climate science
Ray Ladbury says
Ah, I see James and Ian have received their talking points.
What horsecrap! Dudes, do you think the level of emphasis for the scientific position versus the “skeptic” position even remotely approaches the 97% level of the actual scientific consensus? I do not know of a single other scientific topic where the level of consensus and its portrayal in the media are so divergent.
Ray, I think you’re confusing signal and noise wrt the media coverage. Note how the instant a comment was made on this thread about one study being reconsidered out of 3 under discussion, the thread swerved into political perceptions of climate science/scientists – ignoring the “signal” represented by the other 2 studies and further ones cited in the topic post. We’ve now over 50% of the comments being irrelevant to the topic at hand.
I see news articles on climate science regularly, and very little “anti-climate science” – outside the political arena [might be a Canadian slant]. In addition, the “media problem” James and Ian bring up is irrelevant here as the study wasn’t really even published yet, let alone promoted in the general press, just fodder for bloviators. Please resume the previously scheduled program. ;)
wayne davidson says
#61 Simon, You may be referring to the good folks at Accuweather , some of whom have derided AGW as a joke, however as I note on my blog and website, they are terribly wrong most times with long term forecasts precisely because they don’t “believe” in AGW. They have a problem conceptualizing the impacts from trace gases. There are large successes in prediction with those who include every trace gas even water vapour which makes clouds…
Hank Roberts says
> results may not be entirely as initially presented
You’ve rediscovered Sturgeon’s Law.
It comes as a shock, doesn’t it, the first time you realize it?
Life is full of little surprises. That’s one of them.
Each person discovers it, eventually.
Hank Roberts says
By the way, for James and Ian et al.:
those who argue that uncertainty is a justification for inaction are precisely backwards in their thinking.
Unsettled Scientist says
Regardless of the state of this paper, anthropogenic climate change and global warming are both real. What your post highlights is the misconception in the general public that any new paper could change that. The scientific consensus isn’t swayed by the latest & greatest paper to be published. The consensus is built by taking the totality of evidence into account. When multiple independent avenues of investigation over the course of many years and decades point towards the same conclusion, it becomes the consensus understanding. Whether or not ACC or GW exist is not the interesting scientific question. We are now refining our knowledge of how they work. Any paper showing ACC or GW to not exist, no matter how well done, would need to be backed up by a plethora of papers to follow it, using multiple angles of viewing the world, before it would change the consensus.
Hank Roberts says
and the missing link for what I quoted, if I can get it to stick this time, is:
The costs of uncertainty
Ray:Ah, I see James and Ian have received their talking points.
Yes. Trundle over to WUWT and you can read Ian and James’ lessons as delivered by the charismatic authority figure in charge.
A bobble like Gergis’ is an opportunity to gauge the desperate hunger for real meat on the part of contrarians. They don’t require much substance to stay alive but when the rare treat is offered they become embarrassingly excited.
In any case it’s going to be interesting to see the Gergis rework.
The detrending of the tree cores to remove the age/size effect is not the issue… –Jim
Didn’t word my post as well as I should have — the “detrending” I was referring to (not the best terminology) was in reference McIntyre’s failure to remove the long-term (long autocorrelation time) climate signal from the tree ring data before he ran it through the hosking.sim() R procedure to generate his red noise.
So it appears that McIntyre’s “trendless red noise” was contaminated by long-term “hockey stick” climate signal because of his failure to pre-process the tree-ring data properly before using that tree-ring data as a red-noise “template”.
To my non-expert eyes, this seems like a pretty major oversight on McIntyre’s part — If I’m not totally off-base here, this seems like something that he should acknowledge, especially given the fact that he used his results to imply that Dr. Mann was so inept that he would confuse a random noise artifact with a coherent climate signal.
Further to Hank’s pointer, Lewandowsky’s Uncertainty is not your Friend and The Inescapable Implication of Uncertainty are well worth taking in.
Re Ian @ 70. You are correct. No one involved in then climate change debate will change their mind on the basis of one paper. But fundamental to the case that current climate change is a major concern is evidence that current temperatures are exceptional both in absolute level and rate of rise. The Gergis et al paper is an important addition to that case. ‘IF’ the Gergis et al paper is eventually rejected, the case that current temperatures are exceptional GLOBALLY is severely weakened. It would also indicate that the current peer-review process is inadequate.
[Response: No. Concern about human caused climate change rests on the six points we’ve outlined many times. The relation of today’s temperatures with respect to past periods is certainly of interest – but note that the UNFCCC was signed in 1992 – years before the first multi-proxy reconstruction, and when the anthropogenic signal was barely out of the noise. You are indulging in some serious revisionism here, designed merely to make hay from this particular episode. Secondly, since the Gergis reconstruction was only for Australasia, and indeed was the first for the region, whatever comes of the revisions this will still be the only information from that region. Since this didn’t exist last year, even if you discount this to zero (which won’t be the case), you aren’t any worse off than you were last year. What then has been weakened? And as for peer review, you appear to be under a serious mis-apprehension that peer review is a guarantee of correctness – this is simply not so. Peer review is merely the first step in evaluating any new idea – it is a minimum condition and not sufficient in itself. But this should be obvious, even complete garbage like McClean et al or Soon and Baliunas can get past peer review with a little ‘luck’. – gavin]
Susan Anderson says
re Accuweather, it might be worthwhile to note that Brett Anderson (no relation) who has run their climate change blog forever is excellent (dare I say superb?) and does not burk the facts. In addition, it appears that over time there are others over there who are acknowledging reality. Yes, I know they have Bastardi and doubtless others, but it has changed for the better significantly IMO.
Robert Murphy says
“Yes, I know they have Bastardi…”
Bastardi left Accuweather over a year ago.
But fundamental to the case that current climate change is a major concern is evidence that current temperatures are exceptional both in absolute level and rate of rise.
Restated, as the physics of this situation is quite clear at a nearly intuitive level and extending through outlandishly bulky calculations, it’s essential to contrarians to have alternative means of somehow discounting what’s painfully obvious. A myriad of jackalope hypotheses depend on maintaining the illusion of ignorance of the temperature record as well as being able to dismiss startling observations.
Martin Vermeer says
One more reason that Jim didn’t mention for expecting the Gergis et al. result not to change much, is a couple of simple reality checks that can be done by inspecting the actual manuscript.
See figure S2.2 page 56. Whether you use 27 proxies for the reconstruction, or 14, the resulting curves over the common period are highly similar. They tell the same story, in spite of only half of the proxies in one also being present in the other. Even using only four proxies doesn’t really change the storyline. To me this suggests that the story must be true. And if such large differences in the choice of proxies used produce such minor changes in outcome, why would changes in screening strategy be any more consequential? This stuff is way more robust than most people imagine.
Or look at figure 2 page 47. Here, the reconstruction reproduces every single twist and turn in the instrumental data — not photorealistically, but well enough. Sure, the reconstruction was calibrated against the instrumental record — but, every gory detail? That only makes sense if those proxies really follow temperature. Remember that the recon is just a weighted sum of contributing proxies; calibration determines the weights. The only way the recon can follow the bumps in the instrumental record is if some or all of those proxies already do.
So, this reconstruction may have its problems and may well not be the best that can be extracted from this data, but warts and all it is definitely a valid one.
Susan Anderson says
Robert Murphy @~77
Thanks for the correction. Joe Bastardi’s departure does not change the substance of the rest of what I said. AccuWeather has been gradually altering, and Brett Anderson has never been anything but solid on the facts. I still believe they are moving towards a more reality-based position on climate change and global warming, in line with developments in the world.
john byatt says
“we did it”, no matter how you look at it, we did it, that’s it..
wayne davidson says
77 Robert , nice to know that someone there has some understanding of AGW, it would be infinitely better if they actually refuted those who claimed that trace gases are of no significance. In here lies the difference, and especially the great confusion, contrarians love and live by this confusion, if on one hand one representative says something and the other completely the opposite, how can they represent the same science? How is the lay audience suppose to judge all this? Especially since one view clashes violently against the other. Freedom to speak is great, it reveals the point of view behind the person, but the institution practicing meteorology is equally free to speak, I haven’t heard Accuweather refuting Bastardi while he confidently broadcasted to millions that a trace gas is of no import. I am waiting for this meteorological company to defend correct science in order to clear the air.
Without this, the good work of Mr Anderson is much diluted with junk science having no prediction prowess.
Martin Vermeer — 10 Jun 2012 @ 3:59 PM:
This stuff is way more robust than most people imagine.
(Yeah, I know that I’m gonna sound like a broken record by posting these results here *yet* again — but I’ll risk boring the regulars in the hopes of catching the attention of some of the new lurkers who happen to pop in here.)
Now, this doesn’t have anything to do with the Gerges et al. data, but it’s still a nice example what kind of results you can get from a totally $#@!ing robust data-set.
Some time ago, I tried generating global-average temperature estimates from very small numbers of GHCN stations (using *raw* data).
Divided up the planet into just 4 grid-cells, picked a single *rural* station per grid cell (i.e the station with the longest temperature record in that grid cell), and computed average temperature anomaly results from just those 4 *rural* stations via a brain-dead-simple anomaly-averaging procedure.
Repeated the process several more times by successively increasing the number of grid-cells (whilst keeping the grid-cell areas as close to constant as possible) and selecting 1 *rural* station per grid-cell as described above.
That would be *raw* data from exclusively *rural* stations, lurkers — so issues involving UHI or data “homogenization” have been taken off the table here.
Results here: https://si0.twimg.com/profile_images/2190396997/NASA-GISS-vs-Globally-Scattered-Rural-Stations.jpg
As you can see, data from only a few temperature stations is needed to see a clear global-warming signal. And by the time you get to ~70 (out of thousands) of stations, you get results that track the official NASA/GHCN results pretty darned closely.
The take-home lesson for new lurkers here is: A brain-dead-simple averaging procedure, applied to raw data collected from a very tiny percentage of the GHCN stations, still produces global-average temp results that match the official NASA/GISS results *very* closely.
The take-home lesson for lurkers here is: In spite of what Anthony Watts and other deniers have been telling you for gawd-knows how many years, the surface temperature record is way more robust than most people imagine.
Ian @ 64:
…though admittedly not in the direction you proposed
D. Robinson says
The reason the paper was so important was because it purported to show an “Australian hockey stick”. They started with 62 proxies, discarded 35 leaving 27 and have a whopping 2 proxies going back 1000 years and 0 of them actually from Australia.
They made a big deal about screening de-trended data to eliminate the obvious statistical problems of pre-screening for your desired signal. Now it seems likely they will remove that statement and screen the paleo-climate way instead, (well this proxy matches our signal, so we are going to use it to independently confirm our signal, this one doesn’t match our signal, so we’re not going to use it to disprove our signal).
The paper originally showed it was less than one tenth of a degree C warmer today than 1000 years ago with an uncertainty of 2 tenths of a degree (nice). It’s not going to be a ‘stronger more robust’ paper when it’s re-submitted without the de-trending statement. The uncertainty will increase.
[Response:No, you have a number of things factually incorrect. First, their reconstruction is for the entire Australasian region, the boundaries of which they explicitly define (by lat/long). Second, they most emphatically did not make a “big deal” about their detrending of the data before calibration–indeed they under-stated it, describing it with only a couple of sentences. You wouldn’t make such a statement if you had actually read their manuscript. Rather, Climate Audit has made the very big deal about it, as is their wont. Third, your assessment of how and why screening of proxies is done is just plain wrong, I absolutely guarantee that. And you have no basis for knowing whether the paper will be stronger or weaker after their re-assessment of the situation. You are simply guilty of believing what they promulgate endlessly at Climate Audit, without making your own investigation of the issue.–Jim]
D. Robinson: The reason the paper was so important…
So, to be all Perry Mason about it, you stipulate that if the paper is corrected and the results do not change, you will continue to find it important? That is to say, your belief about the importance of the recent change in temperature will be swayed?
Important, or not important? I’m guessing that for a lot of folks the answer is, “it depends.”
Re: Jim (response to Martin – 85). What everyone can reliably predict, on both sides of the debate, is that the paper will be re-submitted relatively unchanged, but with reference to ‘screening de-trended data’ removed from the description of the methodology. Your own comments, here and in another place, have indicated this would be acceptable to your side of the debate.
[Response:Negative. Nobody can predict what their re-examination of their paper will produce, nor what the Methods section will state. And I have never said anything remotely like what you claim, anywhere. Furthermore I don’t have a “side”, regardless of what you imagine–Jim]
Amazing how quickly these discussions swerve out of any rational basis. There’s a wealth of information in D. Robinson and oakwood’s remarks but it mostly doesn’t pertain to Gergis et al.
The prejudice seems to be that Gergis et al is a mini-conspiracy dove-tailed with a larger plot. The results of the paper are predefined as described by CA and crew. The two recent comments by D. Robinson and oakwood neatly follow McIntyre’s narrative:
Looking ahead, the easiest way for Gergis et al to paper over their present embarrassment will be to argue (1) that the error was only in the description of their methodology and (2) that using detrended correlations was, on reflection, not mandatory. This tactic could be implemented by making only the following changes:
[McIntyre imaginary edits as repeated here by D. Robinson and oakwood]
“Had they done this in the first place, if it had later come to my attention, I would have objected that they were committing a screening fallacy (as I had originally done), but no one on the Team or in the community would have cared. Nor would IPCC.
So my guess is that they’ll resubmit on these lines and just tough it out. If the community is unoffended by upside-down Mann or Gleick’s forgery, then they won’t be offended by Gergis and Karoly “using the same data for selection and selective analysis”.”
I’ll hazard a guess that McIntyre’s expecting the conclusions of the paper to remain unchanged. Whether his remarks are inoculation against disappointment or sincere belief remains even more speculative.
BTW, McIntyre’s use of words such as “forgery” is exactly why his followers shouldn’t be surprised when other people find his language distracting and counterproductive. If you’ve not already soaked in that style of debased hyperbole it’s quite conspicuous.
Good grief, all you have to do is just print the words “hockey stick” and the crazies come out in force.
[Response:Disturbing is the word for it.–Jim]
Jim, simply give us here a succinct and brief statement on how you would handle the issue. Your statements have been unclear. I recall you seemingly to agree with the Gergis screening process and seemed to insist on the detrended procedure. Later you referred to either selection process – detrended or not detrended – could be used.
[Response:How I would handle what issue?. I’ve already made my position clear through numerous comments, many of which I’ve had to repeat over and over again at Climate Audit, because of all the misdirections and misinterpretations they engage in over there. I’ve already said there are arguments that can be made either way regarding what time scale of data to use during calibration, and I have never even remotely insisted on their detrending approach. You almost surely got such an interpretation from what’s been said at Climate Audit by somebody or other. I don’t have time to launch into some extended discussion of calibration methods choices here. This stuff is all discussed in the literature and dendrochronology core texts like Fritts etal, Cook and Kairiukstis et., but if I get the time, I’ll do a post on it. UPDATE: I further note, that your comment is a verbatim quote of a question posed by someone at Climate Audit. I mean, you can’t even come up with your own
D. Robinson, Gergis and colleagues appear to have used an abundance of caution in constructing their record as is plain when reading their paper(manuscript is still available for those interested; see upthread for link). For folks who’ve bothered to read or even just skim the paper, Gergis’ conclusion is obviously not based solely on two proxies though that’s apparently what some of us are led to repeat. We don’t even have to go past the abstract to get that:
“Applying eight stringent reconstruction ‘reliability’ metrics identified post A.D. 1430 as the highest quality section of the reconstruction, but also revealed a skilful reconstruction is possible over the full A.D. 1000–2001 period.”
Notice that there’s a distinction drawn between the later and earlier portion of the record?
One of the striking things about McIntyre’s critique is how he’s able to invert Gergis’ meticulous approach to data quality and recast it as nefarious.
If you’re very bothered by a diminishing number of proxies go ahead and toss the earliest 400 years, but remember you can’t fill in those missing years with your imagination. You’re left with a record that’s worse, if you’re keen on “flat.”
On the other hand, if you prefer more proxies, drape the entire Gergis record on the ensemble of other similar reconstructions and watch it vanish; the Gergis result is hardly a surprise and fussing over the number of early proxies in the reconstruction isn’t going to make things pleasingly unbent. More proxies whether they come in ones or twos or by the dozen only help cement what’s fairly obvious at this point.
As usual, the lesson here is to actually look at the paper in question– look at everything– not just follow instructions.
Deep Climate says
#90 Jim, a post laying out the real issues would be a useful antidote, but I can understand you might have better things to do.
It seems to me that Gergis et al have at least three choices.
a) They could stick with the screening methodology exactly as described. But this would apparently result in only 8 proxies in the reconstruction, as far as I can tell.
b) They could adjust the methodology to what was actually done (i.e. not detrend proxies and temp series before screening). This seems to be what McIntyre expects. But I would be surprised if this were done without at least exploring other approaches, given that this was a key, explicitly justified, element of the original methodology.
c) They could relax some of the other screening criteria, but still apply to detrended series. Here Mann et al 2008 gives some possible changes.
The screening process requires a statistically significant (p < 0.10) correlation with local instrumental surface temperature data during the calibration interval. Where the sign of the correlation could a priori be specified (positive for tree-ring data, ice-core oxygen isotopes, lake sediments, and historical documents, and negative for coral oxygen-isotope records), a one-sided significance criterion was used …
Presumably using p < 0.1 and one-sided significance screening (eminently justified, IMHO) would result in a proxy set somewhere between 8 and 28 in size (although at least one tree-ring and one coral proxy would get tossed).
Or they could do all of the above (or other variations) and compare the robustness of the resulting reconstructions.
[Response:Common practice is to use non-detrended data and to calibrate on annual-scale data over the instrumental period, as validated by split calibration and validation periods and some specific validation (aka “verification”) statistics. So, if that’s what happened, that’s really all they have to say, and then report the results. The other, broader misconceptions in dendro-climatology, particularly wrt screening of proxies, are what need to be written about, given the enormous amount of confusion and outright false statements that have been generated at Climate Audit on this topic.–Jim]
Re: Jim (87) and dbostrom (88). Let’s just see what happens. I will be pleased if my prediction is wrong.
Hank Roberts says
> a verbatim quote of a question posed by someone at Climate Audit
The Internet, it’s a series of tubes.
Most of them transfer copypaste — from one location to another.
Oakwood: I will be pleased if my prediction is wrong.
As we’ve been requested to be attentive attribution and due credit by the CA folks, just for the record Oakwood is repeating Steve M.’s prediction.
For my part I’m left to think that “the medium is the message.” Or massage, as the case may be…
Deep Climate says
[JB: … Common practice is to use non-detrended data and to calibrate on annual-scale data over the instrumental period.]
I don’t disagree with that, of course, but the authors initially wrote:
For predictor selection, both proxy climate and instrumental data were linearly detrended over the 1921–1990 period to avoid inflating the correlation coefficient due to the presence of the global warming signal present in the observed temperature record.
The “on hold” statement reads:
While the paper states that “both proxy climate and instrumental data were linearly detrended over the 1921–1990 period”, we discovered on Tuesday 5 June that the records used in the final analysis were not detrended for proxy selection, making this statement incorrect. Although this is an unfortunate data processing issue, it is likely to have implications for the results reported in the study. The journal has been contacted and the publication of the study has been put on hold.
“Likely to have implications for the results” suggests the authors are at least considering alternatives to simply specifying screening with non-detrended data.
[Response: Yes, thanks for clarifying that. I didn’t mean to imply that their results themselves wouldn’t change, only that they don’t need to do some kind of massive re-working of their entire analysis, if in fact they had simply followed standard procedures but mistakenly reported otherwise.–Jim]
John Mashey says
Sayeth John Tukey:
‘Far better an approximate answer to the right question, which is often vague, than the exact answer to the wrong question, which can always be made precise.’
I’ve long wished he were still around to comment on temperature reconstructions.
Maybe if we borrow the medium Fred Singer must of used to connect with Seitz for 2 years.
re: gavin comments in #75 on peer review and luck, for such as Soon and Baliunas. Dana1981 did a nice synopsis at SkS on Pal review. Luck is nice. The right editor is much better.
Martin Vermeer says
> Luck is nice
“Luck” with editors/reviewers is not always nice, if an in hindsight embarrassing paper makes it to publication :-(
Martin Vermeer says
D. Robinson, we know from the instrumental record that temperatures have trended upward over Australasia as they have globally. This — what you call “the signal” — we do not need proxies for to tell us, we knew that already. The interesting thing is what happens further back, where we don’t have instrumental data. But tell me, would you actually trust as temperature proxies, proxies that fail to repond to this clear signal?
[Response:The logic of many of those questioning tree ring analysis goes like this: (1) tree rings are maybe marginally OK as a climatic proxy, as long as you don’t do any type of screening of supposedly “bad” sites; you have to take all the data, or none of it, based on an apriori decision of whether or not a certain species is a climatic responsder, from which you can’t deviate after you’ve collected the data, (2) a sizeable fraction of your sites don’t pass a given screening criterion, therefore you can’t use those sites, and therefore, any sites of that species, (3) therefore tree rings can’t be used for paleo-climatic estimates at all and if you try to do so, you are guilty of believeing in, and executing, the “Screening Fallacy”, which they suppose, with nebulous definition and no actual demonstration of validity, is some kind of inviolate law.–Jim]
“you are guilty of believeing in, and executing, the “Screening Fallacy”, which they suppose, with nebulous definition and no actual demonstration of validity, is some kind of inviolate law”.
The law of course being, no hockey sticks.