New analyses of proxy data for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years. It is also likely that, in the Northern Hemisphere, the 1990s was the warmest decade and 1998 the warmest year (Figure 1b).
naturally, this was a red rag to the septics. Its was based, as it says, on Jones et al., 1998, Mann et al., 1998, 1999 and Briffa, 2000. How does this stack up, when compared against more recent reconstructions?
The answer is, extremely well. There is a nice pic on wikipedia (and I've inlined it above) which shows 10 different reconstructions. Looking at this pic we see that
- the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years is true for all of them (and for those that go back further, it looks true of the previous 1000 years too)
- It is also likely that, in the Northern Hemisphere, the 1990s was the warmest decade is also true
- and 1998 the warmest year also true (it happens not to have been exceeded since 1998, and most likely not earlier)
Another interesting feature of those graphs is that they all pretty much agree on the temperature at the peak of the MWP as being about 0 on a scale that has "now" as about 0.4 (with the caveat of resolution). The major differences are on the depth of the LIA - about 1600, there is little agreement.
Which is why (you just knew I was coming to this didn't you) all the ho-ha over MBH98 is interesting statistically (perhaps) but irrelevant scientifically. It also ought to be irrelevant politically.
To debunk another couple of myths: idiots sometimes assert that the Hockey Stick (ie, MBH98/99) underpins Kyoto. This is nonsense for any number of reasons, but the most obvious is that Kyoto was negotiated in 1997 and you need to believe in reverse causality to think that a 1998 paper underpinned it.
Another one is pointed out by this RC post: The famous conclusion of the IPCC, “The balance of evidence suggests that there is a discernible human influence on global climate”, does not depend on any reconstruction for the past millennium. It depends on a detailed analysis of 20th Century data. In fact, this conclusion is from the 1995 IPCC report, and thus predates the existence of quantitative proxy reconstructions like the “hockey stick”.
Septics focus on MBH98 because they think they have something to say about it. People, naturally, respond. All this tends to give a rather unbalanced view of where the science is. The palaeo reconstructions are important, but only one strand. There is lots and lots of D+A (DAtDA?) that people tend not to discuss much, rather in the same way that few people discuss detailed solutions of GR much: its just too complex for anyone except specialists.
Note, BTW, that "likely" is defined thus: In this Summary for Policymakers and in the Technical Summary, the following words have been used where appropriate to indicate judgmental estimates of confidence: virtually certain (greater than 99% chance that a result is true); very likely (90-99% chance); likely (66-90% chance); medium likelihood (33-66% chance); unlikely (10-33% chance); very unlikely (1-10% chance); exceptionally unlikely (less than 1% chance). The reader is referred to individual chapters for more details.
O wise one,
How come the 2004 point on the pic is higher than anything else, if 1998 was the warmest year so far?
A good question, Oh Wife, which I expect other people are wondering too.
There is an easy answer; I offer a prize (of some unspecified nature; possibly merely the recognition of having answered) to the first non-climatologist to supply it.
Give that person a cigar... and a rapid-response prize too.
the chaotic mixture of the spaghetti graph shows, first of all, that the error in determining the temperatures a few centuries ago is roughly of order 0.5 Celsius degrees - just look at the differences.
This is above the alleged differences between the present era and the past centuries. So your statement that the present era is warmer has less than 1-2 sigma confidence level, and the probability that it is wrong is about 50 percent.
The different papers used in the multicolored graph are inconsistent with each other, given the small errors they claim to have achieved, and I am really baffled how such an inconsistent picture may be described by the words "extremely well" that you used. Are we looking at the same picture?
All this inconsistency between the graphs - inconsistency that appeared despite the fact that the different papers used very much the same input data and they often shared one or two (or more) discredited scientists - is evidence for the statement that the error in determining the past climate is much greater than what all these guys claim. The variations as a function of time have also been much greater than in any of these papers, including Moberg who admitted much larger variations than the other guys, as explained by von Storch et al. and others.
The statement that the hockey stick hypothesis was not crucial for the Kyoto movement is unrealistic. The pictures appeared at the very last page - as a punch line - of the synthetic 2001 IPCC report.
The "smoothing filter" is another example how sloppy the approach of the climate "reconstructors" is. If you smooth the data over an N-year interval, then you cannot assign it to the last year of this period.
If you assign it to the middle year instead, then your calculation is statistically irrelevant because you can't know what the future temperatures - that should affect the result for 2004 - are. The conclusion is, of course, that the fact that 2004 happens to be higher than the previous data points in the graph has no scientific consequences and it is likely that it will go down once the smoothed temperature for 2004 is computed correctly in the future.
Your comparisons with GR are outrageous. In physics, we certainly do not use your crackpot policies of brainwashing the scientific public with insights that they "are not able to verify". If someone cannot verify a statement about GR, then she cannot verify it, and she cannot be used as additional evidence for any statement about GR whatsoever.
The fact that you apparently follow a different policy and endorse data that you don't understand only means that your field is really a field of crackpots who copy nonsense from each other - not quite a field of science. I apologize to one or two exceptions whom I know in your field, but you are definitely not one of them.
All the best
Thanks for the post and especially for your patient answers to my previous comments and critiques.
I hope you will continue to be patient while I continue to wonder about MBH. I would like to emphasize that my point of view is nearly orthogonal to Lumo's on almost every point of the debate, but I think that the MBH result, even if superceded, still is important.
If the methodology had severe flaws, and climatolgists jumped uncritically to its defense, it tends to undermine the credibility of all climatology results.
Let me focus on one point - the fact that, as Mann admitted, they used the mean of only the 20th century data rather than the whole sample. I don't think that this can possibly be proper. I consulted a lot of statistics books, and all say you should use the mean of all the data. The reason seems obvious: if you use a false mean, the the covariances all have a bias.
The climatologist cited on this point in the Dutch article is Hans van Storch, the author of a widely praised book on statistical methods for climatology and no scientific lightweight. In his defense, Mann claims that he did it that way because it was "standard in climatology." I hope that's not true. He also said he got fewer significant PC's that way.
Well duh! If you introduce a bias, it's completely plausible that the first PC will just recover that bias!
Finally, painful as it is, I have to agree with Lumo that the comparison with GR doesn't hold up - In GR, if you can't derive a result, you don't understand it.
CIP, I must be missing something obvious regarding the 20th century data issue, so do you have a link to a complete discussion of it? I would point out to you that much of the defensiveness about M&M has to do with their obvious bias. Why should Mann (or anyone else) give them the time of day, especially now that McIntyre is attacking the entire field (von Storch included)?
Oh, and William, I see from http://climatesci.atmos.colostate.edu/?p=70 that your continued tilting at RP Sr.'s tattered windmill has officially become a thankless task. Call me Sancho...
And geez, I didn't even see the exciting contest until a day after it was over! I *knew* the answer was smoothing! I coulda been a contender! Find out when CS is off-line before you do this again. :)
Lumo: I assert that string theorists have sought to brainwash me with insights they cannot verify. Let's start with the entire field... Also I think it's weird that with your devotion to precision you would refer to "one or two" climate scientists whom you would not freely insult to the point of slander. If you meant 1.5, say so. On your point about the smoothing, bear in mind that 2004 may not be adjusted downward quite as much as you think, as 2005 will very likely be warmer than 2004 and looks to be on track for a new record. Sorry.
Oh dear. "Nice" Lubos didn't last very long.
Please folks: be polite, or be deleted.
Lumo, while general relativity has been tested, string theory is simple fiction. Hmmm....
GR/D+A: I'm not surprised Lumo missed the point; I am surprised CIP did.
The point is that people tend to concentrate on discussing temperature graphs because they think they understand that (whether they do or not is another matter). Its pretty obvious to most people that they don't understand the D+A stuff, so they tend not to discuss it. I'm talking about non-specialists here, of course; the specialists do understand it.
But this is a problem, because if your real interest is understanding the current state of knolwedge in detecting and attributing climate signals, then D+A is exactly what you should be looking at, and the Hockey stick stuff is a side show.
Finally, teasing Lubos about string theory is fun, but if you're really hard enough you should be doing it on his blog where he can bash you back...
Steve Bloom - "Why should Mann (or anyone else) give them the time of day, especially now that McIntyre is attacking the entire field (von Storch included)?"
Mann has no obligation to give M&M the time of day. He does have an obligation to either show that credible critiques are incorrect or concede their points. Science isn't (or shouldn't be) politics. MBH, in generating their PCA, subtracted the twentieth century mean from their data rather than the overall mean.
Belette - Perhaps you could explain what point it was that I missed re D+A/GR.
Lubos - you make so many errors, its hard to know where to start. You say "The different papers used in the multicolored graph are inconsistent with each other, given the small errors they claim to have achieved". I very much doubt youve troubled yourself to find their error estimates, though the MBH ones are in the TAR. But to assert from that, that all is uncertain is quite wrong. No-one seems to find a MWP that was as warm as, or even approaching, now: and all the grpahs show that; a Point you refuse to see. As for Kyoto, it really does seem as if you believe in reverse causality - perhaps this is a feature of string theory.
CIP - Re conceeding, I think you are wrong on many levels. I strongly suspect you've been reading too much M&M, which is bad for you (you say "If the methodology had severe flaws, and climatolgists jumped uncritically to its defense" but these are both big Ifs. The first is probably false; the second also rather doubtful). Firstly, the idea that one paper instantly overturns the existing viewpoint is naive, scientifically (and you're a scientist, you should know this). It wasn't true for Einsteins 1905 papers, and it hasn't been true since, even in the case where the papers were correct. In the normal course of events, papers would go to and fro for a few years, and the thing would settle down, either by one side conceeding, or more likely by one side fading away. An example is the how has the currrent antarctic ice sheet been there question. But in this case, Mann has published extensively rebutting M&M's allegations, you'll find refs in the RC posts, you can read them if you like (there is a Rutherford et al in J Clim). Re D+A/GR: the point is the one I explained in the previous comment just above.
Steve - I'm afraid you'll have to get up early to beat CSea! RP: Oh dear, he has gone off the rails. Now I will have to do some GCM runs. I think he feels the need to be "different". I'm quite happy with the consensus.
BTW, this is definitely worth a read. Look especially at the figure at the end... "In summary, MM05 show that the normalization employed by MBH98 tends to bias results toward having a hockey-stick-like shape, but the scope of this bias is exaggerated by the [MM's] choice of normalization and [MM's] errors in the RE critical value estimate."
Belette - The Huybers paper was exactly what I was looking for - a dispassionate analysis. I also think that it ratifies my comment about the bias introduced by the MBH normalization (also pointed out by M&M). Thanks much for the reference. I would have been far less annoyed with MBH if they had figured that stuff out on their own, instead of the sort of snow job defense they actually mounted.
PS - I don't recall actually reading M&M. I think my doubts about started with reading Mann's defefense on RC.
Not that anyone should trust my recall of events - I certainly don't.
Incidentally, it seems that I am the only person on this forum who has read all the relevant papers by MBH and MM, as well as responses of von Storch and others. Not even CIP can compete. ;-)
Hi Lubos. Ah, but I've read a von S preprint that you haven't :-). Keep checking GRL.
Meanwhile, please keep the comments polite, or no-one will be able to read what you write.
In exchange for pointing me towards this great Onion article, I'll re-post a Lubos comment (sans profanity) that got deleted. This doesn't imply that I agree with it - far from it - and the misunderstanding about PC1 is unfortunately widespread. But Lubos wrote:
Hi Capitalist and Imperialist Pig, given what you wrote just now - which looks almost exactly equivalent to what I think about the interrelations between bias and PCs (of course that strong enough bias will be manifested as PC1) and the difference between solving equations and doing politics (of course that one can only deduce something quantitative from GR if he can at least partially solve the equations) - I am afraid that you will eventually be arrested as a true Capitalist and Imperialist Pig by friends like William Connolley. ;-). One comment where my accent could be different. You know, I like and admire von Storch a lot, and it is always a pleasant experience to interact with him remotely. But the level with which you are ready to make very different conclusions just because the name that appears is von Storch as opposed to a different name seems a bit over the justifiable edge. Von Storch probably knows how to do statistics better than most icehockey players, including the stars of the NHL :-), but still, this science is no string theory and it is certainly conceivable that someone learns how to do it as well as Hans, too. A quote by "Steve Bloom" is very typical: "Why should Mann (or anyone else) give them the time of day, especially now that McIntyre is attacking the entire field (von Storch included)?" [deleted] Why should they dedicate time to M&M if it could turn out that something has been wrong with the whole field? Very interesting question. Guess what's the answer. It's one of the primary jobs of a scientist to eliminate the possibility of big errors in their work, ESPECIALLY huge, widespread, and far-reaching errors. [deleted]. Guess why von Storch does not seem to be threatened by M&M. I hope that no one expects me to respond to WC. I see nothing to respond. Belette, drink some more milk and ask your brother or father on the picture what you're doing wrong. Best wishesLubos -- Posted by Lumo to Stoat at 10/14/2005 02:00:48 PM
Sorry, some formatting lost.
I have a question regarding the Huybers paper: The information he got from Jones and Moberg (2003) seems to have played an important role in his analysis. Obviously MBH98 wouldn't have had that available. As far as I can see, Huybers doesn't discuss the implications of this. Was J&M(2003) critical to his determination of a bias in MBH98?
Steve - It looks to me like the only role the J&O paper played was in showing that there was no advantage to any funky normalization. Both MHB and MM erred by choosing non-standard normalizations.
I think that one of Huybers' more interesting suggestions was that it was better to forget the whole PCA and just look at averages - in other words, the simplest approach looks best.
The Huybers paper has been out there in one form or another for about six months. It is recently accepted with some modifications. More interesting is McKitrick's response http://www.climateaudit.org/?p=369 and the response for GRL. I await Mann, et als. response to both.
Finally, as Huybers points out most of the substance of MMs argument rests with their claims about the Bristlecone pine series, although they really don't come to grips with MBH 99s discussion of this. Certainly this is a question for Malcolm Hughes to answer rather than just a simple reliance on Idso and ?? (I forgot)...
BTW - Why don't climatologist's post to the Physics ArXiv? Isn't it time to get science past the "I'll show this paper to a few of my buddies" and the world can wait for a couple of years to see it in dead tree form stage?
SB - the J&M 2003 will only be an update of previous Jones instrumental series, so MBH98 would have access to virtually equivalent data.
Huybers seems to have decided that with his normalisation, PC1 is nearly the average. He then goes on to declare that similarity to the average is the appropriate metric, and therefore you don't need PCA. This seems rather questionable to me.
Meanwhile, he has forgotten that its not just PC1 used in the reconstruction.
Arxiv: its not used. Its not the way climatology is done. And why would we use the physics one anyway? Preprints of everything online would be nice, but if journal policy is not to publish pre-published research (Nature is certainly like that; I suspect Science too) then you can't do it.
Re Arxiv: I predict that such facilities will grow in impact. There is a (hardly used) atmosphere-ocean section already.
Astronomy and HEP also publish in Nature etc, so I don't see that argument holding much water.
FWIW, I generally look for rapid publication rather than "high status" journals for my work.
Anyone have a picture of the spaghetti graphs without the instrumental part? (since the justification for the proxies back into history is their correspondance to observed temp changes now). Like to see what it looks like. My usual impression is that it is not as dramatic. (that doesn't mean that 20th century temps didn't go up, it means that the proxies are not that reliable going back.)
im havin fun......
the answer to Miriam brod's question is obvious.......the article said that 1998 was the warmest year of the 20th century....2004 might have been warmer, but it is a new century now
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