# Temperature Record of the Last 1000 Years **URL:** \ **Category:** Great Debates\ **Created:** [November 10, 2007, 5:16pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935 "2007-11-10T17:16:54Z")\ **Posts on this page:** 20\ **Page:** 7
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 8, 2007, 5:00pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/121 "2007-12-08T17:00:50Z")
Righto, back again. **brazil84** , it seems to be pretty apparent that you don’t understand at least a good half of what everyone else is writing and are probably just mentally skipping it, perhaps without even realising. So really what we need to do first is figure out where your understanding is breaking down. First question: Would you say that as the average global temperature rises and falls that every location on earth will rise and fall in temperature by the same amount? ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 8, 2007, 5:30pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/122 "2007-12-08T17:30:49Z")
[QUOTE=wevets] You don’t think longer moving averages decrease sensitivity towards trends? [/quote] I would say that it depends on the trend. For example, if there is an upward trend that lasts 5 years, a 100 year moving average probably won’t pick it up. On the other hand, a long term trend might be easier to see against year to year fluctuation if you use a longer moving average. But why won’t you answer my question? It’s a very simple question: Let’s define an “elbow” as a point where there is a large change in the slope of the graph. All things being equal, a graph with a 40 year smooth will have equal or fewer elbows than a graph with a 5 year smooth. Right? > [@](#): > > I provided cites for my views on moving averages, could you do the same? Why don’t you just answer my question? It might be that we’re on the same page here. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 8, 2007, 5:33pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/123 "2007-12-08T17:33:07Z")
[QUOTE=Sage Rat] Righto, back again. **brazil84** , it seems to be pretty apparent that you don’t understand at least a good half of what everyone else is writing [/quote] It depends on the poster. Anyway, perhaps you are the one who doesn’t understand. > [@](#): > > First question: > > Would you say that as the average global temperature rises and falls that every location on earth will rise and fall in temperature by the same amount? I would say probably not. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [December 9, 2007, 12:11am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/124 "2007-12-09T00:11:52Z")
Well, I’m not sure if its been mentioned or not, because my eyes have glazed over at times reading the thread, but I would strongly recommend that anyone interested in the topic read [this thread](http://www.climateaudit.org/?p=2322#more-2322) from beginning to end. Then you can come back and tell us if you found any factual errors in the presentation. The hockeystick is deader than dead, and all of Michael Mann’s friends and supporters can’t put Humpty back together again. w. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 9, 2007, 3:13am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/125 "2007-12-09T03:13:33Z")
[QUOTE=intention] Well, I’m not sure if its been mentioned or not, because my eyes have glazed over at times reading the thread, but I would strongly recommend that anyone interested in the topic read [this thread](http://www.climateaudit.org/?p=2322#more-2322) from beginning to end. Then you can come back and tell us if you found any factual errors in the presentation. [/QUOTE] Yes…I can find some. For example, McIntyre cherrypicks quotes by quoting this long section from the report: > [@](#): > > ``` > Spurious Principal Components: McIntyre and McKitrick (2003) [actually McIntyre and McKitrick 2005a] demonstrated that under some conditions, the leading principal component can exhibit a spurious trendlike appearance, which could then lead to a spurious trend in the proxy-based reconstruction. To see how this can happen, suppose that instead of proxy climate data, one simply used a random sample of autocorrelated time series that did not contain a coherent signal. If these simulated proxies are standardized as anomalies with respect to a calibration period and used to form principal components, the first component tends to exhibit a trend, even though the proxies themselves have no common trend. Essentially, the first component tends to capture those proxies that, by chance, show different values between the calibration period and the remainder of the data. If this component is used by itself or in conjunction with a small number of unaffected components to perform reconstruction, the resulting temperature reconstruction may exhibit a trend, even though the individual proxies do not. Figure 9-2 shows the result of a simple simulation along the lines of McIntyre and McKitrick (2003) (the computer code appears in Appendix B)…. > > ``` > > Principal components of sample data reflect the shape of the corresponding eigenvectors of the population covariance matrix. The first eigenvector of the covariance matrix for this simulation is the red curve in Figure 9-2, showing the precise form of the spurious trend that the principal component would introduce into the fitted model in this case. This exercise demonstrates that the baseline with respect to which anomalies are calculated can influence principal components in unanticipated ways. (STR Preprint, 86) while ignoring [section: > [@](#): > > As part of their statistical methods, Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions. A description of this effect is given in Chapter 9. **In practice, this method, though not recommended, does not appear to unduly influence reconstructions of hemispheric mean temperature; reconstructions performed without using principal component analysis are qualitatively similar to the original curves presented by Mann et al. (Crowley and Lowery 2000, Huybers 2005, D’Arrigo et al. 2006, Hegerl et al. 2006, Wahl and Ammann in press).** (bolding added) So, in other words, yes, this method is a potentially dangerous one to use but, no, it did not in fact make a difference in this case. This would hardly be the first case when a scientist has gotten the right answer with the wrong (or a not completely robust) method. One reason this happens is that most good scientists will actually do the calculation a few different ways, so while he may write up this particular technique, he may well have verified the results with another technique. The NAS panel do agree with McIntyre and McKitrick more in regard to the issue of robustness with respect to the proxy choices but that is a different issue…and the fact that “the Mann et al. (1999) reconstruction that uses this particular principal component analysis technique is strongly dependent on data from the Great Basin region in the western United States” was in fact something that [url=[http://wdc.obs-mip.fr/paleo/pubs/millennium-camera.pdf](http://wdc.obs-mip.fr/paleo/pubs/millennium-camera.pdf)]was already pointed out by Mann et al. (1999) themselves](]this[/url): > [@](#): > > It is furthermore found that only one of these series{PC #1 of the ITRDB data{exhibits a significant correlation with the time history of the dominant temperature pattern of the 1902-1980 calibration period. Positive calibration/variance scores for the NH series cannot be obtained if this indicator is removed from the network of 12 (in contrast with post-AD 1400 reconstructions for which a variety of indicators are available which correlate against the instrumental > record). Though, as discussed earlier, ITRDB PC#1 represents a vital region for resolving hemispheric temperature trends, the assumption that this relationship holds up over time nonetheless demands circumspection. Clearly, a more widespread network of quality millennial proxy climate indicators will be required for more confident inferences (ITRDB stands for the International Tree Ring DataBank [all from North America] and it is noted elsewhere the Principle Component (PC) #1 is dominated by the western U.S. region.) And, elsewhere in that paper, Mann et al. say: > [@](#): > > In using the sparser dataset available over the entire millennium (Table 1), only a relatively small number of indicators are available in regions (e.g., western North America) where the primary pattern of hemispheric mean temperature variation has significant amplitude (see Fig. 2 in MBH98), and where regional variations appear to be closely tied to global-scale temperature variations in model-based experiments [Bradley, 1996]. These few indicators thus take on a particularly important role (**in fact, as discussed below, one such indicator [PC #1 of the ITRDB data] is found to be essential**), in contrast with the post AD 1400 reconstructions of MBH98 for which indicators are available in several key regions [e.g., the North American northern treeline (“NT”) dendroclimatic chronologies of Jacoby and D’Arrigo, 1989]. (bolding added) The reason why this statement is so interesting is the McIntyre and McKitrick made such a big deal about finding a directory on Mann’s website that had the word “CENSORED” or something like that in the directory name that showed how the reconstruction looks in the absence of that data. This was their smoking-gun proof that Mann et al. were essentially perpetrating fraud, i.e., intentionally covering up negative results. Of course, if you are really going to censor a result, there are probably better ways of doing than reporting it in a paper published in Geophysical Review Letters!! ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [December 9, 2007, 3:29am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/126 "2007-12-09T03:29:05Z")
I could have sworn this had been brought up before, either in this thread or the BBQ Pit thread. Are rehashing the same points again? ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 9, 2007, 8:20am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/127 "2007-12-09T08:20:55Z")
[QUOTE=intention] and all of Michael Mann’s friends and supporters can’t put Humpty back together again. w. [/QUOTE] I think that’s the real question for this thread. The pro-hockey stick people seem to be saying that even if Mann did things he shouldn’t have done, if you do things right you still get a hockey stick. Of course, one then needs to define “hockey stick,” which I tried to do earlier: > [@](#): > > (1) A temperature reconstruction of the last 1000 years; > > (2) Relatively little temperature variation between 1000 and the early 20th century (maximum of 0.5 degrees C from between highest anomaly and lowest anomaly); > > (3) A dramatic and relatively steady increase in temperature (perhaps 1 degree C) between the early 20th century and the present; and thus > > (4) Temperatures in recent years that are unprecedentedly (in the last 1000 years) high, both in absolute terms as well as in the rate / magnitude of change. The real question, it seems to me, is whether these conclusions survive scrutiny. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [December 9, 2007, 9:00pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/128 "2007-12-09T21:00:00Z")
jshore, you do not dispute the truth of McIntyre’s quotes. I note you say he cherry picks by not including this quote: > [@](#): > > As part of their statistical methods, Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions. A description of this effect is given in Chapter 9. In practice, this method, though not recommended, does not appear to unduly influence reconstructions of hemispheric mean temperature; reconstructions performed without using principal component analysis are qualitatively similar to the original curves presented by Mann et al. (Crowley and Lowery 2000, Huybers 2005, D’Arrigo et al. 2006, Hegerl et al. 2006, Wahl and Ammann in press). Unfortunately, you are cherry picking here. All the quote shows is that 1. The method Mann used is in fact wrong. You did notice that part? 2. If you include the discredited bristlecones, you can get the hockeystick shape by using OLS or any one of a number of matters. If that is supposed to invalidate the numerous problems with the Mann corpus of claims, I fear you’re betting on the wrong horse. Yes, you are correct, they said you can use any number of methods to get a hockeystick from bad data … is that intended to impress us? w. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 10, 2007, 1:25am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/129 "2007-12-10T01:25:11Z")
Thanks for your reply, **intention**. [QUOTE=intention] Unfortunately, you are cherry picking here. [/quote] I don’t understand your statement at all. In what way did I cherry pick? McIntyre purposely withheld information from his readers (and we know he couldn’t possibly have missed the remark that I quoted since in another quotation, he quoted both a piece before it and a piece immediately after it with “…” in between). I gave you the full quote in that section on that subject, as well as the full quote that McIntyre had given, and then even referred to the sentences following the quote that I gave which were more in agreement with McIntyre and McKitrick on a tangentially-related but different point. > [@intention](#): > > All the quote shows is that > > 1. The method Mann used is in fact wrong. You did notice that part? Did you miss the part where I said: > [@jshore](#): > > So, in other words, yes, this method is a potentially dangerous one to use but, no, it did not in fact make a difference in this case. This would hardly be the first case when a scientist has gotten the right answer with the wrong (or a not completely robust) method. One reason this happens is that most good scientists will actually do the calculation a few different ways, so while he may write up this particular technique, he may well have verified the results with another technique. > [@intention](#): > > 1. If you include the discredited bristlecones, you can get the hockeystick shape by using OLS or any one of a number of matters. > > If that is supposed to invalidate the numerous problems with the Mann corpus of claims, I fear you’re betting on the wrong horse. Yes, you are correct, they said you can use any number of methods to get a hockeystick from bad data … is that intended to impress us? First of all, the bristlecones are not “discredited”. There are certain concerns about that data, as there is with lots of the different temperature proxy data. As I noted, it was Mann et al. themselves that noted in their 1999 paper that the results (and the quality of the fit they could obtain to the instrumental temperature record during the period of overlap) was strongly dependent on data from that region, noted some concerns with that data and how they had tried to address them, and noted that “Clearly, a more widespread network of quality millennial proxy climate indicators will be required for more confident inferences.” Again, you are hampered by some binary notion that data is either perfect or totally discredited. In fact, in real science at the cutting-edge of any field, there are always limitations in the quality of the data and needs for improvements. And, that is why the IPCC in both the TAR and AR4 chose to assess the probability that the Northern Hemisphere temperatures were warmer in the latter half of the twentieth century than in any previous century in the last 1000 - 1300 years as a “likely” statement, i.e., \>66% of being true. So, basically, what McIntyre and McKitrick have shown is: (1) That the principle components technique that Mann et al. presented is not robust and can be dangerous to use in the sense that it can lead to hockey-stick shapes from data that does not in fact contain it, although that this did not happen in this case since other ways of analyzing the data give the same result. This result is certainly interesting and relevant to those who actually might want to use the technique in the future but turns out to be irrelevant to the results actually presented. [I think Mann et al. have further technical arguments about how the hockey stick shapes that McIntyre and McKitrick came up with from synthetic data would not have actually passed their significance tests but this gets into arguments about the best significance tests to use and so forth that frankly I haven’t taken the time to understand.] (2) The sensitivity to certain data in the reconstruction that was already pointed out by Mann et al. in their 1999 paper. I suppose one can give M&M a little more credit here for sort of expanding on this issue…which does seem like an important factor for future data improvements, as was in fact noted by Mann et al. in 1999. So, of these two points, one is irrelevant unless you are an actual practitioner planning to apply this technique to your data and the other is relevant but already noted by Mann et al. and thus presumably pretty well-understood by the scientists in the field and incorporated in their assessment of the uncertainties regarding the results. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 10, 2007, 12:15pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/130 "2007-12-10T12:15:59Z")
[QUOTE=brazil84] I would say probably not. [/QUOTE] Second question: If I was to ask 100 people to graph the fall of a marble (distance/time) in a vacuum, should I expect 100 different looking graphs? ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 10, 2007, 12:43pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/131 "2007-12-10T12:43:20Z")
[QUOTE=brazil84] The real question, it seems to me, is whether these conclusions survive scrutiny. [/QUOTE] Yes, to within 66% probability. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 10, 2007, 12:55pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/132 "2007-12-10T12:55:29Z")
[QUOTE=Sage Rat] Second question: If I was to ask 100 people to graph the fall of a marble (distance/time) in a vacuum, should I expect 100 different looking graphs? [/QUOTE] I imagine that at least a few of the graphs would look pretty similar. So I would say “probably not.” Anyway, since I have been answering your questions, maybe you could try to answer mine. 1. Given your apparent statement that the Esper 2002 temperature reconstruction is not intended to represent a global average, would agree that it makes no sense at all to splice in the instrumental global temperature average to the Esper 2002 graph? 2. Given your apparent statement that it’s worthless to ponder over whether the Esper 2002 proxy measurement would have a “blade” if it were extended from 1992 to 2007, do you agree that **jshore** ’s earlier implication that the extension would in fact have such a blade is meaningless? ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 10, 2007, 12:58pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/133 "2007-12-10T12:58:21Z")
[QUOTE=Sage Rat] Yes, to within 66% probability. [/QUOTE] Please show me a cite that says there is at least a 66% probability that there has been relatively little temperature variation between 1000 and the early 20th century (maximum of 0.5 degrees C from between highest anomaly and lowest anomaly), and I will study it. Thank you. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 10, 2007, 2:38pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/134 "2007-12-10T14:38:43Z")
[QUOTE=brazil84] 1. Given your apparent statement that the Esper 2002 temperature reconstruction is not intended to represent a global average, would agree that it makes no sense at all to splice in the instrumental global temperature average to the Esper 2002 graph? [/quote] Why yes, yes I would. Point in fact, I said so many times. For instance: > [@Sage Rat](#): > > Looking at a single source outside of it’s conjunction with as many other data points (including the instrumental temperature) is meaningless. Debating whether there would be a hockey stick if you carried [Esper’s] out to 2007 is equally as meaningless as debating whether there wouldn’t be a hockey stick if bristlecones were screwed up in Mann’s graph. > [@brazil84](#): > > 1. Given your apparent statement that it’s worthless to ponder over whether the Esper 2002 proxy measurement would have a “blade” if it were extended from 1992 to 2007, do you agree that **jshore** ’s earlier implication that the extension would in fact have such a blade is meaningless? **He said** that Esper’s graph _does appear_ to follow the instrumental average global temperature up to the point at which it cuts off, so it’s reasonable to assume that it would continue to do so. **I would say** that basing your results on that would be foolhardy for making a multi-billion dollar decision, but still a reasonable path to follow if you are simply responding to some fool who is trying to prove that because one **local area** graph doesn’t appear to have an upturn, that this proves anything. Of the options, it _is_ more likely that Esper’s would follow the instrumental temperature from a basic eyeballing. “More likely” might only be 60%, but it is still the winner. > [@brazil84](#): > > Please show me a cite that says there is at least a 66% probability that there has been relatively little temperature variation between 1000 and the early 20th century (maximum of 0.5 degrees C from between highest anomaly and lowest anomaly), and I will study it. Thank you. [http://boards.straightdope.com/sdmb/showpost.php?p=9164082&postcount=8](http://boards.straightdope.com/sdmb/showpost.php?p=9164082&postcount=8) ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 10, 2007, 2:44pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/135 "2007-12-10T14:44:27Z")
[QUOTE=brazil84] I imagine that at least a few of the graphs would look pretty similar. So I would say “probably not.” [/QUOTE] Question Three: If I was to ask 100 people to graph their _view_ of a marble falling through a vacuum, but where each of them had to view the fall through a _different_ distorted glass, what would you say would be the best way to determine the actual graph from the 100 different results? (Obviously, this would be without knowing the basic physics math to simply simulate the occurance.) ---
**Author:** ![Lobohan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lobohan/32/79_2.png) [@Lobohan](https://boards.straightdope.com/u/Lobohan)\ **Post date:** [December 10, 2007, 5:53pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/136 "2007-12-10T17:53:05Z")
[QUOTE=Sage Rat] Question Three: If I was to ask 100 people to graph their _view_ of a marble falling through a vacuum, but where each of them had to view the fall through a _different_ distorted glass, what would you say would be the best way to determine the actual graph from the 100 different results? (Obviously, this would be without knowing the basic physics math to simply simulate the occurance.) [/QUOTE] Obviously the best choice is to use the graph that best supports your political biases, ignoring the vast majority of the others that point to something very different. I thought I’d give Brazil a break and field this one for him. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 11, 2007, 10:41pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/137 "2007-12-11T22:41:41Z")
[QUOTE=Sage Rat] Why yes, yes I would. Point in fact, I said so many times. [/quote] Then I have no idea what your point was in Post #94. > [@](#): > > **He said** that Esper’s graph _does appear_ to follow the instrumental average global temperature up to the point at which it cuts off, so it’s reasonable to assume that it would continue to do so. No, he said this: > [@](#): > > Well, it doesn’t have a very dramatic a “blade” but the reason is that it ends before most of the recent (late 20th century / early 21st century) warming. Another possible reason it doesn’t have a “blade” is that the proxy isn’t closely measuring the instrumental temperature. After all, if you cut off Mann’s hockey stick at 1992 instead of 1998, it would still be a hockey stick. It’s also possible that the instrumental records are wrong. But that’s not the reason **jshore** is claiming. He is claiming that the reason there is no blade is because the proxy is cut off at 1992. I am asking for a cite. > [@](#): > > [http://boards.straightdope.com/sdmb/showpost.php?p=9164082&postcount=8](http://boards.straightdope.com/sdmb/showpost.php?p=9164082&postcount=8) Can you quote the language you are relying on? I don’t see it. Thanks. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 11, 2007, 10:50pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/138 "2007-12-11T22:50:38Z")
[QUOTE=Sage Rat] Question Three: If I was to ask 100 people to graph their _view_ of a marble falling through a vacuum, but where each of them had to view the fall through a _different_ distorted glass, what would you say would be the best way to determine the actual graph from the 100 different results? [/quote] I would probably ignore the 100 results completely and just derive the path of the marble from physical principles. > [@](#): > > (Obviously, this would be without knowing the basic physics math to simply simulate the occurance.) Why is that obvious? Anyone who has taken physics in high school or college can look up the necessary formulas in a textbook. But assuming you are trying to graph the movement of a marble based on peoples’ observations, and there’s no a priori knowledge of the marble’s movements, I don’t see any best way (or any way) to do the problem. Any other questions? ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [December 12, 2007, 2:39am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/139 "2007-12-12T02:39:34Z")
[QUOTE=jshore] Thanks for your reply, **intention**. I don’t understand your statement at all. In what way did I cherry pick? McIntyre purposely withheld information from his readers (and we know he couldn’t possibly have missed the remark that I quoted since in another quotation, he quoted both a piece before it and a piece immediately after it with “…” in between). I gave you the full quote in that section on that subject, as well as the full quote that McIntyre had given, and then even referred to the sentences following the quote that I gave which were more in agreement with McIntyre and McKitrick on a tangentially-related but different point. [/quote] McIntyre linked to the original report. How is that withholding information? … [QUOTE=jshore] First of all, the bristlecones are not “discredited”. There are certain concerns about that data, as there is with lots of the different temperature proxy data. As I noted, it was Mann et al. themselves that noted in their 1999 paper that the results (and the quality of the fit they could obtain to the instrumental temperature record during the period of overlap) was strongly dependent on data from that region, noted some concerns with that data and how they had tried to address them, and noted that “Clearly, a more widespread network of quality millennial proxy climate indicators will be required for more confident inferences.” [/quote] Some of the many problems with Mann’s “adjustment” for the bristlecone problem are discussed [here](http://www.climateaudit.org/?p=2350). [QUOTE=jshore] Again, you are hampered by some binary notion that data is either perfect or totally discredited. In fact, in real science at the cutting-edge of any field, there are always limitations in the quality of the data and needs for improvements. And, that is why the IPCC in both the TAR and AR4 chose to assess the probability that the Northern Hemisphere temperatures were warmer in the latter half of the twentieth century than in any previous century in the last 1000 - 1300 years as a “likely” statement, i.e., \>66% of being true. [/quote] Hmmm. The NAS report says: > [@](#): > > While ‘strip-bark’ samples should be avoided for temperature reconstructions, attention should also be paid to the confounding effects of anthropogenic nitrogen deposition (Vitousek et al. 1997), since the nutrient conditions of the soil determine wood growth response to increased atmospheric CO2 (Kostiainen et al. 2004). (STR Preprint, 50) Now, they didn’t say "the data is neither perfect nor totally discredited, it’s somewhere in between. The didn’t say “use the data but be careful with it”. They didn’t say “the bristlecones are not discredited”, as you say. They said the bristlecone data should be avoided. Sounds pretty binary to me, there’s “should be avoided” and “should not be avoided”, and in this case, they should be avoided. I find it incredible that you, and Michael Mann, are still arguing that the bristlecone data is somehow valid. The NAS findings regarding bristlecones are supported (and preceded) by other scientists. The NAS said don’t use it. Graybill and Idso said don’t use it. Rob Wilson said don’t use it. Heck, Biondi et al (including MBH co-author Hughes) said (emphasis mine): > [@](#): > > The average of those sites [a network of high-elevation temperature-sensitive tree-ring sites in the Great Basin and Sierra Nevada of Hughesand Funkhouser, unpublished], plotted in Figure 5, is based on many ring-width series, each one being 500 years or longer, without individual growth surges or suppressions and from “strip-bark” five-needle upper forest border pines of great age. **Such a record is not a reliable temperature proxy** for the last 150 years as it shows an increasing trend in about 1850 that has been attributed to atmospheric CO2 fertilization [Graybill and Idso, 1993] Why is that so hard for you to understand? [QUOTE=jshore] So, basically, what McIntyre and McKitrick have shown is: (1) That the principle components technique that Mann et al. presented is not robust and can be dangerous to use in the sense that it can lead to hockey-stick shapes from data that does not in fact contain it, although that this did not happen in this case since other ways of analyzing the data give the same result. This result is certainly interesting and relevant to those who actually might want to use the technique in the future but turns out to be irrelevant to the results actually presented. [I think Mann et al. have further technical arguments about how the hockey stick shapes that McIntyre and McKitrick came up with from synthetic data would not have actually passed their significance tests but this gets into arguments about the best significance tests to use and so forth that frankly I haven’t taken the time to understand.] [/quote] Yes, I have commented before on the convenient way that time works in your world, you seem to have time for everything except things that might disagree with your ideas … in particular, the idea that the synthetic data “would not have actually passed [Mann’s] significance tests” is laughable, given Mann’s refusal to release the results of his significance testing of his own results, so I can see how you might not have time to investigate that aspect of the discussion … > [@jshore](#): > > (2) The sensitivity to certain data in the reconstruction that was already pointed out by Mann et al. in their 1999 paper. I suppose one can give M&M a little more credit here for sort of expanding on this issue…which does seem like an important factor for future data improvements, as was in fact noted by Mann et al. in 1999. > > So, of these two points, one is irrelevant unless you are an actual practitioner planning to apply this technique to your data and the other is relevant but already noted by Mann et al. and thus presumably pretty well-understood by the scientists in the field and incorporated in their assessment of the uncertainties regarding the results. Since Mann did not give an “assessment of the uncertainties regarding the results” resulting from including data which the NAS says do not use, I fear I don’t have any idea what this last point means. A simple check would have been to redo his calculations without the bristlecones, to incorporate that uncertainty … but ooops, we can’t look at that result, because Mann either didn’t do it, or didn’t report it if he did do it. The Wegman report said: > [@](#): > > Where we have commonality, I believe our report and the [NAS] panel essentially agree. We believe that our discussion together with the discussion from the NRC report should take the ‘centering’ issue off the table. [Mann’s] decentred methodology is simply incorrect mathematics …. I am baffled by the claim that the incorrect method doesn’t matter because the answer is correct anyway. > **Method Wrong + Answer Correct = Bad Science.** > > The papers of Mann et al. in themselves are written in a confusing manner, making it difficult for the reader to discern the actual methodology and what uncertainty is actually associated with these reconstructions. > > It is not clear that Dr. Mann and his associates even realized that their methodology was faulty at the time of writing the [Mann] paper. > > We found MBH98 and MBH99 to be somewhat obscure and incomplete and the criticisms of MM03/05a/05b to be valid and compelling. > > Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis. Seems pretty clear to me … according to one of the nation’s premier statisticians, Mann’s analysis doesn’t support his claims. Finally, I note that you have not challenged any of the facts offered in the cited thread. The NAS committee and the Wegman Reports did not find a single error in McIntyre’s analysis of the Mann paper. Not one. Take that as your starting point. You say above: > [@jshore](#): > > That the principle components technique that Mann et al. presented is not robust and can be dangerous to use in the sense that it can lead to hockey-stick shapes from data that does not in fact contain it, although that this did not happen in this case since other ways of analyzing the data give the same result. The problem is that the Mann method mines for hockeysticks, as you agree. Combine that with a single piece of bad data, like the stripbark pines, and presto! Out pops a hockeystick. Since the method mines for hockeysticks, and the dataset supported that mining, I’d like some evidence that it did not happen in this case as you claim. The fact that other methods can replicate the hockeystick only means that those methods are depending on the bad data as well, it does not mean that Mann’s method did not mine for a hockeystick in this case. I close by repeating Wegman’s statement: > [@](#): > > Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis. If you want to argue with [Wegman](http://www.galaxy.gmu.edu/stats/faculty/wegman.html) about how Mann’s analysis is not statistical garbage, be my guest … until then, I’ll take his statement as the final word. Mann’s analysis doesn’t support his results. w. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [December 13, 2007, 5:08pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/140 "2007-12-13T17:08:49Z")
[QUOTE=brazil84] Why is that obvious? [/QUOTE] Because otherwise your answer to the question would have no bearing on the topic at hand. (I’m not asking these questions just for heck of it.) Please answer the question, making the assumption that the movement of the marble cannot be determined except through observation. [Previous page](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935.md?page=6) [Next page](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935.md?page=8)