# 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:** 5
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [December 2, 2007, 12:37am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/81 "2007-12-02T00:37:12Z")
[QUOTE=GIGObuster] :rolleyes: Yes and Mann was overall happy with the conclussion, the Hockey Stick was not debunked, and speaking of not reading: **jshore** already pointed out the item that that year in the 1930’s being hotter does not affect the overall concussion. [/quote] I have to say this needs even more clarifications, I’m still stuck in the 1930’s (Sorry **jshore** ) I was attempting to refer to the 90’s and after \*\*jshore’s \*\* #8 post it was clear that this debunking you are talking about remains wishful thinking. And I did mention Mann was on the record saying that he was overall happy with the NSA commission’s report. However, the quote: “Overall, the 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.” Does not come from the NAS report, it comes form the Wegman report that was set by the politicians to investigate Mann and the Hockey Stick, for that report Mann had an answer: [http://209.85.173.104/search?q=cache:ai\_AfNEWYycJ:republicans.energycommerce.house.gov/108/hearings/07272006Hearing2001/Mann.pdf+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.&hl=en&ct=clnk&cd=5&gl=us](http://209.85.173.104/search?q=cache:ai_AfNEWYycJ:republicans.energycommerce.house.gov/108/hearings/07272006Hearing2001/Mann.pdf+committee+believes+that+Mann%E2%80%99s+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.&hl=en&ct=clnk&cd=5&gl=us) (You need to scroll down to see the whole testimony.) TESTIMONY OF DR. MICHAEL E. MANN ASSOCIATE PROFESSOR, DEPARTMENTS OF METEOROLOGY AND GEOSCIENCES PENN STATE UNIVERSITY AND DIRECTOR, PENN STATE EARTH SYSTEM SCIENCE CENTER BEFORE THE SUBCOMMITTEE ON OVERSIGHT AND INVESTIGATIONS OF THE COMMITTEE ON ENERGY AND COMMERCE > [@](#): > > The report by Wegman, et al., looks only at our earliest work. Wegman’s report > does not look at any of our more recent studies, or the work of dozens of other climate scholars. That omission is striking because these researchers have found the same basic “hockey stick” temperature history. Nonetheless, Wegman’s report does not examine whether the use of statistical conventions he suggests undermine our original work have been employed in more recent work by my co-authors and me, or of the other climate scientists engaged in reconstruction work. > > Whatever merit one assigns to Wegman’s criticisms, they go to the first, and necessarily most tentative, of all of the reconstruction data and ignore the enormous amount of diverse and sophisticated work that has followed. > > For this reason, the narrow focus of the Wegman report misses the point. The “hockey stick” is not simply an isolated or aberrational finding my co-authors and I reached only once, in one study. On the contrary, it is a finding that every climate scientist who has performed a detailed examination of the available data has reached, because the hockey stick figure is driven by the data. The Wegman report does not acknowledge the key point made in the recent NAS report, namely, that many researchers have come up with the same basic “hockey stick” reconstruction (i.e., a reconstruction that is within the estimated uncertainties of the Mann et al reconstruction) based on the use of different proxy data sets or different statistical methods (see Exhibit A). Nor does the report acknowledge any of the work that my collaborators and I have been engaged in during recent years seeking to refine the original methods we developed a decade ago. > > These refined methods, unexamined by Wegman, et al., yield essentially the same result as our original methods, although they use different statistical techniques (see Exhibit B). Moreover, Wegman has not been careful to represent our findings accurately. For instance, Wegman and his co-authors have stated in their report: "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.” > > **We never made the sort of definitive statements attributed to us by Wegman**. In the abstract of our 1999 article in Geophysical Research Letters we stated > that “[w]e focus not just on the reconstructions, but on the uncertainties therein, and important caveats…expanded uncertainties prevent decisive conclusions for the period prior to A.D. 1400.” We concluded by stating that, “…more widespread high resolution data are needed before more confident conclusions can be reached…” It is hard to imagine how much more explicit we could have been about the uncertainties and limitations. > > Perhaps the most serious omission in the Wegman report, however, is its failure to > acknowledge that its central focus — the conventions used for centering in the Principal Components Analysis used to represent certain tree-ring proxy data — has no significant implications on the results of our analysis. The hockey stick pattern derives from the data, not in the PCA. Nonetheless, Wegman’s report claims that the PCA centering convention used to represent the North American tree-ring data network in our 1998/1999 studies is responsible for the “hockey stick” shape of our reconstruction. But the report’s conclusion does not follow from its premise. Even accepting that certain statistical conventions that were used in our original studies might not be optimal under some circumstances, **the use of alternative conventions yields the same “hockey stick” figure.** > > Nowhere does the Wegman report even acknowledge that its assertion that our > reconstruction is a function of PCA centering conventions was rejected by the NAS. On page 116 of the NAS Report, the NAS notes that the PCA procedure used by Mann et al. “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.” ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [December 2, 2007, 1:09am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/82 "2007-12-02T01:09:52Z")
[QUOTE=brazil84] Lol. So what? What’s he gonna say? That he’s furious he’s been debunked? [/quote] [looks at Mann’s testimony]Why should he be if others confirmed his results? As the New Scientist took a look, and assuming they asked questions, the result in 2007 was to say it is a myth to say the hockey stick was debunked. Unless you can point to current researchers dumping the conclusions this statement of yours is indeed wishful thinking. > [@](#): > > Here’s a question for you: > > Is anyone citing MBH for the proposition that the 1990s were the hottest decade of the millenium? I don’t think this means much since the Real Climate piece is titled “Dummies guide to the latest “Hockey Stick” controversy” the reason why I quoted that article was to show other reconstructions also got the Hockey Stick. > [@](#): > > The splicing problem; the divergence problem; and the strip-bark problem, to name a few. And as you are showing here that you are still missing that what the NAS took from Mann they also took from the ones using that data as the definitive evidence to discredit the Hockey Stick. The more problems you are making of this evidence then the more unreliable are the critics that used that evidence to claim it was hotter on the middle ages. The Hokey Stick does not depend on this data alone. > [@](#): > > Cites please. Already mentioned, and once again you show you are not checking the links. > [@](#): > > 😕 I have no idea what you are saying here. If you had checked the first post I made, you would had noticed I’m referring to that German high-school teacher curve chart that was used before in an attempt to discredit the hockey stick. However, IIRC that chart of Beck was also posted by you in a previous discussion also looking to discredit the hockey stick. Looking at the points Real Climate mentions, I have to conclude that the ones claiming that the hockey stick was debunked got debunked already. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 2, 2007, 1:14am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/83 "2007-12-02T01:14:59Z")
[QUOTE=Sage Rat] Yes, and? _10 studies_ came to a hockey stick result. Conjoined. Averaged. Combining data sources. Taking more faith in separate data than one. [/quote] Sorry, but that’s NOT what you said before. Here’s what you said before: > [@](#): > > The reason there are a whole bunch of different lines is because different researches independentally tried alternate methods to determine historic temperatures and/or to see if past results were replicable. Arguing over bristlecones is silly when 10 studies come to the same results using methods that were in majority probably not reliant on bristlecones. For instance, #10 is based on glaciers, #8 is based on boreholes and meteorology, #5 on tree rings, etc. Studies have been done on coral and lake sediments as well, though I’m not sure if those are included in the picture. > > **Science doesn’t assume fact unless different sources and methodologies come to the same result** , and the results of others can be replicated if one uses the same methods. Bolding added. Clearly you were implying that the 9 different proxies each independently produce the same (hockey stick shaped?) result. And that just isn’t true. Anyway, the chart you linked to doesn’t show what the average of the 9 proxy studies is. Not that it would necessarily make any sense to simply average them. It’s not as though there isn’t any overlap. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 2, 2007, 1:23am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/84 "2007-12-02T01:23:42Z")
[QUOTE=GIGObuster] [looks at Mann’s testimony]Why should he be if others confirmed his results? [/quote] Some authority stated that at least two of his conclusions were not supported by his analysis. That’s why he would be unhappy. Although most people wouldn’t admit it. > [@](#): > > I don’t think this means much I’ll take that as a “no.” Personally, I doubt that anyone is citing Mann for the proposition that the 1990s were the hottest decade of the millenium. > [@](#): > > And as you are showing here that you are still missing that what the NAS took from Mann they also took from the ones using that data as the definitive evidence to discredit the Hockey Stick. 😕 > [@](#): > > Already mentioned, and once again you show you are not checking the links. In which post #? > [@](#): > > If you had checked the first post I made, you would had noticed I’m referring to that German high-school teacher curve chart that was used before in an attempt to discredit the hockey stick. However, IIRC that chart of Beck was also posted by you in a previous discussion also looking to discredit the hockey stick. Looking at the points Real Climate mentions, I have to conclude that the ones claiming that the hockey stick was debunked got debunked already. The fact that you cannot give a coherent answer to my earlier question makes me think that you are probably guilty of both sins. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [December 2, 2007, 1:46am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/85 "2007-12-02T01:46:43Z")
[QUOTE=brazil84] Some authority stated that at least two of his conclusions were not supported by The fact that you cannot give a coherent answer to my earlier question makes me think that you are probably guilty of both sins. [/QUOTE] This thread will last longer (with happier participants) if everyone sticks to wrangling over the data and avoids editorializing on other posters’ modes of participation. [/Moderating] ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [December 2, 2007, 2:23am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/86 "2007-12-02T02:23:38Z")
[QUOTE=brazil84] The fact that you cannot give a coherent answer to my earlier question makes me think that you are probably guilty of both sins. [/QUOTE] And you wonder why I think this is now a useless discussion? To me it is clear a formal debunking of the Hockey Stick requires the climate researchers to look at the evidence and all to refute the research completely, again, the only thing you showed so far is that the Hockey Stick of Mann was amended, the problems with the Bristle cone evidence cuts both Mann and the critics of Mann that rely on this evidence. It is obvious that the current researchers advised the New Scientist about what was the current state of the Hockey Stick, and the New Scientist looked at the evidence and commission reports, then they published the conclusion that “It is a myth to say the hockey stick was debunked” Q.E.D. regarding the OP. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 2, 2007, 2:24am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/87 "2007-12-02T02:24:59Z")
[QUOTE=brazil84] Clearly you were implying that the 9 different proxies each independently produce the same (hockey stick shaped?) result. And that just isn’t true. [/QUOTE] Well, since “hockey stick shaped” is a fairly ill-defined term, it is hard to argue precisely if this is true or not. All of them show a pronounced upturn in the temperature in recent times and have the temperatures in the Medieval times lower than they are in the late 20th century. Some of them have a bumpier “shaft” than Mann et al.'s and which is the more correct result is still being debated in the literature. (It is also worth noting that the original Mann graphs had fairly decent-sized error bars so that much of the variation that other studies have found still lie within the error bars of Mann et al.) As to whether the 1990s was likely the hottest decade and 1998 likely the hottest year, the NAS report said that they felt that this conclusion of Mann et al.'s was the least supportable because they felt there just wasn’t the temporal resolution in all of the proxies to determine something like which single year was the hottest (or even which decade). However, Mann et al. have noted in response to this that they never meant this as a claim based on the resolution of their measurements but rather as a statement based on a combination of their results with statistical arguments. I.e., that the previous warmest general period was enough below the 1990s that it would have been statistically very unlikely to have a decade as warm as the 1990s during that period…and likewise for 1998 as the warmest year. Anyway, this is clearly a point that will generate more discussion and study in the future. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [December 2, 2007, 4:13am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/88 "2007-12-02T04:13:00Z")
[QUOTE=GIGObuster] And you wonder why I think this is now a useless discussion? [/QUOTE] Replying on the personal level does not help it get better. If you think the discussion has lost validity, simply walk away from the thread. [/Moderating] ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [December 2, 2007, 6:11am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/89 "2007-12-02T06:11:47Z")
[QUOTE=tomndebb] Replying on the personal level does not help it get better. If you think the discussion has lost validity, simply walk away from the thread. [/Moderating] [/QUOTE] Point taken. Following common definitions of what a debunking is this discussion is over. The hockey stick was not debunked. However the only loose item to me that remains, is that it needs to be clarified if the definition of debunking used by the OP is a valid one. If a couple of authorities claim that something was debunked and this is valid, then we might as well say that the idea that “HIV causes AIDS” was debunked when more than a few authorities say so. (sadly, it is true that some authorities do insist on this) It is clear to me a debunking in science requires the mainstream or the consensus to uphold that debunking. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 2, 2007, 12:17pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/90 "2007-12-02T12:17:24Z")
[QUOTE=jshore] Well, since “hockey stick shaped” is a fairly ill-defined term, it is hard to argue precisely if this is true or not. [/quote] That’s true, and I suppose it would be worthwhile to precisely define the “hockey stick.” But putting that aside for the moment, can you please take a look at the blue line in this chart: [http://www.wooster.edu/geology/tr/esper1.jpg](http://www.wooster.edu/geology/tr/esper1.jpg) Will you agree that that is NOT a hockey stick? ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 2, 2007, 6:14pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/91 "2007-12-02T18:14:29Z")
[QUOTE=brazil84] Will you agree that that is NOT a hockey stick? [/QUOTE] 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. If you look at [this](http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png) image, the curve you show (the light green one in this image) seems to agree quite well with the instrumental record at the time that it ends. However, by ending when it does, it misses over 0.4 C of the warming in the instrumental record. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 2, 2007, 6:37pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/92 "2007-12-02T18:37:56Z")
[QUOTE=jshore] 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. [/quote] It runs through 1992. Do you have a cite for the claim that the Esper 2002 proxy measurement would have a “blade” if it were extended from 1992 to 2007? ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 2, 2007, 8:44pm UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/93 "2007-12-02T20:44:59Z")
By the way, after thinking about it a little, I would say that the essential aspects of the “Hockey Stick” are as follows: (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. * * * If the Hockey Stick were true, it would certainly support claims of AGW. ---
**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 3, 2007, 1:08am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/94 "2007-12-03T01:08:52Z")
[QUOTE=brazil84] It runs through 1992. Do you have a cite for the claim that the Esper 2002 proxy measurement would have a “blade” if it were extended from 1992 to 2007? [/QUOTE] If you look at the [one picture](http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png), you’ll note that the black line is recorded (non-proxy) temperature. Assuming that Esper’s really is a measurement of temperature, it will parallel the actual temperature. If it doesn’t, then it isn’t a measure of the temperature. ---
**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 3, 2007, 1:52am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/95 "2007-12-03T01:52:49Z")
[QUOTE=Sage Rat] If you look at the [one picture](http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png), you’ll note that the black line is recorded (non-proxy) temperature. Assuming that Esper’s really is a measurement of temperature, it will parallel the actual temperature. If it doesn’t, then it isn’t a measure of the temperature. [/QUOTE] Too late to edit: Or, of course, it’s in a wierd location that doesn’t track with the global average very well (the danger with relying on a single source of data.) ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 3, 2007, 2:06am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/96 "2007-12-03T02:06:43Z")
[QUOTE=brazil84] It runs through 1992. Do you have a cite for the claim that the Esper 2002 proxy measurement would have a “blade” if it were extended from 1992 to 2007? [/QUOTE] It doesn’t look to me like the line really extends to 1992…Maybe it uses data through 1992 but they use this low-pass 40-year filter so they are not getting an average all the way to that year. As **Sage Rat** notes, the most recent few decades are best documented by the actual instrumental temperature record. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [December 3, 2007, 2:08am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/97 "2007-12-03T02:08:21Z")
Hope this doesn’t hijack the thread, but it seemed a good place to ask several GW related questions. [QUOTE=Sage Rat] If you look at the one picture, you’ll note that the black line is recorded (non-proxy) temperature. Assuming that Esper’s really is a measurement of temperature, it will parallel the actual temperature. If it doesn’t, then it isn’t a measure of the temperature. [/QUOTE] I’ve seen that chart before myself. My question(s) have always been: Was the Medieval Warming Period only considered a local event (i.e. in Europe or in the Northern Hemisphere), or was this a global event? Were the glaciers in Greenland smaller then than today…if not, why was Greenland more habitable then than now? If the glaciers WERE smaller then, was the sea level much higher (I don’t think it was but going from memory)…if not, why not (I assume the answer to this was that the MWP WAS a local as opposed to a global event, but if I knew I wouldn’t need to ask)? What is the level of uncertainty (plus/minus) of the temperature projections before anything before global temperatures were measured in any kind of systematic ways globally using some temperature baseline (Celsius/Fahrenheit)? -XT ---
**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 3, 2007, 2:11am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/98 "2007-12-03T02:11:23Z")
[QUOTE=xtisme] I’ve seen that chart before myself. My question(s) have always been: Was the Medieval Warming Period only considered a local event (i.e. in Europe or in the Northern Hemisphere), or was this a global event? [/QUOTE] > **[Medieval Warm Period](https://en.wikipedia.org/wiki/Medieval_Warm_Period)** > > The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from about 950 CE to about 1250 CE. Climate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event. Some refer to the MWP as the Medieval Climatic Anomaly to emphasize that climatic effects other than temperature were also importa Th... ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [December 3, 2007, 2:31am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/99 "2007-12-03T02:31:50Z")
From Sage Rat’s cite: > [@](#): > > Initial research > > The Medieval Warm Period was a time of warm weather around 800-1300 AD, during the European Medieval period. Initial research on the MWP and the following Little Ice Age (LIA) was largely done in Europe, where the phenomenon was most obvious and clearly documented. > > It was initially believed that the temperature changes were global [2]. However, this view has been questioned; the 2001 IPCC report summarises this research, saying “…current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of ‘Little Ice Age’ and ‘Medieval Warm Period’ appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries”.[3] The National Oceanic and Atmospheric Administration (NOAA) states that the “idea of a global or hemispheric “Medieval Warm Period” that was warmer than today however, has turned out to be incorrect” and that those “records that do exist show is that there was no multi-century periods when global or hemispheric temperatures were the same or warmer than in the 20th century”.[2] > > Palaeoclimatologists developing regionally specific climate reconstructions of past centuries conventionally label their coldest interval as “LIA” and their warmest interval as the “MWP”.[4][5] Others follow the convention and when a significant climate event is found in the “LIA” or “MWP” time frames, associate their events to the period. Some “MWP” events are thus wet events or cold events rather than strictly warm events, particularly in central Antarctica where climate patterns opposite to the North Atlantic area have been noticed. Ok…so, initially it WAS apparently viewed as a global phenomena but now ‘this view has been questioned’. Any thoughts on the extent of the questioning and whether this is widely accepted? It says Europe was ‘where the phenomenon was most obvious and clearly documented’…does that mean additional data has come to light? -XT ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [December 3, 2007, 3:05am UTC](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935/100 "2007-12-03T03:05:36Z")
[QUOTE=Sage Rat] If you look at the [one picture](http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png), you’ll note that the black line is recorded (non-proxy) temperature. Assuming that Esper’s really is a measurement of temperature, it will parallel the actual temperature. If it doesn’t, then it isn’t a measure of the temperature. [/QUOTE] Before I respond to this, can you explain what you mean by “parallel”? [Previous page](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935.md?page=4) [Next page](https://boards.straightdope.com/t/temperature-record-of-the-last-1000-years/425935.md?page=6)