Talk:Medieval Warm Period/Archive 4

So, was the MWP cooler than the present globally?
People seem keen to introduce some doubt into the lede of this article again, despite the reference cited saying " The Medieval period is found to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally." in its abstract. The point of contention - "globally the Medieval Warm Period was cooler than recent global temperatures" or "globally the Medieval Warm Period may have been cooler than recent global temperatures" - seems completely settled by the wording "falls well below recent levels globally." I don't see any new global studies to call this into question, so I have reverted. I'll fix some of the awful grammar next. --Nigelj (talk) 21:39, 22 October 2013 (UTC)


 * You do realize that this statement cannot be supported in the absolute. Since there are no direct measurements of temperature from the MWP it is impossible to say emphatically that it was absolutely colder than the temperatures of recent.  These tests require statistical interpretation, and to make a clearly absolute statement goes against scientific analysis.  Even the abstract is not clear on the statement, but I would guess that the actual paper would have a hypothesis test with a statistical value.   Ha!  Figures it would be a Mann paper.  Arzel (talk) 00:00, 23 October 2013 (UTC)
 * We go by the reliable source - doesn't matter what we think about the source. (Also fixed typo in this section header) Vsmith (talk) 00:52, 23 October 2013 (UTC)
 * Yes, Dogma. I see that Mann, of the flawed Hockey Stick graph is the source of this statement, so I am not surprised at his conclusion.  I find it impossible to believe that all sources come to this same conclusion.  Plus, I would like to see what the actual paper says, not just the abstract.  Arzel (talk) 05:07, 23 October 2013 (UTC)
 * If you have serious sources that differ, bring them. The cited paper has been published in Science, one of the more prestigious and selective scientific journals. The paper also is available for free here if you register (which also is free). Alternatively, you could ask at WP:REX. --Stephan Schulz (talk) 06:39, 23 October 2013 (UTC)
 * Why don't we just the actual source . Mann even states "Comparisons over the Pacific sector and neighboring regions, by contrast, are of limited utility, given the inability of the GISS-ER model to reproduce the aforementioned LaNiña–like feature of MCALIA pattern, which strongly affects the Pacific basin. There is no evidence of a positive NAOAO response in the NCAR simulation (Fig. 4). The observed patterns of change, even when averaged over multicentury intervals, are unlikely to be entirely forced in nature, as there is also a potentially important role for purely internal, natural variability (9). Consistent with this view, we find that individual realizations of the GISSER transient response to the MCA-LIA solar forcing difference yield patterns that differ modestly in their details. For at least one realization, for example, the reconstructed warm anomaly over Western Europe is reproduced. In most cases, the basic features discussed above are nonetheless evident (SOM Text)."  Thus Mann even admits that his simulation model is unable to reflect accurately the some aspects of the Pacific and yet you believe this is adequate for an absolute statement?  I am not asking for much, only that the so called scientists here use actual scientific methodology.  You all know damn well that statistical variation does not allow absolute statements like we are making here, and I find it extremely hypocritical to be claiming a scientific basis for the statement when actual scientists (like myself) live within the constraints of statistical methodlogy.  But then I guess the message is more important than correct scientific interpretation.  Arzel (talk) 14:31, 23 October 2013 (UTC)
 * Wait, so now Mann is a reliable source to you? Weren't you just trashing him in your comments above? Or are his papers just suitable as a source when you think they confirm your bias? Anyway, please present clearly which edit you would like to make to the article accompanied by its reliable source and it of course can be discussed. Regards. Gaba  (talk)  15:10, 23 October 2013 (UTC)
 * No need to feign surprise. For many years that person has been polluting and corrupting Wikipedia with ideologically driven edits, on topics selected because of ideological opposition or adherence. He's the opposite of a good WP editor. -- Jibal (talk) 11:44, 6 February 2014 (UTC)

, when you say in your edit summary, "The word "appears" was in a qualifier to "substantially" to the previous sentence "which appears to substantially exceed that of the modern late–20th century (1961–1990) baseline"", where are you quoting the phrase "which appears to substantially exceed that of the modern late–20th century (1961–1990) baseline" from? --Nigelj (talk) 17:01, 23 October 2013 (UTC)


 * he is quoting from the full article:
 * The reconstructed MCA pattern is characterized by warmth over a large part of the North Atlantic, Southern Greenland, the Eurasian Arctic, and parts of North America, which appears to substantially exceed that of the modern late–20th century (1961–1990) baseline and is comparable to or exceeds that of the past one-to-two decades in some regions.
 * You can access if you register for free here. Regards. Gaba  (talk)  17:57, 23 October 2013 (UTC)

Opening attack on Wikipedia and eds of this article removed by me per WP:TALKNewsAndEventsGuy (talk) 09:18, 20 June 2014 (UTC) the MWP was, in fact, global in scope. Please see this paper as one of the many peer-reviewed papers demonstrating that the MWP was global in scope (and warmer than today's climate, but one ideological hurdle at a time). To preempt cursory dismissals, I know the paper linked may be interpreted as showing only "local" Pacific Ocean climate, but that would miss the fact that it addresses deep OHC which changes slowly and in response to global factors. The papers supporting a global MWP number far too many to link them all (many papers simply show the MWP in other locales, but a sufficient number show the MWP in a reasonably diverse distribution of locations as to demonstrate that the localised assertion of the MWP is specious at best). Please note that, until recently, the MWP was simply accepted as being global in scope and thus it is only since papers like the one used in this article that controversially (and without sufficient supporting evidence) claimed the MWP was local that most published papers made clear that the MWP was explicitly global. Scott.Balfour (talk) 04:45, 20 June 2014 (UTC)
 * @ Scott.Balfour, you've linked one paper which only gives non-subscribers access to the abstract. What, exactly, does "recent decades" mean? The author of the paper is reported as describing their reconstruction as indicating that the Pacific mid-depths have generally been cooling over the last 10,000 years until a minimum about 300 years ago in the "Little Ice Age", followed by slow warming at a very slow rate, then a much faster increase since about 1950. Doesn't seem to tally with your account. You're completely wrong in your assertion that "until recently, the MWP was simply accepted as being global" the IPCC First Assessment Report in 1990 discussed "a shorter Medieval Warm Period (which may not have been global)", and a significant paper on the topic is Hughes, Malcolm K.; Diaz, Henry F. (1 March 1994), "Was there a ‘medieval warm period’, and if so, where and when?", Climatic Change. So, what else have you got wrong? . . dave souza, talk 10:51, 20 June 2014 (UTC)
 * "one paper which only gives non-subscribers access to the abstract" - Correct. Sadly, many papers created, in part, with money from government are restricted behind paywalls. This is a systemic problem. Despite the copyright issues, many of those paywalled papers can be found in other locations, though I am unsure of their legality and thus did not link to any.


 * "What, exactly, does 'recent decades' mean" - You need to ask the authors. The authors seem to quite like the term and use it in several contexts (to include the 17+ year "pause" in the surface temperature anomoly). I would presume it to be around 1950 as evidenced by statements like "IPWP SSTs are within error of modern (~1950 CE) values between 900 and 1200 CE during the Medieval Warm Period (MWP) and are colder by 0.75 T 0.35°C between 1550 and 1850 CE during the Little Ice Age (LIA), followed by nonmonotonic warming in the past 150 years (26)." (Yes, I deliberately chose a full sentence that states the MWP was essentially the same temperature as "modern" times, but given another sentence states "We show that water masses linked to North Pacific and Antarctic intermediate waters were warmer by 2.1 T 0.4°C and 1.5 T 0.4°C, respectively, during the middle Holocene Thermal Maximum than over the past century. Both water masses were ~0.9°C warmer during the Medieval Warm period than during the Little Ice Age and ~0.65° warmer than in recent decades." you can deduce that the Indo-Pacific Warm Pool (IPWP) is not wholly representative of the work.)


 * “the Pacific mid-depths have generally been cooling over the last 10,000 years until a minimum about 300 years ago in the "Little Ice Age", followed by slow warming at a very slow rate, then a much faster increase since about 1950. Doesn't seem to tally with your account. “ - I fail to see how it doesn't. The HTM was approx 2.1 deg C (or 1.5 if you wish) warmer than the last 100 years. Falling temperatures over 10,000 years would mean that MOST of the temperatures prior to the endpoint would be above the endpoint. “Cooling” is a DECREASE in temperature over time. The MWP was around 1000 CE which is around 1000 years ago. The stated minimum was 300 years ago. Unless that “slow warming” was sufficient to exceed in 300 years what declined in 700 years, your first sentence quoted is clearly equivalent to what I described and thus rebuts your second sentence. Of course, see the quote above clearly indicating that the last 300 years of warming did not do as the caveat described.


 * “You're completely wrong in your assertion that 'until recently, the MWP was simply accepted as being global' … 1990 discussed...” - Perhaps you should have asked (as you did of the author's statement) what “recently” means. We're talking about something that happened around 1000 years ago with reconstructions in thousands of years. 20 some odd years IS “recently”.


 * “So, what else have you got wrong?” - When you find one thing, let me know.


 * Since “one paper” isn't sufficient despite explicitly refuting the subject, I have undertaken to provide one example (of many) of a paper for every continent demonstrating the MWP on that continent. I simply do not understand how all this more recent information has not been assimilated.


 * FOR MODS: I understand (as mentioned in the first paragraph) that these links may be problematic. They are provided to preempt the initial complaint. If they violate anything of wikipedia or law or just good taste, please feel free to remove all offending links.


 * Debunking the IPCC (a governmental body administrated by politicians, not scientists) on the MWP heterogeneity: (Esper, J. and Frank, D. 2009. The IPCC on a heterogeneous Medieval Warm Period. Climatic Change 94: 267-273) - while this paper states that there is insufficient information either way, it focused on the sources from the IPCC and did not necessarily comprehensively cover the literature. At best case, this refutes the lede statement about heterogeneity.


 * MWP in Africa: (Tyson, P.D., Karlen, W., Holmgren, K. and Heiss, G.A. 2000. The Little Ice Age and medieval warming in South Africa. South African Journal of Science) - clearly shows a MWP in South Africa.


 * MWP in America (North): (Clegg, B.F., Clarke, G.H., Chipman, M.L., Chou, M., Walker, I.R., Tinner, W. and Hu, F.S. 2010. Six millennia of summer temperature variation based on midge analysis of lake sediments from Alaska. Quaternary Science Reviews 29: 3308-3316.) - “Comparisons of the TJuly record from Moose Lake with other Alaskan temperature records suggest that the regional coherency observed in instrumental temperature records (e.g., Wiles et al., 1998; Gedalof and Smith, 2001; Wilson et al., 2007) extends broadly to at least 2000 cal BP. For example, climatic events such as the LIA and the Medieval Climate Anomaly (MCA; peak warmth around 1000 cal BP) occurred largely synchronously between our TJuly record from Moose Lake (Fig. 4C) and a d 18 O-based temperature record from Farewell Lake on the northwestern foothills of the Alaska Range (Hu et al., 2001; Fig. 4D).”


 * MWP in America (South): (Sepulveda, J., Pantoja, S., Hughen, K.A., Bertrand, S., Figueroa, D., Leon, T., Drenzek, N.J. and Lange, C. 2009. Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44°S). Quaternary Research 72: 400-409.) - “The reasonably good correlation between our results (particularly SST) and other continental and marine archives from central-south Chile, Peru, and Antarctica corroborates the sensitivity of northern Patagonia for tracking latitudinal shifts of the SWW. This correspondence also confirms the occurrence of globally important climatic anomalies such as the MCA and the LIA, as well as ENSO-related climatic variability, within the northern Patagonia region.”


 * MWP in Antartica: (Hall, B.L., Koffman, T. and Denton, G.H. 2010. Reduced ice extent on the western Antarctic Peninsula at 700-970 cal. yr B.P. Geology 38: 635-638.) - “Therefore, we conclude that ice was at or behind its present position at ca. 700–970 cal. yr B.P. and during at least two earlier times, represented by the dates of shells, in the mid-to-late Holocene. Thus, the present state of reduced ice on the western Antarctic Peninsula is not unprecedented.”


 * MWP in Asia: (Aono, Y. and Saito, S. 2010. Clarifying springtime temperature reconstructions of the medieval period by gap-filling the cherry blossom phenological data series at Kyoto, Japan. International Journal of Biometeorology 54: 211-219.) - “The general pattern of change in the reconstructed temperature series in this study is similar to results reported by previous studies, suggesting a warm period in Asia corresponding to the Medieval Warrn Period in Europe.”


 * MWP in Australia: (Williams, P.W., King, D.N.T., Zhao, J.-X. and Collerson, K.D. 2004. Speleothem master chronologies: combined Holocene 18O and 13C records from the North Island of New Zealand and their palaeoenvironmental interpretation. The Holocene 14: 194-208.) - “A marked positive d18Oc excursion characterized the late Holocene between 0.71 and 0.57 ka, and it coincided with a positive d13Cc excursion at 0.66 ka. This suggests that the interval was warm and dry, so reduced precipitation may be partly responsible for the relatively high d18Oc values. This warm peak is a little later than the equivalent in western North Island [12], but both could represent a delayed southern counterpart of the Medieval Warm Period of western Europe.”


 * MWP in Europe: ab initio.
 * Scott.Balfour (talk) 15:27, 20 June 2014 (UTC)
 * @ Scott.Balfour, you seem to have misunderstood my comment about your last sentence above, which in full was "Please note that, until recently, the MWP was simply accepted as being global in scope and thus it is only since papers like the one used in this article that controversially (and without sufficient supporting evidence) claimed the MWP was local that most published papers made clear that the MWP was explicitly global." That's a bit incoherent, but seems to be asserting that "the MWP was simply accepted as being global in scope" until Mann's reconstructions, clearly that's false as I just cited two sources that predate Mann's first publication. . .dave souza, talk 16:55, 20 June 2014 (UTC)
 * @ Scott.Balfour, your citing papers about localised warm periods, apparently to support your assertion that the MWP was global, looks specious at best, to use your phrase. Local or regional reconstructions are interesting, but are not a substitute for hemispherical or global reconstructions and trying to compare them is original research. Per policy, don't do that. . dave souza, talk 16:55, 20 June 2014 (UTC)
 * "since papers like the one....I just cited two sources [like]..Mann's" - Clearly, the misunderstanding is yours, but this part of the conversation is irrelevant and petty. Please address the issues and not your misunderstandings.
 * "papers about localised warm periods, apparently to support your assertion that the MWP was global, looks specious at best" - Please take the time to read the material including the ORIGINALLY noted paper that demonstrates global scope. This combined with EVERY CONTINENT showing trends of warming at the period of the MWP should be sufficient without having to quote a paper that links them all together. By definition, no study can show a global scope by examining a locale (unless there are factors that explain a global scope like the original paper cited...hence why I led with it), but that does not mean multiple studies demonstrating the same trends over multiple locations are somehow incredibly coincidental. When the preponderance of the evidence is against a hypothesis, it is the onus of the contradicting hypothesis to demonstrate how the preponderance of evidence is incorrect. The preponderance of evidence clearly tends toward a global MWP. At the least, it shows that the MWP article should clearly state that the MWP has been demonstrated to have happened relatively simultaneously on every continent without contradicting statements that it is supposedly local (or miraculously local simultaneously on every continent) when evidence shows otherwise. The article could even cite the above references for the support.
 * Clearly, there is significant resistance to the facts. What criteria must be satisfied for this to reconciled? How many papers must be cited refuting the contents of this article for it to be changed? Is there some example of an explicit sentence from one (or more) scientific papers that you could give as an example that would be convincing? To clarify, I would like an example sentence that is purely hypothetical that you would find convincing. I will then spend even more time scouring the copious literature demonstrating the global scope of the MWP for a similar statement. In the meantime, I would suggest you take some time to read the cited papers.Scott.Balfour (talk) 17:35, 20 June 2014 (UTC)
 * "This combined with EVERY CONTINENT showing trends of warming at the period of the MWP should be sufficient without having to quote a paper that links them all together." That is the spittin' definition of impermissible original research ("OR"). It will be OR the next time you say it, and the next time after that too. NewsAndEventsGuy (talk) 18:06, 20 June 2014 (UTC)
 * IPCC FAR -
 * Such fluctuations include the Holocene Optimum around 5,000-6,000 years ago, the shorter Medieval Warm Period around 1000 AD (which may not have been global) and the Little Ice Age which ended only in the middle to late nineteenth century. [Executive summary with no citation]


 * There is growing evidence that worldwide temperatures were higher than at present during the mid-Holocene (especially 5,000-6,000 BP), at least in summer, though carbon dioxide levels appear to have been quite similar to those of the pre-industrial era at this time (Section 1). Thus parts of western Europe, China, Japan, the eastern USA were a few degrees warmer in July during the mid-Holocene than in recent decades (Yoshino and Urushibara, 1978, Webb et al, 1987, Huntley and Prentice, 1988, Zhang and Wang, 1990). Parts of Australasia and Chile were also warmer. The late tenth to early thirteenth centuries (about AD 950-1250) appear to have been exceptionally warm in western Europe, Iceland and Grenland (Alexandre, 1987, Lamb, 1988). This period is known as the Medieval Climatic Optimum. China was, however, cold at this time (mainly in winter) but South Japan was warm (Yoshino, 1978). This period of widespread warmth is notable in that there is no evidence that it was accompanied by an increase of greenhouse gases. [Observed Climate Variation 7.2.1] [Figure 7.1 “Schematic diagrams of global temperature variations since the Pleistocene on three time scales” adjacent to the quoted remark shows the MWP clearly warmer than current temperatures *shrug*]


 * Temperature changes of this magnitude in the Earth's history have been associated with shifts in the geographic distribution of terrestrial biota. For example, the boreal forests of Canada extend well north of the current timber line during the Medieval Warm Epoch (800 to 1200 AD), a time when temperatures in that region were about 1 deg C warmer than today's. At that same time, farmers in Scandinavia grew cereal crops as far north as 65 deg latitude (Lamb 1977). [from Effects on Ecosystems 10.0]


 * That would be the totality of support in the IPCC FAR for the MWP being local. I'll agree to disagree on the fact that the IPCC is not and never will be a scientific entity nor a publisher of scientific papers. Regardless, it would seem that the claim rests on Yoshino, 1978 saying that China was cold at the time. (Zicheng, P., Xuexian, H., Xiaozhong, L., Jianfeng, H., Guijian, L. and Baofu, N. 2003. Thermal ionization mass spectrometry (TIMS)-U-series ages of corals from the South China Sea and Holocene high sea level. Chinese Journal of Geochemistry 22: 133-139.) and (Ge, Q., Zheng, J., Fang, X., Man, Z., Zhang, X., Zhang, P. and Wang, W.-C. 2003. Winter half-year temperature reconstruction for the middle and lower reaches of the Yellow River and Yangtze River, China, during the past 2000 years. The Holocene 13: 933-940.) and (He, Y.-X., Liu, W.-G., Zhao, C., Wang, Z., Wang, H.-Y., Liu, Y., Qin, X.-Y., Hu, Q.-H., An, Z.-S. and Liu, Z.-H. 2013. Solar influenced late Holocene temperature changes on the northern Tibetan Plateau. Chinese Science Bulletin 58: 1053-1059.) and others clearly demonstrate the MWP time frame being warmer not colder. Even taking the IPCC report as a sole source, saying “may not have” might as well say “may have”. They are equally valid. Saying the MWP may not have been global by no means states the MWP was not global. It simply states they do not know.


 * WAS THERE A 'MEDIEVAL WARM PERIOD', AND IF SO, WHERE AND WHEN? -
 * “Because of generally sparse data worldwide around the turn of the first millennium, it is impossible at present to conclude from the evidence gathered here that there is anything more significant than the fact that in some areas of the globe, for some part of the year, relatively warm conditions may have prevailed. This does not constitute compelling evidence for a global 'Medieval Warm Period'”.


 * Just as in the IPCC, “does not constitute compelling evidence for a” might as well say “does not constitute compelling evidence against a”. They are equally valid. The “proof” that the MWP wasn't global is a paper stating it doesn't know? More recent evidence (that I have cited) shows there IS evidence for a global MWP. They didn't know. Science has advanced. We're now much closer to “we know it was global” than “we think it was local”.


 * Both of these citations by you suffer from the problem of oversimplification. Instead of taking the time to actually see what was said specifically, people read something like the executive summary and assume it is a certainty (instead of the explicitly stated uncertainty) and off they go! Neither source (one paper and one political document) refute that the MWP was global. Instead, they both express uncertainty as to whether it was or was not. That is not a position. It is specifically NOT a position on the issue.


 * The phrase "original research" (OR) is used on Wikipedia to refer to material—such as facts, allegations, and ideas—for which no reliable, published sources exist.[1] This includes any analysis or synthesis of published material that serves to reach or imply a conclusion not stated by the sources. To demonstrate that you are not adding OR, you must be able to cite reliable, published sources that are directly related to the topic of the article, and directly support the material being presented. - Clearly, the ARTICLE on MWP is trying to do "OR" by "reach or imply a conclusion not stated by the sources". On the other hand, I have simply suggested that the articles be cited as showing warming in each region and that the "OR" be removed from the article where it makes unsupported claims that the MWP was local. Not to mention the fact that you still have yet to address the clear refutation of locality in the first paper cited (as I have noted numerous times now). You really should read your own links before linking them. At any point, do you plan on addressing anything in the cited material or answering any of my questions? If this isn't really a "talk" but another forum to suppress evidence, I'll stop wasting my time. All you need to do is tell me that it doesn't matter what evidence is cited. It simply will not be changed.Scott.Balfour (talk) 19:07, 20 June 2014 (UTC)
 * This talk page is for discussing article improvements, it's not a forum. Please post specific proposals for article improvement, showing exactly what changes you'd like to see, proposing sample text and citing the references you propose for any additional information. Kthanx,. . dave souza, talk 19:21, 20 June 2014 (UTC)
 * I just tried to do just that. My extensive editing was summarily rejected as automatically "unconstructive". Are there any suggestions for how I could submit the appropriate changes without triggering this filter? Was it just because it was so long?Scott.Balfour (talk) 21:27, 20 June 2014 (UTC)
 * I should probably clarify after reading what I wrote. I wrote a "this is what it says/this is what it should say" post and tried to post it here in the talk section. I wouldn't even begin to try to edit the article page until there is much more clarification of how the proposed edits should look etc. So, please don't panic that the article is changed. If it changes, it won't be me until I explicitly state here in talk that I am going to make changes. Scott.Balfour (talk) 22:07, 20 June 2014 (UTC)
 * "Are there any suggestions for how I could submit the appropriate changes?"
 * Suggestion1 - use formatting to distinguish between your remarks and things you quote directly. "It was a dark and stormy night...."

- Citation goes here


 * That way it displays like this, making it a heap easier for the rest of us to instantly know when you are quoting and when you are speaking. The way I did that was to type "It was a dark and stormy night...."

- Citation goes here (and I displayed how to type it using the nowiki tag)
 * Suggestion2 - before you click save, click "preview".  Read it all thru to see if the formatting clearly tells us when you are speaking and when someone else is.
 * Suggestion3 Even better is to simply put the citation in "REF" tags as explained in WP:Citing sources, and adding a reflist to this thread.


 * Might have others later, but that's the most important that comes to mind right now. When others have to work to decipher, you're not helping your case.
 * NewsAndEventsGuy (talk) 22:48, 20 June 2014 (UTC)

Formatting unquestionably wasn't the issue. Regardless, formatting will certainly improve readability. I am going to remove indentation as it's going to be long enough anyway. I am going to break these down to smaller bits in the hope that, if nothing else, I can find what offends the filter. I would propose something like:

"The Medieval Warm Period (MWP), Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region that may also have been related to other climate events around the world during that time, including in China[1] and other countries,[2][3][3][4][5][6][7] lasting from about AD 950 to 1250.[8] It was followed by a cooler period in the North Atlantic termed the Little Ice Age. Some refer to the event as the Medieval Climatic Anomaly as this term emphasizes that effects other than temperature were important.[9][10] Despite substantial uncertainties, especially for the period prior to 1600 for which data are scarce, the warmest period of the last 2,000 years prior to the 20th century very likely occurred between 950 and 1100, but temperatures were probably between 0.1 °C and 0.2 °C below the 1961 to 1990 mean and significantly below the level shown by instrumental data after 1980. Proxy records from different regions show peak warmth at different times during the Medieval Warm Period, indicating the heterogeneous nature of climate at the time.[11] Temperatures in some regions matched or exceeded recent temperatures in these regions, but globally the Medieval Warm Period was cooler than recent global temperatures.[8]"

The Medieval Warm Period (MWP), Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate lasting from about AD 950 to 1250. It was followed by a cooler period in the North Atlantic termed the Little Ice Age. Some refer to the event as the Medieval Climatic Anomaly (MCA) as this term emphasizes that effects other than temperature were important.[9][10]. Since the 1990s, the global extent of the MWP has been questioned. “Because of generally sparse data worldwide around the turn of the first millennium, it is impossible at present [1994] to conclude from the evidence gathered here that there is anything more significant than the fact that in some areas of the globe, for some part of the year, relatively warm conditions may have prevailed. This does not constitute compelling evidence for a global 'Medieval Warm Period'”. However more recent papers have shown evidence “supporting the idea that the...MWP...were global events”.

Despite substantial uncertainties, especially for the period prior to 1600 for which data are scarce, the warmest period of the last 2,000 years prior to the 20th century very likely occurred between 950 and 1100. Different studies place the temperatures of the MWP colder than to approximately 0.9 deg C above 20th century temperatures. Several large-scale studies have been published demonstrating that data sparseness and low replication before about 1200 introduce random variations in the single records and increase uncertainty in any subsequent hemispheric scale average (Cook et al. 2004; D’Arrigo et al. 2006; Frank et al. 2007b). This evidence should not be confused with spatially heterogeneous temperatures during MWP. Given the wide acceptance of the AR4 and the notion of a more chaotic climate towards the Dark Ages, it thus seems relevant to recall that we currently do not have sufficient widespread, high-resolution proxy data to soundly conclude on the spatial extent of warmth during MWP. Scott.Balfour (talk) 00:22, 21 June 2014 (UTC)

Under Initial research "The warm period became known as the MWP, and the cold period was called the Little Ice Age (LIA). However, this view was questioned by other researchers; the IPCC First Assessment Report of 1990 discussed the "Medieval Warm Period around 1000 AD (which may not have been global) and the Little Ice Age which ended only in the middle to late nineteenth century."[13] The IPCC Third Assessment Report from 2001 summarised research at that time, 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".[14] Global temperature records taken from ice cores, tree rings, and lake deposits, have shown that, taken globally, the Earth may have been slightly cooler (by 0.03 degrees Celsius) during the 'Medieval Warm Period' than in the early and mid-20th century.[15][16] Palaeoclimatologists developing region-specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP".[15][17] 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."

The warm period became known as the MWP, and the cold period was called the Little Ice Age (LIA). However, this view was questioned by other researchers; the IPCC First Assessment Report of 1990 discussed the "Medieval Warm Period around 1000 AD (which may not have been global) and the Little Ice Age which ended only in the middle to late nineteenth century."[13] The IPCC Third Assessment Report from 2001 summarised research at that time, 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".[14] Since that time, other studies have showed evidence “supporting the idea that the .. MWP … were global events”. Palaeoclimatologists developing region-specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP".[15][17] 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 may be wet events or cold events rather than strictly warm events.

Scott.Balfour (talk) 00:23, 21 June 2014 (UTC)

Under Globally "A 2009 study by Michael Mann et al. examining spatial patterns of surface temperatures shown in multi-proxy reconstructions finds that the MWP shows "warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally."[8] Their reconstruction of MWP pattern is characterised by warmth over large part of North Atlantic, Southern Greenland, the Eurasian Arctic, and parts of North America which appears to substantially exceed that of the late 20th century (1961–1990) baseline and is comparable or exceeds that of the past one-to-two decades in some regions. Certain regions such as central Eurasia, northwestern North America, and (with less confidence) parts of the South Atlantic, exhibit anomalous coolness."

A 2013 study by Yair Rosenthal et al. examining ocean heat content (OHC) by high-resolution proxy records from sediment cores found that "water masses linked to North Pacific and Antarctic intermediate waters were warmer by 2.1 +/- 0.4°C and 1.5 +/- 0.4°C, respectively, during the middle Holocene Thermal Maximum than over the past century. Both water masses were ~0.9°C warmer during the Medieval Warm period than during the Little Ice Age and ~0.65° warmer than in recent decades” and “[t]he inferred similarity in temperature anomalies at both hemispheres is consistent with recent evidence from Antarctica (30), thereby supporting the idea that the HTM, MWP, and LIA were global events” . Certain regions such as central Eurasia, northwestern North America, and (with less confidence) parts of the South Atlantic, exhibit anomalous coolness.[8]

Scott.Balfour (talk) 00:24, 21 June 2014 (UTC)

Under North Atlantic "Using sediment samples from Puerto Rico, the Gulf Coast and the Atlantic Coast from Florida to New England, Mann et al. (2009) found consistent evidence of a peak in North Atlantic tropical cyclone activity during the Medieval Warm Period followed by a subsequent lull in activity.[19]"

The paragraph should be deleted as off-topic unless there are to be additional paragraphs in other sections noting local storms and whatnot. Scott.Balfour (talk) 00:25, 21 June 2014 (UTC)

Under North America "The 2009 Mann et al. study found warmth exceeding 1961–1990 levels in Southern Greenland and parts of North America during the Medieval climate anomaly (defined for this purpose as 950 to 1250) with warmth in some regions exceeding temperatures of the 1990–2010 period. Much of the Northern hemisphere showed significant cooling during the Little Ice Age (defined for the purpose as 1400 to 1700) but Labrador and isolated parts of the United States appeared to be approximately as warm as during the 1961–1990 period.[8]"

The 2009 Mann et al. study found warmth exceeding 1961–1990 levels in Southern Greenland and parts of North America during the Medieval climate anomaly (defined for this purpose as 950 to 1250) with warmth in some regions exceeding temperatures of the 1990–2010 period. Much of the Northern hemisphere showed significant cooling during the Little Ice Age (defined for the purpose as 1400 to 1700) but Labrador and isolated parts of the United States appeared to be approximately as warm as during the 1961–1990 period.[8] Other studies have found “climatic events such as the LIA and the Medieval Climate Anomaly (MCA; peak warmth around 1000 cal BP) occurred largely synchronously” at sites like Moose Lake, Alaska.

Scott.Balfour (talk) 00:26, 21 June 2014 (UTC)

Under Other regions "The climate in equatorial east Africa has alternated between drier than today, and relatively wet. The drier climate took place during the Medieval Warm Period (~AD 1000–1270).[31] A sediment core from the eastern Bransfield Basin, Antarctic Peninsula, preserves climatic events in the Little Ice Age and Medieval Warm Period.[32] The core shows a distinctly cold period about AD 1000–1100, illustrating that during the "warm" period there were, regionally, periods of both warmth and cold. Corals in the tropical Pacific Ocean suggest that relatively cool, dry conditions may have persisted early in the millennium, consistent with a La Niña-like configuration of the El Niño-Southern Oscillation patterns.[33] Although there is an extreme scarcity of data from Australia (for both the Medieval Warm Period and Little Ice Age) evidence from wave-built shingle terraces for a permanently full Lake Eyre[34] during the 9th and 10th centuries is consistent with this La Niña-like configuration, though of itself inadequate to show how lake levels varied from year to year or what climatic conditions elsewhere in Australia were like."

The climate in equatorial east Africa has alternated between drier than today, and relatively wet. The drier climate took place during the Medieval Warm Period (~AD 1000–1270).[31] One study in South Africa showed that “medieval warming was characterized by highly variable conditions. Maximum warming at Makapansgat at around 1250 [AD] produced conditions up to 3-4 deg C hotter than those of the present”.

A study of a sediment core from the eastern Bransfield Basin, Antarctic Peninsula, preserved climatic events in the Little Ice Age and Medieval Warm Period.[32] The core shows a distinctly cold period about AD 1000–1100. However another study concluded “that ice was at or behind its present position at ca. 700–970 cal. yr B.P. [or convert that to 980-1250 AD?] and during at least two earlier times, represented by the dates of shells, in the mid-to-late Holocene. Thus, the present state of reduced ice on the western Antarctic Peninsula is not unprecedented” Which would suggest warmer climates during the time of ice recession. [Maybe leave out the "forced" conclusion...or the whole paragraph as debunked?]

Corals in the tropical Pacific Ocean suggest that relatively cool, dry conditions may have persisted early in the millennium, consistent with a La Niña-like configuration of the El Niño-Southern Oscillation patterns.[33] Although there is an extreme scarcity of data from Australia (for both the Medieval Warm Period and Little Ice Age) evidence from wave-built shingle terraces for a permanently full Lake Eyre[34] during the 9th and 10th centuries is consistent with this La Niña-like configuration, though of itself inadequate to show how lake levels varied from year to year or what climatic conditions elsewhere in Australia were like. A study of Oxygen and Carbon isotopes found evidence that “could represent a delayed southern counterpart of the Medieval Warm Period”.

Scott.Balfour (talk) 00:29, 21 June 2014 (UTC)

Please note that I'm not saying the article must say any of this. The above DOES however represent a "balanced" take on the MWP unlike the current article (contravening wikipedia's guidelines). If the current article even had the single most important reference (yes, that same one that I initially linked), it would be moving well toward a balanced article. Scott.Balfour (talk) 00:33, 21 June 2014 (UTC)

Suggestion zero (I really should have started with this one) Read the talk page guidlines; go to bed, read them again; write up your idea for article improvement; when done compare to the talk page guidelines again before posting. One thing it says is "Use separate subsection headings to discuss multiple changes If you arrive at the "discussion" part of the WP:BRD cycle, and the subject involves a number of separate changes you would like to see, try to break down the different changes, and your reasons and reliable sources for each one, under separate subsection headings. Mashing it all into one long post makes methodical progress almost impossible. (bold added)"

- WP:TALK NewsAndEventsGuy (talk) 00:36, 21 June 2014 (UTC)
 * Hence why I broke it into seven sections. They each have their own subheading. Are you saying that I should take this into a separate (new) talk section for each section of the article that needs correction? That was not made clear by my (prior) reading of talk guidelines. If that is what is desired, I will be happy to do so. As to the reasons, the reasons are all clearly laid out either previously or in the "corrected" text in brackets. All sources are from scientific journals and hence "reliable" by wikipedia standards (Although the IPCC doesn't qualify under wikipedia standards, but I didn't use it. I merely left in other, current references that use it.). Anything else? Again, if the desire is for me to create new talk sections, I will do that. I would like clarification if that is the case as to how many new talk sections would be appropriate. Scott.Balfour (talk) 01:37, 21 June 2014 (UTC)
 * How about picking a single subsection of the existing article and just talking about that one, while saving the rest for later? NewsAndEventsGuy (talk) 02:06, 21 June 2014 (UTC)
 * Source [8] (the Mann paper) is cited in the Lede (twice), Initial research, Globally, and North America. I was thinking to not go over the same thing multiple times. Also, the lede impacts the other sections. However, I am happy to take them one at a time if it will make it easier. I didn't see an answer as to whether it should be in a new talk section or not, but I'll put it in one anyway. Scott.Balfour (talk) 02:24, 21 June 2014 (UTC)
 * That's backwards. The other sections are supposed to "impact" the lead.  See WP:LEAD NewsAndEventsGuy (talk) 02:47, 21 June 2014 (UTC)
 * Heh. NOW I see this. C'est la vie! Reference [11] is only in the lede. Nowhere else is the "heterogeneous" stuff mentioned. Should I move that to the "Global" section and correct it? When the time finally comes to correct the lede (if the desire is to delete the section I made below, I don't mind), it can then be re-addressed?Scott.Balfour (talk) 03:06, 21 June 2014 (UTC)
 * Rather than delete it, I've hatted it until this is resolved. It will eventually be archived unless reopened, or if you wish you're welcome to delete it yourself. . dave souza, talk 05:21, 21 June 2014 (UTC)
 * See WP:WALLOFTEXT as suggested guidance: it's very hard to follow what changes are being proposed. Smaller bites would be good, with proposed changes highlighted in some way. Overall, you seem to want to introduce newer studies: we mustn't give undue weight to an isolated study, particularly a regional study of ocean temps, even though a reviewer suggests a broader impact. Conveniently, AR5 gives an overview or synthesis of studies up to and including part of 2013, so that provides a good basis for revamping this article. I'll start a new section below. . dave souza, talk 05:21, 21 June 2014 (UTC)
 * Alas, I will likely be frequently guilty of "WALLOFTEXT". My threshold for "excessive" seems to be well beyond most people's. I have never in my life looked at text and thought "that's a wall of text". I also learn most quickly by example. Could someone be so kind as to take any portion of my proposed changes and give me an example of what would not be a wall of text conveying the same information? Finally, thanks much for taking care of my lede mistake.Scott.Balfour (talk) 07:12, 21 June 2014 (UTC)
 * If you study WP:WALLOFTEXT and talk page guidelines each day for a week, and cruise talk pages looking for long threads, you'll no doubt find lots of examples of working through complex topics in bite size pieces. If you don't figure out how to do that yourself, my guess is that you won't make much headway but you will suck up a lot of other eds' time.  My experience when this has happened in the past is that eventually eds start to wonder if WP:CIR applies.  The best way to avoid that is to invest some learning time by studying the procedures and looking for examples.  You can also find examples of what not to do by perusing the archives at WP:ANI.NewsAndEventsGuy (talk) 10:45, 21 June 2014 (UTC)
 * Separately, "...even though a reviewer suggests..." My quotation of global scope was directly from the paper. I have no idea who or what reviewed this paper, and I would not consider using sources outside the paper when citing the paper. Again, please read the provided material. It is desperately hard to not be talking apples to apples. Scott.Balfour (talk) 07:12, 21 June 2014 (UTC)
 * As discussed below, it's early days for evaluation of this paper which has to be done by scientists, not Wikipedia editors. There's clearly some good stuff in the paper, but it's very questionable to suggest that ocean temps from one small area overturn all the research using proxies across the globe, and it looks like a minor aspect being taken out of context. . dave souza, talk 10:50, 21 June 2014 (UTC)
 * This is conducting "OR" where the editor is making inferences without a third party citation. The paper was quoted in context within the reasonable limits of brevity. If you see the quotes as out of context, please explain. Scott.Balfour (talk) 13:25, 21 June 2014 (UTC)

No, it was warmer than it is now 1000 years ago. This is very inconvenient to global warming activists and so they deny it. Just as they do with the satellite lower troposphere measurements and the tidal gauges — Preceding unsigned comment added by 2600:100A:B127:6565:C1DF:EAD3:AD99:C354 (talk) 11:30, 14 March 2017 (UTC)

Mann Hockey Stick graph should be deleted next to main article
The Mann hockey stick graph which appears next to the main article has been conclusively discredited and should never appear in an article in Wikipedia. Let's try to keep this as scientifically rigorous as possible without taking sides people. I won't go into all the research that has gone on to prove the hockey stick false, do your own investigation. Suffice to say that even the IPCC in AR5 has stopped supporting that graph (of course they never go back and apologize for using it in AR4 - but let's not get into a cat fight here). — Preceding unsigned comment added by 122.106.169.23 (talk • contribs) 23:27, 10 January 2016‎
 * You're wrong on all counts, and your trolling fails to meet talk page guidelines. . . dave souza, talk 23:41, 10 January 2016 (UTC)
 * I didn't know there were guidelines on How To Troll nowadays; how the world advances William M. Connolley (talk) 07:46, 11 January 2016 (UTC)

Welcome to wikipedia. You will find that any science article about climate must conform to catastrophic man made climate change theories and use activists like Michael Mann as their sources instead of real science — Preceding unsigned comment added by 2600:100A:B127:6565:C1DF:EAD3:AD99:C354 (talk) 11:32, 14 March 2017 (UTC)

Consequences?
Should there be a section on consequences of this warm period for the medieval world? The vikings being able to get into the North Atlantic and to Iceland, Greenland and North American, the changes in populations that occurred and so forth? And same when the warm period ended? — Preceding unsigned comment added by 86.178.219.54 (talk) 11:26, 12 January 2014 (UTC)
 * The vikings are covered in Medieval Warm Period, other effects are also discussed. . . dave souza, talk 11:16, 20 June 2014 (UTC)


 * A bit less obviously, but just as well attested, the cooling of the North Atlantic from 1300 on (meaning the entire northern half, not just the seas roughly N of a line Maine to the Bay of Biscay), meant fewer and relatively less forceful storms and cyclones. The sea tended to become a bit calmer, and one would safely infer that in the 11th to 13th centuries the Atlantic was a more storm-ridden ocean than it was to become by the late 15th century and later. Some relevance for Columbus, Magellan and others. 83.254.150.36 (talk) 22:29, 23 July 2014 (UTC)
 * Sources? . .dave souza, talk 22:48, 23 July 2014 (UTC)

The consequences are that overall life on earth increased. Warming is very good for life. Cold is bad. This is why they call it "optimum", or at least they did before climate change activists got involved and started science denial, which has taken over wikipedia... — Preceding unsigned comment added by 2600:100A:B11E:9E5D:496A:BDA9:888E:243B (talk) 05:16, 31 March 2017 (UTC)
 * So, no sources for your blethering. . dave souza, talk 12:01, 31 March 2017 (UTC)

Disputes on the Medieval Warm Period
A section with that title was added, but seems to merely duplicate a point already covered in the lead:
 * ''Current research shows that climate change was much more complicated than early studies suggest. Several now believe that the concept of a Mediaeval Warm Period is based on some false premises, and that it only occurred in some areas.

So, I've deleted it in the meantime, and moved it here for further discussion if needed. . . dave souza, talk 15:53, 30 April 2017 (UTC)

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