Talk:Medieval Warm Period/Archive 3

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Archive 2 Archive 3 Archive 4

Evidence from Japan

There is one warm/humid interval from AD 750 to 1200, and two cold/dry intervals from AD 1 to 750 and 1200 to present in Japan[1] ---

  1. ^ Kazuyoshi Yamada; et al. (2010). "Late Holocene monsoonal-climate change inferred from lakes Ni-no-Megata and San-noMegata, northeastern Japan". Quaternary international. 220: 122–132. Retrieved 2010-08-05. 
It appears to be a reliable source and a short paragraph on it could be added to the "Other regions" section. Cla68 (talk) 07:48, 5 August 2010 (UTC)

The vines of Southern England, oh, those endless vines

This will be my last contribution to any global warming related article on Wiki. There are pages and pages in the archives of the various relevant Wiki pages, countless other websites presenting both sides of the debate and surely every argument and counter argument has surely been made several times now. I am aware that the Wiki consensus is against me and my fellow sceptics and we are just going to agree to differ on this one I think. Surely the debate has gone on too long and we are all sick of it by now? But one last time ... Vine is a common street name all over Southern England and why? Because grapes were once grown all over Southern England. It's too cool for that now. Ergo England was much warmer in the Middle-ages than it is now. And, as England does exist in a climate bubble, the world was much warmer than it is now. Ergo the the famous hockey stick graph that is shown in many Wiki articles depicting the present period as the warmest period for the last 2000 years inaccurate. So if global warming is happening we will grow grapes all over Southern England again and this will be pleasant not catastrophic as the Warmists would have us believe. The Warmists have been banging on about global warming since the 1980s and no great disaster has befallen the planet. ( For the record I have no car and have not flown in three years. I wonder how many of the Warmists here can say that? So my opinion on this subject carries no environmental impact at all.) SmokeyTheCat 07:51, 14 August 2010 (UTC)

As a fellow sceptic, I'm sorry to see you say that. You might, of course, care to note that grapes are now being grown commercially even in Scotland,[1][2] and have been for many years in England.[3][4] While it's potentially pleasant for us, people in some other countries might disagree with you about the way things have been going in the last half century. .. dave souza, talk 12:49, 27 August 2010 (UTC)
Smokey, we shouldn't editorialize on article talk pages, but if I understand right, warmists (and I don't mean to imply anything pejorative by using that term) believe that there could very well have been a warming period in the British Isles during that time period, but it doesn't necessarily mean that it was global in nature. It could have been a local phenomenon. Anyway, we just report what the sources say. Cla68 (talk) 12:59, 27 August 2010 (UTC)

Antartic ice cores: 'moveable term'

William M. Connolley, I reworded that section because I had to read the current text 3 times in order to understand what it was trying to say. Did it mean that: people use MWP to mean different times periods? Temperature ranges? Or localities? By using 'term' here, it seems to imply at least one of these.

Or does the sentence mean that during the MWP, temperatures varies across geographical areas? Or that it was very cold during some periods of the MWP and only 'warm' in others?

Lastly, I'd just like to mention the WP policy, Wikipedia is not a dictionary so the article should focus of topic of warm climate during the medieval period, rather than the term MWP. Ashmoo (talk) 10:52, 27 August 2010 (UTC)

Kaufman et al.

Kaufman, D. S.; Schneider, D. P.; McKay, N. P.; Ammann, C. M.; Bradley, R. S.; Briffa, K. R.; Miller, G. H.; Otto-Bliesner, B. L.; Overpeck, J. T.; Vinther, B. M.; Abbott, M.; Axford, M.; Bird, Y.; Birks, B.; Bjune, H. J. B.; Briner, A. E.; Cook, J.; Chipman, T.; Francus, M.; Gajewski, P.; Geirsdottir, K.; Hu, A.; Kutchko, F. S.; Lamoureux, B.; Loso, S.; MacDonald, M.; Peros, G.; Porinchu, M.; Schiff, D.; Seppa, C.; Seppa, H.; Arctic Lakes 2k Project Members (2009). "Recent Warming Reverses Long-Term Arctic Cooling". Science. 325 (5945): 1236–1239. doi:10.1126/science.1173983. PMID 19729653.  looks relevant, worth summarising related points. . . dave souza, talk 12:04, 11 September 2010 (UTC)

A false statement

"the warmest period prior to the 20th century very likely occurred between 950 and 1100"

This is simply false. The Big Bang was warmer, at least. This statement has to be bounded in some way. — Preceding unsigned comment added by Fimbulfamb (talkcontribs) 13:12, 28 January 2011 (UTC)

Good point, the source clearly bounds it as being within the last 2,000 years and I've added clarification accordingly. Grammatical improvements will be welcome, the long sentence isn't ideal. As for warmer times, we probably don't have to go back to the Big Bang, "It is likely that earlier periods with higher than present atmospheric CO2 concentrations were warmer than present. This is the case both for climate states over millions of years (e.g., in the Pliocene, about 5 to 3 Ma) and for warm events lasting a few hundred thousand years (i.e., the Palaeocene-Eocene Thermal Maximum, 55 Ma)."[5] There does seem to have been caution about this in 2007,[6] don't know if more recent research has firmed this up. . . dave souza, talk 15:17, 28 January 2011 (UTC)

Interesting new RS: Medieval Climate Anomaly

Special issue, Medieval Climate Anomaly, PAGES (Past Global Changes) Newsletter, 25 March 2011 Hat-tip to Eduardo Zorita, --Pete Tillman (talk) 21:42, 1 April 2011 (UTC)

Is this a joke?

Even after several readings it is not clear whether this is something I've misunderstood (the most likely reason); or whether this is an error; or whether this is meant to be a joke. The caption says "The 16th-century Skálholt map of Norse America", but when you look at the English description, it's a map not of America but of .. well, clearly something else. What is the true story here? Old_Wombat (talk) 12:22, 16 July 2011 (UTC)

No, I think it's right. It is a map of the north Atlantic, with the British Isles bottom right, Greenland top left, and the North American coast running down the left side. Squiddy | (squirt ink?) 12:35, 16 July 2011 (UTC)

Aha. Thanx for that. Someone's changed the text, too. Old_Wombat (talk) 10:12, 19 July 2011 (UTC)

Cannot tel a lie, medunnit. Text is now "1690 copy of the 1570 Skálholt map, based on documentary information about earlier Norse sites in America." Think it needs mention of North Atlantic? dave souza, talk 12:13, 19 July 2011 (UTC)

Wow, I had not intended to make this into anything grand. No, Dave, it is fine and comprehensible as it is. Old_Wombat (talk) 09:34, 20 July 2011 (UTC)

Paleoclimatology-related article needing attention

Roman Warm Period was created this July apparently as a spin-off from this one and has been tagged for verifiability. I've made a start. --TS 00:27, 23 September 2011 (UTC)

Earth And Science Letters ikaite formation

Earth and Planetary Science Letters (Volumes 325–326, 1 April 2012, Pages 108–115) has an article about recent work using ikaite formation: "This ikaite record qualitatively supports that both the Medieval Warm Period and Little Ice Age extended to the Antarctic Peninsula." Uncle uncle uncle 18:30, 27 March 2012 (UTC)

I don't think it is terribly exciting. The MWP was episodic; wherever you look, you'll see stuff saying it was there, but other stuff saying it wasn't William M. Connolley (talk) 21:07, 27 March 2012 (UTC)
I would say it is more exciting than the contrived tree ring proxy. It does confirm what most already knew, that the MWP was not limited to England. Arzel (talk) 21:40, 27 March 2012 (UTC)
It's verry verry exciting according to the Daily Mail and the GWPF, and proves IT'S ALL A HOAX. Speaking of which, some panto. Grabs popcorn. . . dave souza, talk 21:49, 27 March 2012 (UTC)
Anyway, back to the paper itself. The main interest seems to be the introduction of a new proxy, with specific relevance to the West Antarctic Paninsula and other cold areas such as Greenland.[7] They seem less excited about the claimed correlation of changes with the European MWP and LIA, detail is needed about just how they established that relationship. . dave souza, talk 22:38, 27 March 2012 (UTC)

Zunli Lu:

“It is unfortunate that my research, “An ikaite record of late Holocene climate at the Antarctic Peninsula,” recently published in Earth and Planetary Science Letters, has been misrepresented by a number of media outlets.

Several of these media articles assert that our study claims the entire Earth heated up during medieval times without human CO2 emissions. We clearly state in our paper that we studied one site at the Antarctic Peninsula. The results should not be extrapolated to make assumptions about climate conditions across the entire globe. Other statements, such as the study “throws doubt on orthodoxies around global warming,” completely misrepresent our conclusions. Our study does not question the well-established anthropogenic warming trend.”

Rather more exciting, always nice to see deniers corrected. Perhaps useful for the GW controversy article? . . dave souza, talk 20:20, 31 March 2012 (UTC)
What larks. Good evidence that we should always give new stuff time to settle before considering it for inclusion William M. Connolley (talk) 20:56, 31 March 2012 (UTC)
Tip of the hat dave souza, talk 22:46, 31 March 2012 (UTC)

Graphs should go left to right

In English Wikipedia, it would be a lot more readable and intuitive if graphs had the past on the left and the present or future on the right. Could someone have a go at changing the long-term graph to be around the other way? It could probably be done in an image editor if it's too hard to generate it again from the data. Carl Kenner (talk) 06:32, 19 May 2012 (UTC)

I'm not too sure about that. Graphs typically go in the direction of increasing values on the X axis, and the X axis is labeled "years before present", a somewhat technical dating style that is not equivalent to "years before present" ;-), and not trivial to map to normal calendar years. --Stephan Schulz (talk) 10:39, 19 May 2012 (UTC)

New Zealand

There's a new, quite thorough, study[8] out this week about the Australasian region, and specifically New Zealand. It seems to contradict the other New Zealand information in this article. The new study shows the Medieval Warm Period did not affect the region. The study did confirm the Little Ice Age though. Carl Kenner (talk) 05:25, 19 May 2012 (UTC)

I had a go at adding the new information from that study myself. I removed New Zealand from the list of the regions in the first paragraph, but retained the information from that source in the New Zealand part of the other regions section, since we no longer have sufficient evidence of the MWP in New Zealand to justify singling it out in the first paragraph. I added the new study to the start of the New Zealand section. I haven't formatted the citation very well, and my writing may not be the best, because I'm very sick at the moment and my brain is foggy, so feel free to improve those parts.

And I think we need to fix the second paragraph, but I wasn't sure how, so I left it as is. I guess we either need to talk about a specific region or be less confident or indicate Australasia as a likely exception. But I can't do that on my own.

By the way, the new graph for Australasia is here: [9] for those interested. Carl Kenner (talk) 06:23, 19 May 2012 (UTC)

Please note that Ref 35 (Gergis et. al.) has been withdrawn from publication, so should probably not be quoted in the article. The paper had not yet been published, though it had been accepted for publication. Flaws were discovered (see and the publishers have "put it on hold". Emmenjay (talk) 16:57, 9 June 2012 (UTC)

I have now made the above change: removing references to the discredited paper from Gergis et. al., Journal of Climate, 2012. The paper was withdrawn before publication. Emmenjay (talk) 12:21, 10 June 2012 (UTC)

Your interpretation is dubious. But the paper should not have been used pre-publication William M. Connolley (talk) 13:19, 10 June 2012 (UTC)
I think the major point to bear in mind is that if we're all awaiting the next publication on the topic with baited breath, perhaps we're doing it wrong. Aren't there some decent review papers that give the long view? --TS 20:17, 10 June 2012 (UTC)

William M Connolley -- could you please expand on that. Exactly what is dubious? I didn't think I was interpreting anything. My understanding of the facts are as follows:

  1. The paper has not yet been published.
  2. Serious errors were found in the paper.
  3. The authors requested that it be withheld while the errors were addressed
  4. The publisher agreed and removed the paper from it's web site
  5. This makes the paper unsuitable as a reference

Do you think I have the facts wrong, or do you have some other objection? (I'm not looking for an argument -- I really want to understand your point of view and possibly learn something from you.) --Emmenjay (talk) 15:59, 16 June 2012 (UTC)

Without speaking for WMC, but then this isn't his talk page, perhaps the problem is your very dubious source. Or it may be the Screening Fallacy Fallacy. Anyway, as WMC agrees, the paper should not have been used pre-publication. . . dave souza, talk 16:27, 16 June 2012 (UTC)
Well, you (and WMC) are, of course, entitled to your opinion, but I don't find the source to be dubious. Steve McIntyre's opinions are not mainstream and are not popular with many mainstream scientists, but he generally presents his facts pretty well. In this case, the paper was withdrawn before publication because it contained errors. The authors confirmed that in an email displayed on the site.
The authors of the paper acknowledged the problems with screening and said that they had taken measures to mitigate that by de-trending the data before doing the filtering. However when the work was checked, it became apparent that they had not done that.
Although the (pre-publication) release of the paper got some mainstream publicity, I haven't spotted much about the withdrawal in mainstream sources. It was mentioned in the comments at Real Climate, but there wasn't a lot of detail.
I did not quote Steve McIntyre's opinions on the topic, which are more controversial and less likely to be included in Wikipedia. So I don't think there was anything dubious. If course, that is just my opinion and you are welcome to express a contrary opinion if you feel the urge to do so.
--Emmenjay (talk) 02:44, 18 June 2012 (UTC)

Viking settlements

I've reworded the bit about the Viking settlements dying out. Okay they could have assimilated, or moved and become lost in subsequent population shifts. But the point is that they "vanished from history" which is the new wording I use. --TS 02:10, 25 May 2012 (UTC)

No problem with your wording, but the preceding words lack any citation and it's WP:SYN to suggest that they've something to do with the MWP. To clarify this aspect, I've split the para and added a cn tag.
On second thoughts, maybe it's inaccurate to say they "vanished from history" as our Vinland article says "the 13th Century Grœnlendinga saga, which provides a circumstantial account of the discovery of Vinland", "Sixteenth century Icelanders realised that the "New World" which European geographers were calling "America" was the land described in their Vinland Sagas" and "was taken up by later Scandinavian scholars such as bishop Hans Resen." So the memory lingered in history, but their fate was unknown.
On the more important aspect of how this info is supposed to relate to the MWP (or MCA) Parks Canada - L'Anse aux Meadows National Historic Site - History doesn't indicate any need to postulate a MWP as an explanation. Indeed this suggests the Norse may have returned home because of clashes with the Skraelings (the locals) . dave souza, talk 07:17, 25 May 2012 (UTC)
p.s. for anyone thinking grapes=warm climate, apparently Vitis riparia has been known to withstand temperatures as low as -57 °C (−70 °F). . . dave souza, talk 07:32, 25 May 2012 (UTC)


This whole article seems too ambiguous and written by the climate change crowd to try and convince us that this warm period was no big deal. However, it is a big deal and shows that human caused climate change could be wrong. For example, it uses words like, "could be", "may", probably, etc. IMO this article should be re-written to be less biased. — Preceding unsigned comment added by Jerryel (talkcontribs) 19:21, 23 November 2011 (UTC)

Ah, that nasty climate change crowd who are trying to change the climate by pumping greenhouse gases into the atmosphere. However, this is a science article and has to fully and accurately show the uncertainties in the scientific findings. As a science article, it has to be biased towards reality rather than the religious certainties of those denying the science. Of course, if you can be more specific we can review detailed proposals to change the wording where you have verification that such changes are justified. . dave souza, talk 20:53, 23 November 2011 (UTC)

--I agree with the first comment. This article smells biased and political. It tries to assert that the MWP was regional only, and might be related to other global events, and then gives a smattering of those other events as a token reference. The article ignores the fact that hundreds of papers document the MWP as global in nature and synchronous in timing. This is a political entry and I advise all scientific minded people to ignore it. (talk) 00:18, 27 November 2011 (UTC) CG

Sources?. . . dave souza, talk 00:59, 27 November 2011 (UTC)
Hundreds of papers say it was global? Really? Like Dave, I'd love to see the evidence. I prefer Harvard citation myself.VsevolodKrolikov (talk) 17:50, 28 November 2011 (UTC)

--I too agree with the first comment. The CRU emails clearly demonstrate the desire of global warming conspirators to get rid of the Medieval Warm Period. This page is a shameless revision of known science in support of the conspiracy and unworthy of Wikipedia. Regrettably, it is not the only Wikipedia page that has been hijacked to support a political end. (talk) 01:01, 5 February 2012 (UTC)

Your shameless allegation is clearly based only on your political bias. As for "the conspiracy", conspiracy theories don't fly here. . dave souza, talk 07:08, 5 February 2012 (UTC)

--Global or Local? This links to a collection of studies about the Medieval Climate Anomaly in my dropbox.

It appears that climate anomalies were global but the dating is ambigeous. Maybe it's just as global as the warming is now, where some areas -especially in the north- seem significantly warmer but other areas hardly. talk —Preceding undated comment added 08:02, 9 January 2012 (UTC).

And where is this published? Please see WP:RS. --Kim D. Petersen (talk) 02:47, 5 February 2012 (UTC)

There is a good discussion of this very issue in the IPCC report; it is the first reference in the article: [10], if you missed it. See especially box 6.4 William M. Connolley (talk) 10:31, 5 February 2012 (UTC)

There's a database of MWP related, peer-reviewed papers maintained by a Dr. Craig Idso. It contains papers written by more than 1000 scientists from more than 400 institutions in more than 40 countries which confirm the reality of the MWP and that it was global, not regional, and at least as warm as today and probably warmer. Some examples are; Huang et al (1998) - Dansgaard (1969); Schonweise (1995) - Tyson et al - Kitawaga and Matsumoto (1995) - Noon et al (2003) - Gupta et al (2005) - Wilson et al (1979) - Keigwin (1996) - Esper and Scweingruber (2004). This article should be changed to reflect this reality. — Preceding unsigned comment added by NerdNinja9 (talkcontribs) 08:18, 20 March 2012 (UTC)

Ah, Craig D. Idso of the Heartland Institute's NIPCC! As a science article this doesn't show alternative realities promoted by libertanian "think tanks". Out of interest, what Huang et al (1998)? Evidently not this, and why not go to 2008? Perhaps because they show the maximum of the MWP at or slightly below the reference level, the minimum of the LIA about 1 K below the reference level, and end-of-20th century temperatures about 0.5 K above the reference level? . . dave souza, talk 09:13, 20 March 2012 (UTC)

Agreed. I removed a sentence that says temperatures were "probably" below what they were in 1960 which smacked of BS. — Preceding unsigned comment added by (talk) 03:09, 19 July 2012 (UTC)

Restored per source. . . dave souza, talk 03:45, 19 July 2012 (UTC)


The world section is poor; its just a random collection of papers where the MWP, or something warm that people label the MWP, was found William M. Connolley (talk) 15:32, 24 July 2012 (UTC)

New rant

Mann's hockey stick has been discredited by McIntyre and McKitrick in "Corrections to the Mann, et al., Proxy Data Base and Northern Hemisphere Average Temperature Series, Environment and Energy14 (6), 1998, pp 751 -771

Similarly, the archeological and anecdotal evidence clearly indicates at least in the Northern Hemisphere it was much warmer then today, e.g. Extremely productive vineyards in the British Isles and the previously stated conditions in Greenland. Finally, there is convincing evidence that Mann included temperatures that were greatly overstated because of the Urban Heat Island effect for his uptick in temperature. When these measurements are juxtaposed with the highly accurate satellite measurements it is clear that minimal warming has occurred since the late 1970's. The Medieval Warm Period at its peak was 1.2'C higher than today and when using the accurate satellite data from NASA a global increase in temperature of .19'C occurred from 1970 to 1998--this was corroborated by Drs. Roy Spencer and John Christy at the University of Alabama's Earth System Science Center. Likewise, average global temperatures have stabilized since 1998. The temperature readings from the Surface Stations are highly skewed because of environmental issues like the previously mentioned "Urban Heat Island" effect. VPfund2012 (talk) 20:57, 21 September 2012 (UTC) Victor Pfund

You deserve some credit for getting every denialist meme into a couple of paragraphs William M. Connolley (talk) 21:07, 21 September 2012 (UTC)
Ah, but what about the the urban heat island in Antarctica? Also, it's impressive how M&M as cited above seem to have produced their E&E paper in 1998, attacking MBH99. No doubt some more of the Dr. Who effect. Do give my regards to Jones the Steam. . . dave souza, talk 21:35, 21 September 2012 (UTC)
I'd missed that one. Its actually " the Mann, et al. (1998), Proxy Data Base" [11], Vol. 14, No. 6, 2003 William M. Connolley (talk) 08:12, 22 September 2012 (UTC)

Initial research

This section has got badly broken, and needs to return to a much earlier version William M. Connolley (talk) 18:17, 10 October 2012 (UTC)

Oh, and making Hughes and Diaz available ( would be sensible William M. Connolley (talk) 18:19, 10 October 2012 (UTC)

Link to "Can Medieval Heat Cool Warming Worries?"

I recently added a link to this interesting pop-sci article by Matt Ridley. WMC reverted, commenting "This is a science article".

Here's Ridley's opening paragraph:

A flurry of recent scientific papers has tried to measure the warmth of the "Medieval Warm Period" (MWP) of about 1,000 years ago. Scientists have long debated whether it was cooler or warmer than today, and whether the warmth was global or regional. The point for nonscientists: If recent warming has precedents, some might find it less alarming.

We try to aim Wikipedia science articles at general readers, which is precisely what Ridley is doing. The Wall St Journal, one of the USA's two leading national newspapers, hired Ridley to write a popular science column, no small endorsement. WMC's objection appears unfounded. --Pete Tillman (talk) 20:10, 17 November 2012 (UTC)

The WSJ publishes any amount of trash on GW. You're trolling William M. Connolley (talk) 23:46, 17 November 2012 (UTC)
"The WSJ publishes any amount of trash on GW." Is that best argument you can make: WP:I don't like it. Good grief. Reinstated. Pete Tillman (talk) 01:57, 18 November 2012 (UTC)
That is a pretty neutral article. It does not make one claim or the other, only opens up the discussion regarding the published science....which is what science is all about. Arzel (talk) 07:44, 18 November 2012 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── By "pretty neutral" you seem to mean blatant misinformation. Starting near the opening:

Until the late 1990s, researchers generally agreed that the MWP was warmer than today and that the "Little Ice Age" of 1500-1800 was colder.

"Researchers generally agreed" is contradicted by the 1995 SAR, "a clearer picture may emerge as more and better calibrated proxy records are produced. However, at this point, it is not yet possible to say whether, on a hemispheric scale, temperatures declined from the 11-12th to the 16-17th century. Nor, therefore, is it possible to conclude that global temperatures in the Medieval Warm Period were comparable to the warm decades of the late 20th century." The claim that "That graph helped to persuade many people (such as me) that recent temperature rises were unprecedented in scale and speed in at least 1,400 years" is odd, as Mann, Bradley and Hughes 1999 only covers 1,000 years. The various studies are isolated, not a general assessment, and Viscount Ridley of Northern Rock seems to be basing his assessment on the Center for the Study of Carbon Dioxide and Global Change, a completely unreliable source. We should not expect our readers to have to check out misinformation. . dave souza, talk 08:28, 18 November 2012 (UTC)

And as Pete notes, "The point for nonscientists: If recent warming has precedents, some might find it less alarming." Very soothing, but everyone agrees that recent warming has precedents: for example, the PETM which isn't really all that reassuring. . . dave souza, talk 08:36, 18 November 2012 (UTC):
Um. PETM did occur, but not exactly recent. Roman Warm Period appears to have been warmer (in some places) than MWP (ims). We can certainly agree that the climate has changed in the past, is changing now, and will change in the future. The reasons for the current changes are currently being debated, and aren't clear.
Dave, you aren't required to agree with all of what this article says (or like the author), but it seems to me to be a worthwhile link for our readers.The editors at the WSJ thought it worth presenting. Your "misleading" point is debatable, and "blatantly false denialist misinformation" diff is (imo) flat wrong, and pejorative to boot. And "Viscount Ridley of Northern Rock" appears close to a WP:BLP vio? Best, Pete Tillman (talk) 19:25, 18 November 2012 (UTC)
Having lost the argument you're now reduced to threats William M. Connolley (talk) 19:55, 18 November 2012 (UTC)
Nope, and stop that. I don't believe this is a WP:Civil comment. --Pete Tillman (talk) 01:46, 19 November 2012 (UTC)

Mirror on Greenland

Archaeologists Uncover Clues to Why Vikings Abandoned Greenland - SPIEGEL ONLINE refers to an interesting study with detail including dates which would be useful here. The study itself seems to be Arneborg, Jette; Lynnerup, Niels; Heinemeier, Jan; Møhl, Jeppe; Rud, Niels; Sveinbjörnsdóttir, Árný E. (2011–2012). "Norse Greenland Dietary Economy ca. AD 980-ca. AD 1450: Introduction". Journal of the North Atlantic : Special Volume 3: Greenland Isotope Project:Diet in Norse Greenland AD 1000—AD 1450. 3: 1–39. doi:10.3721/037.004.s303.  Possibly worthwhile, but paywalled. . . dave souza, talk 18:42, 11 January 2013 (UTC)

Possibly. But it appears to say that, even though the climate cooled, that wasn't the reason for the abandonment. So it doesn't affect any climate reconstructions, just the social bits? William M. Connolley (talk) 21:34, 11 January 2013 (UTC)
That's the very point, that the cooling of the climate led to changes in their diet but their settlements continued for a couple of hundred years before being abandoned for social reasons, with no indication of the starvation or disease suggested by some commentators. Thus worth clarifying, so I've had a go. Citing Der Spiegel rather than the paper. . dave souza, talk 21:07, 12 January 2013 (UTC)
Oh look, the paper (pdf). Am too tired now to rethink our wording, but it looks hopeful. . dave souza, talk 21:13, 12 January 2013 (UTC) See also [12][13]. . 21:26, 12 January 2013 (UTC)
I've read what you've written, and the paper itself, and that seems reasonable. Of the paper: clearly they've done a vast amount of hard work. However, I rather miss a "conclusions" section William M. Connolley (talk) 20:55, 13 January 2013 (UTC)

Heterogeneous nature?

Can someone clarify what this means from the second paragraph:

The heterogeneous nature of climate during the Medieval Warm Period is illustrated
by the wide spread of values exhibited by the individual records.

What is meant by "heterogeneous"? What is meant by "individual records"? I initially thought "individual records" meant "different locations" and I was going to clarify, but then I realized it could also mean individual data points in a stream of data points that have a fair amount of noise (an ordinary thing in the world of data). Which meaning (if either)? Also, that still leaves the question of what is meant by "heterogeneous". "Heterogeneous" seems out of context for either meaning of "individual records". The sentence needs to be clarified by some who knows what was intended, please. (talk) 23:58, 20 February 2013 (UTC)

The "MWP" was both spatially and temporary heterogeneous. Global temperature may have been slightly higher, but different local temperature records show maximum temperatures at different times. --Stephan Schulz (talk) 00:20, 21 February 2013 (UTC)
It's a close paraphrase of the caption to Box 6.4 fig. 1 from the AR4, so I've tried translating it into more common English as "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." It may be worth showing that figure as an illustration. . dave souza, talk 09:09, 21 February 2013 (UTC)

Correcting the Lede

This discussion has been closed. Please do not modify it.
The following discussion has been closed. Please do not modify it.

The current lede is:

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]

Please see (Rosenthal, Y.; Linsley, B. K. & Oppo, D. W., 2013. Pacific Ocean Heat Content During the Past 10,000 Years. Science 342: 617-621) as an example of a peer-reviewed paper stating that the MWP was global. It is 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, thereby supporting the idea that the HTM, MWP, and LIA were global events”. HTM=Holocene thermal maximum. MWP=Medieval Warm Period. LIA=Little Ice Age. This renders the lede inaccurate in regards to the claim that the MWP was a "warm climate in the North Atlantic region", "cooler period in the North Atlantic", "temperatures were probably between 0.1 deg C....."

Please see (Esper, J. and Frank, D. 2009. The IPCC on a heterogeneous Medieval Warm Period. Climatic Change 94: 267-273) that clearly refutes the lede where it states "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". The Esper, et al paper states "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".

Because of these newer papers, I suggest the lede be changed to:

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 [1]. It was followed by a cooler period 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'” [2]. However more recent papers have shown evidence “supporting the idea that the...MWP...were global events”[3].

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[4] to approximately 0.9 deg C above 20th century temperatures[5]. 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.[6]

The above reference in a quote might be confusing, but I just don't know what would be acceptable by wikipedia standards to remedy the situation. Also, I welcome corrections and changes that reflect the current status of knowledge on the topic.

Scott.Balfour (talk) 02:44, 21 June 2014 (UTC)

I'll offer the first correction on myself. I noticed earlier that I state " the temperatures of the MWP colder than to apprixmately 0.9 deg C above...". My cut-and-pasting zealotry got the wrong number. It is not 0.9 but 0.65 and should be "approximately [or ~]0.65 deg C". Scott.Balfour (talk) 02:56, 21 June 2014 (UTC)
Premature? See Scott.Balfour's comment at 03:06, 21 June suggesting this section may be deleted. Hatted until this is resolved. . . dave souza, talk 05:05, 21 June 2014 (UTC)


To cover more recent research, 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. The Summary for Policymakers and Technical Summary both have concise overviews, I'll copy one into a quote box. Detail is provided in "5. Information from Paleoclimate Archives", including references to the various studies and a lot about regional impacts and ocean warming. . . dave souza, talk 05:31, 21 June 2014 (UTC)

There is high confidence that annual mean surface warming since the 20th century has reversed long-term cooling trends of the past 5000 years in mid-to-high latitudes of the Northern Hemisphere (NH). For average annual NH temperatures, the period 1983–2012 was very likely the warmest 30-year period of the last 800 years (high confidence) and likely the warmest 30-year period of the last 1400 years (medium confidence). This is supported by comparison of instrumental tempera- tures with multiple reconstructions from a variety of proxy data and statistical methods, and is consistent with AR4. Continental-scale sur- face temperature reconstructions show, with high confidence, multi- decadal periods during the Medieval Climate Anomaly (950–1250) that were in some regions as warm as in the mid-20th century and in others as warm as in the late 20th century. With high confidence, these regional warm periods were not as synchronous across regions as the warming since the mid-20th century….. [AR5 Technical Summary]

AR5's WG1 publish deadline had passed March 15 2013. The cited (Rosenthal, et al 2013) paper was published November 2013. It could not have been part of the evaluated work.
The IPCC is a governmental body ("Invitations to participate in the sessions of the Panel and its Working Groups, Task Forces and IPCC workshops shall be extended to Governments and other bodies by the Chairman of the IPCC."). The "principles" document clearly states "The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation." It specifically focuses on human-induced climate change instead of "climate change". Per WP:Questionable sources (see? getting the hang of these cites!) "Questionable sources are those that apparent conflict of interest." Their own documents show them to have a conflict of interest. I think it would be far better to read over any or all documents you care to from the IPCC and locate the papers sourced and instead reference them. It completely avoids the extremely problematic issue of citing a questionable source. Scott.Balfour (talk) 07:01, 21 June 2014 (UTC)
I'm sorry but that is nonsense. The IPCC publications have been widely described as the best and most authoritative overviews of climate science, by individual scientists, including e.g. Lindzen and Christie, by National Academies of science, and by a multitude of other scientific bodies. "But there is government involved" is about as useful and mature an argument as "lalala". General service announcement: A full copy of the paper can be found at one of the author's websites here. --Stephan Schulz (talk) 07:35, 21 June 2014 (UTC)
I went through the trouble of finding and reading scientific papers published in science journals. I did this because sources like the IPCC can so easily be shown to be biased. However, if the bar is so low, let me quote the NIPCC's (I didn't even bother looking at this source until a few minutes ago because I knew the cries of bias would come.) 2013 fourth report Chapter 4:

The IPCC concludes “there is high confidence that the Medieval Climate Anomaly was not characterized by a pattern of higher temperatures that were consistent across seasons and regions” (p. 5–4 of the Second Order Draft of AR5, dated October 5, 2012). Quite to the contrary, an enormous body of literature clearly demonstrates the IPCC’s assessment of the Medieval Climate Anomaly (MCA) is incorrect. The degree of warming and climatic influence during the MCA indeed varied from region to region, and hence its consequences were manifested in a variety of ways. But literally hundreds of peer-reviewed scientific articles confirm it occurred and was a global phenomenon.

It is equally valid and as scientific as the above quote from the AR5. However, I do not propose citing this source for the MWP article and consider it as biased as the IPCC. Scott.Balfour (talk) 08:08, 21 June 2014 (UTC)
Also, please restrict your comments coincident with the wikipedia policy WP:No personal attacks. "this is nonsense" "mature an argument as 'lalala'" etc. are clearly outside the scope of the linked document and are not useful to the improvement of the MWP article. Scott.Balfour (talk) 08:18, 21 June 2014 (UTC)
The NIPCC is not "equally valid and as scientific" - as much as the IPCC is recognised by the scientific community, the so-called NIPCC (a small group of deniers sponsored by a conservative think tank) is panned. If you bring up these fake sources, you are not helping your position. I'm glad to hear that you "went through the trouble of finding and reading scientific papers published in science journals". But I find it a bit hubristic to assume that you can do a better job of it than the many many scientists, with multiple levels of review, that make up the IPCC working groups. As you wrote above, the Rosental et al. paper was published after the AR5 cut off - so where is your sign of bias? Indeed, the paper was published so recently, that it has barely been cited and commented upon in formal publications. See here and Talk:Global warming/FAQQ21. --Stephan Schulz (talk) 08:42, 21 June 2014 (UTC)
I am merely noting a seven month old paper that the "many many scientist" did not have to review at the time of review. I am not claiming a better job of reviewing. I am claiming they did not review it. I suppose you could say any review is better than none, but I don't think that is the issue in this context. As for my sign of bias, I have proposed changing the clear bias for the MWP article to reflect both sides. I clearly noted in the talk that I kept in IPCC references (amongst other things). If you can parse through my poor formatting, you'll have a clearer picture of my attempted neutrality (as per wikipedia guidelines) Scott.Balfour (talk) 13:23, 21 June 2014 (UTC)
(A) That's not what "conflict of interest" means
(B) "That is nonsense" is a reference to an argument. Unless my wife says it, a personal attack would be "NewsAndEventsGuy is an idiot".
(C) We also have the ongoing problem of WP:RECENTISM and using primary sources. Part of the idea behind the professional scientific literature is to publish so others can rebut/confirm/expand/etc, and that is sometimes a painfully slow process. Individual papers published in the last few months need time to register on and impact the authors' colleagues. It is often better to use literature review articles and WP:SECONDARY sources.
NewsAndEventsGuy (talk) 10:35, 21 June 2014 (UTC)
And of course the IPCC WG1 reports are literature review carried out by leading experts in topic areas. As a couple of data points, the press release for the Rosental et al. paper gives what one might call an antisceptic assessment. A distinguished professor with expertise in the topic area gives useful first pointers in this article, though of course deniers will automatically disregard everything he says. . . dave souza, talk 10:58, 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) 13:23, 21 June 2014 (UTC)
(In reference to NewsAndEventsGuy above, but I didn't want to "cut in" a talk)Conflict of interest as defined by citation for conflict of interest states "interests other than professional considerations" (like an institutional mandate to focus on one of many aspects of "climate change"). It would seem my reading of the definition differs than yours.
"Recentism" is another area where my reading of the definition must be in conflict of yours. I see no part of the linked page that decribes a "reliable source" as being evidence of "recentism". I agree that I am most certainly using primary sources. Most, if not all, of the citations for the MWP are primary sources. It seems systemic to the subject instead of an editor.
It seems to me that this is straying and is not managing to "stay on topic" of the MWP. The IPCC is controversial with claims of "conflict of interest" by Prof. Robert Stavins (former IPCC Co-Coordinating Lead Author of Chp 13 WG3) or claims the "delgations have a political agenda" (and other negative things) by Dr. Richard Tol. These two examples are probably two of the more well-known, but far from comprehensive. I suggest that either the problematic IPCC information is balanced to remain neutral via refuting sources (NIPCC, Papers like the one I've cited previously, etc.) or simply take the IPCC's references and grab the relevant paper. I don't want to supress any information. I simply want a more neutral stance and reflection in the article of more current understanding.
I did note before that the IPCC has problems as a "reliable source." I'm not sure why an IPCC AR section was thus created. Perhaps it would be better to create a new section for the first section of the body of the MWP article and I'll propose edits and do my very best to provide "friendly" formatting. Scott.Balfour (talk) 13:23, 21 June 2014 (UTC)

Proposed changes to Section "Initial Research"

Scott Balfour proposes to change Section "Initial Research" so that the new text will read as follows NewsAndEventsGuy (talk) 13:59, 21 June 2014 (UTC)

[First paragraph unchanged]
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 AgeLIA[1] 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, Rosenthal, et al published a paper in 2013 that showed evidence “supporting the idea that the HTM, MWP, and LIA were global events”[2]. 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 thusmay be[3] 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.
  1. ^ My reasoning is the LIA abbreviation was previously defined. MWP is abbreviated. No point spelling it out.
  2. ^ (Rosenthal, et al 2013) [Reasoning is this reflects more current knowledge. I don't like the fact that HTM is undefined and welcome suggestions as to how to not distort the text but still convey the meaning without ambiguous “alphabet soup”.]
  3. ^ My reasoning is this last sentence has no citation and may fall under the category of “OR”. Therefore, it would be prudent to simply change a definitive declaration into a softened version. If some source actually says what was originally written, a better edit would simply be to cite the source.

Scott.Balfour (talk) 13:50, 21 June 2014 (UTC)

I admit I've read almost nothing about LIA and MWP, but changes 1 and 3 look reasonable. I'm still forming my opinion about change 2. NewsAndEventsGuy (talk) 14:07, 21 June 2014 (UTC) And congratulations on the large leap in methodical presentation of your ideas. NewsAndEventsGuy (talk) 14:08, 21 June 2014 (UTC)
OK, I'm opposed to change 2, for the RECENTISM arguments stated previously. We have to let time give others a chance to assess this paper and for the professionals to debate it. In particular, whether that paper really slam dunks your proposition (that MWP was global) is the subject of debate in comments at "Oceans heating up faster now than in the past 10,000 years, says new study". That's a blog post, so isn't RS for the article, but the back and forth arguments just demonstrate the logic in being slow to push single recent papers that are ploughing new ground. If a bunch more RSs start saying "global" building off of this research, then by all means we should revisit the question. But that'll be awhile. And in any case, you left out the part that says some inferences "support the idea" of global nature, and the next sentence saying they lacked additional data to look into that further. So at best they've identified some interesting material to follow up on. That's quite different than how you're portraying their findings. Which highlights another pitfall with primary sources - it's hard to read them correctly. NewsAndEventsGuy (talk) 14:25, 21 June 2014 (UTC) (oops sorry about overlooking the "supporting the idea" part. Apologies. NewsAndEventsGuy (talk) 15:31, 21 June 2014 (UTC)
While I was away, I had a thought on this section. I think I've missed the forest for the trees. The heading is "Initial Research" (which would presumably specifically exclude things like "recent research"). As such, it is probably inappropriate to include the Rosenthal reference on that alone. However, that comes back to WHY I missed the forest. The title is bad. It isn't initial research into the MWP. That happened decades (or centuries if you discount scientific rigour) ago and is not reflected in this section. Perhaps the best idea for this section is to just give it a meaningful heading? "Research in the 1990s"? "Initial Research into MWP Locality"? Something that makes more sense. And thanks for the compliment on formatting! Scott.Balfour (talk) 03:51, 22 June 2014 (UTC)

Orphaned footnotes?

Just noticed (8 August 2014, about 3:00 pm USA EST) that footnotes ("References") 9, 10, and 11 are nowhere referred to in the text of the article -- or, if they are, the trackback links don't work. How did that happen?

Apologies, I've never done this before so I'm not sure how the " (talk) 19:09, 8 August 2014 (UTC)" signature is conventionally used.

Thanks for raising this point, if there was a problem it seems to have been fixed now. Thus, in the References section the "9^" at the start of the line has a link at "^" which takes you up to the end of the sentence supported by the citation. Hope that works for you now, and conventionally the signature goes at the end of your last sentence, thus: dave souza, talk 21:31, 8 August 2014 (UTC)