Talk:Medieval Warm Period/Archive 2

Archive 1

Archive 2

Archive 3

Archive 4

I'm confused

From the article:

"A radiocarbon-dated box core in the Sargasso Sea shows that sea surface temperature was approximately 1°C cooler than today approximately 400 years ago (the Little Ice Age) and 1700 years ago, and approximately 1°C warmer than today 1000 years ago (the Medieval Warm Period).[11] However, all the reconstructions, as shown above, appear to indicate that it was not."

What is this actually saying, in the context of the rest of the text? Doesn't the last sentence there just cancel everything else out?

Inspector Baynes 22:06, 16 October 2006 (UTC)

The last sentence is because global warming believers claim that old warming or cooling must have been local events, and there couldn't have been global warming events. (SEWilco 05:08, 17 October 2006 (UTC))

Its an odd sentence, I hope I didn't write it. To make sense, it would have to say "...it was not global" or somesuch. The easiest thing to do seems to be to remove it William M. Connolley 08:31, 17 October 2006 (UTC)

The graph is a complete fraud for reasons stated above. 19 Dec 2009 —Preceding unsigned comment added by 74.132.27.108 (talk) 16:15, 20 December 2009 (UTC)

biographies of living persons

I've removed extended discussion concerning a reference to a website that contains claims that breach our biographies of living persons policy. Obviously we won't be citing that website because it's contrary to policy. All editors are reminded that extended discussion and defence of such sources is not to be undertaken on Wikipedia. Simply remove the source material when and where it appears. --TS 14:29, 21 December 2009 (UTC)

Ice Core Data Graph

It would be nice to add this ice core data graph that shows Medieval Warm Period very well:

http://www.foresight.org/nanodot/wp-content/uploads/2009/12/histo5.png

References:

1. Alley, R.B. 2000. The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19:213-226

2. http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2475.html

3. Vostok Ice Core Data: http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2453.html

—Preceding unsigned comment added by VotusW (talk • contribs) 02:30, 22 December 2009 (UTC)

The Foresight graph is not from a reliable source (and it's quite unclear what it shows). The Alley paper is on the younger Dryas and talks about Greenland only, as does the data from NOOA. I don't know how the Vostok data comes into this - it's from the other side of the world. I've looked at the Alley GISP data set, and it really is useful for long-term developments only - it has no data from the last 100 years, and it also seems to be very raw, in that there are e.g. unexplained doublets in them. --Stephan Schulz (talk) 08:34, 22 December 2009 (UTC)

-This is Ice Core Data - it's important for the raw information / data. This is why people come to Wikipedia - not for someones opinion, but for the raw info. This graph show the Medieval Warm Period very clear. It's missing around 60-70 years. But, I do not understand why do you need to compare Medieval Warm Period to the last 100 years? Source is reliable. I don't understand why graph that made from NOOA Ice Core Data, by the Foresight Institute is not reliable? --VotusW (talk)

No, raw data is not what people come too Wikipedia for. Please see WP:PRIMARY. We need to be very careful about using primary sources - they typically need expert interpretation. In this case, the data gives some evidence for temperatures in one single location, not about a global or hemispherical MWP. The Foresight Institute is not a RS for climate science, and it is unclear if they plotted the data in the first place - all we can say is that the plot is on their server. I replotted the last 1500 years of the GISP data, and my plot looks only somewhat similar to the one on the Foresight site. It's not clear what they did to produce this graph- its certainly not a direct plot. --Stephan Schulz (talk) 16:35, 22 December 2009 (UTC)

-This graph was made by Foresight Institute & by J. Storrs Hall: http://en.wikipedia.org/wiki/J._Storrs_Hall Source - "Alley, R.B. 2000. The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19:213-226" & NOOA. http://nsidc.org/data/docs/agdc/nsidc0121_alley/index.html Do you have any graph with Ice Core Data in "all locations"? Why don't use this one also? --VotusW (talk)

The graph has no attribution and no legend, unless there is another page than the one you link to. I don't know J. Storrs Hall, but the article looks like a fan biography - it certainly does not meet our standards for reliable sources. But that's neither here nor there. We have no evidence that the graph was produced by him, and even if it were, it would still be self-published by someone who is not an expert in a relevant field. No, Alley is not a source for this plot, it's a description of the full 50000 year reconstruction. --Stephan Schulz (talk) 11:01, 23 December 2009 (UTC)

Suggested changes

The sentence that begins with "Studies by Michael Mann et al. find that the MWP..." seems to suggest the broad conclusion is only from Mann studies. Others appear to concur (Esper et al., Moberg, etc.).

[1]

Also, the recent Mann et al. study is cited. It would be nice to include an image from ths study showing regional variation.

[2]

Gmb92 (talk) 20:54, 22 December 2009 (UTC)

I've corrected "studies" into the singular; there is only one. Arguably we shouldn't ref that; it is too new. Don't blame me guv (well not much). As for Esper/Moberg etc - do they do patterns? I didn't think so, just a global total William M. Connolley (talk) 23:18, 22 December 2009 (UTC)

Since the section is titled "Globally", it seems it would apply at least in part to the global average. Maybe there should be two separate paragraphs, one discussing global (or hemispheric) averages which has been covered extensively in the peer-reviewed journals and one for the regional variation as covered in the recent Mann et al. study. At the same time, the global or hemispheric average is discussed in the Initial Research section and includes a graphic of northern hemisphere reconstructions, so that might be redundant. It just seems the "Globally" section is lacking given the body of multi-proxy studies covering hemispheric and global average reconstructions. Gmb92 (talk) 00:24, 23 December 2009 (UTC)

Article protected?

Any particular reason why this article is proteced? 216.153.214.89 (talk) 07:58, 22 December 2009 (UTC)

As it says: Note: This page has been semi-protected so that only established users can edit it... 2009-12-22T00:43:46 Stephan Schulz (talk | contribs) protected Medieval Warm Period [edit=autoconfirmed] (expires 00:43, 25 December 2009 (UTC)) [move=autoconfirmed] (expires 00:43, 25 December 2009 (UTC)) ‎ (Excessive vandalism) (hist) William M. Connolley (talk) 09:15, 22 December 2009 (UTC)

For purposes of clarity and impartiality can I ask: Who are the 'established' editors and what political organisations on the web are they affiliated with? For example, you are a member of realclimate.org which is funded by an eco-energy company.Greg hill (talk) 09:38, 22 December 2009 (UTC)

I'm not. It isn't William M. Connolley (talk) 09:44, 22 December 2009 (UTC)

In this context, the term "established editors" simply means autoconfirmed editors. To edit the article you need to have held the account for at least four days (that's right, days, not weeks or months), and to have made at least ten edits anywhere on Wikipedia in those four days. --TS 10:31, 22 December 2009 (UTC)

...and you need to set your secret decoder ring to C-A-B-A-L! --Stephan Schulz (talk) 10:47, 22 December 2009 (UTC)

Isn't this article about the Medieval Warm Period?

This article should reflect the fact that it's about the MWP?! In stead there's a lot of information about the MWP's relationship to global warming- perhaps we need another article about this issue? What's really missing from this article though is a discussion about what caused the MWP? And then perhaps a broader description of its effects during this period (the vikings are very interesting, but I'm sure their settling of Greenland wasn't the only significant effect of the MWP.) Joe Gain 95.113.5.250 (talk) 11:21, 31 December 2009 (UTC)

Is there? We have on small section on that topic, and one or two comparisons of MWP temperature to 20th century temperatures. That does not seem excessive to me. I don't think we understand the MWP very well - we don't even know if it was global, and I don't think there is a good understanding of what caused it. Climate records are sparse and we are just now beginning to model global climate in the relevant time frame. --Stephan Schulz (talk) 12:18, 31 December 2009 (UTC)

Per Stephan: other than speculation, I don't think there is much good stuff on the origin. Probably we need more on its reality - the current mish-mash of "evidence" is poor William M. Connolley (talk) 12:25, 31 December 2009 (UTC)

Proposed article update

I am going to update this part of the text in the article as it is no longer correct.

The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of warm climate in the North Atlantic region, lasting from about AD 800–1300. 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

Bold highlights are the parts i would like to change. The first is to extend the area from just the north Atlantic based on this peer reviewed paper It clearly shows the mwp was a world wide climate event and not a localized one as is suggested in the opening paragraph.

I also take exception the the term "some refer" (medieval climatic anomaly) To the best of my knowledge only michael mann has used this term. Plus 600 odd years should not be called an "anomaly". Thoughts on the above please --mark nutley (talk) 10:19, 26 December 2009 (UTC)

Please read previous discussions before proposing changes; e.g., see the "Sentence not supported by citation..." section above where your second point is addressed. Short Brigade Harvester Boris (talk) 13:53, 26 December 2009 (UTC)

Seen it now thanks, i see no consensus there for the text to remain the same as it currently stands. We can move this part of my proposed edits to there though.

any thoughts on the first point? mark nutley (talk) 14:16, 26 December 2009 (UTC)

Singular focus on a single paper is never worth anything. It is about a specific location, and thus doesn't reflect the globe. What does the assessment reports say? (IPCC, US CCSP) As for your "only mann" thing - that is rather easy to show wrong[3] --Kim D. Petersen (talk) 18:38, 27 December 2009 (UTC)

I`m not focusing on a single paper, this is the third study from new zealand which shows it too went through the MWP.

This is definate evidence that it was more than likely a global event and not confined to the north atlantic as is written in the lead of the article. And could you tell me please which study is used to state the the MWP was confined to the north atlantic regions only? --mark nutley (talk) 19:23, 27 December 2009 (UTC)

ANY evidence of the MPW outside of the region the MPW is supposed to have been localized to, tends to falsify the hypothesis I would think. It's not our call to say which is correct, but at the very least we shouldn't be taking the side which seems to have been proven false. Edgespath24 (talk) 12:14, 29 December 2009 (UTC)

And that is the actually interesting thing about this "New Zealand MWP" paper — not only is the MWP hard to tell apart from where the Little Ice Age should be, it also has the absolute minimum at around 1010 — right where the European MWP has its peak. Lars T. (talk) 00:36, 31 December 2009 (UTC)

Honestly, why do we use Mann's information??? His hockey stick was shown not to work. There is much more supportive data supporting the medevil warm period being just as warm as today, or around that. I think a new graph supported by many times more scienctist should be posted showing the med-evil warm period and the little ice age define as should be. Can you tell me why or why not. —Preceding unsigned comment added by Matthurricane (talk • contribs) 00:56, 28 December 2009 (UTC) Matthurricane (talk) 01:00, 28 December 2009 (UTC)

On the contrary. Mann's methods have received some criticism, some of it even justified, but the reconstruction (especially with the error bounds) has been generally vindicated. That said, we don't show "Mann's Hockey Stick", but rather an ensemble of 10 different reconstructions, only one of which is "the Hockey Stick", and 7 of which have no input by Mann. See the description at File:2000 Year Temperature Comparison.png. --Stephan Schulz (talk) 22:29, 28 December 2009 (UTC)

It's undue weight and asserting that the MWP was local, rather than global, is the extraordinary claim which needing extraordinary proof. I'll remove it. Edgespath24 (talk) 11:14, 29 December 2009 (UTC)

You might want to discuss that first, i believe with the new paper i have posted we can say that the mwp covered more than just the north atlantic, but removing stuff without talk leads to revert wars. And on that note does anyone actually have any input to this proposal? mark nutley (talk) 11:32, 29 December 2009 (UTC)

Well I agree with you. Given that there is evidence world-wide for the MWP, it's incorrect to say it was just local. We should certainly say that Mann thinks it was. As for the issue re: the "Medieval Climatic Anomaly" term, I don't have a problem with it and the linked citataion attributes the term to Stine, not Mann - "This led Stine to argue that a better term for the overall period was the “Medieval Climatic Anomaly” (MCA), which removes the emphasis on temperature as its defining characteristic." Edgespath24 (talk) 12:07, 29 December 2009 (UTC)

No, it is not undue weight - since that is what the parity of references say: the MWP was most likely a NA phenomenon. The trouble here is that you are confusing issues, a NA phenomenon may have global impacts, but the impacts are not by necessity of the same kind. (ie. some places show cooling, drying, flooding ...) The signal is strongest in the NH and slight in the SH, and has a significant impact in the NA area, and a smaller in other areas. Cherry-picking single sources can and will always give the result that you want, but a review of the literature, which takes all sources into account, show differently. --Kim D. Petersen (talk) 13:00, 29 December 2009 (UTC)

OK well it's obviously your position that it was localized, but it is still undue weight. We can't definitively say it was localized when there is clear contraindicating evidence and ongoing research on the matter. Edgespath24 (talk) 21:13, 29 December 2009 (UTC)

This isn't a question of whether Kim or you or I say it's localized. Our positions don't matter. The only question Wikipedia asks is what do the reliable sources say. --TS 21:32, 29 December 2009 (UTC)

I agree. As reliable sources have found evidence of it in NZ (and other places) we should not be saying it was localized. Edgespath24 (talk) 00:05, 30 December 2009 (UTC)

If you can find evidence not in single papers, but in reviews of the literature, then I'll concede that we have a reliable source to challenge the orthodoxy. --TS 00:13, 30 December 2009 (UTC)

So now peer reviewed papers aren't enough? Sounds like you're proposing a novel standard to avoid NPOV on this issue. Edgespath24 (talk) 00:18, 30 December 2009 (UTC)

One, two or even three peer reviewed papers have never been enough. This isn't the place for original research. --TS 00:28, 30 December 2009 (UTC)

Wow. So citing papers appearing in the peer reviewed literature (which happen to contradict some editor's preferred view) have now somehow become original research. That's another novel interpretation of WP rules. Edgespath24 (talk) 00:39, 30 December 2009 (UTC)

Citing papers in the peer reviewed literature is fine. Citing some outliers to overrule the result of reviews of the field is not. --TS 00:41, 30 December 2009 (UTC)

Which is why I rewrote without picking sides. Your objection only makes any sense if I'd written it to say it was global. Edgespath24 (talk) 01:01, 30 December 2009 (UTC)

The paper you like so much is an example of the effect already discussed in the article: "Palaeoclimatologists developing region-specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP"" -- in this particular case, the reconstruction (Fig. 3 in [4]) shows distinct cold period at around the time the MWP was at it's warmest in Europe, and it's warm period very much to the end, when temperatures in Europe were mostly back to normal. That's not a global MWP, if anything it's evidence for the suspected see-saw between the hemispheres. --Stephan Schulz (talk) 03:35, 30 December 2009 (UTC)

If you can cite that analysis, then add it to the article. However, unless you can provide strong evidence that the MPW is universally considered to be a localized phenomenon, it's inappropriate to present it as such. Edgespath24 (talk) 05:32, 30 December 2009 (UTC)

You have things reversed. You will have to document that it was world-wide by citing papers that say that it was world-wide. A methodology that consists of editors looking at regional or local reconstructions, and concluding by themselves that it must be global is original research. --Kim D. Petersen (talk) 02:21, 31 December 2009 (UTC)

I've added a NPOV tag until this is sorted out. Edgespath24 (talk) 05:34, 30 December 2009 (UTC)

Overkill, mate. All we have to do is to be careful to distinguish what we know for certain (the MWP was a fairly pronounced warm climate anomaly in the North Atlantic) from what is is a bit less certain (the MWP extended to other parts of the world). And keep in mind that even if it was global it could be manifested in different ways in different regions: Broecker[5], while arguing that the MWP was a global event, notes that Antarctica was substantially colder during the MWP. How about a sentence like "The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of warm climate in the North Atlantic region that may have been part of a global climate anomaly." Short Brigade Harvester Boris (talk) 05:49, 30 December 2009 (UTC)

Not bad boris, if i may add a bit? "The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of warm climate in the North Atlantic region and which new research (cite above paper here) shows it may have been part of a global climate anomaly." mark nutley (talk) 09:09, 30 December 2009 (UTC)

The "new research shows" bit doesn't belong because people have suspected the MWP may have been global for a long time. Short Brigade Harvester Boris (talk) 14:36, 30 December 2009 (UTC)

Good compromise. --Kim D. Petersen (talk) 02:22, 31 December 2009 (UTC)

If it has been suspected that the MWP was a global event then why does the article lead focus on the NA? why does it not say it was a global event? And i hate the word Anomaly for the MWP 600years is not an anomaly :) --mark nutley (talk) 11:29, 1 January 2010 (UTC)

Article probation

Please note that, by a decision of the Wikipedia community, this article and others relating to climate change (broadly construed) has been placed under article probation. Editors making disruptive edits may be blocked temporarily from editing the encyclopedia, or subject to other administrative remedies, according to standards that may be higher than elsewhere on Wikipedia. Please see Wikipedia:General sanctions/Climate change probation for full information and to review the decision. -- ChrisO (talk) 02:46, 2 January 2010 (UTC)

Rewrite - Relation to modern climate issues

I think this section has to be rewritten. Taken alone, a niave reader may take this section to mean that this issue creates significant and credible evidence against anthropogenic global warming. This is WP:UNDUE. I suggest rewording There are credible arguments both for and against such a hypothesis to While there have been acadmic arguments both for and against such a hypothesis, the debate has had little impact on the general scientific consensus for man-made gobal warming. Objections? NickCT (talk) 20:10, 4 January 2010 (UTC)

As this article is about the MWP and not AGW i think rewriting it to what you say is wrong, this is about facts, not spin. --mark nutley (talk) 22:54, 6 January 2010 (UTC)

I took this out:

The Medieval Warming Period has been the subject of political and scientific debate, over the possibility that the occurence of such warming in the past might indicate that modern global warming might not be a product of manmade factors. There are credible arguments both for and against such a hypothesis. A scientific study begun in 2009 aims to examine evidence both for and against that hypothesis.

on the grounds that it isn't acceptable. This is far too much "false balance". The idea that cliamte is 50-50 on whether this argument makes sense is wrong: the balance is that pretty well everyone agrees that the MWP isn't the slightest evidence against current GW being anthro? Who put this stuff in? (I do hope it won't turn out to be me) William M. Connolley (talk) 23:12, 6 January 2010 (UTC)

I discover that this text came in quite recently [6] just before Christmas William M. Connolley (talk) 08:59, 7 January 2010 (UTC)

Have you actually got a reliable source for that claim? the balance is that pretty well everyone agrees that the MWP isn't the slightest evidence against current GW being anthro if not i would have to suggest a revert mark nutley (talk) 09:36, 7 January 2010 (UTC)

Could we please not waste time on nonsense? Just look at the sci-op articles, or anywhere else. And even by your own logic you're wrong: you certainly don't have a RS for opinion being 50-50 so have no grounds for a revert William M. Connolley (talk) 09:52, 7 January 2010 (UTC)

Where is the credible evidence? Can you cite some? The references certainly do not support it - and as far as i know, neither the NAS, US CCSP or the IPCC even remotely indicate such a possibility. (in fact quite the opposite is the case). --Kim D. Petersen (talk) 12:03, 7 January 2010 (UTC)

I do think the onus is on the editor to support the edit. --TS 12:51, 7 January 2010 (UTC)

per what tony just wrote, WMC until such a time as you can post reliable sources proving what you have said above i would ask you to replace the removed text, thank you. --mark nutley (talk) 14:02, 7 January 2010 (UTC)

You've got Tony backwards. He said, until the original edit can be supported it should be out. At least that is what I think he said. Tony? William M. Connolley (talk) 14:16, 7 January 2010 (UTC)

You have my meaning right, William. Apologies to all for the ambiguity. The sources do not seem to establish the existence of the credible evidence claimed in the original edit. Multiple reconstructions suggest that the current warming is of a greater magnitude and a more rapid acceleration in the 1000-year context than can be explained without taking into account the known effects of fossil fuel-based industrialization during the past 150 or so years. This is the scientific consensus and it would be misleading to suggest otherwise. --TS 14:12, 8 January 2010 (UTC)

Hey guys. Interesting debate. I just want to chime in and say that I'm in strong agreement with William M. Connolley when he says This is far too much "false balance". The idea that cliamte is 50-50 on whether this argument makes sense is wrong. The section read similar to something saying "It was cold outside yesterday. Scientists are still trying to figure out whether this disproves global warming". Unless it can be demonstrated through RS that MWP really posses a significant challenge to scientific consensus on GW, I find this hard to swallow. I think the section probably ought to be in the article, but really has to be totally reworked for NPOV. NickCT (talk) 14:26, 8 January 2010 (UTC)

Here we have WMC and KDP gatekeping an AGW related article in the true spirit of Climetsgate —Preceding unsigned comment added by 76.67.242.195 (talk) 20:12, 17 January 2010 (UTC)

Suggestion-- Removal of Image

There is previous discussion above in the talk page regarding issues with the current graphic image. I suggest a vote on whether or not remove the image. People who support removal should vote Support - Removal of Image and people who support retention should vote Oppose -- Removal of Image. Please include your wiki username with the 4 tildes after your vote.

It should be noted that the current image was created by a wikipedia editor from multiple sources (see File:2000_Year_Temperature_Comparison.png), unfortunately most of the sources are referenced only by abstract links. Thus the situation is that no one can verify that the graphic was correctly generated. Please follow the link I provide in this paragraph, review the sources referenced for the image, and verify for yourself that you cannot actually validate the data. Because the image itself is neither directly available from a secondary source, nor can the data used to generate the image be verified (and thus we cannot exclude WP:OR), I vote to remove.

Support - Removal of Image SunSw0rd (talk) 22:20, 6 January 2010 (UTC)

Votes are evil. See WP:VOTE. And what do you mean with "described by abstract links"? All the sources are clearly described and available via any good library. Also see Wikipedia:OR#Original_images - images are explicitly allowed under WP:OR. Moreover, it's substantially the same as Fig. 6.10 in the IPCC AR4 ([7], page467). --Stephan Schulz (talk) 22:58, 6 January 2010 (UTC)

Votes are evil. Note that Wikipedia:OR#Original_images states that images can be excluded if they introduce original ideas. I'm not convinced that's happening here, and I'm willing to give the creator the benefit of the doubt. For kicks and giggles I'm going to Oppose -- Removal of Image NickCT (talk) 23:19, 6 January 2010 (UTC)

If the has not been published in some other journal or publication then it is by definition self-published and not acceptable. If it is, as has been suggested, it would be synthesis of material. One only has to ask if this was text would it be viewed as synthesis of material and/or self-published. If the answer to that is yes, then there is no question that it should not be used. Arzel (talk) 00:44, 7 January 2010 (UTC)

I seriously suggest you read the previous discussion, where both the general and the specific claim have been rebutted. Creating original images is actually encouraged, and this graph is equivalent to a similar one in the AR4. --Stephan Schulz (talk) 00:54, 7 January 2010 (UTC)

I've removed references to "Vote". We don't vote (nor for that matter do we "!vote".) --TS 10:27, 7 January 2010 (UTC)

The grounds for removal appear to be most of the sources are referenced only by abstract links. Thus the situation is that no one can verify that the graphic was correctly generated. This is incorrect, obviously. Anyone can follow the abstract links, retreive the data and check William M. Connolley (talk) 11:17, 7 January 2010 (UTC)

There is even a direct link to the data given in the text for the image (aside the paper refs). --Kim D. Petersen (talk) 12:05, 7 January 2010 (UTC)

From the above commentary it appears that most responders believe that the data is accessible. I assert this is not correct. For example, see this link [here] -- the first link provided for the image. Note that a subscription is required. The data does not appear to be in the public domain. Therefore it is NOT accessible. Yet we have an image that purports to be in the public domain, generated from data that is not in the public domain. On what basis can this data be verified, and on what basis can the image be claimed to be in the public domain?

When citing quotations, the quotations typically are copyrighted, and they don't have to be on line. But images are required to be public domain. They also should be accurate. But here we have an image that is based on non-public domain data. It is in fact a graph that appears to fall under Wikipedia:Non-free_content#Images_2 (Unacceptable use/Images/#10 A chart or graph). SunSw0rd (talk) 15:10, 15 January 2010 (UTC)

Last line in the text for the image (Summary) tells you exactly where to download the data (except for the black line, where the data url is given in its description). For instance for the first line - the data is found here[8] --Kim D. Petersen (talk) 15:15, 15 January 2010 (UTC)

Moreover, there is a fundamental misunderstanding. The image is free, so Wikipedia:Non-free_content does not apply. The data is free, as pure data is not protected in most jurisdictions. Access to the paper containing (one instance of) the data may not be free. But that is no different then citing a paper that is not available for free, or a book that is not available for free. That is, by ancient and undisputed consensus, acceptable. In fact, in many cases its a necessity, as many of the best sources are not available for free. See WP:PAYWALL. If you want to verify one source in particular, WP:WikiProject Resource Exchange will often be able to obtain a copy for you. --Stephan Schulz (talk) 15:50, 15 January 2010 (UTC)

Carbon dioxide levels

Why does this article not mention what atmospheric carbon dioxide levels were 1000 years ago? That would seem a crucially important bit of data. Recent studies have shown current CO2 levels the highest in 15 million years, when temperatures were 5 to 10 degrees Fahrenheit higher than they are today, and sea levels 75 to 120 feet higher than today.[9][10] Badagnani (talk) 07:28, 29 December 2009 (UTC)

This is yet another article that needs some serious research applied to it. • Ling.Nut 08:35, 29 December 2009 (UTC)

I'm sure this information can be found; it's just surprising that no one has mentioned or added it yet. Badagnani (talk) 10:16, 29 December 2009 (UTC)

Around 280ppm ± 4ppm[11] - just about the same as it has been for the rest of the Holocene. The reason it hasn't been added is that it isn't mentioned or considered relevant in reliable sources on the subject. --Kim D. Petersen (talk) 10:50, 29 December 2009 (UTC)

Not to sure were you get 280ppm kim, i have read upwards of 400ppm in a paper by Ernst-Georg Beck. —Preceding unsigned comment added by Marknutley (talk • contribs) 12:18, 29 December 2009 (UTC)

And if you believe Beck, then i have a bridge that i want to sell :-) My figures are from the Law Dome ice-core - but could have been from any other such proxy measurement. (sediment, stomata, sponge, ..) --Kim D. Petersen (talk) 12:52, 29 December 2009 (UTC)

Beck is an academically acceptable source. Nothughthomas (talk) 14:35, 29 December 2009 (UTC)

No, sorry - neither is it peer-reviewed nor is it published in a reliable source (not to mention that it is non-sense, and contradicted by all academic sources on this subject that i've seen. Jaworowski's publication record for this, seems to be in LaRouche magazines (which aren't reliable sources either, in fact they are practically banned on WP)) --Kim D. Petersen (talk) 18:02, 29 December 2009 (UTC)

But beck`s findings correspond with Zbigniew Jaworowski`s findings, or is he also not any good :) (what bridge btw?) mark nutley (talk) 15:58, 29 December 2009 (UTC)

Sorry, but Beck is a biology school teacher with no particular competence on climate or CO2 measurement. I also don't think he has published anything on the MWP (if yes, do you have a ref or a link?), but his 200 year CO2 concentration is completely discredited -see [12]. --Stephan Schulz (talk) 16:02, 29 December 2009 (UTC)

Beck does not understand that surface measurements in vegetated or urban areas are not representative because of the diurnal cycle of the atmospheric boundary layer. The primary sources and sinks are at the surface, so that when mixing is limited (as by an inversion) concentrations fluctuate greatly. Or may be he does understand, and... Short Brigade Harvester Boris (talk) 16:12, 29 December 2009 (UTC)

Consensus appears to be in favor of using Beck. Now let's move on. Nothughthomas (talk) 17:38, 29 December 2009 (UTC)

Try pulling the other one. --Kim D. Petersen (talk) 18:03, 29 December 2009 (UTC)

Sorry Nothughthomas, i see no consensus in favor of beck, i see two in favour and three against, current consensus is against i`m afraid. I see no objections to Zbigniew Jaworowski however. mark nutley (talk) 18:01, 29 December 2009 (UTC)

Both Beck and ZJ are jokes, but this isn't the place to discuss why. If you want to retain any kind of credibility, you need to drop them. If for some reason you don't understand this well enough to know why, then by all means ask on my talk page William M. Connolley (talk) 21:05, 29 December 2009 (UTC)

Naturally WMC you think them a joke, as you do anything which may oppose agw :) so tell me how about Segalstad he backs up jaworowski does he not? mark nutley (talk) 08:46, 30 December 2009 (UTC)

Would you mind listing actual sources instead of name-dropping? I have yet to see a source by Beck discussing CO2 concentrations during the MWP - in fact, I still don't believe it exists. So please provide the sources by Jaworowski and Segalstad (and Beck, if you really want to adopt him). Thanks. --Stephan Schulz (talk) 09:08, 30 December 2009 (UTC)

Sure mate, give me some time to look them up and post though as i`ve a lot on today :) mark nutley (talk) 09:23, 30 December 2009 (UTC)

[outdent]Sorry it has taken so long to reply, as requested here are the links to the studies i mentioned above.

• Statement written for the US Senate Committee on Commerce, Science, and Transportation by Prof. Zbigniew Jaworowski
• Becks paper(so yes stephen it exists :) )
• Segalstad`s paper

I Hope this helps the discussion move along --mark nutley (talk) 10:37, 8 January 2010 (UTC)

There is just the trouble that you actually confirm Stephan's disbelief. None of these papers address the MWP. And i still have a bridge to sell :-) --Kim D. Petersen (talk) 10:51, 8 January 2010 (UTC)

As I suspected, this is Beck's well-known (and deeply flawed) paper discussing chemical CO2 measurements during the 19th and 20th centuries. It does not make any claims about CO2 levels during the time period of the MWP, as far as I can tell. Indeed, the word "medieval" does not appear. None of the plots goes back further than 1700, and none of his plots (as opposed to referenced data) goes back further than 1810. --Stephan Schulz (talk) 10:51, 8 January 2010 (UTC)

Strange, the article i got those from had an image credited to beck which went back to 1000 and up to the present day. Let me recheck that article again, i suspect they may have lead me astray :) mark nutley (talk) 11:18, 8 January 2010 (UTC)

Beck and ZJ are both crap (insofar as their views on past CO2 go). On the off chance that you're interested in why, then [13] is for JZ; [14] for Beck. Or if you prefer more invective, [15] William M. Connolley (talk) 12:05, 8 January 2010 (UTC)

Thanks for the links, i`ll look through the arguments presented on them however they appear to be blogs? mark nutley (talk) 12:42, 8 January 2010 (UTC)

Links, we all got links, lottsa, lottsa links to real official peer reviewed papers, and comments. OTOH, seriously, it really is hard to take Beck seriously if you know anything about meteorology. As Ralph Keeling pointed out in E&E, if Beck was right you would be blown over by the CO2 rushing in and out of the atmosphere. And as for J, well, if you want a peer reviewed evaluation, just link thee to Some are Boojums [16] which reproduces a comment from Hans Oeschger in Environ Sci. & Pollut. Res. 2 (1) 1995, pp. 60-61 that starts:

It is with great hesitation that I write in reply to the paper by JAWOROWSKI, this paper deserves little attention. But unfortunately, he has succeded in publishing similar articles in journals and thus has induced considerable confusion regarding the reconstruction of ancient atmospheric compositions by the analysis of air occluded in polar ice of known age. We hope that this reply will help to clarify the issue. JAWOROWSKI is correct in one point. The glacier studies of ice cores are fundamental for one of the most important issues of the century and are of great importance for succeeding centuries.

This sort of thing is a sure mark that the editors realize they made a big boo boo.Eli Rabett (talk) 13:12, 8 January 2010 (UTC)

[outdent]Sorry Eli, why would co2 be blowing in and out of the atmosphere if it is only 350ppm? or even higher in fact? What is E&E btw? mark nutley (talk) 13:21, 8 January 2010 (UTC)

Sorry Mark, I've been away. E&E is Energy and Environment, reading its Wikipedia entry should help explain what went on. The point is that Beck's claims would mean that enormous amounts of CO2 were moving in and out of the atmosphere in very short times. That is physically impossible, thus Beck must be wrong. Eli Rabett (talk) 02:35, 20 January 2010 (UTC)

CO2 levels

Can the atmospheric CO2 levels during the Medieval Warm Period please be added? Is it possible that they are not known? Badagnani (talk) 04:15, 8 January 2010 (UTC)

The answer to that was already produced in the other thread: around 280ppm. --Kim D. Petersen (talk) 07:01, 8 January 2010 (UTC)

The best we have is from ice cores and 280 ppm is pretty much what you get. Take a look at the Law Dome data here http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/icecore.html Eli Rabett (talk) 02:41, 20 January 2010 (UTC)

---

The graph is inaccurate

It shows that the current temperature is hotter than in the MWP. This is wrong. If Greenland was capable of supporting colonisation it must have been much warmer than it is today. I would like to see a better graph. SmokeyTheCat 07:55, 8 April 2007 (UTC)

It was, in fact, warmer. See here. I really think that the graph should be removed, it seems to go against the evidence. Codingmonkey 07:09, 9 April 2007 (UTC)

Being a perceptive chap I'm sure you noticed that you ref says in the Sargasso Sea not globally William M. Connolley 07:31, 9 April 2007 (UTC)

Good catch, I missed that. However, the Sargasso Sea does cover a large part of the North Atlantic Ocean. Nevertheless, since you say that global temperatures were lower in the MWP then present day global temperature, may I have the source? Codingmonkey 15:41, 9 April 2007 (UTC)

I removed the graph as we seem to have agreement that it was not accurate.  SmokeyTheCat  •TALK• 20:12, 19 August 2007 (UTC)

Not so fast, please. These are the best reconstructions we have available. Raymond Arritt 20:21, 19 August 2007 (UTC)

I still think that the graph is inaccurate and that seems to be the consensus here.  SmokeyTheCat  •TALK• 08:12, 23 August 2007 (UTC)

You are wrong William M. Connolley 08:28, 23 August 2007 (UTC)

You are finished. 19 Dec 2009 —Preceding unsigned comment added by 74.132.27.108 (talk) 16:19, 20 December 2009 (UTC)

Or, in more detail: The graph is sourced to a large number of reliable sources. Your personal opinion on Viking colonization is not. You might also want to look at entry in our GW FAQ. --Stephan Schulz 08:32, 23 August 2007 (UTC)

All the graph sources go back to the East Anglia Climategate fraudulent computer code which multiplied temperature changes since 1940 by up to 2.6X and then they disposed of the raw data to cover it up. Global Warming FAQ is no longer worth the cyberspace it is written on. 19 Dec 2009 —Preceding unsigned comment added by 74.132.27.108 (talk) 16:52, 20 December 2009 (UTC)

These "reliable sources" wouldn't happen either to be papers authored by the CRU correspondents complicit in the Climategate fraud or to depend secondarily upon the "research" duplicitiously published by these AGW "hide the decline" thieves and liars? 71.125.130.14 (talk) 16:49, 20 December 2009 (UTC)

Get an up to date graph, this hockey stick stuck in 2004 is ridiculous and an embarrassment to wikipedia. Don't you wiki censors know how ludicrous this graph is ? —Preceding unsigned comment added by 76.67.239.216 (talk) 03:24, 29 October 2009 (UTC)

Agreed. This graph has been thoroughly discredited yet wikipedia still uses it as a reference? I don't understand. —Preceding unsigned comment added by 208.178.63.106 (talk) 21:24, 23 December 2009 (UTC)

• It’s the bias in this article and others on Wikipedia that first triggered me to suspect the climate-extremists. Anyone can see there’s something not right here, a fundamental tenet of climate scepticism is the warm period. There should at LEAST be a controversies section. You must acknowledge this. Your doing your 'cause' more harm than good by neutering this article whihc could be a great resource for enquiring minds. D —Preceding unsigned comment added by 90.204.251.108 (talk) 03:31, 22 January 2010 (UTC)

Sentence not supported by citation - propose deletion or at least correction

The article leads the reader to believe that a number of scientists refer to the Medieval Warm Period as the "Medieval Climatic Anomaly":

Some refer to the event as the Medieval Climatic Anomaly as this term emphasizes that effects other than temperature were important.[1]

It seemed interesting, so I read the actual reference, but it says no such thing. The reference is from what appears to be either an unpublished working paper or an informal presentation. Nevertheless, the only reference in it that is relevant to the above sentence propsed for deletion is as follows from page 3 (emphasis added):

This led Stine to argue that a better term for the overall period was the “Medieval Climatic Anomaly” (MCA), which removes the emphasis on temperature as its defining characteristic.

Here we see that it isn't "some" but a single thinly referenced person Stine making the claim, and the claim is characterized as an argument. Clearly, the reference provided not only fails to support the sentence, it actually serves to argue against its inclusion. I don't want to remove it until others have a chance to comment. -- Knowsetfree (talk) 05:11, 15 December 2009 (UTC)

There are now two cites, the second added by Kim, citing a book, if he could be so kind as to check the wording as to how "Medieval Climatic Anomaly" is framed in the book, as Knowsetfree makes a valid point that (our text) "this term emphasizes that effects other than temperature were important" is not the same as (the source) "which removes the emphasis on temperature as its defining characteristic" although it is close. Without knowing what is in the second source, it is impossible to tell if that rephrasing is close enough or not. Kim, let this remind you that no good deed (adding another source) goes unpunished (PITAs like me asking what they say) :p Gerrard Winstanley (talk) 17:59, 24 December 2009 (UTC)

Check the diff :-) I only changed the reference format, i don't have the Le Roi book. But the Stine in question is Scott Stine - and is referring to this paper:

Stine, Scott (1994). "Extreme and persistent drought in California and Patagonia during mediaeval time" (PDF). Nature. 369 (6481): 546-549. doi:10.1038/369546a0.

I'll request the book and check it possible - but that will be at some time in the next year. --Kim D. Petersen (talk) 22:45, 24 December 2009 (UTC)

Sheesh these diffs are tricky things :-) Sorry for not spotting that you expanded the two cites. I found that Uncle uncle uncle spotted that there were two references in one and separated them, but when the original two-in-one was put in, I don't know. It took many clicks to find where they split into two and I've already had enough hunting for tonight, so whoever added gets away with not being hassled for info by me... for now :p Thanks for requesting the book, I think it's important to ensure absolute veracity of what it is that make some prefer this term to MWP, but it's not urgent. I'll stop being a pain in the aerosol now and not ask anything else until after the festivities are done.Gerrard Winstanley (talk) 23:30, 24 December 2009 (UTC)

Medieval Climatic Anomaly and Medieval Climate Anomaly both have more than 15000 hits on Google Scholar, so the term is certainly in significant use. --Stephan Schulz (talk) 08:03, 15 December 2009 (UTC)

15000 hits is rather small, and since when did "Google" become a valid reference for whether an term is popular in the scientific community? —Preceding unsigned comment added by 60.56.161.188 (talk) 15:45, 19 December 2009 (UTC)

Note Google Scholar, not Google. Google Scholar is certainly a good source for prevalence in the recent scientific literature, and 15000 is significant. --Stephan Schulz (talk) 15:59, 19 December 2009 (UTC)

Stephan – I think you must have searched without quotes. Google Scholar gives me only 270 results for "medieval climatic anomaly" (with quotes). Is 270 statistically significant? Hotlorp (talk) 01:39, 15 February 2010 (UTC)

I agree in part with the objection raised in this section. Please see my article edits here and here, taking note to read the 1st edit summary in particular. I do not think we should be polarizing the introduction. There is no need to make the introduction a political football. This issue is already too politicized. Wikipedia should stay above the fray. 216.153.214.89 (talk) 05:37, 21 December 2009 (UTC)

From GeoRef:

• 279 peer-reviewed journal sources for "Medieval Warm Period"
• 6 peer-reviewed journal sources for "Medieval Climatic Anomaly"
• 18 peer-reviewed journal sources for "Medieval Climate Anomaly"

The latter examples are clearly used, especially recently, but are also clearly in the minority. I would keep them for clarity's sake. But I don't like the explanation given by the article. A better explanation would be, Although Europe, where the term originated, experienced warming, other parts of the world experienced different changes in climate. This has led some researchers to instead use the term "Medieval Climate Anomaly". Then some refs, of course, probably from around the Pacific. Awickert (talk) 16:01, 21 December 2009 (UTC)

FWIW the textbook that I use for my intro course calls it "Medieval Climate Anomaly." (But I emphasize to the students that MWP is the more common term.) Short Brigade Harvester Boris (talk) 18:30, 24 December 2009 (UTC)

Graph

That graph is extremely inaccurate. It shows that the warm period was not nearly as warm as today, which is untrue. The medieval warm period, as shown from historical evidence of inhabitation of places that are currently uninhabitable do to extreme cold. I am going to delete it. Handbook3 (talk) 22:46, 5 February 2010 (UTC)

You'll need some faint shred of evidence to support your contentions, I'm afraid William M. Connolley (talk) 22:54, 5 February 2010 (UTC)

All historical sources in Europa, North America and Asia tell about a Medieval Warm Period which was warm and more humid than as today. Haabet 22:04, 10 February 2010 (UTC)

That seems unlikely: you are suggesting that the old chroniclers wrote "temperatures this year are far higher than in the 20th century"? I doubt it. What *are* you referring to? William M. Connolley (talk) 11:47, 15 February 2010 (UTC)

Medieval Warm Period

The graff is a mix of incompatibility systems: Plants(yield) and measuring of temperatur. The different plants on different locations give different informations. Plants from dry locations give any global information (because the showers fall random) opposite plants from windy regions which get a influenced of all the earth. The danish oak and Norwegian red pine are on intense influence of the sunspots (and volcano), because the sunspots change the winds global.Haabet 12:46, 16 February 2010 (UTC)

I would have thought vikings buried in greenland (which is no longer green) would prove temps were warmer in the MWP than they are today mark nutley (talk) 16:51, 15 February 2010 (UTC)

Greenland was never green, overall. Bits of it are green now. What you have is an anecdote William M. Connolley (talk) 17:14, 15 February 2010 (UTC)

Not really. The same places have been inhabited by the Norse, Thule, modern people, and those before all of them. The Norse sagas mention its non-greenness. And it was inhabited by the Norse before the MWP. The end of the MWP, however, spelled Greenland's downfall because sea ice blocked trade and supply routes. Awickert (talk) 17:27, 15 February 2010 (UTC)

Lol, an anecdote? Yes people buried in the now frozen ground is an anecdote, that`s not evidence of it being warm, not the now frozen farmland. Of course the WMP was warmer than todays temp`s. Ten bucks you don`t see fields of barley there any more do you :) mark nutley (talk) 18:01, 15 February 2010 (UTC)

Do you have evidence for your claims? I do for mine, if you're interested in responding to them. Awickert (talk) 18:40, 15 February 2010 (UTC)

(edit conflict)Yes, an anecdote. Greenland isn't 100% covered in ice, and has never been "really" green since the last interglacial (at the very least), as the anecdotal evidence goes. The major mistake you make here though (before i go further), is to assume that anyone is disputing an MWP in Greenland, none do... The controversy is over the spatial extent of the MWP, and how the effects were globally. What everyone agrees about though, is that the North Atlantic area was warm in the MWP. As for the rest: Please see Talk:Global_warming/FAQ Q10, and the pictures displayed there. As for Barley[17] it will grow there now. You may also want to see Greenland#Etymology. Greenland was never a farming community (except for dairy and sheep farming which is common also today, do remember that milk comes from various bovines) in Viking times, but a hunting community... while they did grow stuff, they had to import most of their goods (including wood), which they payed for with skins and Walrus ivory[18] --Kim D. Petersen (talk) 18:42, 15 February 2010 (UTC)

@ Awickert the evidence is in the ground. @ kim, not anecdotal, if the ground was warm enough for burials and said ground is now permafrost then it follows it was warmer there then than now. That is empirical not anecdotal. [19] Says 400 farms, that is a farming community mark nutley (talk) 18:50, 15 February 2010 (UTC)

Is said ground still in permafrost? And here is something to think about: If X°C is the temperature that ground thaws from permafrost, how long does it take for the ground to be warmed up to that temperature? (lets say temp was Y (Y>X) during the Vikings, and the temperature now >Y - does that mean that the ground where the Vikings were buried wouldn't be permafrost? In effect think rate of warming). --Kim D. Petersen (talk) 19:01, 15 February 2010 (UTC)

"The evidence is in the ground" is not very helpful. Evidence is historical and scientific sources. Since you linked to one, be careful before you draw conclusions. If artifacts are buried, there has been deposition, and therefore what was once in the active layer may now be permafrost. Such as, As the archaeologists dug through the permafrost and removed the windblown glacial sand that filled the rooms. This is why we can't do original research and must instead rely on published sources. Awickert (talk) 00:24, 16 February 2010 (UTC)

Evidence seems to be J T Houghton, G J Jenkins, J J Ephraums, Eds,, "Climate Change; The IPCC Scientific Assessment". 1990 . Cambridge University Press, p.202 with this graph, copied in this article. Suggest locating a copy of this source and finding the relevant graph. --199.173.226.236 (talk) 17:29, 17 February 2010 (UTC)

Sigh. That graph is a schematic, based on a 20 year out-of-date assumption informed mostly by European anecdotal evidence. It's not a reconstruction and was never described as one. And it is not "evidence" for anything we discussed in this section. --Stephan Schulz (talk) 18:55, 17 February 2010 (UTC)

MWP and LIA in IPCC reports William M. Connolley (talk) 20:27, 17 February 2010 (UTC)

Request for disclaimer with regard to 'Global Warming' related posts.

Insofar as there is a lack of proof of 'Global Warming' it should be noted on all pages related to the subject that it is only a theory. There is a multitude of evidence, some of which has been cited by others on this discussion page, that the data involved is subject to question.

In addition, there is an overwhelming amount of evidence that this phenomenon is not in correlation with the data provided by the IPCC. With the scientific doubt involved in IPCC publication, it is reasonable to doubt that this period has been accurately represented by the IPCC.

With plenty of sources available to provide opposing evidence, this page is in need of a major update. There is a long list of sources for the current information on the page, but the validity of said sources is in question. At the least this should prompt a review of the material and request for the alternate scientific representation.

Thus, I request that an effort be made to obtain the full information available on the topic, rather than a single sided viewpoint. I also request that a review be made for other postings which do not represent a secondary viewpoint with regard to topics of contention.

Also, in answer with regard to the sea temperature sample: The truth is that sea temperature changes less than ground/air temperature. Sea temperature data has been highly ignored in favor of urban sampling over the last couple of decades (along with rural temperatures not being recorded as diligently as urban temperatures). If an accurate representation were desired, all the temperatures would be based on sea temperature. However, all the indicators we have currently fall within error levels for the interpretation of data with regard to climate change. In other words, we really don't know anything about it. With regard to this period, however, there is evidence of people living in greenland (where there are now glaciers)... so maybe it was warmer? However, this could also be a result of differences in ocean currents, or one of hundreds of other things. —Preceding unsigned comment added by 192.212.253.17 (talk) 22:21, 8 February 2010 (UTC)

Evolution is also a theory; gravity is also only a theory; etc. Points are agreeable, but slapping a "global warming is just a bunch of jabberwocky from slackjawed non-scientists searching for free grant money" label onto every article would be manipulation of reader POV by presentation. Ignore this ridiculous tripe. --199.173.226.236 (talk) 17:25, 17 February 2010 (UTC)

Rm graph: why

SEW added the hand-drawn graph. I removed it. As a useful graph for MWP studies, its very poor, indeed quite misleading. It hasonly historical interest.If it belongs anywhere it belongs...on MWP and LIA in IPCC reports. Oh look, its there already. William M. Connolley 09:55:05, 2005-09-03 (UTC).

http://www.atmos.washington.edu/2001Q2/211/groupE/maya_files/image003.jpg

What have you got against the image? Care to explain how exactly Greenland was green in the Medieval period when, according to your lot, it was colder than now?

You are the one 'misleading' by essentially deleting an important period from history. Never let facts get in the way of the Global Warming Religion. Mixino1 13:22, 26 January 2007 (UTC)

What I've got against the image is explained in MWP and LIA in IPCC reports, with refs. The graph is a sourceless schematic that has been obsolete for years and shouldn't be used. Its also not a freely usable image. As to greenland, etc, thats quite another matter William M. Connolley 13:36, 26 January 2007 (UTC)

Your only interest is in keeping the facts from the public. Like many pages on Wikipedia, this one has a load of interferers making sure the facts are diluted and emaciated. I seriously fear for the environmental lobby's lasting effect on science being taken seriously. Obviously, for those that have sidelined climate change into a religion, the interests of science are no longer of any merit. I notice you refuse to answer the pertinent question - which is no more than I would have expected. Mixino1 02:21, 28 January 2007 (UTC)

I'm confused about the graph in this article. It makes it seem as if the MWP was actually colder then it is now. However, this article clearly states:

Results from a radiocarbon-dated box core show that SST was ~1°C cooler than today ~400 years ago (the Little Ice Age) and 1700 years ago, and ~1°C warmer than today 1000 years ago (the Medieval Warm Period).

This article was published in 1996 and temperature has risen a marginal amount since 1996. Clearly the MWP was warmer then it is now. Therefore, the graph that is show in this article is misleading/completely false. Codingmonkey 02:30, 8 April 2007 (UTC)

As Mr. Connolley pointed out below, the above article refers to the Sargasso Sea. Nevertheless, as I stated below, I would like Mr. Connolley's sources that demonstrate that global temperatures were lower in the MWP then they are today. Codingmonkey 15:44, 9 April 2007 (UTC)

As soon as the coding factors that were used to multiply temperature changes since 1940 by as much as 2.6X in East Anglia's (now missing) raw temperature data are removed, the recent spike disappears entirely. This whole AGW thing is a fraud according to the emails and computer programs from East Anglia. Mr. Connolley may use his absolute power at Wikipedia to remove this statement and ban me as he has done to 5000 articles and 2000 editors. But the jig is up. You got that, Mr. Connolley? 19 Dec 2009 —Preceding unsigned comment added by 74.132.27.108 (talk) 16:04, 20 December 2009 (UTC)

No, no, no, no and no. --Stephan Schulz (talk) 04:02, 30 December 2009 (UTC)

It looks like Mr. Shultz has "No" arguments. Honestly, there aren't the instrumental data supporting the 20th century spike in the graph available and CRU publicly declared them lost during the Climategate controversy. So I think the use of the graph in MWP article is from scientifical point of view discredited as infamous "Nature's trick" and literally unsuported. Moreover the article and attached graphs should be about by the real data supported MWP desribed by PR articles, not about a Mr. Connolley imagined warming in recent decades. So I would suggest to use this image instead. —Preceding unsigned comment added by 94.113.129.238 (talk) 15:52, 16 February 2010 (UTC)

If you manage to put two errors into a simple for of address, how can you expect to be taken serious on anything? Especially if you keep repeating nonsense. And "no", self-published images without reasonable pedigree are not acceptable. --Stephan Schulz (talk) 19:29, 16 February 2010 (UTC)

"If you manage to put two errors into a simple for of address"?!?? Are you serious? Is that an argument?

Nobody here really cares about either your or Connolley's PhD's, as they are in completely unrelated fields. Besides, as wikipedia isn't Germany, we can call you whatever we want, without losing any credibility. As for that graph, as far as I can tell almost every single image has references, so your assertion that it is 'without reasonable pedigree', and that it is 'nonsense', is a hollow one.

Here, http://www.co2science.org/data/mwp/scientists.php, is a list of the scientists cited in the construction of that image. And here's a list of studies used for each and ever point on that graph http://www.co2science.org/data/mwp/mwpp.php. Enough pedigree?

On the other hand, you propose we use the results of Briffa, Jones and Mann. Definitely not the least controversial figures in the current debate.

Why don't you guys (you, Connolley et al) just give up. You have been misinforming the public and scaring kids for way too long.213.61.134.138 (talk) 13:41, 24 February 2010 (UTC)

Hockey Stick

http://www.john-daly.com/hockey/hockey.htm This seems very well thought out; very well discussed; and well cited. It seems there is some controversy surrounding the Medieval Warm Period, among other things. I'm not sure if this belongs in this article (at least, it doesn't extensively) or in the Global Warming or Climate Change articles. --199.173.226.236 (talk) 17:22, 17 February 2010 (UTC)

It's a self-pulished and unreviewed piece of crap. It belongs into the dustbin of history, but certainly not into any of our articles on the science of climate change. --Stephan Schulz (talk) 18:59, 17 February 2010 (UTC)

It is well referenced (33 sources) The author has written books in the subject, (e.g. The Greenhouse Trap) as well as articles and papers for New Zealand Science Monthly magazine, 1996 National Greenhouse Response Strategy Review, Climate Change (University of Western Sydney), etc., so he is an "expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications" (fulfils Wikipedia:Reliable sources#Self-published sources (online and paper); the website is referenced sources which share the same point of view, so this part of the reliable sources guideline is also fulfilled. Why shouldn't it be included in the article? Why does it belong in the "dustbin of history"? --Joshua Issac (talk) 18:28, 18 February 2010 (UTC)

It is well referenced (33 sources)... - this is the State of Fear defence - it has refs, so it muct be some use. That argument is false William M. Connolley (talk) 18:55, 18 February 2010 (UTC)

Per wp:rs i have used this to change the lede, that along with the new zealand paper i mentioned above proves the WMP was global and not confined to europe and the north atlantic mark nutley (talk) 19:20, 18 February 2010 (UTC)

Stephen i reverted your revert due to the fact that as pointed out above this is a wp:rs mark nutley (talk) 21:25, 18 February 2010 (UTC)

You have used what? This discussion is not a RS, and neither is Daly. If you are talking about the Cook et al paper as evidence for a global MWP, I can only suggest that you read it again. It does not make that claim - in fact, it claims an unusual cold spell at the time "the" MWP (i.e. the one in the North Atlantic region) was in full swing. --Stephan Schulz (talk) 21:28, 18 February 2010 (UTC)

I refer you to joshua`s statement above mark nutley (talk) 21:30, 18 February 2010 (UTC)

Joshua is wrong. --Stephan Schulz (talk) 21:30, 18 February 2010 (UTC)

Sorry no, you are Self-published material may, in some circumstances, be acceptable when produced by an established expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications mark nutley (talk) 21:56, 18 February 2010 (UTC)

But the trouble is that the above mentioned publications aren't in "reliable third party publications". Bantam books isn't a science publisher, it is a popular book publisher. The "1996 National Greenhouse Response Strategy Review" isn't by Daly - but a submission to by Daly (and no indication of what or whether there was acceptance or context). "New Zealand Science Monthly" is a popular science magazine, not a peer-reviewed one. The "Climate change" journal he is talking about is not the Springer version - but some local publication. etc etc.

In other words: Daly is not an expert on the topic, and his views haven't been published by reliable third-party publications, that could tally for exceptions to SPS. --Kim D. Petersen (talk) 22:20, 18 February 2010 (UTC)

Not at all, Bantam is an established and reputable publisher, Thus any books published by them are wp:rs Since when do you have to be peer reviewed to write about history? New Zealand Science Monthly is also wp:rs What we have here is certain editors once again trying to redifine the rules about wp:rs to suit their POV. This is not acceptable, the same discussion is underway on the IPCC article. I would also point out in the section above both yourself and short brigade both agreed that the MWP was a worldwide event, why are you now changing your mind? There are also papers from china which show the MWP. To say it was not global is wrong. mark nutley (talk) 19:09, 19 February 2010 (UTC)

Bantam is not an academic publisher, and no, not all books published by a mainstream publisher are reliable sources. See Holy Blood and Holy Grail, for example. You are missing subtle differences here. The MWP was not global. It may have been part of a global climate event, but that did (most probably) not express itself as a significant global warm period, because warmer and colder episodes happened at different times at different places, partially canceling each other as far as global temperatures are concerned. --Stephan Schulz (talk) 19:26, 19 February 2010 (UTC)

Not according to the ref`s i just used to rewrite the lead, it was global the proof is there, it is pointless to deny it mark nutley (talk) 19:30, 19 February 2010 (UTC)

Sorry to be so blunt, but you have not shown any sign that you understand the sources you reference. And what you did in your last edit is a clear case of WP:SYN - in fact, more or less a textbook example of why synthesis is dangerous. --Stephan Schulz (talk) 19:56, 19 February 2010 (UTC)

Hey Mark. I reverted your good faith edit to the lead. I have issue with the wording "with evidence from China [1] New Zealand [2] and other papers". China and New Zealand are countries. Did you mean to say "and other countries"? NickCT (talk) 19:57, 19 February 2010 (UTC)

Sorry yes, but why revert instead of adding that? mark nutley (talk) 21:14, 19 February 2010 (UTC)

Mark - I reverted because I wasn't 100% sure you meant to say countries. It seemed to me that there would have been a danger of sticking words in your mouth. NickCT (talk) 22:46, 19 February 2010 (UTC)

Fair enough, i have rewritten like you suggested and it does read better like that :) mark nutley (talk) 09:43, 20 February 2010 (UTC)

After having read through this talk page, I have to agree with Schulz that the source originally offered by 199.173.226.236 does not constitute RS. While I'd agree that self-published work by an experert in the field can be RS, I don't think this particular piece meets the mark. Given the sensitivity surrounding subjects of the nature covered by this article, I suggest we try to stick to peer-review literature. NickCT (talk) 20:10, 19 February 2010 (UTC)

I don't believe there's any policy basis for the suggestion that we try to stick to peer-review literature. If there is a policy basis, please point me to it, so I can debate the bad polity. I'm fine with a rule that says, roughly, if two sources disagree, peer-review trumps non peer-review, but I don't agree that we can unilaterally decree that only peer-reviewed articles are allowed. Please note this is a general statement, I don't know how I'd weight in on the acceptability of the Daly piece, my initial inclination is to reject, but the proper course is to debate the merits.--SPhilbrickT 19:07, 21 February 2010 (UTC)

On scientific issues we try to stick (just as in any other content area) to the most reliable sources that we have, and that is peer-reviewed material. Please remember that the reliability of all sources are determined by the amount, and thoroughness, of editorial oversight that they receive - you do not get much more editorial oversight than with peer-review. That is the basis for WP:RS/WP:V. And in this particular case (since it is science) we have an abundance of scientific literature to stick by, even minority opinions will by necessity be peer-reviewed. As for merit, in science, that is determined in the scientific literature. --Kim D. Petersen (talk) 19:29, 21 February 2010 (UTC)

Could someone go over this and improve the references? The lead should summarise the article, but has a lot of links which don't seem to be used in the body of the article. It would be a lot clearer if links in the lead could be followed down to the reference and up again to find the relevant region where a climate event is claimed. . . dave souza, talk 13:01, 22 February 2010 (UTC)

Revision proposal - IPCC

It would be good to revise this article by removing parts derived from IPCC reports. IPCC reports are not a reliable source as they contain numerous erros. One glaring example is the claim that 55% of Netherlands is below the sea level. ("U.N. climate panel admits Dutch sea level flaw") —Preceding unsigned comment added by 141.157.191.154 (talk) 19:46, 20 February 2010 (UTC)

Like all human endeavors, the IPCC reports are not perfect. They are still the best sources that we have - and that's even acknowledged by people like Lindzen and Christy. I think we only use the WG1 report (and material derived from it) in this article. WG1 is the hard science, and I'm not aware that any error has been found in that. --Stephan Schulz (talk) 19:57, 20 February 2010 (UTC)

Could you elaborate please? Why to use the WG1 report only? Is WG1 better/more reliable than later reports? How to avoid the confusion and distrust among casual readers who very likely heard about the recent IPCC problems? There are many trustworthy sources that can be used instead of IPCC, don't you think so? —Preceding unsigned comment added by 141.157.191.154 (talk) 20:41, 20 February 2010 (UTC)

WG1 is not later or earlier - it's just the working group on "The Physical Science Basis" that produces a report on this topic. WG2 is on "Impacts, Adaptation and Vulnerability" and WG3 on "Mitigation of Climate Change". The complete IPCC Fourth Assessment Report contains these mostly independently produced parts. We use the WG1 report only because that contains a discussion of past climate. --Stephan Schulz (talk) 20:48, 20 February 2010 (UTC)

I apologize for my ignorance, when you say "we use", do you mean that there is some authority on Wikipedia to make such decisions? Where to find information about it? How to secure permission for my edits or find which sources are accepted by you? (I apologize also if my responses/ questions are hasty and not not prompt, but I am working at this time and can spare time only occasionally :( ) —Preceding unsigned comment added by 141.157.191.154 (talk) 20:59, 20 February 2010 (UTC)

The IPCC reports are without question WP:RS. As to the sea level stuff, you're wrong [20] William M. Connolley (talk) 21:44, 20 February 2010 (UTC)

I looked at the link you provided. It did not contradict what I mentioned as a IPCC error. It said only that the Dutch government was to be blamed for IPCC mistake by providing misleading information. I find it a little strange, if I were working at IPCC I would notice such error immediately as I remember physical map of Europe. Such large depressions are rare, they are near Caspian Sea but they are still above the local sea level.141.157.191.154 (talk) 22:03, 20 February 2010 (UTC)

What do you mean by sea level? . . . dave souza, talk 22:06, 20 February 2010 (UTC)

Good question. In case of Caspian Depression being below sea level it must refer to the level of the oceans as Caspian Sea is below them. Hmm, maybe I picked the wrong example, but it rather reinforces my point that real depressions are rare and small. Claim that 55% of Netherlands is in depression is so extraordinary that it should be noticed by a high school student, when the intergovernmental scientific clearing house fails to do so it raises some questions. Don't you agree?141.157.191.154 (talk) 22:15, 20 February 2010 (UTC)

You seem to have forgotten that the Netherlands incorporates land reclaimed from the sea by raising dikes round the land, not by raising the land level. In addition, the Dutch environment agency's correction gives its 26% figure as land below Normaal Amsterdams Peil, which apparently equates to mean Sea level, so more land will be below high tide level. There are several definitions of the area below sea level, and the Dutch Ministry of Transport uses the figure 60% (below high water level during storms). Perhaps you'd like to tell them they're wrong? . . dave souza, talk 22:40, 20 February 2010 (UTC)

Risk of flooding in this case includes river flooding. Whatever, I have to go back to my work :( 141.157.191.154 (talk) 22:49, 20 February 2010 (UTC)

I oppose the suggestion to remove all references to IPCC documents simply because some errors were found. I also reject the notion that we should declare WG1 "clean", implicitly accepting a rejection of other sections. This would just lead to untenable proposals to divide RS sources in those segments acceptable and those not. (I trust it is obvious that a particular error, once verified, can no longer be used.) There may well be a hurdle, in terms of numbers of errors, beyond which an other RS becomes non-usable, but the IPCC is close to any such plausible hurdle.--SPhilbrickT 19:20, 21 February 2010 (UTC)

RS's are already divided in to segments. The sources that receive the most editorial oversight are the most reliable. --Kim D. Petersen (talk) 19:31, 21 February 2010 (UTC)

Procession and succession template

I notice that the template was removed. I couldn't find any discussion on this template here on the current talk page or in the archives. I assume that the medieval warming period was preceeded and succeeded by other periods in which the earth's climate did something. So, is it unreasonable to have such a template? Cla68 (talk) 22:29, 4 March 2010 (UTC)

I think it's fine, unless somebody dislikes the fact that these periods do not abut one another (chronologically, they are somewhat fuzzily defined in the first place, and there are usually gaps in time between one and another). But overall, I'd be in favor of having a succession box to help people navigate. And as long as there are dates on the periods, someone could notice that there is a gap. One issue here could have been the inclusion of the "Migration period pessimum", a little-used term, in this box.

I also noticed that there's a discrepancy in the dates of the MWP, which I will fix, Awickert (talk) 22:41, 4 March 2010 (UTC)

I assume that there may be different names for the various periods and disputed dates for when each started or ended, but that can be noted in the articles for each. Cla68 (talk) 00:15, 5 March 2010 (UTC)

So then we will have an successor entry here (but no predecessor) and an predecessor at Little Ice Age as well as an successor that will constantly be deleted by "skeptics" (not that there is even an article yet). Yeah, that sounds like an improvement to Wikipedia. Lars T. (talk) 00:21, 5 March 2010 (UTC)

What exactly is your rationale for not including it? I couldn't understand what you said. Cla68 (talk) 00:25, 5 March 2010 (UTC)

I was surprised to find that this article even had a succession box. How long had it been there? At first glance it seems about as sensible as having a successor box on British Invasion or Vorticism. --TS 00:45, 5 March 2010 (UTC)

Agreed. In a trivial sense everything that occurs is always preceded by something and followed by something else, but that doesn't always reflect a meaningful "succession." In the case of climate, there's not an agreed succession of eras or epochs in the fashion of the geologic time scale. Short Brigade Harvester Boris (talk) 00:55, 5 March 2010 (UTC)

Here are the periods as I understand them (will source later) starting from 7000 BC:

• Holocene (Climate) Maximum- 7000-3000 BC
• pre-Roman Cold period- 3000-200 BC
• Roman warming period- 200 BC-540 AD
• Dark Age Cooling period- 540-900 AD
• Medieval Warm Period
• Little Ice Age- 1300-1814 AD
• Modern Warming period- 1814-1970
• Little Cooling period- 1970-1983
• Recent warming- 1983-2000 Cla68 (talk) 00:58, 5 March 2010 (UTC)

I guess we could add another period "Temperature lull" for 2000-2009 since temperatures have not significantly risen or dropped since 2000. I was thinking of starting an article on that topic anyway. Cla68 (talk) 01:24, 5 March 2010 (UTC)

After reading the comments and thinking some more, I think that a more useful thing would be a "climate of the Holocene" navbox at the start of the article, with periods, events, and dates in chronological order. That will avoid the succession box issues that can overcategorize subtle fluctuations.

I'm not sure that all of the climatic periods listed here are accepted terms and/or dates, but that sounds like a good start that can be sorted out.

If you want to write an article on the recently +/- constant temperatures, a good place to start would be a recent article by Solomon et al. (2010). As a matter of fact, that's the only science I've seen that's said anything about it, so it may well be the only place to start! I'd be willing to help some, but not too much; too afraid that an article like that would turn into a troll convention. And it might be good to wait until someone else writes something about it so there isn't just one scientific work. But let's continue this facet of the discussion elsewhere so as to not get too off-topic. Awickert (talk) 02:23, 5 March 2010 (UTC)

I'm going to look up the different climate periods in Infotrac and ProQuest NewsStand to try to find the generally accepted name for each and more sources before I try starting an article on any of them. That might take me a few days, at least. Cla68 (talk) 04:12, 5 March 2010 (UTC)

A climatic period of 13 years makes no sense - that's about one solar cycle, as far as climate is concerned that is noise. Do you have a reliable source for this succession as a whole and for the weirder individual periods? --Stephan Schulz (talk) 07:44, 5 March 2010 (UTC)

I haven't started looking in Infotrac yet, and it will probably have to wait until after the weekend. If I don't find enough sources, then the article doesn't get done. I understand that the "Little cooling period" is already covered in the Global cooling article. I suspect that I might find sources that indicate that we're still in the Modern Warm Period, since the dates appear to coincide with the industrial revolution. Don't most supporters of the IPCC's stance on AGW state that the current warming period coincides with the industrial age? Cla68 (talk) 08:01, 5 March 2010 (UTC)

I second AW's suggestion of a "climate of the holocene" as making more sense that a succession box. Cla68's delineation of 1814-1970, 1970-1983, 1983-2000, 2000-2009 just isn't going to work. Hopefully we can just quietly drop that idea rather than have another long discussion of the same old issues all over again William M. Connolley (talk) 11:55, 5 March 2010 (UTC)

I started Template:Quaternary climate, and I suggest that we move the "succession" discussion there. Note that there is also Template:Holocene, which organizes things differently, and might just run parallel to the new one (unless someone thinks it's worthwhile/propoer to integrate: I'm no paleoclimatologist, so I'm not touching it at the moment. Re: Cla68, all the scientists with whom I associate say that we were still coming out of the Little Ice Age through the Industrial Revolution (and perhaps up to ~1950). Awickert (talk) 16:12, 5 March 2010 (UTC)

WMC, if this discussion has taken place before, please link to it. As I said at the beginning of this thread, I checked the archive for this page and didn't see any discussion of the climate periods. I'll continue discussion of the climate periods over at the template as suggested by Awickert. Cla68 (talk) 22:08, 5 March 2010 (UTC)

Warm, cold, wet, dry

I added an intro to the "evidence" section saying that some of the evidence for warmth was, errm, about dryness. Or sometimes, wetness. I think this is useful: otherwise, people reading the article are going to be confused: its about the MWP they will think, why are we talking about dryness? O2RR removed it, but didn't trouble himself with discussing why, which seems rude William M. Connolley (talk) 21:02, 16 March 2010 (UTC)

No ref for it, so i removed it as well. mark nutley (talk) 21:43, 16 March 2010 (UTC)

WMC i have again had to remove your wp:or would you please be so kind as to actually get some ref`s to support new text? mark nutley (talk) 17:52, 19 March 2010 (UTC)

Read the text and learn William M. Connolley (talk) 21:38, 19 March 2010 (UTC)

Not only do I see no source for this, but it has severe POV problems. The rest of the article expresses doubt about any and all reconstructions for the period, yet somehow this one statement can be made with no qualifiers of any kind? Fell Gleaming^(talk) 17:57, 15 April 2010 (UTC)

You can add qualifiers I suppose if you can think of any. To me it seems like an obvious description of what follows; the "dubious" is clearly wrong William M. Connolley (talk) 20:54, 15 April 2010 (UTC)

Those 2 sentences Will wrote are just a brief (and accurate) summation of the section it introduces. It doesn't need a ref. And I found the article as a whole to be quite accurate. Although I'm certainly no expert on the MWP, it matches what Brian Fagan has written.--CurtisSwain (talk) 23:02, 15 April 2010 (UTC)

Rv: why

I took this out [21]. It is from the source, and it is important. It isn't at all clear why FG decided it could be omitted William M. Connolley (talk) 20:54, 15 April 2010 (UTC)

And another one: [22]. The graph is dubiously sourced, probably OR, and more importantly (even if correct) just shows one location. The labels aren't even in English. It claims to show "temperature in the central Greenland" which *probably* means it is from an ice core, or stacked series, who knows. But even if it showed all Greenalnd from a good source, it still wouldn't be appropriate William M. Connolley (talk) 20:56, 11 May 2010 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Medieval Warm Period/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)

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The article gives very little information about its topic itself, namely the medieval warm period in Europe and its implications for life at the time. It emphasizes too much all kind of information about specific incomplete measurements in other parts of the world and tries to downplay the subject itself. If I lived in Europe at the time I would have felt teh effect however and was not aware of global means. Why is that? This is not a (climate)political debate, there are other and better places to do that. I am here for raw or commented quality information on the subject itself, the global story and the opinion of factions I am quite capable of finding myself in the places where they are prime subject. It is troubling to me that this article presents a one-sided perspective from climate alarmists while ignoring substantial evidence against claims made herein. Specifically, the Medieval Warming Project at http://www.co2science.org/data/mwp/mwpp.php suggests that the preponderance of studies conclude that the MWP was substantially warmer than today's temperatures (see http://www.co2science.org/data/mwp/quantitative.php for details). The substantial reliance on the work of Mann and Jones, whose ethics and/or competence have been called into question by disclosures in the ClimateGate scandal makes this article a mockery of scientific process and completely unworthy of Wikipedia. I strongly recommend a more balanced approach that admits that there is substantial disagreement by reputable scientists (see list at http://www.co2science.org/data/mwp/scientists.php) with the conclusions presented here and offers readers the competing evidence until such time as there is a scientific conclusion on the matter that replaces the imaginary political "consensus" represented by this article. Sapienthetero (talk) 07:09, 19 January 2011 (UTC) == Validity as representation of scientific consensus == The article is weak, as a previous comment notes, in its lack of detail on the effects on life at the time. It does not seem to be politically tendentious, but it is suspect scientifically because of its reliance on the study by Mann et al., whose claim that the MWP was not warmer than today has been challenged credibly by many peer-reviewed studies summarized well enough by Singer and Avery (2007) and elsewhere. It egregiously fails to note possible explanations for the warming and subsequent Little Ice Age based on the well established Dansgaard-Oescher oscillation. — Preceding unsigned comment added by 173.163.199.189 (talk) 22:12, 10 July 2014 (UTC)

Last edited at 22:13, 10 July 2014 (UTC). Substituted at 21:36, 3 May 2016 (UTC)