Talk:Holocene climatic optimum

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Temp range[edit]

(William M. Connolley 19:39, 4 Mar 2005 (UTC)) +4 oC didn't very likely to me. The Vostok core [1] shows nothing like that. RealClimate [2] (google hit #3 for "HCO temperature") says the term is outdated and the warmth is mostly NH summer. Google hit #4 shows us fig 1 (its IPCC '90 fig 7.1, which has no source) with approx +1 oC, but this is schematic only. The IPCC TAR doesn't show it much either But I'm not an expert on this (perhaps DF is?... I'll ask).

Stoat. Your systematic attempt to bugger the historical data is appalling. You ought to be locked up for this crime. This is one of the most dishonest threads on the wiki. Because essentially you have ignored the evidence and instead put in what the falsified computer models would have predicted. —Preceding unsigned comment added by (talk) 20:40, 19 December 2008 (UTC)

I revised the article based on my understanding of the issue, including the restoring the +4 °C within its proper context. However, I am not entirely current on this issue so there may be additional changes needed based on recent research, such as you are citing. Dragons flight 21:42, Mar 4, 2005 (UTC)
(William M. Connolley 22:10, 4 Mar 2005 (UTC)) OK. I like your edit comment... I may try to find the GRIP/GISP data.
Which is the "recent research" he is citing? The RealClimate article, with climate simulation studies? Is that the source of all the boreal qualifications? Anything based on the real world? (SEWilco 08:26, 5 Mar 2005 (UTC))
(William M. Connolley 10:42, 5 Mar 2005 (UTC)) The RC piece contains references, to actual papers, unlike your first version, or indeed your two links above.
My version of the article is based on a personal understanding of the issue that could very well be out of date. In revising it I didn't actually review any of the references WMC gave, however, my understanding has been that the changes in temperature usually aren't reported in low to mid latitude sediments (and similar proxies), but can be easily seen at high latitudes towards both poles. However, in retrospect I am probably understating the importantance of the HCO to low latitude climate change. My understanding has been that while there are not apparent changes in temperature at most low latitude sites, that there is abundant evidence of changes in precipitation and plant distributions suggesting significant changes in atmospheric circulation patterns and weather. I would presume that such circulation changes could affect temperatures at some local sites and perhaps that is the case at the Peruvian sites SEWilco is mentioning, however if my understanding is still accurate then any such low latitude temperature changes would be geographically limited anomalies and not part of the typical pattern. I will reiterate however that I am rather out of date on this issue so the consensus may well have shifted. Dragons flight 16:50, Mar 5, 2005 (UTC)
* Part of the difficulty in finding info is wading through all the studies around the North Atlantic, with all its complications due to three streams of different temperatures waving across the playing field, with stuff bouncing off the backstop Urals. For example, one study combined 500 pollen cores to find European regional changes — an impressive data processing task which not surprisingly shows variations across the area ("traditional" HCO warming over Northern Europe in summer). "The temperature of Europe during the Holocene reconstructed from pollen data" doi:10.1016/S0277-3791(03)00173-2 (SEWilco)
I found this plot [3] which is similar to what I remember learning, but perhaps even more restricted. I would agree though that sorting through all the relavant recent studies would be an ugly mess. Dragons flight
* Undoubtedly there have been circulation changes as various limits were crossed. But at what point do many "local" circulation changes become a global effect? Are many climate changes around Amazonia considered as only an "Amazon region" effect, or considered as being a "South American continent" effect? And are changes in the Amazonian boreal winter Hadley cell regional, or a change in the global circulation of which it is a part? And is a global shift in the ITCZ merely a change in many local precipitation patterns? doi:10.1098/rstb.2003.1434 (SEWilco)
It wouldn't surprise me if the circulation changes were reasonably global, though obviously it can be hard to establish that. Since apparently you are really looking into this, I will be interested to see how good a case you can find/build. Dragons flight
* It is inconvenient that there is so much landmass in the higher latitudes, so most low latitude sites are within "geographically limited" areas. (SEWilco 05:48, 6 Mar 2005 (UTC))
Well, I presume your interest is in comparing such past climate change to recent climate change. Unfortunately that does mean figuring out whether the effects were truly global. Obviously regional effects would still matter a great deal to people that happen to live in the affected region. I recall being told that the precipation related changes in Africa and Asia impacted where early humans chose to live, but I wasn't very certain about this so I didn't put it in. Dragons flight 07:34, Mar 6, 2005 (UTC)

Vostok plot[edit]

  • (SEWilco) I haven't used IDL, but perhaps something like this would help the plot (and maybe xtickunits='time' or xtickformat='(I6)' on 'plot'?):
xyouts, 30000, -350, 'D-O events', charsize = 0.5, alignment = 0.5
plots, 30000, -355
plots, [27500,30000,28500], [-378,-355,-378], /continue
xyouts, 12500, -325, 'Younger Dryas', charsize = 0.5, alignment = 0.5
plots, 12500, -330
plots, 12500, -370, /continue
xyouts, 6000, -310, 'Optimum', charsize = 0.5
plots, 5000, -320
plots, [5000,7000,7000], [-315,-315,-320], /continue

Page move?[edit]

(William M. Connolley 14:30, 11 Mar 2005 (UTC)) Before too many links get created... shouldn't this be Holocene climatic optimum (no caps)?

  • Depends on usage, and I started by following one usage. But I agree for several reasons. Somene will rename soon and add a redirect to deal with the capitalized form. I'd do it now but the WP DB is having difficulties and this can wait. (SEWilco 20:26, 11 Mar 2005 (UTC))

New pic: new text?[edit]

(William M. Connolley 23:51, 21 Mar 2005 (UTC)) With the new pic (thanks DF) there seems to be a need to revise the text (anyone for an extended hockey stick :-). The current:

The Holocene Climate Optimum warm event consisted of increases of up to 4 °C near the North Pole (in one study, winter warming of 3-9°C and summer of 2-6°C in northern central Siberia)[1] ( Northwestern Europe experienced warming, while there was cooling in the south.[2] ( The average temperature change appears to have declined rapidly with latitude so that essentially no change in mean temperature is reported at low and mid latitudes. Tropical reefs tend to show temperature increases of less than 1 °C. In terms of the global average, the typical shift was probably between 0.5 and 2 °C warmer than the mid-20th century (depending on estimates of latitude dependence and seasonality in response patterns).

no longer looks like a reasonable summary of the pic (or at least the first bit). Perhaps those interested need to see if they like the pic... one could perhaps quibble that simply averaging all the data is too simple. Or maybe its the best we can do for now. In particular, The Holocene Climate Optimum warm event consisted of increases of up to 4 °C near the North Pole (increases over what?) doesn't seem to fit: the max wiggles are +1.5.

But, if we were to accept the pic, then a better intro would, in my opinion, not pick out the most exciting T rises but start with the global picture and particularise. Thus it could start with something like:

The holocene (last 10kyr since end of ice age) has been, globally, a period of fairly stable temperatures. During the HCO, between 4-8 kyrBP, temperatures reached about 0.25 oC above 20C averages; late 20C temperatures exceed this... and then particularise.
So you're trying to fit the data to the picture? How did you get from '0.5 and 2' mid-20th century to 'about 0.25'? Because that's 0.25 of 20C average, while 0.5-2 is relative to 1950, the Origin of B.P.? (SEWilco 09:41, 22 Mar 2005 (UTC))

(William M. Connolley 10:10, 22 Mar 2005 (UTC)) No: I'm trying to fit the text of the page to the data in the picture. Mostly, to the thick black line for the overall picture. The thick black line gets about 0.25 oC above the 20C average. Individual records get higher, of course, but this is no surprise. But we're comparing them to the *global* 20C record. If you looked at individual stations you could find some even larger trends for 20C. I'm saying that the overall description should *start* from the global picture and work downwards - not start from the most exceptional records, which present a misleading impression of the degree of warmth then.

I think that depends on how one intends to define the HCO. If, as most people believe, the HCO is at best a regional phenomenon in terms of temperature, then I have no problem with starting from the local and extraordinary claims if one is willing emphasize that such changes are local and extraordinary, and then go on to say that the HCO probably only represented a mild warming on global scales. Dragons flight 16:57, Mar 22, 2005 (UTC)
HCO refers to the global warming event, mild or otherwise, not regional extremes. And you have run a poll on what most people believe about HCO? And how many HCO-peaking global sources do you need in Image:Holocene Temperature Variations.png in order for it to have been a global event? (SEWilco 22:07, 22 Mar 2005 (UTC))
To clarify, I meant that the HCO is generally regarded in the scientific literature as a major temperature event only at high northern latitudes, and perhaps a mild event on global scales. I don't object to leading off the article by describing the largest reported changes so long as it is properly qualified to indicate that on global scales it is usually believed to be more mild. Dragons flight 22:32, Mar 22, 2005 (UTC)
"Only"? Where else would one expect heat to cause a major temperature event other than where it is cold? Does a glacial era cause a major temperature event at the poles? I wouldn't expect equatorial and southern oceans to get much hotter without a lot of that heat being spread to higher latitudes. (SEWilco 06:54, 23 Mar 2005 (UTC))

There still seems to be a mismatch between the diagram and text of the Global Effects section. The diagram indicates that the peak average Holocene temperature (black thick line?) is less than in 2004, yet the text says the typical shift was probably between 0.5 and 2 °C warmer than the mid-20th century. Since the temperature shift since mid-20th century is less than 0.5C then we are cooler now than then. Something's wrong. --Michael C. Price talk 23:00, 17 March 2007 (UTC)

Since this has come up again, I've edited the text to fit the graph. The text was, anyway, sourceless, unlike the graph William M. Connolley 22:05, 18 March 2007 (UTC)
The only number I see amongst the referenced abstracts is 1.6±0.8°C, i.e. not 0.5 C. --Michael C. Price talk 00:09, 19 March 2007 (UTC)
Thats only one part of the world, not global William M. Connolley 09:42, 19 March 2007 (UTC)


The milankovitch section (DF?) is completely unref'd. However I left it. I took out the sunspots pic, because (if we believe the M section) its irrelevant. It also doesn't seem to be ref'd in the text. William M. Connolley 20:25, 9 May 2006 (UTC)

Thermal optimum[edit]

The article Middle Jomon about Japan links to Thermal optimum which says merely "The thermal optimum (between 4000 and 2000 BC), was a period when temperatures reached several degrees Celsius higher than the present, and the seas were higher by 5 to 6 meters" with no source. Should Thermal optimum be redirected here? I do not see the statement here about the sea level. Edison 17:30, 8 January 2007 (UTC)

According to sea level the statement about SL is simply wrong. I doubt the T stuff too (except locally). Anyway I've changed the link to HCO and removed the dodgy text William M. Connolley 18:57, 8 January 2007 (UTC)


I'm not an expert on this subject but I came here because global warming interests me. Could someone speak about the CO2 levels at this time period please. Since this is such a topic of interest now days. Bryanpeterson 16:30, 10 May 2007 (UTC)

Warmer not colder then today[edit]

undid William's changes, as the graph clearly does show every line (but the yellow-orange line) going above the most current recorded temperature (2004), and is consistant with the text.

Please check the image page for the graph. Each of the colored graphs seems to be local/regional figures, with a large amount of uncertainty - so you shouldn't conclude anything from it. --Kim D. Petersen (talk) 08:28, 4 September 2008 (UTC)
More, you could just as easily write "0.5 to 2 *colder*" than mid-20th-C by looking at the individual lines - why should we be interested in pickin gout the warm side of the wiggles? William M. Connolley (talk) 08:49, 4 September 2008 (UTC)

polar bears[edit]

The first thing I thought of when I read this article was: how did the polar bears survive this time period? The earth is not yet as warm today as it was then, and the polar bears are having a hard time now, so I was just wondering how they managed back then. If anybody knows, it might make an interesting addition to the article? -ErinHowarth (talk) 21:15, 10 November 2008 (UTC)

The earth is not yet as warm today as it was then - who says? William M. Connolley (talk) 23:25, 15 December 2009 (UTC)

warmer or cooler?[edit]

The first paragraph ends with this: "In terms of the global average, temperatures were probably colder than present day (depending on estimates of latitude dependence and seasonality in response patterns)." It disagrees with the remainder of the article. If this is substantiated by studies using observed or inferred data (as opposed to GCMs) then those studies should be cited. Otherwise, it should be removed as unverifiable. (talk) 13:41, 18 February 2009 (UTC)

Which bits does it disagree with? And where do the GCMs come in? William M. Connolley (talk) 23:24, 15 December 2009 (UTC)
Oops, I see the text went. Never mind, I've restored it William M. Connolley (talk) 23:29, 15 December 2009 (UTC)
No source cited to provide evidence that "global average, temperatures were probably colder than present day" —Preceding unsigned comment added by (talk) 22:20, 11 March 2010 (UTC)

Meaning of 'optimum'[edit]

What is the meaning of the word 'optimum' in this context? Is it intended to say the temperature was 'good'/'optimal' in that period, or merely that it was highest? --Raboof (talk) 23:35, 19 December 2009 (UTC)

The use of the word "optimum" likely comes from the early days of paleoclimatology, when many of the pioneers were Scandinavians. Since stuff like fossil pollen indicated that the mid-Holocene was the warmest time, it was termed as the climatic "optimum" since up in the frigid north the weather's regarded as optimal when it's as warm as possible! In a global context it is indeed a strange term - someone living in North Africa or Southern California might well consider a cooler or moister climate more optimal. It seems most modern papers on the subject use the term "Holocene thermal maximum" - I would actually argue that this page could be moved under that name. —Preceding unsigned comment added by Ssalonen (talkcontribs) 23:23, 15 July 2010 (UTC)

Does a graphic of ancient temperatures need data on recent tempertures?[edit]

Discuss. FX (talk) 17:29, 19 March 2012 (UTC)

An odd way of phrasing the question. To answer the question you meant to ask "it is useful context" William M. Connolley (talk) 18:33, 19 March 2012 (UTC)

That brings up another issue. Does it educate and inform us about the article? The last climactic optimum? Or represent something else? For example, a graphic of the sea level rise since the last glacier period would not show the minute amount of sea level rise occurring now. Is that relevant to an article about sea level?FX (talk) 02:05, 20 March 2012 (UTC)

Changed the unneeded commentary to make it understandable.FX (talk) 02:17, 21 March 2012 (UTC)

I reverted this [4] because it is (a) unsourced and (b) wrong. The warming is easily large enough to be seen. Where are you getting your false info from? William M. Connolley (talk) 09:42, 21 March 2012 (UTC)

William M. Connolley wrote "Note that the recent warming is not shown on the graph." William M. Connolley wrote "The warming is easily large enough to be seen."

Which is it? If it's large enough to see, then we can see it on the graph. Are you trying to make a claim here? The facts are that the climactic optimum had global temperatures higher than present, a higher sea level than present, and much less ice at the poles than at present. Well, according to all the scientific evidence that is. Are you trying to imply the present global temperature is higher?

If so, that is certainly relevant, and you should state your sources. FX (talk) 12:07, 21 March 2012 (UTC)

The facts are that the climactic optimum had global temperatures higher than present. I disagree. If you believe this, please cite your sources. You appear to believe that "all the scientific evidence" supports your view, so sources can't be hard to come by. Don't forget to note the "2004" value plotted on the graph, and note that temperature has risen since then.
Which is it? If it's large enough to see, then we can see it on the graph: you've misunderstood. The temperature series plotted on that graph doesn't include the recent instrumental record. If it did, it would be visible. If you don't understand these issues, it would be best to refraim from editing the article until you do William M. Connolley (talk) 12:20, 21 March 2012 (UTC)

If you are claiming current temperatures are higher than the climactic optimum, then it would be prudent to share with us your secret sources. As for the graphic, if 2004 is visible on the graphic, then recent temperatures are shown on the graph. There has been no warming (trend) of late, so including 2011 on the graphic wouldn't change what it shows at present.

But please, share with us why you claim the current climate is warmer than the historic Climactic optimum. We would all be most interested. Would certainly change the article a lot. FX (talk) 12:50, 21 March 2012 (UTC)

I'll start with the 2004 point plotted on the graph. I don't see why you think now-was-warmer-than-then would change the article. Have you considered reading it? Meanwhile, you asserted that the climactic optimum had global temperatures higher than present but I've asked and you've presented no evidence. If you've got none, fine, I'll give up asking William M. Connolley (talk) 13:39, 21 March 2012 (UTC)

The ridiculous claim you are making goes against all scientific evidence, since the beginning of climate history. The sea levels from the climactic optimum is probably the best known evidence of the event itself. The solid and repeated evidence of this is the basis of why they even know the event occurred.

2004 Nature, 431, 56-59 DOI: 10.1038/nature02903 Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch Stott, L., Cannariato, K., Thunell, R., Haug, G. H., Koutavas, A., Lund, S.

If you are trying to claim you know more than all the experts and pros who study these things, please show your sources. FX (talk) 14:36, 21 March 2012 (UTC)

The sea levels from the climactic optimum is probably the best known evidence of the event itself? File:Post-Glacial Sea Level.png
Stott et al.: [5]: you're making the same mistake as you did with the graph on this page. Those are results from sediment cores, so they don't have the most recent era on them. Guessing, at least the last 100 years are missing. And... (less importantly) that is just one region William M. Connolley (talk) 15:41, 21 March 2012 (UTC)

The Holocene Transgression[edit]

It truly would be an impossible feat for anyone to change the entire historic record, in order to further some agenda. A real encyclopedia, by it's nature untouchable by political winds, gives a rational and reasoned explanation of the recent historic events of our planet.

The HOLOCENE TRANSGRESSION, a well known name to any real student of climate history, appears in thousands and thousands of papers, textbooks and in any real history of sea levels. etc etc Ad nauseam

It's absence from Wikipedia seems hardly an unfortunate accident. It's absence from the article under discussion, is almost criminal in it's ignorance. It's absence, the Holocene Transgression, would almost beg for a creation event. Yet.. I was quite unaware until of late of the concerted efforts by some to try to write their own version of climate history. That the well known climactic optimum has become yet another Wikipedia political article, beset by the well known revisionists, perhaps just another nail in the collective coffin, of reasonable and intelligent who scoff at finding balance and truth when it comes to science here.

Yet hope springs eternal. Hence the oft times useless talk page.

I challenged another editor to provide sources for his wild claims. A quick investigation into history shows there is little chance of that fruitful action. Be that as it may, it has brought forth the crux of the matter, in regards to the current article, despite the dismaying state of things.

(addendum) Since the above I see my scant powers of prediction were on the money. It seems the very essence of the climactic optimum is vacant from certain minds. The original discovery of the warm period was spurred by the raised beaches, or recent origin, worldwide. While the majority are around 3 meters, uplift from rebounding places many much higher. This does not point to a great rise, but the land rising up. This is basic basic stuff of climate history. The inland flooding, the river deltas, this is not even in question amongst the scientific community. Pick up any encyclopedia and it is just there.

Fascinating that anyone would not know this. FX (talk) 16:00, 21 March 2012 (UTC).

That should save a bit of effort. Before some crank starts demanding evidences. Read it and weep. FX (talk) 16:09, 21 March 2012 (UTC)

Don't argue with sources, add your own[edit]

Read it and weep. FX (talk) 16:39, 3 April 2012 (UTC)

The very basis of knowing there was a climactic optimum is the SEA LEVELS and raised beaches around the world, caused by it. Denial of this, and especially removing it from Wikipedia is against everything Wikipedia stands for.

From 3000 to 2000 BC a cooling trend occurred. This cooling caused large drops in sea level and the emergence of many islands (Bahamas) and coastal areas that are still above sea level today. A short warming trend took place from 2000 to 1500 BC, followed once again by colder conditions. Colder temperatures from 1500 - 750 BC caused renewed ice growth in continental glaciers and alpine glaciers, and a sea level drop of between 2 to 3 meters below present day levels.

The period from 750 BC - 800 AD saw warming up to 150 BC. Temperatures, however, did not get as warm as the Climatic Optimum. During the time of Roman Empire (150 BC - 300 AD) a cooling began that lasted until about 900 AD. At its height, the cooling caused the Nile River (829 AD) and the Black Sea (800-801 AD) to freeze.

FX (talk) 16:41, 3 April 2012 (UTC)

The website does not give references.
Their claim, that it was during that time globally significantly warmer stands in direct opposition to what the IPCC sais here:
"... concepts such as ‘mid-Holocene thermal optimum’, ‘altithermal’, etc. are not globally relevant and should only be applied in a well-articulated regional context. Current spatial coverage, temporal resolution and age control of available Holocene proxy data limit the ability to determine if there were multi-decadal periods of global warmth comparable to the last half of 20th century." . --Hg6996 (talk) 06:03, 11 October 2012 (UTC)

Misused and falsely cited reference, section Global Effects[edit]

Reference number 4, "Tropical Pacific Climate at the mid-Holocene and the Last Glacial Maximum" was used to assert the following, "Average global temperatures were probably colder than today." There are problems with this. First, the editor did not use the complete title of the article, which is "Tropical Pacific Climate at the mid-Holocene and the Last Glacial Maximum Simulated by a Coupled Ocean-Atmosphere General Circulation Model." Those last nine words are crucial. The authors (Kitoh et al) were not discussing the actual mid-Holocene (or LGM). They were discussing the results of their models. When they stated that temperatures were cooler by 0.35 deg, they were saying that this is what they found in their 200 year simulation for the mid-Holocene. They also stated that their input data was limited and left out important factors. The fact that the editor uses this article to support the citation that the mid-Holocene was generally colder than today despite a much higher sea level indicates that his neutrality is suspect and that he can't find legitimate data to support his claim. I will change this paragraph in the upcoming days if no one can present better data.Badamours (talk) 19:30, 19 August 2014 (UTC)

After taking a look, it's obviously original research. Fxmastermind (talk) 20:37, 25 June 2015 (UTC)

Replaced link for ref #4[edit]

using because the url no longer works. Fxmastermind (talk) 20:36, 25 June 2015 (UTC)

External links modified[edit]

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