The Team (at both realclimate and NOAA) have stated in the strongest possible terms that the Holocene Optimum was restricted to summer in the NH extratropics. Reviewing their positions, realclimate here
The [Holocene Optimum] is a somewhat outdated term used to refer to a sub-interval of the Holocene period from 5000-7000 years ago during which it was once thought that the earth was warmer than today. We now know that conditions at this time were probably warmer than today, but only in summer and only in the extratropics of the Northern Hemisphere.
NOAA (with a very recent update in Nov 2006) stated:
In summary, the mid-Holocene, roughly 6,000 years ago, was generally warmer than today, but only in summer and only in the northern hemisphere.
On a previous occasion, I discussed recent findings of Newton et al with convincing evidence of an MWP in the Pacific Warm Pool (as well as related evidence in Stott’s webpage (the series is identifiable as MD81 although not specifically identified on the webpage.) Here is an important graphic from Stott et al (Nature 2004) showing the location of 3 cores in the PAcific Warm Pool (top) with Mg/Ca temperature series and dO18 salinity series below, about which Stott says the following:
Note how the d18O values become progressively lighter through the Holocene whereas the temperature show a maximum in the early Holocene and decline (in the western Pacific) towards the present. The trend in d18O during the Holocene reflects the progressive freshening of the western tropical Pacific during the mid to late Holocene.
From Stott et al 2004. Blue – Mg/Ca proxy for temperature; red – dO18
Reference: Stott etl al, 2004. Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch, Nature, 431, 56.
Climate Audit 
31 Comments
I went back to the Lorenz (2006) paper to determine whether the Stott et al. (2004) paper was referenced and lo and behold it was not. I guess that since the Lorenz paper stated it wanted to use only alkenone proxies to be “consistent” that it meant that they did not want to even mention other proxy papers. I found the data of Stott tabularized here.
Who is the author of the NOAA page and report linked here?
#2. http://www.ncdc.noaa.gov/paleo/globalwarming/work.html
#1. If you want to read the data from the archive, here’s a simple script:
It’ll be interesting to see the AR4 characterization of this in a few weeks. I suspect ther will be less of a conflict in the science than the speculation here implies.
#3.
Why am I not surprised at the names listed?
Re #6: Yeah, I looked for S. Fred’s name and couldn’t find it.
For a uncensored politics free view on the Holocene Thermal Optimum have a look here.
Re: #8
You can post but not discuss. Its an improvement over RealClimate, I guess.
I agree, Steve B. I would predict the subject as presented by AR4 will be nearly completely conflict free. The consensus view will come through loud and clear — even if sufficient space cannot be found for countervailing data and results.
AR4 concedes that Holocene Optimum warmth in high southern latitudes could not be accounted for by simple Milankowitch. They also cite Stott et al 2004 as showing a warm Warm Pool. So to that extent, the NOAA and realclimate claims are already refuted by IPCC 4AR.
Their line of retreat, for which they cite Lorenz et al 2006 as a single authority – an “unseasoned” article in North’s terms – was that the Holocene Optimum was a time of extratropical warmth, but tropical cooling. Thus no global warmth comparable to the present. Take a look at the thread here http://www.climateaudit.org/?p=1005
There are many excellent citations at Andre’s link. Here’s a good post by Andre summarizing Iriondo on poleward movement of vegetation in southern latitudes in the Holocene Optimum:
Analogies which come to mind are a Gordian Knot, or, a digger standing in a hole now dug to a depth exceeding his or her height. There comes a time when even the most committed ideologues must pause, and think really hard about facing the truth and making confessions about past mistakes. The tap dancing has degenerated into a macabre tragicomic ballet.
RE 9:
John A, reconsider your reply to Andre. For starters, his light sarcasm was directed at Surrealclimate — certainly not CA.
Steve M, where do you find this information? I went to the IPCC website on AR4 and could not find links to chapter reviews, but instead comments on embargoing of the reports until Feb 2, 2007 and the “unhelpfulness” of speculation about report contents.
Since a necessary condition for the creation of cities is an agricultural surplus, to free up labor from farming, the Holocene Optimum may be the factor that put humans on the path to higher development.
RE: #16 – That’s a very perceptive comment. I would not doubt the HO being a factor leading to the birth of civilization.
Just to follow up on #16 & #17, I thought this was a rather good piece by a John Carlisle, found here, which supports your supposition. I suppose that the Romans also must have benefited from the warm period, empire-wise. Would the great cathedrals of Europe have been built without the relative prosperity and ease of life during the MWP (relative to the centuries that followed)? I found Brian Fagan’s “The Little Ice Age” a quite interesting description of what life was like for Europeans prior to and during the LIA.
I am a very amateur observer, btw, but I was happy to note someone’s comment regarding the term “hypsithermal” – I had come across it in E.C. Pielou’s 1991 book “After the Ice Age: The Return of Life to Glaciated North America” and hadn’t seen this term used elsewhere. Very interesting book, btw.
Pielou concludes: There is a wealth of evidence, however, that climate change is never ending. Even if major climatic “steps” are comparatively quick, it is almost certain that the climate in the intervals between steps undergoes continual lesser changes. In the light of present knowledge, therefore, (Margaret) Davis’ view, that disequilibrium in ecological communities is much commoner than equilibrium, is the more acceptable.
It should lead, in time, to a much needed change in popular thought. The notion espoused by so many nonprofessional ecologists — that the living world is “marvelously” and “delicately” attuned to its environment — is not so much a scientifically reasonable theory as a mystically satisfying dogma. Its abandonment might lead to a useful fresh start in environmental politics.
It should lead, in time, to a much needed change in popular thought. The notion espoused by so many nonprofessional ecologists “¢’¬? that the living world is “marvelously” and “delicately” attuned to its environment “¢’¬? is not so much a scientifically reasonable theory as a mystically satisfying dogma.
Speaking of dogma, this implication/assertion has long since been abandoned in the ecological science community.
Variants keep coming up in certain ideologies, though.
Best,
D
Dano’s link is to a google search of the phrase “ecosystem resilience”. Thanks for that Dano, I don’t know how you find the time.
#16,17
Some Historians have argued that it was the Late Roman Cold Period that brought on the conditions for the social break down that we call the Dark Ages. The reasoning is simple: with the shorter growing seasons any agricultural surpluses was lost. The great cities and settlements the Romans established could no longer be supported. Europe was sent into a tailspin from which it would not recover for another 800 years.
RE: #21 – Also, more primitive cultures driven by the increasing cold (and dry) conditions on the steppes, driven southwestward. The furthest advance was the Battle of Catalaunian fields. A cautionary tale for our own times. Yes, I wrote that. We are ill prepared for another cold period – we (the collective we) are so caught up in obsessing about AGW that if we get hit, instead, by a cold period, we’ll be caught with our proverbial knickers down.
#21 I’ve also seen this cold period put forward as the reason for the westward migrations of the various peoples that destroyed the western Roman empire. The Sassanid Persian empire was coming under similar pressure from the east at the same time.
Another example of the changing climate at this time is a Roman villa I have visited near our house in SW France. This villa was abandoned in the late Roman period due to decline in food production. The design is clearly ill suited to the current climate and would be uninhabitable during the winter today. The living rooms are only partly roofed and open onto internal courtyards without windows or doors. There was under floor heating but I can’t see that helping much when the outside temperature is close to 0C and the rooms are open to the elements. The design would make for a great summer residence today but apparently it was inhabited all year round.
That is what upsets me about the hasty current climate change bandwagon. Their perspective is too narrow, and their time frame is too short. They cherry pick their data, and use political pressure to prevent pubication of contrary viewpoints. Just like realclimate censors contrary points of view, in publications censorship is rampant.
This will eventually blow over, but one wonders how much damage to the politcal and economic climate, to say nothing of science, will be done.
One of my favorite books ever is William McNeill’s “The Rise of the West.” He charts the development of civilization through cycles of opening and closing of the “ecumene”, i.e. the various parts of the civilized world. There was a closing of the ecumene (coming together) during the Roman warm period, then breaking off afterward. Another closing took place at the end of the Medieval Warm Period, as a result of accumulated wealth and the search for luxuries in the East.
In the last twenty years the world has seen the greatest movement in history towards eliminating hunger, due to the Green Revolution that was aided by, what else, warmer temperatures.
…and CO2 fertilization!!
Yep just google “Holocene optimum and civilization” together.
Contrary to the RC world experts, “holocene optimum” is not an outdated term at all.
RE 15:
Ken, the Milankowitch cycle ~10 kya produced highest summertime temps (relative) in the NH & the coolest winter temps (the sun was closest in July). The SH was the opposite condition — coolest summer & warmest winter conditions afa solar insolation. Good for melting summer ice in NH, but opposite in SH.
The Milankowitch cycle at the present is pretty much opposite as ~10 kya — orbital distance from the sun is now a max in July in NH. Just my opinion, but some aspects of this, like the LIA being the coldest part of the present Holocene, would lead to think that the current interglacial could end anytime soon.
In a short article in the British Sunday Telegraph, Katie Grant (a historian) made an interesting observation: that, as the medieval optimum faded life expectancy in England fell from 48 to 38. The Black Death probably didn’t help, but she stated it was equally due to the cold.
Isn’t it strange how, in some quarters, it seems cold is good, warm is bad? In England the climate has grown noticeably warmer over the last 40 or 50 years. As I don’t enjoy the cold I think it’s great!
In the Channel 4 program (Swindle) a speaker made some points about the medieval warm period. One of his points didn’t work so well as now there is in fact a thriving English wine industry that has sprung up during the current warm period. But one phrase he used has stuck in my memory: he described the period as ‘a time of riches’. I think that about says it all. How can Gore and his followers get it so wrong?
RE: #30 – Historical revisionism since the Renaissance has lumped the entire period from say, 400ish AD, until late 1300s into one big “Dark Age.” In essence, the revisionists (who had specific agendas in breaking with the past, most prominently, after Martin Luther arose) inflated the real Dark Ages to last an additional 500 years. On top of all that, most people today are so historically illiterate that they tend to, themselves, blur everything from the end of the Roman Empire’s time of power until the age of discovery together. How can anyone, for example, emerge from the Metro onto Ille St. Louise, see the excellent collection of buildings built between 1100 and 1400 AD, and not be in awe? Clearly, those who built them had resources and knowledge, not to mention, enough self esteem as individuals and as an overarching society, to invest in multi generational contruction projects whose outputs were successfully designed to last for thousands of years with proper maintenance. The notion of a poor society, with opressive clergy leading it, in fear of the future, is utterly incorrect, when describing the great builders of the period 800 – 1400 AD. Indeed, it must have been a time of warmth and riches. Those grand cathedrals still don’t need much Air Con.