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The Holocene Climate Optimum

August 19, 2018

By Paul Homewood



Booker commented the other day how one scientist claimed last week that we now have “the highest temperatures on Earth since the last ice age”. The BBC failed to even challenge this statement.

This certainly is not the first time I have heard claims (presented as fact) to this effect.

We have already seen concerted attempts to disappear the MWP, so it is time to reclaim the Holocene Optimum (so named for good reason), which is generally accepted to have run from about 9000 to 5000 years ago

Obviously we had no thermometers around in those days, so nobody knows what the average temperature of the Earth was then. There again, nobody really knows now either.

But there is plentiful evidence that many places were significantly warmer than now. I present some of this evidence below, though this is probably only skimming the surface:


1) Greenland

One of the clearest pictures we have is from ice cores in Greenland:


Not only have temperatures been higher than present for pretty much all of the last 10,000 years prior to the LIA, but the 19thC marked the coldest period of all since the Ice Age, as acknowledged by Jørgen Peder Steffensen, one of the world’s leading experts on ice cores.

Evidence from other sources backs up Steffensen’s findings, for instance:

a) Ribeiro et al.

Analysis of marine sediments in Disko Bay, West Greenland finds that:

a) The past 1500 years have been identified as one of the coldest intervals of the last 7000 years in Disko Bay.

b) This period is inserted in the context of the Neoglacial Advance of the Greenland Ice Sheet starting at c. 5000 years BP and culminating in the Little Ice Age.

c) The late Holocene cooling trend is also consistent with marine and terrestrial records from several records in the N Hemisphere.


b) Kelly & Long

Study of marine shells, moraines etc finds:

a) The Greenland Ice Sheet may have receded tens of kilometers within its present day margins during the early and mid Holocene.

b) This ice sheet recession was likely a response to the warmer temperatures of the Holocene Thermal Maximum (9-5 ka) (e.g., Kaufman et al., 2004), which is registered by Greenland ice cores as ~2.5°C warmer than at present.

c) In many locations the ice sheet and mountain glaciers reached their maximum extents since the early Holocene during the Little Ice Age.






2) Arctic

There is also plenty of evidence of the Holocene Optimum elsewhere in the Arctic:

a) Levac et al

Analysis of sediments in Baffin Bay :

“ From ca. 6400 to ca. 3600 14C yr BP, transfer functions indicate warmer conditions than at present, with SST in August fluctuating up to 5.5°C. After 3600 14C yr BP, the dinocyst record suggests a trend of decreasing temperature toward modern values, marked by recurrent cooling events.”

b) Larsen et al

From lake sediments in Iceland, they conclude:

a) The Langjokull ice cap began to expand about 5500 years ago.

b) The LIA contained the most extensive glacial advance of the neoglacial interval, concluding that “the LIA was the coldest period of the last 8 thousand years.”

c) Ingolffson et al

Study of glaciers in Iceland reveals:

a) During the mid-Holocene climate optimum some of the present-day ice caps were probably absent.

b) Ice caps expanded after 6.0–5.0 cal. kyr BP, and most glaciers reached their Holocene maxima during the Little Ice Age (AD 1300–1900).

d) Koshkarova & Koshkarov

Analysis shows that temperatures in northern Central Siberia were 3 to 9 °C higher in winter and 2 to 6 °C in summer.

e) Fortin & Gajewski

A study of chironomid remains in the sediments central Canadian Arctic showed that summer temperatures were up to 3C higher in the mid-Holocene.




3) North America




Tree line studies, as reported by HH Lamb are clear evidence of declining temperatures since around 3000BC in the White Mountains of California.

Lamb comments:

Study of the Upper Tree Line on the White Mountains in California, similarly indicates warm season temperatures about 2C higher than today all through the warmest millenia, from before 5500 BC until about 2200 BC.

It was after 2000-1500 BC that most of the present glaciers in the Rocky Mountains south of  57 o N were formed and that major re-advance of those in the Alaskan Rockies first took place.


Significantly Lamb also refers to tree line studies from a variety of regions by Vera Markgraf:

Quoting a study by Markgraf in 1974, which encompassed the Alps, Carpathians, Rockies, Japan, New Guinea, Australia, New Zealand, East Africa and the Andes, Lamb writes :-

Summer temperatures in these regions were 2 C higher than now in the warmest postglacial times (around 5000 BC).

The geographical extent of these findings is particularly significant, and debunks the idea that Holocene warmth was somehow just a regional phenomenon.


4) European Alps

As noted above, tree line studies indicate a much warmer climate, even as recently as the MWP.

Again, Lamb believes that:

“at their subsequent advanced positions – probably around 500 BC as well as between 1650 and 1850 AD – the glaciers in the Alps regained an extent, estimated in the Glockner region, at about 5 times their Bronze Age Minimum, when all the smaller ones had disappeared.”



Lamb’s supposition has been backed up more recently by the discovery of the remains of 4000 year old forests at the leading edge of a Swiss glacier. Dr. Christian Schlüchter, one of the world’s leading experts on geology and paleoclimatology, who  made the discovery, stated:

“the region had once been much warmer than today, with “a wild landscape and wide flowing river.””

the forest line was much higher than it is today; there were hardly any glaciers. Nowhere in the detailed travel accounts from Roman times are glaciers mentioned.”


5) Central Russia

Novenko et al, using pollen and macrofossil evidence in the Don Basin region of Central Russia for the time span ranging from the mid-Atlantic period [7.2-5.7 cal. kyr B.P.] to the present, found:

temperatures during the mid-Atlantic period “were warmer than the present, mainly due to the higher winter temperatures,” while noting that mean January temperatures were “about 3-5°C higher than the present climatic conditions.” They also state that in the late Atlantic period, “the mean July and the mean annual temperatures rose to about 2°C higher than the present,” after which, in the middle and late Subboreal period, they indicate that summer temperatures were “about 1-3°C higher than present values,” while noting that that period’s “mean annual temperatures could have been 1-2°C higher.”


6) South America

Thompson states that:

Ancient plant beds, radiocarbon dated to 5000 years ago, are being uncovered as the Quelccaya glacier recedes in the Peruvian Andes.

 Thompson again,analysing ice cores from another glacier, the Huascarán in the north-central Andes of Peru, found:

the climate was warmest from 8400 to 5200 years before present, and that it cooled gradually, culminating with the Little Ice Age (200 to 500 years before present). A strong warming has dominated the last two centuries.”

[Also, note the reference to strong warming in the last two centuries – clearly warming 200 years ago had nothing to do with AGW!]

Other research from the Missouri Botanical Garden, which studies tree lines in the Andes, came to similar conclusions:

During the period from 7500 yr BP to ca. 3000 yr BP temperatures rose about 2°C more, causing another upward shift in the forest line of about 300-400 m higher than today, and thereby reducing the area occupied by páramo.  Finally, at about 2900 yr BP, there was a noticeable lowering of the temperature that marked the last downward movement of the forest and páramo belts to their present-day positions.



7) New Zealand







Figure 2: New Zealand’s estimated mean yearly temperatures since the last ice age. From Fig 5.6 of Ministry for the Environment (1997), based on Salinger (1988).


NIWA (National Institute for Water & Atmospheric Research) have published the above chart, based on cave speleothems, and commented:

The warmest conditions of the present cycle occurred between 10,000 and 6,000 B.P with temperatures about 1°C above modern values. This warmer climate was mild, with light winds and lush forests.


Last thoughts

These temperature patterns lasted for centuries and more. It is sometimes claimed that recent warming has already offset some of the difference, but the temperature proxies we have for the early Holocene don’t have the fine resolution to detect such short term fluctuations in temperature.

We have, for instance, seen in recent years how much effect ocean cycles, such as PDO and AMO, have on global temperature. Even the 2015/16 El Nino lifted temperatures by nearly half a degree.

There have always been these sort of natural cycles. The average temperatures derived from proxies would in reality have included many ups and downs. In short, comparison of current temperatures calculated over the last couple of decades cannot be meaningfully compared with centuries long trends.

While we don’t have global coverage, what we do know is that in many parts of the world, temperatures in the mid Holocene were significantly higher than in recent decades.

  1. Ian Magness permalink
    August 19, 2018 10:37 pm

    Thank you for this compelling research Paul.

  2. HotScot permalink
    August 19, 2018 11:08 pm

    Utterly brilliant Paul.

    Doubtless the GWPF will feature it and Anthony Watts as well.

    The Guardian will of course ignore it, a compliment in itself.

  3. August 19, 2018 11:37 pm

    Reblogged this on Climate Collections.

  4. saparonia permalink
    August 20, 2018 2:58 am

    Impressive post!! I will share it, thank you for all your work.

  5. NeilC permalink
    August 20, 2018 4:29 am

    Excellent post Paul, thank you. Good scientific research, quoting peer reviewed papers.

    You most certainly won’t find this discussed on the Bias Broadcasting Company or in this parliment by mostly ignorant politicians.

  6. Malcolm Bell permalink
    August 20, 2018 8:11 am

    Good stuff. What this suggests is that like it or not the Earth will warm
    somewhat towards historic means. That does not mean chaotic weather but maybe higher sea levels and all that implies – but maybe increased in currently arctic areas vegitation might tahe up and constrain much of that?

    It would be instructive to know more about sea levels in the Roman warm
    period. Comversely what were they in the time of the great Viking voyages of a thousand or so years ago. Both I suspect were also periods of relatively storm free summer sailing conditions. Interesting combination of conditions I think?

    • mikewaite permalink
      August 20, 2018 12:01 pm

      Malcolm, Re your 2 points about the sealevels in the North atlantic during the Viking Age.and storminess.
      I was looking at the history of the Norse settlements(ca 985 – 1450AD) in Greenland and researchers have measured the level of chloride in the south Greenland ice cores as an indication of the storms and the salt spray . They found that the storminess increased markedly during the 14th century , when the settlements began to be cut off from Iceland and Bergen.
      I also compared a 1950 photo of the farmstead on the fiord shore at Brattahlid (Erik the Red’s) with a Google map of the same area , same scale , taken in 2014. The sealevel (bear in mind the Norse settled way inland along the fiords so tidal effects minimised ) is exactly the same after 60+ years, even down to individual large boulders.
      Don’t lose any sleep worrying about flooding sealevel rise.

      • Malcolm Bell permalink
        August 20, 2018 4:22 pm

        Thank you Mike – but I don’t need reassurance about rising sea levels, that was largely the essence of my note: even in the Roman warm period or the warm one that allowed the Vikings to colonise Greenland the sea does not seem to have been much higher. I was looking for evidence for that (I live near the western end of the Roman Wall and it gets down close to water level.).

        Equally I wondered aloud if there were any water retention mechanisms that might kick in to hold the water teleased by the melting ice – like increased vegitation where there is now just Tundra?

        Don’t give a thought to my sleeping, I am content that Earth is sufficiently stable to look after itself -plus or minus a bit. Maybe better minus most of us?

      • Saighdear permalink
        August 21, 2018 7:44 am

        Yes, …. that really stupid Sea-level rise issue…….. Haven’t “they” eva thawt that there are still quite a few of us around from the 50’s, living at rocky shorelines and haven’t seen sea-level rise. Gravel & sandy beaches can be dynamic. Land Masses move / tilt, we’re told, resulting from Ice Age compression, etc. Aah! but yes, when someone takes the time & trouble to look at recorded history facsimiles, the inconvenient truth is resurrected.

  7. Des Kelliher permalink
    August 20, 2018 8:59 am

    I note the warm peak around 5000 years ago followed by a massive cooling. This coincides with the building of the massive Neolithic mounds in Knowth and other sites in Ireland. The subsequent cooling would help explain why we have no other trace of the builders.

  8. August 20, 2018 9:19 am

    Excellent post, Paul – thank you. You also gave me my first chuckle of the day with this:
    ” … nobody knows what the average temperature of the Earth was then. There again, nobody really knows now either.”

  9. paul weldon permalink
    August 20, 2018 10:01 am

    One puzzle that still remains in my memory from 20 years ago dates back to asailing tour of the south Turkish coast. Looking landward towards an ancient harbour probably going back to 5000 years ago, it was clear to see that the entrance had silted up and the coast is now some 2 kms away. What I did not understand is that the harbour entrance appeared to have been a good metre above present sea level. Now, with understanding that sea-level is a proxy for global temperature, it seems logical that the sea-level has risen since the harbour was functional. I wonder if it is the same for Rome, which was also a harbour until silting up. I wouldn’t mind betting when the sealevel from this time is calculated, it was much higher than today. I guess there is archaeological evidence out there, but no one is actually looking.

    • Ian Magness permalink
      August 20, 2018 10:50 am

      Sea level is not “a proxy for global temperature” – never has been, never will be. As with all things in climate and general Earth sciences, it’s much more complicated than that, including setting definitions for what constitutes “sea level” in the first place. For reference, Wikipedia is reasonable on eustatic and isostatic changes.

      • paul weldon permalink
        August 21, 2018 7:54 am

        Well, Ian, just remember that you first heard it used from me! Sea-level rise, as you well know, is often cited in the climate debate. It may not be classed as a proxy, but that is exactly how it is used. The correlation between global temperatures and global sea level doe not seem to be contested. A warming climate means the oceans expand and snow land ice on land tends to melt, both processes adding to the height of the ocean. When a global cooling occurs, the reverse is true. I therefore see no reason not to use sea-level from the past as a proxy for global temperatures. The examples used by Paul in his article suggest that it was some 2 degrees C warmer several centuries back, and I would have thought sea levels would have responded and been some 1-2 metres higher.

    • August 20, 2018 2:17 pm

      It is mainly due to tectonic forces. North Africa is sinking and Turkey etc rising, as the African landmass moves north under the European one.( Think of Alexandria, where the ancient Greek port is now submerged)

      • paul weldon permalink
        August 21, 2018 8:13 am

        On the surface your comment would seem to be correct, except that when one looks deeper, one finds that a.) the Anatolian plate is moving westward as opposed to upwards – the tectonics here are much more complex than you suggest, the northern part of the plate is actually subsiding, and b.) any subsidence in Alexandria was caused by an earthquake back in AD 365. Of course, I take your point though, it would be folly not to take local conditions into consideration, which seems to be when the media/scientists want to push the subject of climate change. Certainly the Anatolian coast has been subject to changes in height above sea-level, but there is also a good case for balancing this against changes due to rises/falls in sea-level. The evidence you have given in the article suggest to me that sea-level would have been higher and it would be interesting to put together any remaining evidence.

      • August 21, 2018 9:47 am

        As I understand it, the general theory is that sea levels have been rising slowly since about 6000BC (with a much sharper rise before). This reflects the fact that ice caps are still continuing to melt since the Ice Age ended.

        However there are fluctuations within this longer trend. Lamb wrote that sea level fell by 2m or more between 2000 and 500BC.Then rose againduring Roman times “finally reaching a high stand around 400AD, comparable with, or slightly above, present” [He wrote this in 1982]

      • August 21, 2018 1:25 pm

        That is interesting because Valencia, Spain, was navigable from the Mediterranean in Roman times via the Rio Turia, and for some time thereafter. I always assumed that the loss of its navigability was due to a combination of a dryer climate, the silting up of the river mouth and the deeper draught of the ships. Maybe a reduction in the level of the Mediterranean was also a contributory cause.

      • paul weldon permalink
        August 22, 2018 7:34 am

        Paul, thanks for your posting. If I remember correctly, the Anatolian culture was around 2000 BC and that fits well to Lamb’s view of a rise in sea-level at that time of 2m. I am now further intrigued about tying up old archaeological sites to sea-level rise, something to research in the winter when I have more time. Should also lead to some interesting visits!

      • paul weldon permalink
        August 22, 2018 7:45 am

        John, that is a very interesting post. Actually, I was in Valencia last spring for ‘fallas’ and to see a good friend. He has quite a knowledge of the local history and also a fan of this site. What did catch my attention was the fact that the shore to the east of the new harbour is now gained about 200 metres deeper, and expect to see erosion occurring the twest soon. The harbour stops sand moving along the coast and is a problem where I live too Baltic coast. Apart from this process, yes, I can imagine sea-levels have played their part, but the drier climate too. Certainly the area was much wetter in Roman times, North Africa was also the ‘bread-basket’ for the Roman empire. I put it down to a northward movement of the polar cell (one of the Hadley cells). I now have good excuse for another visit to Valencia!

  10. Tony Budd permalink
    August 20, 2018 10:04 am

    Thinking of the Roman Warming, there’s a nice piece of evidence in the UK: the excellent Roman Army Museum on Hadrian’s Wall in northern England has no significant snow-clearing equipment but masses of other tools on display. You wouldn’t survive the winter there these days without something fairly hefty to clear the snow.

    • Saighdear permalink
      August 21, 2018 7:55 am

      Ha ha ha! _ Terrific detection work. takes the Cream – no Ice in those days!
      Been watching some free-to-air Foreign Progs on Satellite about the Romans – only now discovering what they also did in their time – But like as in kiddies films where no one dies,( blood is shed) cowboys n indians, never a tornado or hurricane or large scale flooding and generally always blue skies, we just DON’T hear about what the Romans did in mid-winter. As with the Egyptians, the Chinese and others, the Logistics of providing for the Masses of workers we are led to believe were involved in those Massive Civil Engineering Contracts are only NOW beginning to be considered.
      Research is an evolving subject in its own right. “how to do research” …. thought for the day!

  11. August 20, 2018 11:37 am

    Reblogged this on WeatherAction News and commented:

  12. Colin Brooks permalink
    August 20, 2018 11:58 am


    When I first got involved in this debate I would read Bishop Hill, Steve McIntyre’s ‘Climate Audit’ blog and its arch enemy ‘Real Climate’ (for which the arch Villain’ Mr Mann would write) and I am sure you did the same. The kind of facts you discuss were almost common knowledge on the blogs back then.
    However some of the above responses show just how ‘the bad guys’ have managed to shift the arguments away from facts and onto unproven theories and models. Your report brilliantly brings the focus back to where it belongs.

  13. August 20, 2018 12:49 pm

    Some perspective:
    The Antarctic Ice Sheet extends almost 14 million square kilometers (5.4 million square miles), roughly the area of the contiguous United States and Mexico combined. The Antarctic Ice Sheet contains 30 million cubic kilometers (7.2 million cubic miles) of ice.

    Perhaps ‘Hothouse Earthers’ should pay a visit before their next round of insane ramblings.

    • Saighdear permalink
      August 21, 2018 8:02 am

      ‘Hothouse Earthers’ should hang around in Scotland for a summer ( this summer) … from the Borders to the Highlands, Summer fruit crops grown outdoors have NOT done as well as you would have expected from an ever heating climate. The nights were COLD, not cool, fruit was shed or shrivelled, Maize ( sweetcorn to the ‘Hothouse Earthers’ Greenblob) did NOT survive this year – from 5-6ft high last year to less than 5 to 6 INCHES this year, says it all. ….

  14. Don Easterbrook permalink
    August 20, 2018 3:43 pm

    The evidence presented here is but a small sample of the total mass of evidence available. I recognize the Greenland graph presented in this paper as one I published several years ago. It is a temp reconstruction by Alley based on data in Cuffy and Clow 1997. In addition, the oxygen isotope data of Stuiver and Grottes (1997) shows the same temp fluctuations through the Holocene. Lots of data from China and elsewhere all show the same pattern, so the temp changes are indeed global.

  15. August 21, 2018 12:20 pm

    According to ice core records, the last millennium 1000AD – 2000AD has been the coldest millennium of our current Holocene interglacial. This point is more fully illustrated with ice core records on a millennial basis back to the Eemian period here:

    Our current, warm, congenial Holocene interglacial, although cooler than the Eemian interglacial 120,000 years ago, has been the enabler of mankind’s civilisation for the last 10,000 years, spanning from mankind’s earliest farming to the most recent technologies.

    Viewing the current Holocene interglacial on a millennial basis is rational. Sadly it seems that, driven by the need to continually support the Catastrophic Anthropogenic Global Warming hypothesis / religion Climate Alarmists irrationally examine the temperature record at much too fine a scale, weather event by weather event, month by month, or year by year.

    From the broader perspective, each of the notable high points in the current 11,000 year Holocene temperature record, (Holocene Climate Optimum – Minoan – Roman – Medieval – Modern), have been progressively colder than every previous high point.

    Greenland ice core records show that for its first 7-8000 years, the early Holocene, had virtually flat temperatures, including its early high point known as the “climate optimum”. But the more recent Holocene, since a “tipping point” at around 1000BC, 3000 years ago, has seen temperature fall at about 20 times faster than its earlier rate.

    The Holocene interglacial is already 10 – 11,000 years old and just judging from the length of previous interglacial periods, the Holocene epoch should be drawing to its close: in this century, the next century or this millennium.

    Nonetheless, Climate alarmists promoting their views have converted the slight and truly beneficial warming at the end of the 20th century to a Modern high point “Great Man-made Global Warming Catastrophe”.

    The recent warming since the end of the Little Ice Age has been wholly beneficial when compared to the devastating impacts arising from the minor cooling of the Little Ice Age.
    As global temperatures, after their short spurt at the end of the last century, are showing stagnation or cooling for the last twenty years, the world should now fear the real and detrimental effects of cooling, rather than being hysterical about limited, beneficial or probably now non-existent further warming.

    Warmer times are times of success and prosperity for man-kind and for the biosphere.
    But the coming end of the present Holocene interglacial will eventually again result in a mile high ice sheet over much of the Northern hemisphere.
    The reversion to Ice Age conditions will be the real climate catastrophe.
    With the present reducing Solar activity, significantly reduced temperatures, at least to the level of another Little Ice Age are predicted quite soon this century.
    Whether the present impending cooling will really lead on to a new glacial ice age or not is still in question.

    As an interested layman, I would say that the betting is more heavily weighted towards a catastrophically cooling world rather than one that will be overheating because of the comparatively minor CO2 emissions from mankind.

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