Evidence of the Medieval Warm Period in Australia, New Zealand and Oceania

By Sebastian Lüning
Geoscientist and co-author of ‘The neglected Sun’

The climate of the pre-industrial past is of greatest importance to the ongoing climate discussion. Current climate can only be understood when interpreting it in the paleoclimatological context of the past few thousand years. Until not too long ago it was thought that the pre-industrial climate was monotonous and constant. This idea was e.g. promoted by Mann et al. whose famous hockey stick curve featured prominently in the IPCC report of 2001. Over the last 15 years, however, a large number of studies changed this view by providing robust evidence for the existence of significant natural climate variability. Of particular interest are the past 1000 years which commenced with the generally warm ‘Medieval Climate Anomaly’ (MCA, aka ‘Medieval Warm Period’, MWP), that eventually passed into the ‘Little Ice Age’ (LIA), before returning to the warm climate of the current ‘Modern Warm Period’ of the 20th and early 21st centuries.

There have been controversial debates about the existence of the MWP, the level of warming compared to the current climate as well as on regional differences in timing. Meanwhile, the MWP has been documented from all seven continents, as documented by literature syntheses prepared by the CO2Science group. (Australia & New Zealand here and here). In this article we present an independent follow up project, coordinated by geologist Dr Sebastian Lüning, in which we map the MWP across the globe, visualizing the existing literature on a zoomable Google Maps platform. A click on the respective data point opens an information panel which summarizes the results of the study using a common, simplifying scheme. Links to the journal abstract and key figure allow quick access to the data. The MWP Online Map is freely accessible for anyone.

Results are now available for Africa, Antarctica and Australia/Oceania. In the following, we want to present our findings for Australia/Oceania, hoping for reader feedback on additional studies or alternative interpretations. Up to now we have identified 15 study locations in the region (Figs. 1 and 14). Red symbols on the map mark studies where the MWP was characterized by a warming phase, green dots show areas which were wetter during the MWP, yellow dots regions where the MWP saw a reduction in rainfall.

At first sight, green symbols dominate Australia and New Caledonia, indicating that the MWP brought additional rain into the region, compared to proceeding and subsequent times (Fig. 1). This also includes Hawaii (Fig. 14). Temperature reconstructions are only available in the southernmost temperate part of Australia and New Zealand. All available studies show a prominent warming during the MWP (red dots). No studies were found in which the MWP would have been colder than the climate before or afterwards.

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Figure 1: Studies covering the MWP in Australia/Oceania that are included in the MWP Online Map and are discussed in this article.

1. Cave KNI-51, Ningbing Range, eastern Kimberley region

Denniston et al. 2013 in Quaternary Science Reviews

The study covers the last 9,000 years and is based on delta18O isotopes in stalagmites. A strong increase in monsoon precipitation was found for 1000-1200 AD, corresponding to the Medieval Warm Period (Fig. 2).

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Figure 2. Delta18O isotopes in stalagmites in Cave KNI-51, Ningbing Range, eastern Kimberley region, Australia. From Denniston et al. 2013.

2. Swamps on the Atherton Tableland in north Queensland

Burrows et al. 2014 in The Holocene

The study covers the last 4,000 years and is based on peat humification, lithostratigraphy and magnetic susceptibility. A series of wet phases occurred during 900-1400 AD (Fig. 3). The climate was drier before (Dark Ages Cold Period) and after (Little Ice Age) this phase.

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Figure 3. Proxy records of wet phases in Bromfield Swamp, north Queensland. From Burrows et al. 2014.

3. Fournier Swamp, New Caledonia

Wirrmann et al. 2011 in Quaternary Research

The study covers the last 7000 years and is based on pollens and foraminifera. A wet phase is documented for 920-1250 AD, preceded and followed by dry phases.

4. Lake Callabonna

Cohen et al. 2011 in Geology

Cohen et al. 2012 in Quaternary Science Review

Gliganic et al. 2014 in The Holocene

The studies cover the last 50,000 years and feature a paleoshoreline chronology, dated by optically stimulated luminescence (OSL) ages. Cohen et al. 2011 and 2012 found a major pluvial / wet episode in southern central Australia between 1050-1100 AD associated with the Medieval Climatic Anomaly, that briefly interrupts a generally arid playa-dominated period. During this pluvial interval, Lake Callabonna filled to 10-12 times the volume of the largest historical filling (1974) and reached maximum depths of 4-5 m, compared to the 0.5-1.0 m achieved today. Also Gliganic et al. 2014 found an elevated lake level, centred around 1000 AD (Fig. 4).

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Fig. 4. Lake-filling curve for Lake Callabonna. From Gliganic et al. 2014.

5. Blue Lake

Gouramanis et al. 2010 in Paleo3

Climate reconstruction of the past 6000 years based on ostracod assemblages, stable isotope (delta13C, delta18O), Mg/Ca, Sr/Ca and Na/Ca analyses on ostracod valves. The Lake level begins to rise 1000 AD with peak lake filling reached 1300 AD (Fig. 5). High lake level indicates wet phase. Subsequent fall of lake level.

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Fig. 5 Modelled lake level for Blue Lake, South Australia. From Gouramanis et al. 2010.

6. Lake Surprise, Victoria

Barr 2010 in a PhD thesis at the University of Adelaide (unpublished elsewhere?)

The study covers the last 15000 years and is based on diatom flora and diatom conductivity (high values=arid, low values=humid). Barr found a series of droughts 680-1400 AD (with a wet interlude 800-900 AD). Wet conditions 1400-1900 AD were associated with Little Ice Age. This is the only study from Australia/Oceania so far that found a drying trend during the MWP in the region. Nearby studies #5 and #7 did not find similar droughts. We are not aware that the results from Barr 2010 have been published in a peer-reviewed journal, therefore interpretations have to be treated with caution.

7. Lake Keilambete

Wilkins et al. 2013 in The Holocene

The study covers the last 10,000 years and looks at lake levels reconstructed from sediment particle size and ostracod valve chemistry (delta18O and Sr/Ca). A major phase of lake filling, i.e. wet phase was found for 1000-1300 AD (Fig. 6).

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Fig. 6. Lake level history of Lake Keilambete, South Australia. From Wilkins et al. 2013.

8. Core MD03-2611, Murray Canyon, S-Australia

Moros et al. 2009 in Quaternary Science Reviews

The study covers the last 10,000 years and looks at delta18O in foraminifera. A warm period prevailed 1000-1600 AD, flanked by cold events 600 AD (Cold Period of the Migration Period) and 1600 AD onwards (Little Ice Age).

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Fig. 7. Oxygen isotope curve as temperature proxy for the last 10.000 years for foraminifera in a sedimentary core from Murray Canyon, South Australia. From Moros et al. 2009.

9. Mt. Read, western Tasmania

Cook et al. 2000 in Climate Dynamics

The study covers the last 3500 years and is based on tree rings which allowed reconstruction of warm season temperatures. A warm phase occurred 950-1500 AD, followed by Little Ice age cold phase (Fig. 8).

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Fig. 8. Warm season temperature development for Mt. Read in western Tasmania, reconstructed based on tree rings. From Cook et al. 2000.

10. Fiordland, New Zealand (Aurora, Doubtful Xanadu, Waiau, and Calcite Caves)

Lorrey et al. 2008 in Quaternary International

The study covers the last 4000 years and is based on delta18O in stalagmites. A warm phase was found for 900-1400 AD (with a short cool phase 1150-1250 AD) (Fig. 9).

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Fig. 9. Oxygen isotope curve for cave stalagmites in Fjordland, New Zealand. From Lorrey et al. 2008.

11. Oroko Swamp, New Zeland

Cook et al. 2002 in the Geophysical Research Letters

The study covers the last 1100 years and reconstructs summer temperatures based on tree rings. A warm phase has been reported for 950-1500 AD, with a short cold interlude 1000-1050 AD (Fig. 10). A cold phase 1500-1800 AD corresponds to the Little Ice Age.

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Fig. 10. Summer temperatures in Oroko Swamp, New Zealand. From Cook et al. 2002.

12. Cave in NW Nelson District, South Island, New Zealand

Wilson et al. 1979 in Nature

The study covers the last 900 years and is based on delta18O isotopes in stalagmites. The authors report a warm phase 1000 AD (start of data set) to 1400 AD (Fig. 11). Subsequent cooling towards Little Ice Age, with brief renewed warming episode centred around 1500 AD.

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Fig. 11. Oxygen isotope curve for a cave in NW Nelson District, South Island, New Zealand. From Wilson et al. 1979.

13. Caves in Waimoto district, North Island

Williams et al. 2004 in The Holocene

The study covers the last 12,000 years and is based on d13C and d18O isotopes in stalagmites. The authors report a warm phase 1000-1550 AD, peaking around 1250 AD (Fig. 12). Subsequent to 1550 AD, significant cooling occurred associated with the Little Ice Age.

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Fig. 12. Oxygen isotope development in cave stalagmites in Waimoto district, North Island. From Williams et al. 2004.

14. Hawkes Bay (Disbelief and Te Reinga Caves)

Lorrey et al. 2008 in Quaternary International

The study covers the last 4000 years and is based on delta18O in cave stalagmites. A warm phase occurred 750-1250 AD (Fig. 13).

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Fig. 13. Oxygen isotope development in Disbelief and Te Reinga Caves in Hawkes Bay, New Zealand. From Lorrey et al. 2008.

15. Kealia Pond, Maui Island, Hawaii

Pau et al. 2012 in Annals of the Association of American Geographers

The study covers the last 2600 years and is based on palynology, charcoal, and sedimentological analysis of a lake sediment core. The authors report a wet phase 850-1200 AD, plus subsequent short wet spikes around 1350 AD and 1550 AD (Fig. 15). Climate was more arid during other times.

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Fig. 14. Location of the Hawaiian Kealia Pond study by Pau et al. 2012.

 

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Fig. 15. Precipitation evolution in Kealia Pond, Maui Island, Hawaii. From Pau et al. 2012.

Previous regional syntheses

The PAGES 2k Consortium (2013) has recently published a climate reconstruction on a nearly global basis where they present a clear warming for the Medieval Warm Period in Australasia, followed by cooling of the Little Ice Age and warming of the Modern Warm Period (Fig. 16). Closer inspection of the database shows, however, that only a very small number of studies have been used from Australia/Oceania that actually reached back to MWP times. Results therefore need to be treated with caution.

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Fig. 16. Temperature reconstruction on a continent basis for the past 2000 years, as proposed by PAGES 2k Consortium (2013).

Conclusions

The existing studies document, that the MWP is clearly developed in Australia/Oceania. Temperatures have been elevated 950-1500 AD, with only short cooler interludes. Clear subsequent cooling is reported towards the Little Ice Age. Renewed warming occurred during ramp-up towards Modern Warm Period. There is currently no basis to say that the Modern Warm Period might be much warmer than the MWP in the region.

The MWP Mapping Project

The MWP Mapping Project is supported by crowd funding and has now reached a funding level of nearly 50%. If you like what you see, you may consider supporting us with a donation, small or large, which will allow us to reach our funding target and complete this important project. More information here.

The author would be very interested in any reader suggestions, additional literature from the region or alternative interpretations. Contact Email here.

96 thoughts on “Evidence of the Medieval Warm Period in Australia, New Zealand and Oceania

  1. Heresy for sure, i can hear the Team Speak already,”Just because it, the medieval warm period shows up on every continent does not make it global”.
    University of Alberta did some Arctic Lake sediment studies in the 1980s and 90s that indicated the average annual temp for the baffin Island region ran around 6C during that period, compared to +/_ 0.1C of late.

    • I guess it is fair to say that the Medieval Warm Period is known in Europe and certain other areas; there is no evidence of it in the Sea of Islands area, the Mariner Valleys, nor near the volcanoes Loki and Pele.

      I wouldn’t expect to find such evidence.

      Auto, happy with my ‘Sky At Night’ education . . . .

  2. Nice work. Sad that something so well documented needs to be proven again to counter the revisionists. Even sadder that their efforts will be given more media attention.

  3. I wonder will Dr Mann sue them for impuning his ‘good” name because they have effectively destroyed his attempt to erase the MWP ?

  4. Typo in the paper. Waimoto should be Waitomo, I think. In maori , was = water; tomo = hole/cave.

    [Noted, left for review. .mod]

    • Waitomo are well-known caves in New Zealand (disclaimer: I’m a New Zealander). There are no “Waimoto” caves as far as I know (and Google doesn’t seem to know about them either). Well spotted – or, perhaps more appropriately, ka pai.

  5. Oroko Swamp – one of my favourite Climategate emails;

    Hi Keith,

    Here is the Oroko Swamp RCS chronology plot in an attached Word 98 file and
    actual data values below. It certainly looks pretty spooky to me with
    strong “Medieval Warm Period” and “Little Ice Age” signals in it. It’s
    based on substantially more replication than the series in the paper you
    have to review (hint, hint!). In terms of rbar, sample size, and eps, it is
    probably okay back to about AD 980 at this time. I still have 3-4 more
    subfossil sections to process, but it is doubtful that the story will
    change much. When I come over in October, I am thinking about asking
    Jonathan Palmer to come over from Belfast for a visit. What do you think
    about that?

    Ed

    • Thanks Eric
      I was always curious why it was East Anglia that wound up being the smoking gun University ?
      Is their a particular patriarch or a series of connect the personalities to the IPCC that set this particular University up in the world of Climate Studies ?

      • They’re a prominent centre of climate research, and they got unlucky – someone leaked their emails, emails which contained a lot of “intriguing” material.

      • They did not start out that way, Hubert Lamb was an honourable man,most of these proxy data sets seem to back up his reconstruction of climate past.
        Something the “Team” who were supposed to carry on with the project forgot.

  6. Tell me this isn’t true! A Medieval Warm Period without CO2 it’s so wrong on so many fronts. (sarc)

    Does Mann have to return his Noble Prize? Just asking.

    • I saw Mann in a pub once. He offered to buy a round for the house if Penn State won the big game. They won. When the bartender went over to ring the bell, to let everyone in the pub know a round had been bought. Mann insisted the bell not be rung as it would disturb a man fast asleep in the bar. Mann bought the round (I was the only other conscious patron) and the bar remained eerily quiet. As a token of appreciation for not ringing the bell I wrote out an award on a napkin. He did indeed win the “No Bell Peace Prize” that day.

  7. Over at Climate Audit, SteveMc has already shown several fundamental flaws in Pages 2k reconstructions. Fatal flaws. The usual upside down, bassackwards, inverted stuff.
    Saddest part is, the Pages 2k gang eventually publishes partial corrections without acknowledging SM. And Without fixing their general dreck. Classic now indelible examples of ‘climate science’.

    • Of the 7 regions that cover land masses only (29% of the globe at best) for PAGES2k, only 2 covered from 1 AD to present – the Arctic and Europe. Antarctica was represented beginning in 167 AD. Asia begins in 800 AD. South America begins in 857 AD. North America begins in 1204 AD. Australasia begins in 1001 AD. So 4 of the 7 regions of this “global” study of the last 2,000 years have no data from 1 AD to 800 AD.

      Pages 2K Author:
      http://dotearth.blogs.nytimes.com/2013/04/22/study-charts-2000-years-of-continental-climate-changes/?_php=true&_type=blogs&_r=0
      “We also found that temperatures in some regions were higher in the past then they were during the late 20th century and that, the longer the individual site record, the more likely it was to show prior warm intervals, which is consistent with the long-term cooling trend. In Europe, for example, the average temperature between AD 21 and 80 was warmer than during AD 1971-2000. But temperatures did not fluctuate uniformly among all regions at multi-decadal to centennial scales. For example, the transition to colder regional climates between AD 1200 and 1500 is evident earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere.”

      “The Arctic was also warmest during the twentieth century, although warmer during 1941–1970 than 1971–2000 according to our reconstruction….”

      “In Europe, slightly higher reconstructed temperatures were registered in A.D. 741–770, and the interval from A.D. 21–80 was substantially warmer than 1971–2000. Antarctica was probably warmer than 1971–2000 for a time period as recent as A.D. 1671–1700, and the entire period from 141–1250 was warmer than 1971–2000.”


      http://www.nature.com/articles/sdata201426
      “Here we present an Arctic regional temperature reconstruction that revises the one published recently by the PAGES 2k Consortium. The revisions include updating records using more recent published studies from three sites, and correcting several errors discovered following publication of the PAGES 2k Consortium article.”

      Specifically:
      1. Three records were removed because of insufficient evidence that they are sensitive to temperature.
      2. Sections of five records that were interpreted by the authors to violate criterion 5 were removed.
      3. The interpreted temperature relation of the series from Hvítárvatn was corrected from positive to negative.
      4. A 50-year offset in the ages of the record from Lone Spruce Pond was corrected.
      5. The coordinates of the Copper River tree-ring reconstruction were corrected.

      With these error corrections to the original PAGES 2K reconstruction, the Medieval Warm Period (1,000 AD), as well as much of the entire 0 AD to 1,000 AD period, turns out to be just as warm (if not warmer in some decades) in the Arctic as are modern temperatures. Isn’t it amazing that all of the corrections turned out to suppress the modern temperature, and warm up the past temperatures? Just a coincidence, probably. Here’s what the corrected Arctic looks like as of 2014:

      http://www.nature.com/articles/sdata201426/figures/2

      • Isn’t it amazing that all of the corrections turned out to suppress the modern temperature, and warm up the past temperatures?

        I thought it was really amazing and then I realized that I had made the mistake of conflating ‘corrections’ and ‘adjustments’. It seems that adjustments always elevate modern temperatures and suppress past temperatures. Corrections are clearly a horse of a different colour.

      • Just a coincidence, probably.
        ==================
        probably not. the errors were consistent with expectations, so they were not caught.

        this type of error is a huge problem in science. if the scientists involved in the study, as well as the peer reviewers are all of the same mindset, this makes it unlikely that errors that confirm their beliefs will be caught.

        The problem part is that this goes on below the researchers and reviewers level of consciousness. They are complete unaware that they are biasing the results through their error detection and correction methodology.

        The notion that peer review will catch the errors in scientific papers is nonsense. Peer review is likely to catch those errors the are inconsistent with beliefs. It is unlikely to catch errors that are consistent with beliefs but inconsistent with facts.

        in effect it is a form of unintentional fraud. bias blinds all of us to errors that match the bias. if you believe there was no MWP you will not double check results that confirm this. You will automatically assume they are correct.

        if on the other hand the result show [there] was a MWP, you will check these result for error, because they contradict your beliefs. And if these results contain 2 or more errors for example, you are more likely to find the error(s) that once corrected, will get rid of the MWP, and you are less likely to find the error(s) that restore the MWP.

        this applies to researchers and reviewers alike. the undiscovered errors in the paper are much more likely to confirm than contradict the bias of the participants. in effect, unless the studies are very carefully designed, peer reviewed papers are more likely to tell us what the study participants believe to be true than they are to tell us about the facts.

      • + 10

        Great leaders (scientists should consider themselves leaders) seek out people who disagree with their premise and findings until they generate a better mousetrap. They do this because NOBODY is immune to bias.

    • Great article in general and more about the LIA from an astronomical perspective. About the Milankovich cycles, 41,000 yr and 100,000 year cycles. Also, glaciation advances during LIA in the Alps. About page 36 to 40…

      https://books.google.com/books?id=VYvQ_8I_kTwC&pg=PA29&lpg=PA29&dq=41,000+year+astronomical+events&source=bl&ots=CLNrEDfkw0&sig=k5si49HfHA6wMGhNrYB28VKKkEE&hl=en&sa=X&ved=0ahUKEwj18r2liqDKAhUGPiYKHY1sCMsQ6AEIMTAD#v=onepage&q=41%2C000%20year%20astronomical%20events&f=false

  8. If not for the industrial revolution mankind would not only have progressed technologically but would not be able to support the global population of today. Whatever, the increase in biomass because of a increase in its nutrient (Co2) has allowed a greater sustainability of life for humans. Counterintuitive to the reasoning of subjective physics, I know, but so also is the existence of deity.

    And who knows what phenomenon will determine the eternal existence of man? But really, a climate scientist?

  9. Interesting as this is it has no connection to the current warming (which is apparently not happening, you cant have it both ways) nor Sebastian’s long discredited Sun warming explanation. This confused situation has resulted from an irrelevant authority ( a geologist who has worked for a gas company) playing climate scientist – he should stick to his area of expertise.

      • Double down cheeky. I guess if the first time doesn’t work try harder ?
        Pay attention to that little crinkle in your brow when you make that sort of attack.
        It’s your brain trying to get thru to remind you that a fact is a fact no matter its source.
        Your brain also tells you to check for bias, not misuse that protective mechanism to protect your bias.

        Alarmists should try other versions of the deny, distort, confuse approach. Attempting to belittle those who disagree or question their claims is slowly alienating them from the very masses they need for the movement.

        I can help you become a mass movement leader, but you have to be open to learning.

    • Since you appear not to be well informed let me spell it out for you.

      1920’s to 1940 – warming trend most US temperature records set at this time
      Pause
      1960’s to mid 1970’s – cooling trend UEA and federal government were warning of imminent ice age
      Pause
      1980’s to 1998 – Warming Period gives rise to AGW hysteria
      Pause

      Given that the next cooling period has not yet manifested its still relatively warm however given that the Atlantic Multi decadal Oscillation is entering a cold phase this may not last especially when the current el Nino ends.

    • Get with the real program WTF, it is precisely the legitimate subject matter for a geologist – ya know ‘geo’, earth, ology, study of? I’m a geologist (and engineer) and I studied paleoclimate in the 1950s and from textbooks that were written decades earlier. I was even born on the lake bottom of the former Lake Agassiz formed at the beginning of the Holocene from melting back of the Laurentide Ice Sheet – it made the Great Lakes look rather pond-like and its remaining basin is Lakes Winnipeg, Manitoba and smaller lakes.

      I’ve mapped some of the shrinking shorelines as the lake drained to the north – I found one magnificent barchan sand dune (crescent -shaped like those in Saudi Abrabia) on one of the western shore stages of the lake with the beach to the east and below this windblown feature. All this was, of course, covered by a jack pine forest with a nice dry floor we refer to as ‘park land’ because it is so pleasant to walk through. Oh the barchan? 10,000 years ago, the prevailing wind was from the northeast I found easy to determine!!

      And the weather was variable, with chains of cold winters that froze up the water exits and stabilized the lake for decades to form a good beach with backing sand dunes. Then, another string of warmer years that thawed the exits, the lake falling to a new stable shoreline with development of a lower beach and sand dunes. And I’m only a mineral exploration geologist, mining engineer and metallurgist, not a stratigrapher- sedimentologist type.

      • Gary: anyone who lived and studied in Manitoba should have trouble buying into the climate change dogma. I have lived and worked to the west of you for 50 years, and taught both geomorphology and climatology. The field trips include terminal moraines as the dominant landscape features of the area, remnant glacial lakes on the uplands, under fit streams in meltwater valleys, the delta of the Assiniboine River which forms an edaphic desert near Carberry, and “northern” rocks the size of pianos strewn across the prairies. Those who ignore the obvious history of the earth only show their own ignorance. I have long believed that today’s physicists, mathematicians, and modellers should have to take courses from geologists/physical geographers and synoptic climatologists to gain at least some perspective on the climate issue.

      • There are lots of studies that would benefit the technical fields, including how to communicate risk management effectively (honestly).

      • In the latter half of the 1990’s,as a minerals exploration geologist, I concurrently ran a gold project in the western Yukon Territory as well as a gold project in Far Northern Queensland. Country rock at both projects was deeply weathered granite – what you’d expect in sub-tropical Australia but definitely not what you’d expect in sub-arctic Canada. A thoughtful environmental engineer steered me towards “After The Ice” by E.C. Pielou which triggered my continuing study of palaeoclimatology.

    • long discredited Sun warming explanation
      ==============================
      name one discovery in science that wasn’t discredited hundreds of times before it was finally accepted.

      “why” something happens is the least interesting result in science. underneath every explanation is always another layer of detail, on to infinity.

      The questions that are interesting in science are “who”, “what”, “when”, “where”. Leave “why” for the philosophers.

    • a geologist who has worked for a gas company
      ==============================
      by that reasoning government funded mathematicians and physicists that are should not be publishing climate related papers. most of the big names in “accepted” climate science belong to this group.

      is it any surprise that government funded climate scientists recommend higher taxes as the solution to global warming? For this you need an education? What government funded solution doesn’t involve higher taxes?

      • You mean like these guys?

        James Hansen (PhD in Physics),
        Phil Jones (PhD in Hydrology),
        Michael Mann (PhD in Geology),
        Sir John Mason ( MSc in Physics),
        Sir John Houghton (PhD in Physics),
        Sir John Beddington (PhD in Population Biology),
        David Suzuki (PhD in Zoology),
        Will Steffen (PhD in Chemical Engineering),
        Tim Flannery (PhD in Kangaroo Evolution),
        David Karoly (PhD in Meteorology),
        Matthew England (PhD in Oceanography).
        Stephen Schneider (PhD in Mechanical Engineering)
        Brenda Ekwurzel (PhD in Isotope Geochemistry (hydrology))
        Carl Wunsch (PhD in Geophysics)
        Susan Solomon (PhD in Chemistry)
        Richard Somerville (PhD in Meteorology)
        Richard Alley (PhD in Geology)
        Gavin Schmidt (PhD in Mathematics)

        John Holdren (PhD in Plasma Physics)

  10. Folks, if you haven’t looked at the online tool I suggest you do, it is excellent!

    https://www.google.com/maps/d/viewer?mid=zvwgQ0tAjx_k.keO5eR4ueHXE

    You can click on any rain location where there is a study and it gives you complete info on the range of years studied. methodology, and results. Bust best of all, lest someone sputter that it is not peer reviewed, each summary has a direct link to the paper in the journal it was published in.

    Excellent work!

    • A very interesting map!

      A VERY little number of studies in the US, Europe, Asia, South America as compared to other regions…..
      The temperate climates seem to be very underrepresented. Canada is doing well.

  11. The MWP Mapping Project is supported by crowd funding and has now reached a funding level of nearly 50%. If you like what you see, you may consider supporting us with a donation, small or large, which will allow us to reach our funding target and complete this important project. More information here.

    Excellent article.
    Even better idea for how to fund it.
    Bravo.

  12. lol – they take global warming back to prehistoric times – sure, where there were all those coal mines and tractor trailers and one family of breathers per acre!!!

  13. There are too many different time scales in figures. I am pretty sure that 90 % of readers have no glue how to read them. There should be explanations for special time scales.

  14. So when was the Medieval Warm Period? There isn’t much synchrony in these plots. A complication is that the text seems to mis-read years BP as years AD. Let’s see.

    Sec 1 shows a dip from 1100-1600 BP (350-850 AD). Author says 1000-1200 AD. The plot is high from 1050AD to now.

    Sec 2 claims wet in 900-1400AD. But it sure looks like 900-1400 BP. which would be 550-1050 AD.

    Sec 5 has a spike lake level about 1150 AD, and a dip from 1200-1450AD, then pretty much high (LIA?).

    Sec 6 says dry during 680-1400 which means warm – elsewhere they say dry means cold.

    Sec 7 claims lake levels high 1000-1300AD, but it was higher around 1600-1800.

    Sec 8 claims warm period 1000-1600AD. I’m not sure how to interpret it myself, but 1600 is normally reckoned peak LIA.

    Sec 9 has warmth to about 1500AD.

    Sec 10 has 900-1400AD but with a dip in the middle.

    Sec 11 has 950-1500AD.

    Sec 12 looks like a warm peak around 1400.

    Sec 13 has 1000-1550 AD

    Sec 14 has 750-1250AD, and real cold around 1500.

    So when was the MWP?

    • I’ve copied the first eight figures, and marked on each a red line corresponding to about 950-1250 AD, a common set of dates for the MWP. See how you think they line up. On the last, up is positive – MWP seems to be a cool spell.

      • Nick, detailed correlation and comparison of the data sets will of course be needed and this is just the beginning of the analysis, the data gathering so-to-speak.
        1) There can be regional variations in timing, of course
        2) The various proxies may plot slightly different climate aspects. Needs to be considered
        3) The studies have different age resolutions, some cover the last 10,000 years, other just the last 2,000 years. This willl shift the ages somewhat depending on individual error bars
        4) age dating is patchy and in many cases there may a very limited number of dates for our interval under discussion. The interpolation/extrapolation of ages is based on fairly constant depositional rates which may not always be the case. This impacts negatively the precision of the age dates.
        5) Even within the MWP there are some cold ntervals to be expected. In my opinion solar activity changes are a key driver for the Holocene sub-Milankovic variability. The 90 and 200 year cycles will cause some pulses. Alternatively, ocean autocycles (PDO, AMO, NAO) of 60 years cycle length are likely to be developed.
        Hence, I do not exepect a perfectly synchronous data set. I agree, more study is needed. But this kind of proxy data is much better than no data at all.
        Sebastian

      • Nick, current global warming is not global either. Some places are warming, some are remaining the same, some are cooling. So why should proxy records from 1000 years ago be any different? The fact that they mimic the current warming suggests they have a common cause. The Vikings were burning too much coal.

      • “Nick, current global warming is not global either”

        There’s some warming from that burn; localised around Nick

    • I agree that the evidence is not exactly compelling. It’s a pity us sceptics can’t be a bit more consistent with our scepticism.

      • I have to agree with John Finn. As an Earth Scientist (Geologist) and Geotechnical Engineer, I find proxy data should be treated with caution. If it were not so treated, scientists should be rightly lambasted the same as the alarmists/warmists on the pet AGW theory. A great deal of MWP presence ‘proof’ is based on written records and real history, which is great, but history itself has shown that such records can be miswritten or exaggerated. I don’t doubt the MWP occurred, but identifying its real ‘range’ and lateral extent (compared to modern temperatures) is extremely difficult to pinpoint. From a skeptic perspective, simply being able to demonstrate its existence in a number of ways is more than enough to largely discredit the ‘climate should be constant’ part of the AGW argument and put the alleged recent temp rises well into significantly ‘natural variation’ range. Trying to prove it with further depth is much like putting lipstick on a pig imho (but of course, every little helps!) . just my personal view.

    • So when was the MWP?

      The planet’s temperature is not uniform on any nontrivial spatial or time scale. Judith Curry’s paper on Stadium Waves explains this nicely. For instance, both Europe and China had famines due to crop failures during the LIA but they didn’t occur at the same time. As another example, even when the planet’s temperature is an all time high there will be certain locations that experience record low temperatures (and vice versa).

      Like everything else that concerns Mother Nature, the answer to your question is “That depends”. :-)

  15. Until not too long ago it was thought that the pre-industrial climate was monotonous and constant? Uhm, no. More than half a century ago when I was in school I was taught a wee bit about the existence of the MWP.

    • More than half a century ago
      ==============
      which is what IPCC 1 showed. IPCC 2 erased the MWP, because it didn’t fit the theory. Therefore history must be wrong.

    • I noted the same thing, Art.
      Sebastian is a geologist who must have been exposed to texts and experts who articulated the existence the MWP well before Micky Mann.
      I could understand putting that sentence in the 1st paragraph if he were a youngster just entering the field, or someone who normally lined up with the “consensus team”** and still hoping to maintain membership. Was that an early bone thrown to Peer Reviewers?

      **BTW, I’ve gone through a number of labels to describe folks epitomized by the self named “Hockey Team”. I’ve been accused of showing my bias by my choice of labels (by the same folks who have no problem calling me a Denier). “Warmists” and “Alarmists” didn’t fly. I now describe that group as those on the “Consensus” side. I’m sure someone will find a way to object to that description.

  16. 1. Times are changing… A brand new study with co-authors BRIFFA and OSBORN :http://www.sciencedirect.com/science/article/pii/S0277379115301888 about treerings in Eurasia and Northamerica. From the abstracts: ” N-TREND2015 indicates a longer and warmer medieval period (∼900–1170) than portrayed by previous TR NH reconstructions and by the CMIP5 model ensemble”
    2. Paleo temperature records from locations near the IPWP have a high merrit due to the good correlation of the SST there to the globals. http://www.nature.com/nature/journal/v460/n7259/abs/nature08233.html From the abstracts: ” In particular, the tropical Indo-Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation and responds to remote northern high-latitude forcings… Reconstructed SST was, however, within error of modern values from about AD 1000 to AD 1250, towards the end of the Medieval Warm Period. SSTs during the Little Ice Age (approximately AD 1550–1850) were variable, and 0.5 to 16C colder than modern values during the coldest intervals.”
    MWP was real and global!

  17. Just to clarify, Lake Keilambete is not in South Australia, but is near to the town of Terang in Victoria. Good article otherwise. Well done.

    • whew..as an ex sth aussie I was feeling rather stymied Id never heard of that lake!

      wonder what dates they can slap on the icegouges at Hallet Cove?
      fairly big glaciers slid out to sea there sometime.

      • Seek and ye shall find from official State Govt source-
        http://www.sa.gsa.org.au/Brochures/HallettCoveBrochure.pdf
        In particular-
        “During the Recent ice age about 20 000 years ago,
        sea level was about 130 metres lower than today
        and South Australia’s coastline was about 150
        kilometres south of where Victor Harbor now is.
        The ice cap started to melt about 15 000 years ago.
        Sea level began to rise and reached its present level
        about 6000–7000 years ago.”

        And in case arithmetic is not your strong point that could easily equate to a 16.25mm/yr average sea level rise for EIGHT THOUSAND years compared to the CSIRO’s best estimate of (wait for it folks) 1.6mm/year for last century so don’t forget to call Ian Plimer and yours truly should the sea level begin to drop at the rate of 16mm/year so we can both stock up on the woollies.
        Presumably the IPCC, et al blame aboriginal cooking fires and burnoffs to flush out game as the root cause of all this ice melting? Or are they denying the science?

      • Oops don’t forget to quote all the official sources-
        http://www.cmar.csiro.au/sealevel/sl_hist_few_hundred.html

        “We have used a combination of historical tide-gauge data and satellite-altimeter data to estimate global averaged sea level change from 1880 to 2014. During this period, global-averaged sea level rose about 23 cm, with an average rate of rise of about 1.6 mm/yr over the 20th Century. The sea level record indicates a statistically significant increase in the rate of rise from 1880 to 2014.”

        Golly gosh booga booga folks.

  18. It wasn’t just a warm period – it was an optimum.
    https://www.google.com/search?q=medieval+optimum
    That’s the part we should emphasize.

    optimum (noun)
    1. the best or most favorable point, degree, amount, etc., as of temperature, light, and moisture for the growth or reproduction of an organism.
    dictionary.com

    Optimum: why would you want less?

    • To be fair the term ‘optimum’ was largely adopted by European historians and there seems little doubt that in Europe (and probably China) conditions were optimal for humans. However the evidence for this is simply not there or is ambiguous. The Benin empire in Africa flourished into the 16th century which was well after the end of the MWP.

      In North America there was a 300 year long drought from around 1350 which seems to have played a major part in wiping out the Mississippian culture and Ancient Pueblo culture (the Anasazi) reducing the survivors to a nomadic state. This coincided with the end of the MWP however in South and Central America the end of the MWP coincides with the rise of the Aztec and Inca empires while the Mayan civilization collapsed around the time of the start of the MWP .

      • Keith, Benin is equatorial Africa. It wasn’t cold there!! And similar comment about the Aztec and Inca.

      • tropical jungles are largely immune to warming or cooling. they self-regulate their temperature via clouds. temperatures drop, less evaporation, less clouds, more sun, jungles warm. temperatures increase, more evaporation, more clouds, less sun, jungles cool.

        tropical jungles are pretty much a minimum 27C around the world. this is also the same temperature that naked humans need to maintain their body temperature. Anything less and we radiate more energy that we can generate internally, and we eventually die of exposure. coincidence? not likely. we are a tropical species, originating in the jungles. the jungles are still the same temperature as when we lived there, hundreds of thousands of years ago.

  19. I do find it difficult to compare such differing proxies in any meaningful way. All proxies are ‘bad’ in the sense that they should be treated with due caution for error and range. Cross matching different proxies will only compound any errors and scynchronicity is unlikely to be clearly evident, especially if the ‘lags’ between each event and the susbsequent affect of said proxy is different. As an example, consider how ‘accurate’ stalagmite isotope analysis ‘dates’ might be – or pollen anaysis from sediments. For heavens sake even C14 dating is pretty inaccurate!
    In my opinion, it is perhaps better to think of these proxies as merely potentially indicative rather than good repeatable science. In truth, without better data, palaeoclimatology is largely guessing!

    • Aside from your worry about accuracy, there is confirmation of prior warmer times. That is the message. Imagine the panic if it were the opposite. (thanks davidmhoffer for your link to that site btw)

    • You aren’t impressed either by Scotland having a thriving wine grape industry, sheep and cattle farming in Greenland during the MWP. Nor, I’m sure meter thick ice on the Thames that one sees in paintings of the “Frost Faires”, Swiss villages in the main valleys being bulldozed away by expanding glaciers, the freezing over of the Bosphorus and New York Harbour allowing people to walk to Staten Island during the Little Ice Age! Did you know that George Washington’s forces spirited away cannons stored in Manhattan by dragging them over the ice to New Jersey? Do you know that 1/3 of Finnlanders died of starvation when the cold LIA wiped out crops several years running? Does that help support the admittedly approximate paleoclimate data for you?

      Here is a piece of my paleoclimatology of 10,000yrs ago:

      Gary Pearse
      January 10, 2016 at 7:26 am

      https://wattsupwiththat.com/2016/01/09/evidence-of-the-medieval-warm-period-in-australia-new-zealand-and-oceania/comment-page-1/#comment-2116818

      Not too shabby!!

      • Perhaps you misunderstood my comment. I fully accept the MWP at face value but not such alleged synchronicity between differing proxies – that’s all.

  20. “11. Oroko Swamp, New Zeland”

    New Zeland. Hahaha. There is no such place. This whole study is based on fantasy ;)

  21. Sebastian Lüning
    Geoscientist and co-author of ‘The neglected Sun’

    “. . . the MWP has been documented from all seven continents, as documented by literature syntheses prepared by the CO2Science group. (Australia & New Zealand here and here). In this article we present an independent follow up project, coordinated by geologist Dr Sebastian Lüning, in which we map the MWP across the globe, visualizing the existing literature on a zoomable Google Maps platform”

    Useful project that shows good science communication technology.

    John

  22. “This idea was e.g. promoted by Mann et al. ”

    No, it wasn’t. Why spoil what might have been an interesting blog post with agenda-motivated factual errors?

    And yes, I just wrote a rhetorical question :-)

    • The full quote is:

      Until not too long ago it was thought that the pre-industrial climate was monotonous and constant. This idea was e.g. promoted by Mann et al. whose famous hockey stick curve featured prominently in the IPCC report of 2001.

      I find nothing remarkable about the above statement. What am I missing?

      • CommieBob.

        Nothing remarkable about the statement except that it is unreferrenced and it is wrong. It looks made up to me.

        If they are referring to the Mann et al hockystick graph, there is actually a lot going on within some large confidence intervals. So I do not know where they get “monotonous and constant” from – I call straw-man on this one.

  23. This paper is a call for all those interested in the matter to suggest additional papers and graphs, which need to be included in the analysis……
    Clearly seen is that a MWP exists in the Southern Hemisphere….and that those authors lie,
    which either 1.) produce a MColdP or 2. produce a MFlatP……
    The question came up, where does the MWP start and end? This can be resolved by future
    steps of entering all graphs into a uniform graph model, time as x-, temp as y- coordinates….
    AND ON TOP OF THAT, place the Northern Heisphere graphs onto it.
    The “”Pages 2k consortium (2013)” graph, as shown above, is a highly crude demonstration by using squares and boxes, which disable, on purpose, the visibility of temperature
    acceleration and deceleration on decadal scale, aimed at confusing the detection of the simultaneous course of the MPW. This uniform graph model plus an assembly mean graph will identify the outliers, which all should be removed as scientic crap from climaze science, such as the hockey stick of Mann. JSei.

  24. /Desktop/wpcdf36281.png
    /Desktop/Phanerozoic_Oxygen.gif
    /Desktop/Geocarb III-Mine-03.jpg
    /Desktop/images.jpeg
    /Desktop/PhanerozoicOxygen.jpg

  25. Figure 3 and Figure 10 show a cold period centered at 1000 AD, that’s just where there is a warm period on the Greenland GISP proxy.
    Figure 16 and the graph below, show the 8th century was the warmest part of the MWP for Europe, right when GISP was at its second coldest period in the Holocene.
    Figure 3 also usefully shows the cold period around 1200 BC, which was very warm on GISP.

  26. According to the team, MWP warming is regional because:

    – there is no evidence of widespread warming in the southern hemisphere, but we don’t have enough sample sites there,
    -it’s too expensive to get more sample sites, and
    -the climate science is settled, and so has moved on to other things, so there is no need to get more sample sites.

    And
    -More samples sites might show that the warming is widespread in the southern hemisphere, so:
    -better not get more samples sites.

  27. The figure 16, the temp block diagram of the PAGES 2K CONSORTIUM (2013) clearly shows
    exceedingly hot temperatures in the Antarctica from 400 – 800 AD….. This catches the eye
    immediately. There can be no doubt that those Antarctica studies are badly calibrated and that those scientists are second rate. There is no reason that temps in the Antarctica were exceedingly OUT OF SYNC higher, along over centuries, compared to values of all other continents. Bad/fake/biased/second rate analysis is the only possible explanation for those outlier temp results of the
    consortium. JSei.

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