Medieval Warm Period confirmed via cave study of 3000 years of climatic variations

Remote cave study reveals 3000 years of European climate variation

Roaring Cave in Scotland. A study of its limestone has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman Empire and the Viking Age of expansion. Credit: Courtesy of UNSW

Roaring Cave in Scotland. A study of its limestone has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman Empire and the Viking Age of expansion. Credit: Courtesy of UNSW

From the University of New South Wales:

SYDNEY — University of New South Wales Australia-led research on limestone formations in a remote Scottish cave has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman Empire and the Viking Age of expansion.

The study of five stalagmites in Roaring Cave north of Ullapool in north-west Scotland is the first to use a compilation of cave measurements to track changes in a climate phenomenon called the North Atlantic Oscillation.

‘Our results also provide the longest annual record of this important phenomenon, which has a big impact on the climate in Europe,’ says study leader, UNSW Professor Andy Baker.

‘It confirms that the during the Medieval Warm Period between 1080 and 1430 the oscillation index was in an unusually prolonged positive phase, which brings increased rain to Scotland and drier conditions in the western Mediterranean,’ says Baker, of the UNSW Connected Waters Initiative Research Centre.

‘Our results also reveal there was another persistent positive phase between 290 and 550, which coincides with the decline of Rome and a period of intensified human migration in southern Europe during the Dark Ages.

‘This was followed by a persistent negative phase between 600 and 900 which may have provided warm and dry conditions in northwestern Europe that made it suitable for westward expansion by the Vikings, although the precise timing of this event is contested.’

The study is published in the journal Scientific Reports.

The North Atlantic Oscillation climate index measures the air pressure difference between Iceland and the Azores islands off the Portuguese coast, and is a record of the strength of the westerly winds in the North Atlantic.

Roaring Cave, or Uamh an Tartair, in northwest Scotland, is a shallow cave beneath a blanket of peat that has accumulated during the past 4000 years.

Rainfall levels in this region closely correspond with the strength of the oscillation index in winter, with higher precipitation when it is positive. And the upward rate of growth of stalagmites in the cave is very sensitive to rainfall — the more water in the peat, the more slowly the stalagmites grow.

‘We painstakingly measured the thickness of each annual growth ring in five stalagmites taken from the cave, including one that provides a continuous annual record spanning more than 1800 years,’ says Baker.

By overlapping the five stalagmites they obtained a proxy record of the climate at the cave during a 3000-year period from about 1000 BC to 2000 AD.

‘Our research provides a climate context for some of the big human migration events in Europe and allows us to start building hypotheses about the impact of environment on societal change,’ says Baker.

The team includes researcher from UNSW, the University of Lausanne in Switzerland and the University of Arizona in the U.S.

###

The paper: http://www.nature.com/srep/2015/150611/srep10307/full/srep10307.html

Abstract:

Annually laminated stalagmites can be used to construct a precise chronology, and variations in laminae thickness provide an annual growth-rate record that can be used as a proxy for past climate and environmental change. Here, we present and analyse the first composite speleothem annual growth-rate record based on five stalagmites from the same cave system in northwest Scotland, where precipitation is sensitive to North Atlantic climate variability and the winter North Atlantic Oscillation (NAO). Our 3000-year record confirms persistently low growth-rates, reflective of positive NAO states, during the Medieval Climate Anomaly (MCA). Another persistently low growth period occurring at 290-550 CE coincides with the European Migration Period, and a subsequent period of sustained fast growth-rate (negative NAO) from 600-900 AD provides the climate context for the Viking Age in northern and western Europe.

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96 thoughts on “Medieval Warm Period confirmed via cave study of 3000 years of climatic variations

  1. The warmists insist that the MWP was a local phenomenon limited to northern Europe and Iceland so they will ignore this study. On the other hand they are willing to believe that one tree is a sufficient proxy for the global climate as long as it shows that the MWP doesn’t exist.

    • We could probably make just as complete a climate picture by looking at population distribution and migration over the past 3000 or 4000 years.

    • actually, this study shows that the North Atlantic Oscillation was in a positive phase during these regional warm periods. We already know that there is a strong correlation between changes in the gulf stream current and the North Atlantic Oscillation. So a small increase in the Thermohaline Circulation causes a strong positive North Atlantic Oscillation
      see: http://echorock.cgd.ucar.edu/cas/adai/papers/Dai_etal_THC_JCL05.pdf
      The simulated SST and sea ice spatial patterns associated with the THC oscillations resemble those in observed SST and sea ice concentrations that are associated with the North Atlantic Oscillation (NAO). The results suggest a dominant role of the advective mechanism and strong coupling between the THC and
      the NAO,

      • The warmists can twist themselves into pretzels trying to prove that the MWP wasn’t global. Recorded history contradicts them. http://web.stanford.edu/~moore/HistoryEcon.html During the Roman climate optimum and the Medieval Warm Period people were literate in Europe, China, India, the middle east and northern Africa. We know what was happening and we know when it happened.

      • Hard to read. Too many acronyms.
        See what I mean?
        For the TMA and SSEA in general we know that SOI influence P and thus BA which in turn influence LMM on HY and IS in much of SUS; however SMM may be show an even larger SMMS response.

    • New Zealand caves tell the same story:
      http://co2science.org/articles/V11/N53/C2.php
      So western NH and eastern SH are in synch, along with all other quarters of the globe.
      Holocene Optimum, Old Kingdom Cold Period, Minoan Warm Period, Greek Dark Ages CP, Roman WP, Dark Ages CP, Medieval WP and LIA CP were all global phenomena, with the same causes as the Modern WP.
      The folk wanderings by climate refugees during the cold periods are well attested in written history, from the Sea Peoples to the Vikings.

      • your linked paper cites a period between 900 AD and 1100 AD
        This is consistent with the “seesaw” theory between Southern Hemisphere warming and then the translation to the Northern Hemisphere via the Gulf Stream.
        The new study cited above showed:
        ‘It confirms that the during the Medieval Warm Period between 1080 and 1430 the oscillation index was in an unusually prolonged positive phase, which brings increased rain to Scotland and drier conditions in the western Mediterranean,’ says Baker, of the UNSW Connected Waters Initiative Research Centre.

    • Northern Michigan White Pine actually grow better after a cold hard winter, we have 1/2 dozen of them in the back-back yard that are from 10 to 20 years old and you can point out the bad winters by counting down from the terminal buds and inspecting the growth between the radial branches. Subsequently it’s possible that Mann’s tree ring data has things backwards.
      I know two doctoral level arborists who have said it would be totally impossible to assume any linkage between tree rings and temperature short of analyzing several million specimens along with the soil core samples to give us a complete picture of the immediate environment. And even then, depending on species, it might not be a clear relationship.

      • The Yamal tree rings didn’t just correlate to temperature; they supposedly correlated to GLOBAL AVERAGE temperatures, and thus, one is forced to believe that the actual local temperatures consistently mimicked global temperatures for hundreds of years. I still can’t believe anyone with more than a high school degree would accept such a proxie.

    • MWP was a local phenomenon limited to northern Europe and Iceland
      ===================
      There is no such thing as local warming when talking about the global average. It it warms locally, the global average will increase, unless offset by identical cooling somewhere else.
      So, where did it get colder during the MWP to offset the warming?

      • Where did it get colder? Why, wherever there is a lack of data, just like global warming, today. .

  2. The other main contribution of the study is in the term “unusually prolonged” phases. Would someone get this finding to the honest modelers out there.

  3. Clearly this shows that the Medieval Warm Period was a regional effect caused by a slight increase in the Thermohaline Overturning Circulation (gulf stream current)
    http://echorock.cgd.ucar.edu/cas/adai/papers/Dai_etal_THC_JCL05.pdf
    The simulated SST and sea ice spatial patterns associated with the THC oscillations resemble those
    in observed SST and sea ice concentrations that are associated with the North Atlantic Oscillation (NAO).
    The results suggest a dominant role of the advective mechanism and strong coupling between the THC and
    the NAO,

    and
    https://www.ifm.uni-hamburg.de/institute/staff/quadfasel/documents-quad/meincke_quad.pdf

    • Clearly this shows that the Medieval Warm Period was a regional effect caused by a slight increase in the Thermohaline Overturning Circulation (gulf stream current).

      While the above statement may be correct, I’m fairly sure that the paper discussed does not address your assertion in any way.

    • If the MWP was regional it certainly helped Europe to thrive, and so it negates the doom and gloom message of the warmists. If it was not merely regional then it negates the data assumptions of the warmists. Either way the warmists are wrong. One cannot continue to dance around contradictory evidence, eventually all that circular dancing acts much like a toilet as it’s being flushed.

    • Comparable oscillations happen globally.
      The Roman Warm Period, Dark Ages Cold Period, Medieval WP and LIA uncovered in this study are also found in similar papers covering the whole planet, from a variety of paleoclimatic proxy data.

    • The TOC increasing could no more be called a regional effect than El Nino events in the pacific. The consequences of warmer climate in the North Atlantic has a dramatic effect throughout the Arctic and sub polar regions and probably throughout the N hemisphere and seeing as corresponding MWP events spanning the same period can be found in N america and Greenland (of course) but also mainland Europe and China rather pours doubt on your assertion.
      But there again JM no surprise there, at least you’re consistently listening to the ‘old echos’ eh!

    • Oh, for Pete’s sake. How can five stalagmites from ONE cave system tell you anything about Global or Regional environments? It is one locality that MAY be linked as confirming or weakening evidence of one or more theories.
      In just the same way as tree rings are dependent upon many non-thermal factors, and non-linearly dependent on them, these stalagmites are also dependent upon air flow through the cave system, which cannot be considered to be a predictable proxy for climate.
      Maybe you can infer some confirmation with Scotland paleoclimate theories, but the authors jumped the shark when they imply it confirms Mediterranean climate changes.

      • Roy, this study tells us nothing about the temperature inside the cave.
        Perhaps if you had taken the time to read the article or the study, you would have known that.

      • How? Chemistry.
        This is merely confirmation of a long held and oft repeated conclusion that there was a MWP. I doubt the paper saying anything about it being global as that was beyond the scope of the paper.

      • Medieval Warm Period Project
        Project Overview
        Study Description and Results
        Africa
        Antarctica
        Asia
        Australia/New Zealand
        Europe
        North America
        Northern Hemisphere
        Oceans
        South America
        Project Overview
        What is it?
        Our Medieval Warm Period Project is an ongoing effort to document the magnitude and spatial and temporal distributions of a significant period of warmth that occurred approximately one thousand years ago. Its purpose is to ultimately determine if the Medieval Warm Period (1) was or was not global in extent, (2) was less warm than, equally as warm as, or even warmer than the Current Warm Period, and (3) was longer or shorter than the Current Warm Period has been to date.
        http://www.co2science.org/data/mwp/mwpp.php
        If you do not know about this site and the number of studies showing worldwide existence of both the MWP & LIA, you have lead a sheltered life.
        [CO2Science.org has several thousands articles and papers from the scientific literatrue many hundreds establishing the global nature of the MWP and the benefits of increased CO2 on plant (and thus) animal life across earth. .mod]

    • Fascinating use of logic there.
      One study, finds that the medieval warm period had an impact in Europe, and from this you conclude that is MWP was confined to Europe.
      Perhaps you are once again seeing what you want to see?

      • The following is an extract from a fairly recent paper coauthored by no less a figure of unimpeachable authority for some than ME Mann:
        “Proxy temperature reconstructions indicate that the Medieval
        Climate Anomaly (MCA, roughly 950–1250 AD) was
        warm in many parts of the world (e.g., Hughes and Diaz
        1994; Mann et al. 2008, 2009; Esper and Frank 2009;
        Frank et al. 2010; Ljungqvist 2010; Graham et al. 2011).
        Natural radiative forcing associated with quiescent volcanic
        activity and relatively high solar output may have
        contributed to large-scale warmth (e.g. Crowley 2000). The
        solar forcing may also have modified the large-scale
        atmospheric circulation, inducing stronger mid-latitude
        westerlies in winter and further warming in substantial
        regions of the mid-latitude continents (e.g., Shindell et al.
        2001, 2003). In addition, the internal variability of the
        system, purely driven by its own dynamics, can also be
        responsible for some of the reconstructed changes, in particular
        at regional scale (Goosse et al. 2005a; Servonnat
        et al. 2010).”
        Notice that phrase : “large scale warmth”
        from: H Gosse et al Climate Dynamics, vol 39 pp2847-2866 (2012)

    • Medieval Warm Period was a regional effect
      =================
      Regional warming increases the global average temperature. It is a nonsense to suggest otherwise.

    • There are 6,000 boreholes scattered around the globe which may not provide accurate temperatures but show that the MWP was a global event. That issue cannot any longer be denied.

    • 6,000 boreholes, scattered around the globe clearly show that the MWP was a global event. No longer any issue there. Even the UN only claims our current warming (such as it is) goes by 800 years, and then adds, (with no justification, as usual) that there is a lower probability that it extends 1200 years. In any event, it’s common knowledge that each of the earlier warming periods (before the MWP) were warmer than the more recent one. The IPCC doesn’t even attempt to deal with that.
      Then there is the fact that our current warming (such as it is) began NOT in the mid 1800s, but, by definition, at the bottom of the Little Ice Age, which was in the mid 1600s. That’s 200 years of natural climate warming (since co2 had not begun to rise). But wait, even the most rabid scientists who are proponents of AGW admit that there was not sufficient co2 to impact the global temperature until about 1950, so that extends natural climate warming to 300 years, and also shows that MOST of our current warming was natural.

    • Jai Mitchell
      You might choose to call the AMOC a local phenomenon but it drives the climate of the whole northern hemisphere. It was the shut-off of the AMOC – a downstream result of Antarctic warming and ice sheet collapse during the Holocene inception – that caused the Younger Dryas which was not local – except if you call affecting the whole NH “local”. The AMOC and its inherent nonlinear instability due to the salinity feedback, in contrast to the lack of such instability in Antarctica, that results in the Bipolar seesaw characterized by sudden climate swings of climate in the NH and antiphase smoother oscillation down south.

  4. Ah, so the MWP did happen after all, but warming is still “bad”. Got it.
    But wait; since that warming was natural, then there goes the hockey stick.
    Oops.

    • The MWP was a natural variation, so a 2 deg temp rise from natural causes is GOOD(tm), where a 2 deg temp rise for anthropogenic reasons is EVIL(tm); just like natural CO2 is GOOD(tm), but anthropogenic CO2 is EVIL(tm).

  5. According to Skeptical Science and New Scientist, the idea of a Medieval Warm Period as warm as today is a “myth.” I doubt this study, or any study, will change their minds. True belief trumps observations for alarmists.

    • Louis Hunt: I’ve always found the following a good piece of real world evidence for the warming brigade to ponder. It’s easily found on the internet for anyone to check for themselves.
      The Schnidejoch pass, at an altitude of 2756 metres above sea level, is a pass in the Wildhorn region of the western Bernese Alps, Switzerland.
      Between 2003 and 2010 numerous archaeological finds were recovered from a melting ice patch in the Schnidejoch. These finds date from the Neolithic period, the early Bronze Age, the Iron Age, Roman times, and the Middle Ages, altogether spanning a period of 6000 years and providing some of the earliest evidence of Neolithic human activity at high altitude in the Alps.
      The abundant finds include artifacts made mainly from organic materials such as leather, wood, bark, and fibers.
      The site clearly proves access to high-mountain areas as early as the 5th millennium BC. The chronological distribution of the finds indicates that the Schnidejoch pass was used mainly during periods when glaciers were retreating.
      All this glacial advance and retreat over millenia with no industrialisation and fossil fuel burning!

  6. Great information but I find it interesting a uni from Australia studying caves in Scotland, great gig

    • As an Aussie taxpayer I’m not to sure that Scotland is in need of our research dollars to find out what is already known. Climate cycles in Australia interest me more.

  7. What I see from this, is an obvious case of miscounting rings and years. If you take figure 4 and align the peaks and troughs, it seems obvious that these various records are up to 300 years adrift from each other. However, this is likely – because if you have a very dry decade or century, there will be no rings to count.
    In what way did these scientists allow for this possibility?
    Ralph

    • In the above article it says “the more water in the peat, the slower the stalagmites grow.”
      I don’t understand that because stalagmites grow by calcium carbonate carried in rainwater through the peat and limestone above… The more rainwater, the more the stalagmites grow. Guess I’ll read the study.

      • The more rainwater, the more dilute the solution, and the lower the rate of deposition.

  8. The write-up is confusing to me. Is a “positive” phase associated with warming or is a “negative” phase?

    • It’s not the site. You must wait until the entire home page loads, including all the ads and videos, before you scroll and click. If you are seeing jumbled words, x out and re-load but with patience.

  9. Our results also reveal there was another persistent positive phase between 290 and 550, which coincides with the decline of Rome and a period of intensified human migration in southern Europe during the Dark Ages.
    ____________________________________
    Wishfull thinking, especially if the stalagmite chronology is not correct.
    Besides, the migrations into the Western Roman Empire in the 5th century were caused more by a decadant and pampered population refusing to give their taxes to the army, and even chopping fingers off their sons, so they could not be conscripted. The result was a underpaid, under equipped and largely mercenary barbarian Roman army whose loyalties were questionable.
    And then we have the wonderful Stillicho, a Vandal who became the highest ranking Roman army commander in the early 5th century. And Stllicho, being of divided loyalties himself, decided to pay tribute (protection money) to Alaric and his invading barbarian hoards, rather than attacking them – the infamous ‘pact of servitude’. The result being that Alaric could afford employ his own mercenaries and returned to sack Rome. Any nation that sinks to such a level that it has to employ immigrants with divided loyalties as its senior commanders and politicians, is doomed to certain failure – America’s presidency notwithstanding of course…….. 😉
    The bottom line here, is that there were a multitude of reasons for the fall of the Western Roman Empire, and anyone who merely pins these economic, social, political and demographic upheavals on something as simplistic as ‘climate change’ should be charged with fraud and imprisoned – a nice round twenty years sounds about right for the amount of money these guys are defrauding us.
    Ralph

  10. Not so fast. A new paper coming out by Karl et al, utilizing Viking Longship inlet data, shows the stalagmites were running 1.2C too warm. Nothing to see her folks. Move along.

    • Check that forthcoming Karl et al, paper again, Reg.
      I suspect you read it quickly – it probably says “stalactites”, and reports using the CAGW up-side down Tiljander methodology.

  11. They discovered one of the few places on earth not involved in the global treasure hunt for redistributing wealth based on climate over reach. It was an isolated cave in Scotland covered by peat. Luckily it was not classified as an ice cave.

  12. Medieval Warm Period could not have possibly occurred.
    Bad things only occur due to warmer temperatures, since there is no record of warmer temperatures causing bad things, warmer temperatures in the past could not have possibly happened. Actually since the ice age warmer temperatures have exclusively been shown to be beneficial thereby proving…….oh…. wait a minute.

  13. Australian taxpayers might be puzzled why their money is being spent on a study on the other side of the world. There are few paleoclimate studies of continental Australia. The place is drought prone so more information would be useful for planning water resources. When Jo Nova was asked why so few for Aust, she speculated that they are worried that they might find facts that dont fit the meme.

  14. @Resourceguy
    The other main contribution of the study is in the term “unusually prolonged” phases. Would someone get this finding to the honest modelers out there.

    The only honest modelers I know are making radio-controlled planes and boats…

  15. I am confused after reading that: it confirms the Medieval Warm period between 1000 and 1430 and a similar positive phase occurring between 290 and 550. So warm (and wet in Scotland) conditions during these positive phases. But then it also says that the negative phase between 600 and 900 brought warm and dry conditions in NW Europe. So it was warm (be it with alternating dry and wet periods) from 290-1430?

  16. The authors have commendably archived their data at NOAA very promptly, It looks to me like the data considerably overlaps previously published data from the same cave in 2002. There is more replication but nothing novel.

  17. Interesting. This study also confirms when the tites come down the mites go up… And if you need more proof the mwp wasn’t regional, come to Alaska where glaciers reveal old growth forest dated to 1170ad before the LIA wiped them out. Curious if anyone has drilled the thickest part of the Harding ice field to see if the forest is hiding there as well?

    • He hilariously quipped that the contention was that nothing at all had happened in the world until 1950.
      pished me keks.

  18. Why do you think that the PAST will recycle !!! The only real variable is the Sun !! The Sun has had increased energy output for the last 350 years. If the Solar Cycle is an indication, cooling is upon us; it will just take three years for the oceans to give up their energy….
    What ever you do, don’t look at Antarctica and the massive increase in ice sheets over the last 30 years. Do you really think that this doesn’t matter ????

    • Nonsense. The % change in solar irradiance caused by fairly regular (every century or so) solar diminution creates a statistical decrease in global temperatures that is less than that caused by both noise and sensor error. That said, understanding solar changes measured at the Top Of the Atmosphere is ongoing.
      http://phys.org/news/2015-03-fluctuations-solar.html

  19. If the MWP is dismissed for not being completely global (primarily due to lack of data), then how can they say we have global warming now, since we DO have thirty-year climate records for Antarctica that show absolutely no warming? Of course, then they would have to explain how a well-mixed gas in the atmosphere can result in only local warming.

    • jtom, you misunderstand. The MWP is not global because we haven’t measured everywhere. And AGW is global because we haven’t measured everywhere. This is perfectly consistent. For various values of ‘consistent.’

      • Yes. Not measured = cooler or warmer depending of on what answer is required to ensure nature is conforming to the known truths of the climate models.
        You understand well how the process of how CAGW works, my son. I see fame and fortune in your future.;-)

  20. OK, but in the Climate Science board game one tree ring trumps 50 stalagmites. Just sayin’.

  21. ‘It confirms that the during the Medieval Warm Period between 1080 and 1430 the oscillation index was in an unusually prolonged positive phase, which brings increased rain to Scotland and drier conditions in the western Mediterranean,’ says Baker, of the UNSW Connected Waters Initiative Research Centre.
    ‘Our results also reveal there was another persistent positive phase between 290 and 550, which coincides with the decline of Rome and a period of intensified human migration in southern Europe during the Dark Ages.
    ‘This was followed by a persistent negative phase between 600 and 900 which may have provided warm and dry conditions in northwestern Europe that made it suitable for westward expansion by the Vikings, although the precise timing of this event is contested.’

    Okay, now I’m confused. The Dark Ages was a time of cooler temperatures, right? So a persistent positive phase of the NAO produced both the Medieval Warm Period and the cool Dark Ages? Warm and dry conditions have been produced by both “prolonged positive” and “persistent negative” phases?

    • You are quite justified in your confusion. I made the same point above @ 2:47pm, but nobody seems to react to my comment. Are you and I the only ones who read this piece critically?

      • It could mean that NAO in negative phase produces more rain in SUMMER time (growth season and still warm enough) and the opposite with positive phase, although negative NAO means harsher winters in northern Europe? It depends where you are in Europe…

  22. Did we really need confirmation of the Medieval Warm Period?
    In other news, re cent research has confirmed the existence of the number four, the color red, oceans, and cable television.

    • You’ll find that this “recent research” was funded by the oil industry, so wont be believed by journalists or “progressive” types.

  23. A globally sinchronised MWP peaking during the high Middle Ages (ie after 1000 AD) has never been (to my knowedge) demonstrated. Sadly, this has become a common dogma of sceptics. I explain here:
    https://enthusiasmscepticismscience.wordpress.com/2013/09/09/millennium-idols-smash-the-hockey-stick-but-smash-the-others-too/
    See especially this much touted graph truncated to the millennium:
    https://enthusiasmscepticismscience.wordpress.com/2013/09/22/hubert-lamb-and-the-assimilation-of-legendary-ancient-russian-winters/2008_loehlemccullock_truncated/#main

    • The current warming episode is not uniformly global, the northern latitudes generally and certain N H regions showing more warming than the overall global average.
      I’m an interested layman but it’s my impression that the Lamb graph was necessarily a broad indication of a MWP and not adopted as an “icon” of scepticism whereas the Mann et al. ‘hockey stick’ definitely was, by the alarmists.

  24. Its noteworthy that the cooler temperatures during 600-900 AD drove the Vikings to aggressively colonise warmer countries. This could well be a sneak preview of that will happen on a much larger scale once the Holocene ends for good. Time to hone boat-building skills?

  25. ‘It confirms that the during the Medieval Warm Period between 1080 and 1430 the oscillation index was in an unusually prolonged positive phase..’
    In fact there was a sharp downturn in northwest Europe temperatures from around 1200 which would have to be increased negative NAO:
    http://www.nature.com/ngeo/journal/v6/n5/images_article/ngeo1797-f2.jpg
    ‘Our results also reveal there was another persistent positive phase between 290 and 550, which coincides with the decline of Rome and a period of intensified human migration in southern Europe during the Dark Ages.’
    Probably ~380 to 540 AD, and would have to be increased negative NAO as it was colder in NW Europe.
    ‘This was followed by a persistent negative phase between 600 and 900 which may have provided warm and dry conditions in northwestern Europe that made it suitable for westward expansion by the Vikings, although the precise timing of this event is contested.’
    The 8th century was likely the warmest part of the MWP for Europe, and would naturally have been increased positive NAO, but the century ended in an extreme cold event at 793 AD that would have emptied the Viking larders, with further cold periods in the late 10th and early 11th centuries:
    https://wattsupwiththat.files.wordpress.com/2014/12/esperetal2014b.jpg

    • Also worth noting is the extraordinarily severe cold events in the 1100’s, as noted in the Chronicle of Michael the Syrian, with frequent freezing of the Euphrates and severe frosts.

  26. When faced with hard facts like this, or the ancient dairy farms and vineyards in far north climes that now barely support lichen, Warmists wave off the data by claiming these were just bubbles of warmth, around which was freezing climates raged. Madness.

    • LarryFine

      When faced with hard facts like this, or the ancient dairy farms and vineyards in far north climes that now barely support lichen, Warmists wave off the data by claiming these were just bubbles of warmth, around which was freezing climates raged.

      Well, more troubling in their hypocrisy is the fact that – this year! – when satellites detected ONE single area over the middle of the north Pacific Ocean – undetectable until satellites started surveying the whole earth! – the climastrologists “averaged” that 5 month isolated single-hot-spot-over-the-north-Pacific-Ocean into the “hottest global average temperature of all time!” hyperbolic propaganda.

  27. Here is the best NH reconstruction which shows clearly the MWP.
    http://2.bp.blogspot.com/-4nY2wr6L-WY/U81v9OzFkfI/AAAAAAAAATM/NA6lV86_Mx4/s1600/fig5.jpg
    This is Fig 9 from
    http://climatesense-norpag.blogspot.com/2014/07/climate-forecasting-methods-and-cooling.html
    In conjunction with Figs 5 and 14 and 13 at the same link it is clear that we are now on the cooling side of the millennial temperature peak at 2003. see
    http://www.woodfortrees.org/plot/rss/from:1980.1/plot/rss/from:1980.1/to:2003.6/trend/plot/rss/from:2003.6/trend

  28. Reblogged this on Public Secrets and commented:
    Here’s one to upset the climate alarmists: the theory behind the fraudlent “hockey stick” was that the Earth’s climate was relatively stable until recently, when man began pouring CO2 into the atmosphere. That required the denial (oh, irony!) of cyclic warm and cool periods in the past, since such cycles challenge the theory of runaway warming. This study provides more strong evidence of one of these warm phases, the Medieval Warm Period. Perhaps the Pope should read this, too.

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