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Crock of the Week – “The Medieval Warming Crock”

Written By: - Date published: 5:55 pm, June 26th, 2010 - 25 comments
Categories: climate change - Tags:

Andy said in a comment

It is possible to accept that there are issues with the science, in particular the Hockey Stick, and still be aware that continued emissions of greenhouse gas emissions may cause us problems.

I was thinking about writing a response. But this Crock of the Week explains the issue quite more clearly than I can. But the basic issue as far as I can see is that many CCDs appear to be religiously attached to early work done on ‘global’ temperatures that were almost entirely euro-centric. They ignore the evidence that has subsequently been gathered amongst many scientific groups using a variety of methods that substantially supports Manns early (mid-90’s) ‘Hockey-Stick’.

I get the impression that most CCDs don’t keep up to date with the emerging scientific picture. They prefer clinging to old data rather than embracing the new.

Wikipedia has a good article on the subject of the MWP in the IPCC reports. Notice the dates.

25 comments on “Crock of the Week – “The Medieval Warming Crock” ”

  1. zelda 1

    You mean emerging data like D.W., Rosenthal, Y. and Linsley, B.K. 2009. 2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool. Nature 460: 1113-1116.
    Or in their words Reconstructed SSTs were warmest from AD 1000 to AD 1250 and during short periods of first millennium.

    • lprent 1.1

      I will have a look at it later and offer my opinion on it. Been cleaning today and I’m knackered

    • lprent 1.2

      I’m not going to look this up after the comments I made below. You’re consistently misinterpreting the papers. Seems like a lot of effort to educate a fool yet again

      Do you have a link?

  2. zelda 2

    or if 2009 wasnt recent enough
    Multi-Millennial Fire History of the Giant Forest, Sequoia National Park. Fire Ecology 2010
    A 3,000-year record from 52 of the world’s oldest trees shows that California’s western Sierra Nevada was droughty and often fiery from 800 to 1300, according to a new study led by University of Arizona researchers

        • lprent

          Interesting – but aren’t they reporting on a proxy for the dryness of the local climate?

          What does that have to do with temperature? There is only a loose correlation between temperature and precipitation when you look at where the arid and semi-arid areas are.

          For example, Auckland is hell of a lot warmer on average than Christchurch. But Christchurch has rain shadow effects from some ruddy great big mountains with the wcurrent prevailing winds. Incidentally, You also don’t have to go back far in the geological record to show that shifts in average wind patterns have changed the precipitation levels in the past.

          Read what the papers synopsis says rather than what you want to read into it. Politely saying you’re a fool again..

          • zelda

            What a lot of garbage. Can you even read ?

            The other giant sequoia fire histories (tree rings and charcoal-based) were significantly (P < 0.001) correlated with the Giant Forest fire frequency record and independent climate reconstructions, and confirm a maximum fire frequency during the warm and drought-prone period from 800 C.E. to 1300 C.E.

            The warm AND drought prone period.

            Ill put it in simple terms:
            Tree rings can be dated
            Charring shows when fires occurred on particular tree rings and hence dates
            Tree rings can be used as drought proxies
            hence droughts can be be dated to when fires were more frequent
            Different tree rings in California can be used as temperature proxies ( tree rings used in Hockey Stick proxies!!!)
            hence temperatures can be dated
            hence- warm and drought-prone period from 800 C.E. to 1300 C.E

            Stick to programming and leave the climate science to the experts

            • lprent

              If you look carefully (I realize it is very hard for you to look at the relevant details) at the precis the reference to temperature was to do with the future – not the past.

              The proxy they were examining in the papers was to do with dryness, not temperature. I’d suggest you reread it with somewhat more concentration. Sure – there are probably other papers on temperature proxies – tree-ring growth rate studies. However you didn’t present those, what you presented was a paper on lack of precipitation affecting burn-offs. That has nothing to do with temperature unless you can show a relationship between the two.

              From your lack of grasp of relevant details in this post, I’d suspect that you’d have problems with most intellectual activities that involve details. Pretty damn sloppy. Pretty obvious you know absolutely nothing about the physical processes involved in climate. Perhaps you should go and study it. Start with the basics – the scientific method.

              • zelda

                You mean the part that states 800 CE to 1300CE refers to the future ?
                Tree rings that go back 3000 years do that ?
                The hole you are digging is just getting deeper as your accusations become more wilder.
                Refer to Fig 8 Graph C which shows temperature and fire frequency plotted together for the last 2000 years.
                The temperature during the California Medieval period being warmer than the period before 2000.
                Interestingly it wasnt uniform during this nearly 500 yr period, just as you point out using proxies from NZ from the same period
                The future of course will reveal itself in good time,

                • lprent

                  You’re a bozo. Quote the part of the synopsis that states the burn data relates to temperature in the past.

                  You will find that they looked at past temperatures – but do not say what they are. They correlated the fire frequencies with drought.

                  There are two sentences of relevance.

                  Sequoias can sustain very high fire frequencies, and historically they have done so during warm, dry times. We suggest that preparation of sequoia groves for anticipated warming may call for increasing the rate of prescribed burning in most parts of the Giant Forest.

                  You notice that they haven’t correlated that the warm periods are the dry periods? That is because it is possible to have dry cold periods. This happens in many climates, for instance the Gobi, the coastal deserts of Peru. etc

                  You’re just reading what your fantasies are into the abstract. The full paper may have more information. However they will usually state the conclusions in abstracts pretty clearly.

                  As I said before, you’re too much of a fool to look at science. Look at what is said – not what you wish to read into it.

  3. Adrian 3

    In 1540 the Rhine dried up so much at Frankfurt that the locals including women in long dresses were able to walk across the river and picnic on the other side. This warmth continued until the late 90s when it turned cold and vintners in France could not ripen grapes until about 1612. The most reliable records are from monostries that had vineyards. It is not the current warmish weather we should fear but the “correction” when it comes.

    • lprent 3.1

      Yeah the was a European mwp. There just wasn’t a global one. That was the point of the post.

      I think that you have simply missed the point – perhaps you should read the post and watch the video fir the first time?

  4. Andy 4

    The video doesn’t really explain the core argument of the IPCC that the MWP was not, according to them, a global phenomena.

    We do know that there is plenty of evidence of warmer times – e.g the medieval villages on Dartmoor, the evidence of grape growing in Scotland, the viking graves in Greenland.

    The video brushes off the viking argument but doesn’t really explain why it is not valid.

    Also, the Mann hockey stick graph shown in the video clearly shows proxy data (blue) spliced into instrumental data (red) but makes no attempt to explain why this is a valid technique, and what the “divergence problem” is.

    • lprent 4.1

      The mwp is valid and well documented. However only around the north Atlantic. That is not global. It is wishful thinking to project that to the rest of the world.

      There are other regional warm spots at various times in different parts of the world. All that takes is a shift in the air or water currents. There have been global shifts that are documented which are probably to do with the sunspot activity (have a look for a post I did a few weeks ago). Look at the reasons for the lack of a sunspot record prior to 1850 in the wiki article and at the sunspot site.

      What we don’t see in the available evidence worldwide is a big shift in tempatures across all regions in anything like the size that can be seen in the north Atlantic at the time of the european mwp. The reason is most likely because the gulf stream concentrates heat effects abnormally. A small effect at the tropics becomes a big deal in the near arctic because of the shape of the Atlantic ocean.

      I wrote a post about how it causes the weirdness of north europeans neotinic features last year which are also caused by the weirdness of the north Atlantic. But it is a teeny spot on tbd world. Not that important in climate terms.

      • zelda 4.1.1

        Thats a far too covenient way of explaining it away, only recent of course as the Climategate emails show they have been on a mission to ‘get rid’ of the MWP.
        And what explains the ‘little ice age’ that followed it in Europe up to the beginning of the industrial revolution, which was replicated in little old NZ .

        • lprent

          Umm from memory what you are referring to is cave stalagmites. Always amuses me how CCDs never bother to cite and link to their sources when they make bold assertions. But lets have a look at a number of papers over the years on NZ temperature proxies helpfully put together and labelled with a spurious MWP – see here. I’m using a denialist site simply because it is amusing and they have collected the studies together obviously without bothering to read them.

          Lets look at the MWP, which by your logic should show in NZ just as you’re asserting the mini-ice age did – right? After all they are ‘global’ events.

          Now if you have a look at these studies and the dates on the charts – then compare it to the classic IPCC MWP chart from 1990 http://en.wikipedia.org/wiki/File:Ipcc7.1-mann-moberg.png That has a sharp rise just after 1000, peaks at about 1200 and drops massively from 1300 to 1400.

          Now look at the 1979 study, where the temperature proxy shows a significant rise in temperature between 1300 and 1400, and drop off between about 1380 and 1450 – the exact opposite of what happened in the north Atlantic.

          Ok – maybe just sampling errors or something. Lets see the others. The 2004 study in Waitomo. The graph has a lousy scale, but the text says “The Medieval Warm Period occurred between AD 1100 and 1400”. Umm there is that 1400 again. It looks like the drop in temperatures in NZ was at least a 100 years later than in the north. Moreover, the shape of the drop looks different. I wonder why? Maybe they aren’t the same event as that in the north?

          The next study in 1998 at Lake Tutira uses a different proxy, sediments from storms. That shows the NZ MWP as being at 800-1000. WTF? Perhaps we are looking at different events inside NZ? Ok it was data from a single site. Maybe they don’t have a similar site for between 1200-1400.

          The next study back on stalagmites published in 2008 looked at several sites at east north island. That shows that the warmest period was between 900 and 1000 AD with a marked fall by 1100, and an abrupt drop at about 1300. Ummm so it was higher than the north Atlantic earlier and fell at the right period. Uh – but what about the 1979 study showing the rise AFTER 1100?

          Ok the next one from the same team in 2008 looking at the western south island. Damnit the picture is different again!!! Sure it peaks at before 1000AD (but didn’t the northern Atlantic only start rising at 1000AD?) But there is a massive drop by 1100 – which is different to any of the others and it is bloody cold by 1300

          You will see the same type of temperature variations for the ‘mini-ice-age’ as well. Except there the time variations are more in the order of 50 years or so.

          This is a long and complicated way of saying that you are a fool wasting my time. Read the bloody papers and charts. Ignore the labels that people tack onto the charts. And welcome to the earth sciences variations between sites. This is what makes getting an accurate temperature record hard – even in a teeny little set of islands

          • zelda

            From Sceptical Science -Medieval Warm Period spanned 950 to 1250 AD
            but why wouldnt NZ have a slightly different time scale to Europe.
            As well the studies will allways show significant scatter especailly comparing diiferent types of proxy.

            • NickS

              but why wouldnt NZ have a slightly different time scale to Europe.


              If an event is global, typically that means it’s occurring across the globe, in the same slice of time, not decades, let alone centuries apart, since that would indicate regional patterns. Which in some case can be used to work out if there’s long term regional climate cycles, and provide evidence for long term climatic cycles like ENSO.

  5. Rich 5

    Seems like a lot of effort to educate a fool

    Right. Whatever real science you produce, the idiots will produce some selectively quoted facts to try and refute it.

    Better to just ban them all.

    • lprent 5.1

      🙂 Not worth it. One of the issues about this whole debate is that people need to be educated. You can see how frustrating this must be for real scientists explaining that there is little certainty in earth sciences until you get a whacking great pile of samples from a lot of sites.

      I’m willing to bet that in the selection above that almost all of the effects are local to each site. This is why the 1990 MWP/MIA chart was a compilation of the available data at the time.

      As the number of sampled sites outside of that peculiar north Atlantic area increased, the pattern for that regional area dissipated on a global scale. It wasn’t particularly evident in other regions of the world. It was a local climate – not a global one.

      But of course it made a nice story for the scientifically lazy, complete with little homilies about vikings….. But it has little to do with global climate changes.

      That was the point that Peter Sinclair was making in the video. All of the global information supports the overall picture of the ‘hockey-stick’. That is an alarming global warming in the industrial period with a strong and direct link to the emissions of greenhouse gases.

    • Macro 5.2

      I agree. Trying to discuss anything with them is simply wasting breathe. They don’t want to know, and they always drag up the same old arguments from the denier blogs that have been debunked time and again. Almost every so called “argument” (eg Zelda’s above) is based on a selective extraction of the material that is taken completely out of context and distorts to heck the intention of the paper or published academic article. “Cherry Picking” is scientifically inexcusable, and yet these clowns think they know better than those who publish and subject their work to the criticism of global academia! And then they have the gall to castigate any scientist who calls attention to AGW as “Alarmist”. They are simply wearisome.

      Anti spam says “irritating” – couldn’t have said it better.

      • Beeble 5.2.1

        Is anyone able to add anything to the Amazongate story that is circulating the web right now?

        Despite the “apology” from the Sunday Times, there appears to be no peer-reviewed science backing up the 40% reduction in Amazonian rainforest cover that may be caused by climate change.

        Given that the report on the Amazon was sourced from WWF reports, and that the WWF are set to make $60 billion dollars in carbon credits from a purchase of a remote part of the Amazonian rainforest that is in no immediate danger of logging or exploitation, one could safely assume that there is fairly major conflict of interest here.

        Especially, given the fact that NZ will be robbing pensioners from July 1st to pay carbon criminals, it would be really good to get a handle on this situation really soon, because at the moment it’s looking like a fairly poor outcome for the WWF..

  6. Bomber 6

    Well argued lprent

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