Medieval Treelines #1

Larry Huldén of the Finnish Museum of Natural Science sent me a nice note, mentioning:

I have met Phil Jones in Helsinki during a Climate meeting. My wife had a paper on mediaeval warm period in Finland in which she showed that oak (Quercus robur) forests occurred some 150 km north of the present time limits. Finland was then practically still in the Iron age. Phil Jones tried in many ways to explain that farmers themselves had planted the oak forests, which is complete garbage.

Medieval treelines are a very interesting topic. I’ve collected information on this from time to time and will post up some things that I’ve noticed. Here’s an interesting graphic from the Polar Urals site showing treeline changes. The altitude of trees sampled also changed dramatically over the centuries.
Urals treeline .

Briffa’s temperature reconstruction from the Polar Urals is a staple of multiproxy studies by the Hockey Team. It concluded that 1032 was the "coldest year of the millennium" – a conclusion which seems inconsistent with other evidence. I’ve done a lot of work on the Polar Urals and will mention it on another occasion. I’ve tried to get information on the altitudes of individual trees in order to see what effect the changes in altitude have had on site chronologies. Naturally I can’t get this information.


  1. John A.
    Posted Feb 12, 2005 at 6:06 PM | Permalink | Reply

    But don’t you see? Direct evidence is clearly wrong and multiproxy reconstructions are always to be preferred. Isn’t that so, Dr. Jones?

  2. Douglas Hoyt
    Posted Feb 12, 2005 at 7:04 PM | Permalink | Reply

    Actually, in the year 1035, in England, a frost on Midsummer’s Day was so vehement that the corn and fruit were destroyed. So there were cold years around at that time. Perhaps his chronology is off. Mine is based on what people living at the time said.

  3. Posted Feb 12, 2005 at 7:18 PM | Permalink | Reply

    These are pretty entertaining comments.

    First of all, “1032 was the coldest year of the millenium.” If you look at the blue Moberg pasta graph, 1032 is very close to the hottest year of the millenium. I would conclude that the probability that 1032 was the coldest year of the millenium is roughly equal to 1/1000. ;-)

    The Finnish medieval farmers-environmentalists that extended the forests 150 kilometers to the cold areas are also amusing. Maybe a prediction of this theory is that if you look at the forests with a good enough resolution, you will see the sentence “In the name of Paganic Gods, let’s make a carbon dioxide sink against the devil.”

    Maybe, the name ‘Finland’ is not from ‘Vineland’ because they were eating grapes at many places of the country. Maybe the origin is from “Phil-land”, to appreciate the first future historian Phil Jones who would discover that the medieval Finnish farmers had an environmentalist cult.

    I may imagine that the treeline changes might be one of the best available methods to determine the temperature in the past millenium.

  4. Peter Hearnden
    Posted Feb 13, 2005 at 4:04 AM | Permalink | Reply

    Oh, so good to see you reprint a nice ad hom(s?) at Dr Jones – you have those kind of standards here? OK, I’ll adhere to them!

    And the ‘new boy on the block’ Lubos is here – wow, he’s a real challenge! (ad hom btw – that’s OK right?) Well, whatever, what a gathering of the greats and the nit pickers :) (ditto)

    Sorry guys, time will tell, and it’s wont be a long time. If those of us who see appreciable anthro warming are right you’ll melt away like the snows, otoh, if you’re right then…the gloating will know no bounds and let the pollution of the skys rip! Unhappy days they will be (but, unless the laws of physics are wrong, or Krakatoa blows) it simply wont happen.

    I’m glad my mind and concience is clear. Oh, and if I’m wrong I wont spend fruitless hours trying to show otherwise.

    Now, you can all call me a commie, or a dangerious liberal leftie if you like :) Byeee

  5. Ferdinand Engelbeen
    Posted Feb 13, 2005 at 5:48 AM | Permalink | Reply

    Don’t forget volcanic eruptions, which may reduce temperatures during several years. The Pinatubo eruption did give a temperature drop of around 0.6 K during 2 years. More severe eruptions can cause a “year without a summer”, as happened in 1816, due to the Tambora explosion.

    Around 1100 (+/- 40 years, or 1050 in another reference), there was a large eruption in Eastern China: Baitoushan, see: of Volcanic Explosion Index (VEI) 7, comparable to the Tambora eruption and about 10 times more severe than the Pinatubo (VEI 6).

    Maybe that was the cause of the cold year 1032 in the mid of the warm MWP…

  6. Steve McIntyre
    Posted Feb 13, 2005 at 7:31 AM | Permalink | Reply

    Peter, the comment in question said that the hypothesis that Finnish farmers had planted the oak forest was “garbage”, but did not impugn the motives or credentials of Dr. Jones. I don’t see how the comment is an ad hom. BTW, in one of my posts, I singled out Jones for particular praise for his courtesy. In this case, I’m inclined to agree that the northward movement of oak forests in the medieval period was more likely due to climate than to Finnish farmers. Regards, Steve

  7. John A.
    Posted Feb 13, 2005 at 7:57 AM | Permalink | Reply

    Sorry guys, time will tell, and it’s wont be a long time. If those of us who see appreciable anthro warming are right you’ll melt away like the snows, otoh, if you’re right then…the gloating will know no bounds and let the pollution of the skys rip!

    Terribly sorry but that’s a false dichotomy argument if ever there was one (and rather revealing as well). Those who see "appreciable anthro warming" had better produce better evidence than the Hockey Stick and its derivatives, because I believe that good policy is derived from sound science, properly baselined and replicated by truly independent studies. If McIntyre and McKitrick’s work is correct and the Hockey Stick is false (and even the folks on realcimate have stopped bothering to defend it) then by no means does it advocate increased pollution or anything like it. Of course, in my opinion, the stupidest claim of all is the claim that carbon dioxide, the very lifeblood of the Earth’s biosphere, is a "pollutant". Wherever did that idea come from?

  8. Hans Erren
    Posted Feb 13, 2005 at 9:06 AM | Permalink | Reply

    The treeline graph reminds me of the sea levels as observed in The Netherlands in the last 3000 years.
    My graph is an enlargement from sheet 5 of the presentation on 28 november 2002 at the Met Institute in De Bilt by ir. Douwe Dillingh, director of the RIKZ (National institue for Coast and Sea, The Netherlands)
    Sheet 5 Title: Course of Global sea level according to Moerner

    Now, if sea level rise is an indication for global warming, then this proxy suggests an even warmer Medieval Warm Period…

  9. Jeff Norman
    Posted Feb 13, 2005 at 3:08 PM | Permalink | Reply

    Speaking of treelines…

    The September 2004 edition of National Geographic carried several dire articles detailing the perils of Global Warming.

    One of the excellent photographs in one of the articles was captioned as follows:

    “Tree rings like those in a hemlock log buried for a millennium and uncovered by Alaska’s retreating Columbia Glacier, give geologist Greg Wiles (right) an annual regional temperature record from A.D. 585 to the present.”

    IIRC the photo shows a person, presumably Greg Wiles, boring a core sampler into the aforementioned log.

    Immediately behind the person is a striking view looking upstream at the glacier in its barren, rocky valley. There is no sign of any living tree or evidence that living trees ever grew there aside from the hemlock log featured in the caption and photo.

    Unless the glacier devised some clever way of grabbing the tree and dragging it to higher elevations (not likely), the tree must have come from that elevation (only slightly more likely) or from some higher elevation.

    This log was “buried for a millennium” after growing for ~415 years. While “millennium” may be loosely bounded, this seems supportive of a Medieval Warm Period and a Little Ice Age. I thought these were “supposed” to be climate events limited to Europe and the North Atlantic. I’ll go recheck my atlas but I don’t believe Alaska is in either place.


  10. Steven Holloway
    Posted Jul 21, 2005 at 10:02 PM | Permalink | Reply

    It was snowing in the middle of summer worldwide 6 years after the erruption of Krakatoa in 1894. This was a 12 square mile island reduced to 7 square miles after the erruption. Like Pinatubo, which spewed 20 million tons of HS into the upper atmosphere reflecting 3 per cent of the suns energy, Krakatoa resulted in much greater effect. How many volcanoes like these would be needed to start another ice age?


  11. TCO
    Posted Sep 11, 2005 at 3:21 PM | Permalink | Reply

    To what extent are altitude or northern latitude of trees (or other species) used as proxies. for instance in any of the meta-analyses? Ever published as series on their own for temp reconstruction?

    And I repeat my question of how reasonable it is for a forest to move 150KM. What is the speed at which these things occur? Let’s at least double check and not jump up and down at each thing that “helps our cause”. Our cause is truth.

  12. Steve Sadlov
    Posted Feb 1, 2006 at 6:39 PM | Permalink | Reply

    Oaks are highly successful at reproduction. Their spread is aided greatly by animal transport of seeds. In a humid continental climate I would not see a 150 Km increase in range within 300 years to be difficult to accomplish.

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