Medieval Treeline in Finland

Kultti et al. [Holocene 2006] has just been published in Holocene, showing higher medieval treeelines in northern Finland (27 deg E). This is consistent with the more northerly distribution of oak in medieval Finland reported in Hulden [2001] discussed here and adds to the growing inventory of articles both demonstrating higher medieval treelines and using this to estimate MWP temperatures locally higher than at present, some of which I’ve posted about from time to time Medieval Category. These “local” results from treelines are not limited to the north Atlantic and Greenland, but extend to the Sierra Nevadas (117 W), Sweden, Finland, Polar Urals (65 E) and a Siberian transect (90-100E). I’ll add a comment on Chinese proxies of this type. Kultti et al. also consider information from other proxies and report similar results for all proxies EXCEPT the tree ring width chronology of Helama et al [2002]. Here are some extended quotes.

Kultti et al. report that treeline is a proxy for July temperature, They state that:

During the “‹Å“Mediaeval Warm Period’ the distribution area of pine was 7200 km2 more extensive than at present, and pines were growing at 40-/80 m higher altitudes. For this period, the mean July temperature reconstruction shows /0.55 deg C shift compared with the present….

Their survey of similar results mention:

At the same time, presence of pine has been detected c. 100 m above the current pine limit in Sweden (Kullman, 1998) and 100/140 m above in the Kola Peninsula (Hiller et al., 2001). The same pattern at the upper larch (Larix sibirica) timberline on the Eastern side of the Ural Mountains has also been found; from c. 1000 cal. yr BP to c. 600 cal. yr BP numerous megafossils have been found from above the present tree limit (Shiyatov, 1993). Assuming a lapse rate 0.6 deg C per 100 m, these finds correspond with a shift of/0.6-0.8 deg C in temperatures.The conifer limit during the “‹Å“Mediaeval Warm Period’ appears to have been well above the present conifer limit in extensive areas in Fennoscandia and Russia. This suggests that the climate during the “‹Å“Mediaeval Warm Period’ was even warmer than during the twentieth century in northern Fennoscandia. Most of the quantitative reconstructions from Finnish Lapland (Figure 4) show warmer than at present at c. 1000 years ago (Korhola et al., 2000, 2002; Seppa and Birks, 2001, 2002, Seppa et al., 2002). Only reconstruction made from tree-ring widths suggests colder than at present mean July temperature (Helama et al., 2002)

Their Figure 4 shows the following other reconstructions. The Korhola proxy is used in Moberg et al 2005, where it contributes to the warmish MWP in Moberg. However, this proxy in Moberg is swamped by two non-normal series – the offshore Oman coldwater diatoms and Agassiz melt, discussed elsewhere.

Original Caption. Figure 4 The mean July temperature anomalies from present in the reconstructions from Finnish Lapland. Reconstruction a shows minimum shift in mean July temperatures between 8300 cal. yr BP and present based on this study. Reconstructions from lake sediments (b, c, d, e and f) show deviations from the mean of three uppermost samples. In reconstruction g non-overlapping 100-yr mean deviations from the twentieth century are shown. Reconstructions b and c are from Tsuolbmajavri and d, e and f from Toskaljavri. Reconstructions a, b, c, d, e and f are elevation adjusted for land uplift. Numbers in parentheses in reconstruction a refer to the site number in Table 2

Kultti et al [2006] was submitted on 2 February 2004; the revised manuscript was accepted 19 October 2005. Thus, its submission long preceded the May 2005 data for consideration in the IPCC First Draft and the acceptance long preceded the December 2005 cut-off data, in marked contrast to (say) Wahl and Ammann 2006 or Osborn and Briffa 2006, which met neither date. I wonder if Kultti et al will be incorporated in IPCC 4AR.

Kultti, Seija, Kari Mikkola, Tarmo Virtanen, Mauri Timonen and Matti Eronen, 2006.1Past changes in the Scots pine forest line and climate in Finnish Lapland: a study based on megafossils, lake sediments, and GIS-based vegetation and climate data, The Holocene 16,3 (2006) 381-/391.
Huldén, Lena, 2001. Terra 113, 171-8. Oak barrels and the medieval warm period in Satakunta [Finland] (Finnish) .


  1. beng
    Posted May 16, 2006 at 10:16 AM | Permalink

    Fig4 image doesn’t show.

  2. John A
    Posted May 16, 2006 at 2:50 PM | Permalink

    I seem to remember Larry Hulden asking Phil Jones about these medieval tree lines, with Jones earnestly lecturing Larry that 11th Century Finnish farmers were deliberately planting oaks further north….

  3. beng
    Posted May 16, 2006 at 2:51 PM | Permalink

    The Korhola Chironomids differ considerably from Seppa and Birks Chironomids & from most of the others (but it does show a MWP).

    From these 10000-yr records, the magnitudes of the MWP, LIA, & current warmth are all unremarkable. How remarkable.

  4. John Hekman
    Posted May 16, 2006 at 5:12 PM | Permalink

    Is it possible that there is a significant time lag between warming and higher tree lines? If that were the case, then it could be argued that in fifty or more years, say, the tree lines will be higher than they were during the MWP as a result of today’s “unprecedented” warmth.

  5. Pat Frank
    Posted May 16, 2006 at 5:39 PM | Permalink

    #4, presumably so. However for there to be trees in 50 years, there ought to be sprouts now. After all, we’ve had an unprecedented temperture rise at least since 1975. They’ve had 30 years of increasingly luxuriant growth conditions. So, has anyone noticed a higher sapling-line limit?

  6. Larry Huldén
    Posted May 17, 2006 at 3:59 AM | Permalink

    #2 It was my wife (Lena) who had this dispute with Phil Jones!
    Insects or diatomes in lake sediments are definitely not reliable as indicators of (summer) temperatures. 55 years (1945-2000) statistics from Finland from 16 different waters show that 10 years mean temperature of water surface (1 meter) may suddenly (“chaotically”) jump up or down 1-2 centigrades in relation to air temperatures. This depends on longterm shifts in dominating wind direction causing shifts in wind stress on lakes. As a consequence you can never estimate the air temperature deviation from water temperatures in the past. This must be the cause of difference in the presented results.
    I had a presentation of this in a climate meeting in Italy in 2001 and tried to publish it in The Holocene. Some referee said that he had the impression that the diatoms and insects living in water correlate better with air temperature than with water temperature !!!! After that I realized that I could never get it published.

  7. Tim Ball
    Posted May 18, 2006 at 1:01 PM | Permalink

    I published an article in Climatic Change Vol 8 (1986) titled “Historical evidence and climatic implications of a shift in the boreal forest tundra transition in central Canada.” It showed a shift of approximately 200 km in 200 years in one of the harshest growing environments in the world. This was a shift in latitude and like a shift in altitude appears to be mostly temperature related. Generally it is shown that the treeline coincides with the 10°C summer isotherm. There are some who argue that the isotherm is a response to the treeline not as generally assumed. The movement of 200 km in 200 years underscores the rate of natural change in response to climate change. Even if 50% wrong we still have a 100 km shift in 200 years. There is no evidence of anyone planting trees in this area and during this period.

  8. Steve McIntyre
    Posted May 18, 2006 at 1:05 PM | Permalink

    If one had to pick a proxy to show low-frequency changes, it’s hard to argue against treelines.

  9. jae
    Posted May 18, 2006 at 2:25 PM | Permalink

    #7 I presume the shift was toward higher latitudes. #8. I can’t see much argument against the use of treelines, either.

  10. Tim Ball
    Posted May 19, 2006 at 7:14 AM | Permalink

    #9 Yes, the shift was to higher latitudes, although from Artillery Lake to the Coppermine River the treeline runs more north and south becuase of the influence of the Rocky Mountains on the standing planetary wave of the circumpolar vortex. In this rgion the expansion was less, but still an ‘expansion’ indicating warmer. Samuel Hearne who made the map with the treeline of 1772 noted “wind blasted” clumps of dead trees well north of the treeline of his time. He asked his Indian (Chipewyan) guides about this and they said their ancestors said the treeline used to be further north. Hearne noted this was clear evidence that the world had become colder – a very accurate observation reflecting the conditons of the lowering of temperatures from the Little Ice Age following the Medieval Warm Period. Hearne was well qualified to make these observations. He was a first class biologist (naturalist) whose observations and reports on Arctic Fox are still considered definitive and among the best. He knew all the Latin names for the plants and clearly delineates “the wood’s edge” on his map that is in the Hudson’s Bay Company Archives in Winnipeg.

  11. TCO
    Posted May 19, 2006 at 7:28 AM | Permalink


  12. TCO
    Posted May 19, 2006 at 7:30 AM | Permalink

    hard to measure?

  13. Steve Sadlov
    Posted May 22, 2006 at 1:11 PM | Permalink

    RE: #5. In terms of the Alpine tree lines, the only saplings I see are the ones underneath existing well established trees. I see no saplings at any higher elevations. This is based on an observation made at 2000 Z yesterday, at the tree line, near 39N, ~ 119W. Also of note, given the extreme snow pack (only just now receding at such elevations) this year, saplings have been severely stressed.

  14. Dano
    Posted May 22, 2006 at 4:59 PM | Permalink


    Generally there is a successional order, as trees are dependent upon multiple factors for survival, and understory vegetation gives a better chance at survivorship, thus trees go last. That is: saplings absent expected understory vegetation have a lower chance of survival (fungal communities, bacteria, organic matter in soil). That said, there is no reason to believe an entire community will increase in elevation intact, as current evidence may indicate.



  15. Steve Sadlov
    Posted May 24, 2006 at 10:45 AM | Permalink

    RE: #14. Some nice tap dancing in that paper, I must say. A real piece of work.

  16. Dano
    Posted May 24, 2006 at 12:56 PM | Permalink


    Thanks for sharing the specifics. Let us know whether your comment gets accepted.



  17. Willis Eschenbach
    Posted May 24, 2006 at 3:10 PM | Permalink

    Re 16, Dano, now that you’re on the other side of the fence, perhaps you’re actually starting to get it. Steve Sadlov makes a comment like you have often made, with no specifics at all … I can understand your frustration.

    However, you said much the same to Steve on another thread, your comment was “Let me know, willya, when your groundbreaking paper gets accepted? Thanks!”

    Perhaps the experience of having someone do the same to you will make you stick to specifics … I hope so.


  18. Willis Eschenbach
    Posted May 24, 2006 at 4:43 PM | Permalink

    Re 14, Dano, thanks for an interesting post. However, I’m not sure I understand it. You say:

    Generally there is a successional order, as trees are dependent upon multiple factors for survival, and understory vegetation gives a better chance at survivorship, thus trees go last. That is: saplings absent expected understory vegetation have a lower chance of survival (fungal communities, bacteria, organic matter in soil). That said, there is no reason to believe an entire community will increase in elevation intact, as current evidence may indicate.

    The part I didn’t understand is this. If the saplings likely won’t survive without the understory, and there is no reason to believe the “entire community will increase in elevation intact” (I assume this means trees and understory), then …

    … how does the treeline ever increase in elevation?

    Like I said, I’m not sure I understand your post.


  19. Dano
    Posted May 24, 2006 at 5:42 PM | Permalink


    Hi willis:

    often the treeline increases in concert with understory vegetation, but it doesn’t always have to be that way. Survivorship increases with understory veg., as mychorrizal fungae are more likely to be present, beneficial insects have cover, temps are moderated, organic matter adds nutrients, etc.

    The point above was that one data point is not enough to make an assertion, due to the complexity and interconnectedness of interactions. Certainly if there is sufficient organic matter and nutrients in the soil seeds can germinate and grow without companions. In that area that Steve mentions, the Italians of the late 1800s drove their sheep over the Sierra to escape drought and brought grasses and other exotics with them, so the dynamics of sites in that area have changed considerably.

    BTW, I’ve snowshoed over Carson Pass on Mem. Day weekend before – there’s often lots of snow in that area.



  20. Steve Sadlov
    Posted May 24, 2006 at 7:28 PM | Permalink

    Carson Pass is a bit higher than the site I was at. I was nearby Donner Pass.

  21. Ed Snack
    Posted May 24, 2006 at 9:12 PM | Permalink

    It would seem that treelines are like just about any other proxy, subject to many confounding factors. It is also worth noting that there has been a generally acknowledged increase in temperatures since the LIA (regional or otherwise, being neutral here) and that this has been underway for a reasonable period, there should be one would think at least some evidence for an increase in treeline altitudes.

    Now this may be (pace Dano) not necessarily the trees themselves in all (or even many) situations but at least in a broadly defined “treeline” including understory and possibly soil composition. And (nod to Dano again) at least some sites will have been modified since the LIA times leading to further confounding factors, but at least in theory studies could be made to see if such movements are occurring. After all, assuming that there was a MWP (and I think everyone acknowledges such a thing at least on a regional basis) and that treelines were higher in some places at that time, these treelines had to expand to those altitudes in a relatively short period as well.

    Admittedly this is a crude bit of logic and please correct it if wrong, but would not one expect to see signs of a recovery in the treelines to MWP like levels starting to occur ? These signs may be subtle so maybe studies such as those cited above may not have noticed (or looked for) such evidence.

    I noted these references in a paper on simulated changes:

    Several reports show an increased growth of established trees and saplings above the treeline, which, in places, has increased the tree limit by ca. 100 m (Kjàƒ⣬lgren and Kullman 1998, Kullman 2000, 2002b). Fast-growing saplings have also occurred more than 300 m above the tree limit (Kullman 2002b), and these advances are attributed to a series of warm summers and mild winters (Kullman 2001). This may be a general phenomenon in sub-Arctic and Arctic sites, as a widespread increase in shrub abundance, covering more than 320 km2, has been shown from Alaska (Sturm et al. 2001). Global meta-analyses have also documented significant range shifts toward the poles or toward higher altitudes for many organisms, and a large part of these changes may be attributed to increased global temperatures (Parmesan and Yohe 2003, Root et al. 2003).

    So such work is being done, and maybe results are out there. It would useful to follow up these references and others. An informed discussion is always helpful. Thanks to those who have contributed so far on this thread.

  22. Steve McIntyre
    Posted May 24, 2006 at 11:34 PM | Permalink

    #21. Ed, there’s lots of evidence of rising tree lines. Some authors argue that the response of tree lines is highly lagged and present tree lines do not reflect present temperatures – presumably the saplings at higher elevations when grown will. The treelines are not a real sensitive measure on decadal scales. But for “low frequency” which is the current buzzword, if they haven’t reached medieval treelines yet, then there must have been some medieval interval which was warm.

  23. Jean S
    Posted May 28, 2006 at 5:36 AM | Permalink

    (#2,#6) Not exactly related, but Larry’s famous wife Lena is now even more famous. Her new research on malaria in the 18th century Finland (Finnish archipelago to be exact, I think) was covered today by the main newspaper in Finland, Helsingin sanomat (article here $$$). Nice job!

  24. Ken Robinson
    Posted Jul 6, 2006 at 3:53 PM | Permalink

    For those who haven’t seen it, Roger Pielke’s site has an interesting paper from Harvey Nichols on Arctic treelines here.

    He also tentatively identifies potential correlation between treelines and sunspots.


  25. jae
    Posted Jul 6, 2006 at 4:25 PM | Permalink

    24, Ken: Very interesting paper, indeed. I was especially interested in this statement:

    The changes now apparently beginning may eventually prove to resemble 1) the minor wanning of the late 19th- early 20th century, or 2) the more substantial medieval wanning (roughly 600-1600 years ago), both with some degree of written record and cultural response, or possibly 3) the much longer and more dramatic warming of the middle of our current interglacial period, from 3000-4000y earsa go backt o 8-9000+ yearsa go, known as the Hypsithennal episode( Lamb, 1977). The formerc hangesin the arctic tree-line in Canadac ausedb y these three different warming episodes provide us with a long perspective from which to view the current effects (Nichols 1975). In episode 1), dwarf spruce trees developed upright leaders for severald ecadesb eforeb eing forcedb ack downt o a partially prostrateg rowth fonn by colder climate (Jacoby p.c., d’ Arrigo and Jacoby, 1993). During episode 2), the arctic tree-line extended some tens of kilometers northwards (Bryson et al. 1965; Nichols 1967b, p. 185, 1975, p. 66), then retreated during the late medieval Little Ice Age. The greatest biotic effect was registered during episode 3), the Hypsithermal, when summer temperatures 3-40 higher than the mean pushed the central Canadian tree-line 3-400 kin north of present limit, at a rate of 100-300 metersp er year (Nichols 1967b,1 975;M acdonalde t al. 1993). Similar foresta dvances w ere registeredi n Siberia( Levskovskaya1, 976). In Canadaa, n areao f about5 00,000s quare kilometers of former tundra was afforested during this episode, over several centuries (Nichols 1976).

    (don’t know why it copied so poorly, though)

  26. jae
    Posted Jul 6, 2006 at 4:35 PM | Permalink

    Another interesting statement in the comments section:

    I am certainly quite concerned about the well-known “hockeystick’ graph which so diminishes the Medieval Warming and the Little Ice Age, especially as reflected in the arctic.

    Let me know if this helps.



    Harvey Nichols, Ph.D.
    Professor of Biology.
    Tel. 303 492 5652 (W), 303 494 2700 (H),
    Fax 303 492 8699

    Could this be yet another scientist who does not reflect the “consensus” on AGW?

  27. Steve McIntyre
    Posted Jul 6, 2006 at 6:07 PM | Permalink

    More from this interesting quote:

    The arctic tree-line in the Northwest Territories (NWT) of Canada has only just started to react to warming, so pollen release and cone formation is very apparent, but new spruce seedlings are sparse and are only a few metres distant from their parent trees. By contrast, in the Hypsithermal (the European “Climatic Optimum”) the tree-line was advancing at rates of 200 – 300 metres per year in NWT, attaining northward displacements of ~400 km beyond modern tree-line by 7 – 6000 BP. In the Medieval Warming between ~ 1500 BP and 700 or 600 BP the NWT tree-line extended ~70 km beyond modern. I keep wondering whether there has been too little time for the arctic tree-line to advance noticeably since ~ 1980, at a rate similar to the above, or whether it is possible that the previous warmings were even more substantial in the arctic than we currently recognise. Recall that the pre-Hypsithermal landscape was devoid of trees and their associated mycorrhizae, while now there are uncounted numbers of dwarf trees scattered all over the Low Arctic, ready to colonise the tundra.

    I wonder whether the Hypsithermal warming was even more massive than we currently think, at least in the far north? At the same time the change over a 20 year interval (1970s to 1990s) from dwarf black spruce infertility to fertility at sites up to ~ 250 km beyond modern tree-line is very apparent.

    I am certainly quite concerned about the well-known “hockeystick’ graph which so diminishes the Medieval Warming and the Little Ice Age, especially as reflected in the arctic.

  28. Paul Linsay
    Posted Jul 6, 2006 at 8:34 PM | Permalink

    The intro to Nichols paper ends with an extremely telling observation

    My paleo-ecological studies in 1975 produced a paleo-temperature reconstruction for the past 6000 years based on arctic tree-line position controlled by the summer location of the arctic front. Unpublished comparison with J. Eddy’s reconstruction of sunspot history for the same period demonstrates a close correspondence between the two signals, perhaps hinting at a causal relationship

    Who’d imagine that the sun could have anything to do with the earth warming? Just because solar activity is the highest it’s been in a thousand years couldn’t possibly mean a thing.

  29. TCO
    Posted Aug 3, 2006 at 8:43 PM | Permalink

  30. bender
    Posted Aug 3, 2006 at 8:49 PM | Permalink

    What can I offer you to be a dear and use the link function for those long urls in the first line?

  31. TCO
    Posted Aug 3, 2006 at 9:00 PM | Permalink


  32. bender
    Posted Aug 3, 2006 at 9:40 PM | Permalink

    Where treeline is rising fastest in the northern Rockies it is, ironically, DESPITE warming. In these areas it is fire frequency that is the slow-changing variable modulating treeline. When lightning caused fires are frequent and burn large, mountain-tops stay tree-free longer (colonization rates are slower at harsher elevations). In the 20th century, however, human-caused fire suppression is allowing these natural tree-free grassy meadows to fill in with trees. Not knowing any better, one might ignore the intermediate controlling process (fire occurrence) and conclude that the treeline is creeping up because of the direct effect of temperature rise. But of course, human populations are rising at the same time, and these humans don’t like fires, so fire frequency and size have dropped tremendously in alpine areas. If fire suppression were suspended, the tree line might actually drop under a climate warming scenario!

    This may have no relevance for pre 20th century changes in treeline. But it does show (1) how treeline is controlled by more than one variable, and (2) how spurious correlations can arise very easily with low-frequency processes where you don’t have all the facts about what the rate-limiting processes are.

  33. TCO
    Posted Aug 3, 2006 at 9:42 PM | Permalink

    Is there a good study describing the extent of this confounding factor?

  34. Mark H.
    Posted Aug 3, 2006 at 9:50 PM | Permalink

    I’m just hoping this message will push that long web link OFF the sidebar so my search results stop getting truncated.

  35. bender
    Posted Aug 4, 2006 at 7:30 AM | Permalink

    Re #33 I doubt it, because that would require a set of spatially replicated studies. The process I’m referring to would be relevant only in the northern Rockies where the sub-polar storm track generates alot of lightning caused fires. I will dig for an authoritative reference for you on that – however this alone will not answer the “extent” question.

  36. TCO
    Posted Aug 4, 2006 at 8:30 AM | Permalink

    A specific case study would be a good start. Trying to understand your point about “the fastest moving tree lines” do so from this effect.

  37. beng
    Posted Aug 4, 2006 at 6:15 PM | Permalink

    This has been posted before, bender — still worth repeating regarding arctic treelines. Nichols is a real biologist, seemingly in the Lamb fashion.

  38. bender
    Posted Aug 4, 2006 at 6:23 PM | Permalink

    Interesting. Did you hear they found a hybrid polar/grizzly this spring? Story here

2 Trackbacks

  1. […] discussed one such study (Kultti et al 2006) at CA here (which estimated MWP temperatures as 0.55 deg C higher than at present) in passing in 2006, but, […]

  2. […] discussed one such study (Kultti et al 2006) at CA here (which estimated MWP temperatures as 0.55 deg C higher than at present) in passing in 2006, but, […]

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