New Treeline, Permafrost Evidence Strongly Affirms The Mid-Holocene Was 3°C Warmer Than Today

Newly published macrofossil discoveries from 4 papers strongly suggest that modern warmth may still be about 3°C colder than nearly all of the last 10,000 years.

Image Source: Leunda et al. (2018)

1. Permafrost is still present today in a region that was permafrost-free throughout the Holocene (until the onset of the Little Ice Age)

According to data from a new study (Sannel et al., 2018), subarctic Northern Sweden has yet to rise out of the range of frigid, permafrost-friendly temperatures coeval with of the Little Ice Age (roughly 1400 to 1900 AD).

Permafrost still exists today in regions where there was no recorded permafrost during nearly all of the Holocene, when temperatures were too warm (3°C higher than today) for permafrost to form.

Throughout most of the Holocene, these northern peatlands have not experienced climatic conditions cold enough for permafrost to form.”

These findings strongly suggest that modern warmth is nothing unusual, unprecedented, or even remarkable.  In fact, it may be said that today’s subarctic warmth may only be slightly warmer than the coldest centennial-scale period — the Little Ice Age — of the last 10,000 years.

Sannel et al., 2018

“At all these sites the datings together with the results of the plant macrofossil analyses suggest that permafrost aggradation took place around 600–100 cal. a BP [the Little Ice Age]. … [A]t these sites there are no indications of permafrost inception prior to the Little Ice Age. … Warmer conditions during recent decades have resulted in extensive permafrost degradation in Fennoscandian palsas and peat plateaus (Sollid& Sørbel 1998; Zuidhoff& Kolstrup 2000; Luoto & Seppala 2003; Sannel & Kuhry 2011; Borge et al. 2017).”
At present the permafrost is close to thawing with mean annual ground temperatures just below 0°C (Christiansen et al. 2010; Johansson et al. 2011; Sannel et al. 2016).”
Throughout most of the Holocene, these northern peatlands have not experienced climatic conditions cold enough for permafrost to form.”
“During peatland initiation (c. 10 000–9600 cal. a BP) the climatic conditions in the region were favourable for plant productivity with around 3 °C warmer summer temperatures compared to today (Kullman & Oberg 2015), resulting in relatively rapid peat and net carbon accumulation rates during the early Holocene.”

Image Source: Sannel et al., 2018

2.  Italian Alps tree lines ~460 meters higher than present indicate surface temperatures were 3.1°C warmer during the Mid-Holocene

The modern forest line position in an Italian Alps study area (Badino et al., 2018) is 2,360 meters above sea level (m asl).

Per the data indicated in the graph below, the forest line position averaged between 2,750 to 2,900 m asl during 7400 to 3600 cal yrs BP — about 460 m higher than today’s forest line.

With a temperature lapse rate of 0.67°C/100 m for the region documented in the paper, this indicates temperatures were about 3.1°C warmer than today [4.6 X 0.67°C] during the Mid-Holocene.

Badino et al., 2018

“Between 7400 and 3600 yrs cal BP, an higher-than-today [~2820 m asl vs. 2360 m asl today] forest line position persisted under favorable growing conditions (i.e. TJuly at ca. 12 °C).”
Between ca. 8.4-4 ka cal BP, our site [Italian Alps] experienced a mean TJuly of ca. 12.4 °C, i.e. 3.1 °C warmer than today.”
“[O]ur lapse rate (0.67°C/100 m), [is] slightly steeper than the average of 0.6°C for temperate regions (Barry and Chorley, 1992) was provided at higher spatial resolution.” 

Images Source: Badino et al., 2018

3. The Pyrenees (Spain) timber line exceeded today’s uppermost limit by 300-400 meters ~4,500 years ago, indicating Mid-Holocene surface temperatures were about 2°C higher

The temperature lapse rate for the Pyrenees region is 0.517°C/100 m according to a newly published paper.

“Estimation of near‐surface air temperature lapse rates over continental Spain and its mountain areas … The median NSLR [near‐surface (i.e., non‐free atmosphere) air temperature lapse rates] … Pyrenees −5.17 °C/km  (Navarro-Serrano et al., 2018)

Leunda et al. (2018) have published a study that shows the Mid-Holocene (about 4,500 years ago) Pyrenees timber line was 300-400 meters higher than today’s uppermost limit.

This would suggest that Pyrenees temperatures were about 1.6 to 2.1°C warmer [3.5 X 0.517°C] than today during 4,650-4,200 calendar years before present.

Leunda et al., 2018

“The tree line ecotone was located at the cave altitude from 5,700 to 4,650 cal year bp, when vegetation consisted of open Pinus uncinata Ramond ex DC and Betula spp. Woodlands and timberline were very close to the site. Subsequently, tree line slightly raised and timberline reached the ice cave altitude, exceeding its today’s uppermost limit by c. 300–400 m during more than four centuries (4,650 and 4,200 cal year bp) at the end of the Holocene Thermal Maximum.”

Image Source: Leunda et al. (2018)

4. Tree remnants found northern Sweden mountain sites 600 to 700 meters atop where the 21st century tree line ends imply the Early Holocene (9500 years ago) was 3-4°C warmer than today

The temperature lapse rate for the Swedish Lapland region is 0.6°C/100 m.

Kullman (2018) found tree debris (trunks, cones, roots, etc.) 600 to 700 meters atop modern tree line positions that were dated to about 9,500 years ago.  Accounting for glacio-isostatic uplift, this tree line elevation implies surface air temperatures were 3.6°C higher than today during the Early Holocene.

Kullman, 2018

“The present paper reports results from an extensive project aiming at improved understanding of postglacial subalpine/alpine vegetation, treeline, glacier and climate history in the Scandes of northern Sweden. The main methodology is analyses of mega fossil tree remnants, i.e. trunks, roots and cones, recently exposed at the fringe of receding glaciers and snow/ice patches. This approach has a spatial resolution and accuracy, which exceeds any other option for tree cover reconstruction in high-altitude mountain landscapes.”
All recovered tree specimens originate from exceptionally high elevations, about 600-700 m atop of modern treeline positions.”
“Conservatively drawing on the latter figure and a summer temperature lapse rate of 0.6 °C per 100 m elevation (Laaksonen 1976), could a priori mean that, summer temperatures were at least 4.2 °C warmer than present around 9500 year before present. However, glacio-isostatic land uplift by at least 100 m since that time (Möller 1987; Påsse & Anderson 2005)implies that this figure has to be reduced to 3.6 °C higher than present-day levels, i.e. first decades of the 21st century. Evidently, this was the warmth peak of the Holocene, hitherto. This inference concurs with paleoclimatic reconstructions from Europe and Greenland (Korhola et al. 2002; Bigler et al. 2003; Paus 2013; Luoto et al. 2014; Väliranta et al. 2015).”

Image Source: Kullman, 2018

16 responses to “New Treeline, Permafrost Evidence Strongly Affirms The Mid-Holocene Was 3°C Warmer Than Today”

  1. Yonason


    How does one read tree ring widths of trees that have been dead and gone for centuries, done in by modern cold? Does one just “homogenize,” as with temperatures – you know, make them up? Or does one just ignore the problem, and pretend it doesn’t exist?

    1. Mick J

      A somewhat lively discussion going on at Judith Curry’s place regarding Hockey Sticks and the influence of a few specific series. And whether a graph from RealClimate by Gavin Schmidt is demonstrating the restoration of the MWP when Bristlecones and Tiljander series are removed.

  2. Bitter&twisted

    More “settled science”.😁

  3. John F. Hultquist

    You may also be interested in this report by Harvey Nichols from the late 1970s:
    Historical Aspects of the Northern Canadian Treeline

    From palynological studies it appears that northernmost dwarf spruces
    of the tundra and parts of the forest-tundra boundary may be relicts from times of
    prior warmth, and if felled might not regenerate. This disequilibrium may help
    explain the partial incongruence of modern climatic limits with the present forest
    edge. Seedlings established as a result of recent warming should therefore be found
    within the northernmost woodlands rather than in the southern tundra.

    Has a couple of maps and an old (1958) photo. 9 pages. Many references.

  4. A. O'Brien

    Michael Mann’s Nobel Prize is as fictitious as is his hockey stick.

    1. Skeptik

      Yes, indeed! The Nobel Prize was awarded to the IPCC. This was not one of the three scientific prizes but the Peace Prize – which has always been a reflection of what was at the time political correctness. It would have been more appropriate to award the IPCC the prize for literature – i.e. fiction!

      1. Yonason


        Yasser Arafat
        Al Gore and a perverted railroad engineer
        Barack HUSSEIN Obama

        More like an anti-peace prize, it would seem.

  5. tom0mason

    Older papers that may also be of interest showing more geographically extensive reach for climatically warm periods.
    From 2012

    Variations of the tree line and glaciers in the Central and Eastern Altai regions in the Holocene
    Article (PDF Available) in Doklady Earth Sciences 444(2) · June 2012
    DOI: 10.1134/S1028334X12060244}
    A. N. Nazarov
    Olga N Solomina Russian Academy of Sciences
    Vladimir Myglan Siberian Federal University

    The investigations were carried out in the Central and Eastern Altai regions at the territories of Russia, Kazakhstan, China, and Mongolia…

    Samples dated at 2500–2000 years ago were not found in the Altai region. A new series of dates is referred already to contemporary era (CE or AD), and our results suggest that the period from the second to the sixth centuries AD was marked by expansion of a forest in the Altai region. This warm period coincides with the “Roman optimum” in Europe. It was interrupted by the glacier advance in the sixth century, which also occurred in Southern Tibet, the Swiss Alps,Southern Alaska, and British Columbia (400–600 AD).
    From the eleventh century until the early thirteenth century, the Altai glacier forefields were again covered with forests. The tree line was at the elevation of at least 2450 m. A few waves of cooling and glacier advances resulted in forest mortality about 1206–1256, 1445–1501, and 1642–1736 years ago. The last two dates coincide with an increase in temperatures reconstructed from the Belukha ice core in 1400–1550 and 1650–1750, which in turn coincide with the periods of decreased solar activity.
    Glacier advances were recorded in the Swiss Alps in 1100–1200 [12–14], in the Southern Alaska in 1180–1300 [10], and in British Columbia in 1035–1210 [15]. The following glacier advance occurred in 1350–1450 in Tibet and 1300–1450 in the Alps. In the Altai, the mentioned periods were accompanied by mortality of trees at the tree line and glacier forefields. The following wave of glacier advances started in Alaska and in the Alps in 1600. In the Altai region, the Aktru stage terminated only in 1700s.


    Also from 1993 this may be of interest —

    A 3620-Year Temperature Record from Fitzroya cupressoides Tree Rings in Southern South America
    Antonio Lara1, Ricardo Villalba
    Science 21 May 1993:
    Vol. 260, Issue 5111, pp. 1104-1106
    DOI: 10.1126/science.260.5111.1104

    Where the abstract says


    A tree-ring width chronology of alerce trees (Fitzroya cupressoides) from southern Chile was used to produce an annually resolved 3622-year reconstruction of departures from mean summer temperatures (December to March) for southern South America. The longest interval with above-average temperatures was from 80 B.C. to A.D. 160. Long intervals with below-average temperatures were recorded from A.D. 300 to 470 and from A.D. 1490 to 1700. Neither this proxy temperature record nor instrumental data for southern South America for latitudes between 35° and 44°S provide evidence of a warming trend during the last decades of this century that could be related to anthropogenic causes. The data also indicate that alerce is the second longest living tree after the bristlecone pine (Pinus Iongaeva).

    1. tom0mason

      Also of note is this interesting little piece —

      Apparently some forest are very good at changing their local weather/climate, some may even ‘telconnect’ across the globe —

  6. Penelope

    Wow, what cd be more convincing of higher temperature than that the treeline was higher, as demonstrated by fossilized remains?!

    My favorite graph is one which demonstrates the entire temperature record of the past 17,000 years allowing one to see pictorially our temperature relationship to past ages. It is the 3d graph in this article.

    Don Easterbrook, writing in 2008, was an early predictor of a cooling trend.

  7. “Weekly Climate and Energy News Roundup #337 | Watts Up With That?

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