How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

The Broad View of Holocene Climate from the Swedish Scandes
Volume 16, Number 50: 11 December 2013

In the introduction to his recent contribution to the cause of deciphering the history of climate change over the entire course of the Holocene, Kullman (2013) writes that "in central and northern Scandinavia, our understanding of the Holocene tree line history has been progressively refined over the past 50 years or so by the use of radiocarbon-dated mega-fossil tree remains, preserved above the modern tree line elevation in peat and lakes and under glacier ice," citing the studies of G. Lundqvist (1959), J. Lundqvist (1969), Karlen (1976), Eronen (1979), Aas and Faarlund (1988, 1999), Nesje et al. (1991), Moe and Odland (1992), Kullman (1995, 2000), Selsing (1998), Kullman and Kjallgren (2000, 2006), Helama et al. (2004), Paus (2010) and Oberg and Kullman (2011a, b). And in further expounding on the subject, the Swedish scientist reassuringly states that "fundamental aspects of glacial, Lateglacial and early Holocene plant cover and landscapes in northern Scandinavia, as inferred by this approach (Kullman 2006, 2008), are consistent with independent fossil, genetic and palaeo-geographical data," citing Paus (2010), Paus et al. (2011), Carcaillet et al. (2012) and Parducci et al. (2012). In fact, he contends that mega-fossil analysis is the only methodology that can "accurately document the existence of a certain tree species at a certain spot and at a certain point of time in the past."

Consequently, Kullman goes on to develop what he refers to as "a synthesis of all previously published - and some new - mega-fossils representing principal tree species in the south and central Swedish Scandes." More specifically, the Swedish scientist's study includes a sample of 455 radiocarbon-dated mega-fossils (258 Pinus, 172 Betula, 25 Alnus) that originated from the present-day tree line ecotone and above, thirteen of which had not previously been published. And the resulting history he developed indicates that "summer temperatures during the early Holocene thermal optimum may have been 2.3°C higher than present," which difference, in Kullman's words, "corresponds to a general cooling trend of 0.24°C/century, which matches the Milankovitch model of orbitally-driven climate forcing (cf. Berger, 1988; Esper et al., 2012) and indicates that this mechanism has operated as the ultimate driver of climate change throughout the Holocene."

Focusing on the last two millennia, Kullman states that "the pine tree line was about 100 m higher than today (i.e., early 21st century) c. 1940 and 1300-930 cal. years BP," while noting that "the same applies to birch by c. 1700 and 1300 cal years BP," which clusters "represent the Medieval and Roman times." And he writes that "mega-fossil and tree-ring studies in the northernmost part of the Scandes and adjacent regions display broadly the same features," citing the studies of Karlen and Kuylenstierna (1996), Karlen (1998), Hiller et al. (2001), Shivatov (2003), Kremenetski et al. (2004), Moberg et al. (2005) and Esper et al. (2012), after which he says that "these temperature anomalies were succeeded by a distinct tree line/temperature dip, broadly corresponding to the Little Ice Age."

In commenting further on these findings, Kullman says that "the emergence during the past two millennia of at least two short-term tree line and thermal excursions to higher than present levels (i.e. early 21st century) indicates that the current performance of the ecological and climatic systems is well within the envelope of the natural variability of the late Holocene (cf. Karlen, 2008; Akasofu, 2010; Curry and Webster, 2011; Humlum et al., 2011; Kobashi et al., 2011; Ljungqvist et al., 2012)." And to make this point perfectly clear, Kullman repeats that "the pine tree line (and summer temperature) was consistently higher than present ... during the Roman and Medieval periods, c. 1900 and 1000 cal years BP."

Thus, as we have long contended, and on the basis of real-world data (properly analyzed), Kullman's analysis of tree-line data, along with the results of the many other studies he cites, jointly provide yet another strong amalgamation of evidence that supports the view that there is nothing unusual, unnatural or unprecedented about earth's current level of warmth.

Sherwood, Keith and Craig Idso

Aas, B. and Faarlund, T. 1988. Postglasiale skoggrenser i sentrale sornorske fjelltrakter. Norsk Geografisk Tidsskrift 4: 6-16.

Aas, B. and Faarlund, T. 1999. Macrofossils versus pollen as evidence of the Holocene forest development in Fennoscandia. AmS-Rapport 12B: 307-346.

Akasofu, S.-I. 2010. On the recovery from the Little Ice Age. Natural Science 2: 1211-1224.

Berger, A. 1988. Milankovitch theory and climate. Reviews of Geophysics 26: 624-657.

Carcaillet, C., Hornberg, G. and Zackrisson, O. 2012. Woody vegetation, fuel and fire track the melting of the Scandinavian ice-sheet before 9500 cal yr BP. Quaternary Research 78: 540-548.

Curry, J.A. and Webster, P.J. 2011. Climate science and the uncertainty monster. Bulletin of the American Meteorological Society 92: 1667-1682.

Eronen, M. 1979. The retreat of pine forest in Finnish Lapland since the Holocene climatic optimum: a general discussion with radiocarbon evidence from subfossil pine. Fennia 157: 93-114.

Esper, J., Frank, D.C., Tomonen, M., Zorita, E., Wilson, R.J.S., Luterbacher, J., Holzkamper, S., Fischer, N., Wagner, S., Nievergelt, D., Verstege, A. and Buntgen, U. 2012. Orbital forcing of tree-ring data. Nature Climate Change 2: 862-866.

Helama, S., Lundholm, M., Timonen, M. and Eronen,M. 2004. Dendrochronologically dated changes in the limit of pine in northernmost Finland during the past 7.5 millennia. Boreas 33: 250-259.

Hiller, A., Boettger, T. and Kremenetski, C. 2001. Mediaeval climate warming recorded by radiocarbon dated alpine tree-line shift on the Kola Peninsula, Russia. The Holocene 11: 491-497.

Humlum, O., Solheim, J.-E. and Stordahl, K. 2011. Identifying natural contributions to late Holocene climate change. Global and Planetary Change 79: 145-156.

Karlen, W. 1976. Lacustrine sediments and tree-limit variations as indicators of Holocene climatic fluctuations in Lappland, northern Sweden. Geografiska Annaler 58A: 1-34.

Karlen, W. 1998. Climate variations and the enhanced greenhouse effect. Ambio 27: 270-274.

Karlen, W. 2008. Recent changes in climate: natural or forced by human activity. Ambio, Special Report 14: 483-488.

Karlen, W. and Kuylenstierna, J. 1996. On solar forcing of Holocene climate: evidence from Scandinavia. The Holocene 6: 359-365.

Kobashi, T., Kawamura, K., Severinghaus, J.P., Barnola, M.-M., Nakaegawa, T., Vinther, B.M., Johnasen, S.J. and Box, J.E. 2011. High variability of Greenland surface temperatures over the past 4000 years estimated from trapped air in an ice core. Geophysical Research Letters 38: 10.1029/2011GL049444.

Kremenetski, K.V., Boettger, T., MacDonald, G.M., Vaschalova, T., Sulerzhitsky, L. and Hiller, A. 2004. Medieval climate warming and aridity as indicated by multi-proxy evidence from the Kola Peninsula, Russia. Palaeogeography, Palaeoclimatology, Palaeoecology 209: 113-125.

Kullman, L. 1995. Holocene tree-limit and climate history from the Scandes Mountains, Sweden. Ecology 76: 2490-2502.

Kullman, L. 2000. The geoecological history of Picea abies in northern Sweden and adjacent parts of Norway. A contrarian hypothesis of postglacial tree immigration patterns. Geo-Oko 21: 141-172.

Kullman, L. 2006. Late-glacial trees from arctic coast to alpine tundra. Response to Birks et al. 2005 and 2006. Correspondence. Journal of Biogeography 33: 377-378.

Kullman, L. 2008. Early postglacial appearance of tree species in northern Scandinavia: review and perspective. Quaternary Science Reviews 27: 2467-2472.

Kullman, L. 2013. Ecological tree line history and palaeoclimate - review of mega-fossil evidence from the Swedish Scandes. Boreas 42: 555-567.

Kullman, L. and Kjallgren, L. 2000. A coherent postglacial tree-limit chronology (Pinus sylvestris (L.) for the Swedish Scandes: aspects of paleoclimate and 'recent warming,' based on megafossil evidence. Arctic, Antarctic, and Alpine Research 32: 419-428.

Kullman, L. and Kjallgren, L. 2006. Holocene pine tree-line evolution in the Swedish Scandes: recent tree-line rise and climate change in a long-term perspective. Boreas 35: 159-168.

Ljungqvist, F.C., Krusic, P.J., Brattstrom, G. and Sundffqvist, H.S. 2012. Northern Hemisphere temperature patterns in the last 12 centuries. Climate of the Past 8: 227-249.

Lundqvist, G. 1959. C14- daterade tallstubbar fran fjallen. Sveriges Geologiska Undersokning. Serie C 565: 1-21.

Lundqvist, J. 1969. Beskrivning till jordartskarta over Jamtlands lan. Sveriges Geologiska Undersokning. Serie Ca 45: 1-418.

Moberg, A., Sonechkin, D.M., Holmgren, K., Datsenko, N.M. and Karlen, W. 2005. Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data. Nature 433: 613-617.

Moe, D. and Odland, A. 1992. The influence of the temperature climate on the vertical distribution of Alnus incana (Betulaceae) through the Holocene in Norway. Acta Botanica Fennica 144: 35-49.

Nesje, M., Kvamme, M., Rye, N. and Lovlie, R. 1991. Holocene glacial and climate history of the Jostedalsbreen region, western Norway: evidence from lake sediments and terrestrial deposits. Quaternary Science Reviews 10: 87-114.

Oberg, L. and Kullman, L. 2011a. Ancient subalpine clonal spruces (Picea abies) - sources of postglacial vegetation history in the Swedish Scandes. Arctic 64: 183-196.

Oberg, L. and Kullman, L. 2011b. Recent glacier recession - a new source of postglacial treeline and climate history in the Swedish Scandes. Landscape Online 26: 1-38.

Parducci, L., Jorgensen, T., Tollefsrud, M.T., Elverland, E., Alm, T., Fontana, S.L., Bennett, K.D., Haile, J., Matetovici, I., Suyama, Y., Edwards, M.E., Andersen, K., Rasmussen, M., Boessenkol, S., Coissact, E., Brochmann, C., Taberlet, P., Houmark-Nielsen, M., Krog Larsen, N., Orlando, L., Gilbert, M.T., Kjaer, K.H., Greve Alsos, I. and Willerslev, E. 2012. Glacial survival of boreal trees in Northern Scandinavia. Science 335: 1083-1086.

Paus, A. 2010. Vegetation and environment of the Rodalen alpine area, Central Norway, with emphasis on the early Holocene. Vegetation History and Archaeobotany 19: 29-51.

Paus, A., Velle, G. and Berge, J. 2011. The Lateglacial and early Holocene vegetation and environment in the Dovre mountains, central Norway, as signaled in two Lateglacial lakes. Quaternary Science Reviews 80: 1780-1793.

Selsing, L. 1998. Subfossils of Scots pine (Pinus sylvestris L.) from the mountain area of South Norway as the basis for a long tree-ring chronology. Norsk Geografisk Tidskrift 52: 89-103.

Shiyatov, S.G. 2003. Rates of change in the upper treeline ecotone in the Polar Ural Mountains. Pages News 11: 8-10.