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Little Ice Age (Regional - Europe: Northern) -- Summary
What do studies of the Little Ice Age in Northern Europe reveal about the periods of considerably greater warmth that immediately preceded and followed it?  In this summary we review the findings of several research projects that have provided answers to this important question.

Caseldine (1985) used lichenometry to determine the dates of occurrence of the maximum Little Ice Age extensions of four glaciers in Northern Iceland, as well as their subsequent movements.  This work revealed that their maximum extensions were reached in 1868, 1885, 1898 and 1917.  Since those times, two of the glaciers continued to retreat through the end of the study period (mid-1980s).  The other two, however, slowed, stopped and periodically re-advanced.  In fact, one of them advanced 50 meters between 1977 and 1979, 30 more meters between 1979 and 1981, and 25 additional meters between 1981 and 1983.  Caseldine notes that these advances occurred when mean summer temperature dropped below about 8-8.5C, which occurred several times over the preceding decades, following the significant downward trend in summer temperature that succeeded the broad maximum experienced in the 1930s and 40s.  These observations thus suggest that by the mid-1980s Iceland's climate may not have fully evolved into what may be called the Modern Warm Period, and that remnants of the Little Ice Age may yet be lurking about the fringes of this North Atlantic island.

Andren et al. (2000) conducted an extensive analysis of temporal compositional changes in siliceous microfossil assemblages and chemical characteristics of various materials found in a well-dated sediment core obtained from the Bornholm Basin in the southwestern Baltic Sea.  Their data revealed the existence of an interval of high primary production at approximately AD 1050.  Diatoms of the period were warm water species such as Pseudosolenia calcar-avis, which they describe as "a common tropical and subtropical marine planktonic species" that "cannot be found in the present Baltic Sea."  They also note that what they call the Recent Baltic Sea Stage, which begins at about AD 1200, starts "at a point where there is a major decrease in warm water taxa in the diatom assemblage and an increase in cold water taxa, indicating a shift towards a colder climate," which they associate with the Little Ice Age.  These data clearly indicate there was a period of time in the early part of the past millennium when the climate of the southwestern Baltic Sea was significantly warmer than it is today.  This period of higher temperatures, according to Andren et al., falls within "a period of early Medieval warmth dated to AD 1000-1100," which "corresponds to the time when the Vikings succeeded in colonizing Iceland and Greenland."

A similar course of climatic events was found by Brooks and Birks (2001), who studied midges, the larval-stage head capsules of which are well preserved in lake sediments and are, according to them, "widely recognized as powerful biological proxies for inferring past climatic change."  Their work revealed that reconstructed temperatures for Lochan Uaine in the Cairngorms region of the Scottish Highlands peaked at about 11C during what they refer to as the "Little Climatic Optimum," which we typically call the Medieval Warm Period, "before cooling by about 1.5C which may coincide with the 'Little Ice Age'."  These results, in their words, "are in good agreement with a chironomid stratigraphy from Finse, western Norway (Velle, 1998)," where summer temperatures were "about 0.4C warmer than the present day" during the Medieval Warm Period.  This latter observation also appears to hold for the Scottish Highlands, since the upper sample of the Lochane Uaine core, which was collected in 1993, "reconstructs the modern temperature at about 10.5C" which is 0.5C less than the 11C value they obtained from the Medieval Warm Period.

In a slightly different type of study that focused on moisture, Nesje et al. (2001) analyzed a 572-cm-long sediment core retrieved from Lake Atnsjoen in southern Norway in an effort to determine the frequency and magnitude of pre-historic floods in that region over the past 4500 years.  Analysis of the more recent portion of the record revealed, as they describe it, "a period of little flood activity around the Medieval period (AD 1000-1400)," which was associated with reduced regional glacier activity, as well as "a period of the most extensive flood activity in the Atnsjoen catchment," which resulted from the "post-Medieval climate deterioration characterized by lower air temperature, thicker and more long-lasting snow cover, and more frequent storms associated with the 'Little Ice Age'."

McDermott et al. (2001) derived a δ18O record - with a time resolution they say is "approximately an order of magnitude better than in the North Atlantic cores that record evidence for quasi-periodic (1475 500 year) ice rafting during the Holocene" - from a stalagmite discovered in Crag Cave in southwestern Ireland, after which they compared this record with the δ18O records from the GRIP and GISP2 ice cores from Greenland.  This work, in their words, provided evidence for "centennial-scale δ18O variations that correlate with subtle δ18O changes in the Greenland ice cores, indicating regionally coherent variability in the early Holocene."  They additionally note that the Crag Cave data "exhibit variations that are broadly consistent with a Medieval Warm Period at ~1000 200 years ago and a two-stage Little Ice Age, as reconstructed by inverse modeling of temperature profiles in the Greenland Ice Sheet."  Also evident in the Crag Cave data were the δ18O signatures of the earlier Roman Warm Period and Dark Ages Cold Period that comprised the prior such cycle of climate in that region.  As for the significance of their findings, McDermott et al. state that the coherent δ18O variations on both sides of the Atlantic "indicate that many of the subtle multi-century δ18O variations in the Greenland ice cores reflect regional North Atlantic margin climate signals rather than local effects."  And, of course, their data confirm the reality of the Medieval Warm Period / Little Ice Age cycle (which climate alarmists refuse to acknowledge), as well as the even-more-strongly-expressed Roman Warm Period / Dark Ages Cold Period cycle that preceded it, once again demonstrating there is nothing unusual or unprecedented about the global warming of the past century or so.

Andersson et al. (2003) inferred surface conditions of the eastern Norwegian Sea (Voring Plateau) from planktic stable isotopes and planktic foraminiferal assemblage concentrations in two seabed sediment cores that covered the last three thousand years.  The climate history derived from their study is remarkably similar to that derived by McDermott et al. for southwestern Ireland.  At the beginning of the 3000-year-long Voring Plateau record, for example, both regions were clearly in the end-stage of the long cold period that preceded the Roman Warm Period.  Hence, both records depict warming from that point in time to the peak of the Roman Warm Period, which occurred about 2000 years BP.  Then, both regions begin their descent into the Dark Ages Cold Period, which held sway until the increase in temperature that produced the Medieval Warm Period, which in both records prevailed from about 800 to 550 years BP.  Last of all, the Little Ice Age is evident, with cold periods centered at approximately 400 and 100 years BP, again in both records.  Of particular interest is the fact that neither record indicates the existence of what has come to be called the Modern Warm Period, and that Andersson et al. report that "surface ocean conditions warmer than present were common during the past 3000 years."

Also working with a marine sediment core, this one retrieved from the southern Norwegian continental margin, Berstad et al. (2003) established its chronology over the past 600 years by means of 210Pb measurements and 14C dates, while they reconstructed spring and summer sea surface temperatures from δ18O data derived from remains of different planktonic foraminifera species.  The results of their analyses suggest, in their words, that "summer water temperatures in the Norwegian Current were 1-2C colder than at present most of the time between ca. AD 1400 and 1920."  They also say their data suggest that "the spring water temperature along the southern Norwegian continental margin was 1-3C colder than at present most of the time between AD 1400 and 1700."  In addition, they note that "the cold interval between ca. AD 1400 and 1700/1920 is coincident to the Little Ice Age (LIA)," and within this interval they report that the two coldest periods were coincident with "the solar minima of 'Maunder' and 'Sporer'."

In discussing the implications of their findings for the thermohaline circulation of the ocean and its role in facilitating global climate change, Berstad et al. forthrightly express their opinion that the Little Ice Age was of global extent, which is something that is vociferously denied by climate alarmists.  Berstad et al. note, for example, that "the evidence of the Little Ice Age as a global event, as documented in changes in the atmospheric circulation in the Southern (Kreutz et al., 1997) and Northern Hemisphere (O'Brian et al., 1995), suggests that large-scale changes in ocean and atmospheric circulation were involved," additionally stating that "the findings of increased deep-water formation in the Southern Ocean during the Little Ice Age by Broecker (1999, 2001) and Broecker et al. (1999) further support this interpretation of variability in the thermohaline circulation.  In summation, Berstad et al. suggest that the Little Ice Age was (1) real, (2) really cold, and (3) solar-induced, while they report corroborating evidence for its global extent.

Continuing towards the present, Casely and Dugmore (2004) studied fluctuations of two key outlet glaciers of the Myrdalsjokull ice cap in Iceland (Tungnakvislajokull and Krossarjokull), employing "geomorphic mapping and geochronology based on a combination of historical sources, lichenometry and tephrochronology."  As they describe it, this work revealed "there is geomorphological and tephrochronological evidence for a 'Little Ice Age' maximum Holocene advance of Krossarjokull and Tungnakvislajokull, which probably culminated in two advance phases during the early and mid-19th century."  They also note "there is no evidence of Neoglacial advances of a greater extent," and to drive this point home, they report that, "as elsewhere in the North Atlantic, the Little Ice Age advances at these southwest outlets of Myrdalsjokull are the most extensive during Neoglaciation."  Consequently, it can be appreciated that after reaching what was likely the coldest part of the current interglacial, i.e., the Little Ice Age, it is little wonder the planet would have to warm significantly to return to relative interglacial "normalcy," i.e., temperatures characteristic of the Medieval and Roman Warm Periods; yet climate alarmists continue to rant and rave about what was only to be expected, i.e., that temperatures would rise significantly at the end of the Little Ice Age after having fallen significantly during its development.

Contemporaneously, Roncaglia (2004) analyzed variations in organic matter deposition from approximately 6350 cal yr BC to AD 1430 in a sediment core extracted from the Skalafjord, southern Eysturoy, Faroe Islands, finding that an increase in "structured brown phytoclasts, plant tissue and sporomorphs in the sediments dating to ca. AD 830-1090 indicate increased terrestrial influx and inland vegetation supporting the idea of improved climatic conditions."  She also reports that high "total dinoflagellate cyst concentration and increased absolute amount of loricae of tintinnid and planktonic crustacean eggs occurred at ca. AD 830-1090," concluding that these observations "may suggest increased primary productivity in the waters of the fjord (Lewis et al., 1990; Sangiorgi et al., 2002)."

The "amelioration of climate conditions" that promoted the enhanced productivity of both land and sea at this time, in the words of Roncaglia, "may encompass the Medieval Warm Period in the Faroe region," and indeed it does, for the data of Esper et al. (2002) show, in their words, that the warmest portion of the Medieval Warm Period "covers the interval 950-1045, with the peak occurring around 990."  Thereafter, Roncaglia reports an increased concentration of certain organisms at about AD 1090-1260 that she says "suggests a cooling, which may reflect the beginning of the Little Ice Age."  This finding, too, is in harmony with the findings of Esper et al., which show a dramatic drop in temperature over this period.

Utilizing plant macrofossils, testate amoebae and degree of humification as proxies for environmental moisture conditions in yet another approach to climate reconstruction, Blundell and Barber (2005) developed a "wetness history" from a peat core extracted from Tore Hill Moss, a raised bog in the Strathspey region of Scotland, which begins 2800 years ago and extends all the way to AD 2000.  The most clearly defined and longest interval of sustained dryness in this entire history stretches from about AD 850 to AD 1080, coincident with the Medieval Warm Period as defined by both Roncaglia and Esper et al., while the most extreme wetness interval occurred during the depths of the last stage of the Little Ice Age.  In addition, preceding the Medieval Warm Period was a highly chaotic period of generally greater wetness corresponding to the Dark Ages Cold Period, while dryness peaks representing the Roman Warm Period are also evident in the data.  Consequently, in local contradiction of the climate-alarmist claim that the late 20th century was the warmest period experienced by the globe over the past two millennia, the correlation this study demonstrates to exist between relative wetness and warmth in Scotland strongly suggests that the temperature of the late 20th century was nowhere near the highest of the past two millennia in that particular part of the world.  In addition, Blundell and Barber cite many studies that report findings similar to theirs throughout much of the rest of Europe and the North Atlantic Ocean.  Consequently, the regional challenge this group of studies provides to the IPCC-endorsed hockeystick temperature history of Mann et al. (1999) is quite substantial.

A similar challenge is provided by the study of Linderholm and Gunnarson (2005), who worked with a multi-millennial tree-ring width chronology derived from living and subfossil Scots pines sampled close to the present tree-line in the central Scandinavian Mountains.  This proxy temperature record runs from 2893 BC to AD 2002 and contains several periods of anomalously warm and cold summers, including (1) 550 to 450 BC (Roman Warm Period), when summer temperatures were the warmest of the entire record, exceeding the 1961-1990 mean by more than 6C, (2) AD 300 to 400 (Dark Ages Cold Period), which was "the longest period of consecutive cold summers," averaging 1.5C less than the 1961-1990 mean, (3) AD 900 to 1000, a warm era corresponding to the Medieval Warm Period, and (4) AD 1550 to 1900, a cold period known as the Little Ice Age.  With respect to the latter portion of the record, which encompasses the period of modern global warming, Linderholm and Gunnarson say that this phenomenon "does not stand out as an anomalous feature" and that "other periods show more rapid warming and also higher summer temperatures."  In fact, the last half of the 20th century in their temperature reconstruction actually exhibits cooling.

Finally, in a study that looked at climate and civilization at one and the same time, Berglund (2003) identified several periods of expansion and decline of human cultures in Northwest Europe and compared them with a history of reconstructed climate "based on insolation, glacier activity, lake and sea levels, bog growth, tree line, and tree growth."  In doing so, he determined there was "a positive correlation between human impact/land-use and climate change."  Specifically, in the latter part of the record, where both cultural and climate changes were best defined, there was, in his words, a great "retreat of agriculture" centered on about AD 500, which led to "reforestation in large areas of central Europe and Scandinavia."  Berglund notes that "this period was one of rapid cooling indicated from tree-ring data (Eronen et al., 1999) as well as sea surface temperatures based on diatom stratigraphy in [the] Norwegian Sea (Jansen and Koc, 2000), which can be correlated with Bond's event 1 in the North Atlantic sediments (Bond et al., 1997)."  Next came what he calls a "boom period" that covered "several centuries from AD 700 to 1100."  This interval of time, according to Berglund, proved to be "a favorable period for agriculture in marginal areas of Northwest Europe, leading into the so-called Medieval Warm Epoch," when "the climate was warm and dry, with high treelines, glacier retreat, and reduced lake catchment erosion."  This period "lasted until around AD 1200, when there was a gradual change to cool/moist climate, the beginning of the Little Ice Age ... with severe consequences for the agrarian society."

In conclusion, many types of data, including those related to human enterprise, bear witness to the reality and significance of the natural, i.e., non-anthropogenic-induced, millennial-scale oscillation of climate that created and sustained the Little Ice Age, as well as the Medieval Warm Period that preceded it and the warming that has followed it, but which has not yet returned the planet to the degree of warmth experienced at the peak of that prior warm node of the recurring climate cycle.

References
Andren, E., Andren, T. and Sohlenius, G.  2000.  The Holocene history of the southwestern Baltic Sea as reflected in a sediment core from the Bornholm Basin.  Boreas 29: 233-250.

Andersson, C., Risebrobakken, B., Jansen, E. and Dahl, S.O.  2003.  Late Holocene surface ocean conditions of the Norwegian Sea (Voring Plateau).  Paleoceanography 18: 10.1029/2001PA000654.

Berglund, B.E.  2003.  Human impact and climate changes - synchronous events and a causal link?  Quaternary International 105: 7-12.

Berstad, I.M., Sejrup, H.P., Klitgaard-Kristensen, D. and Haflidason, H.  2003.  Variability in temperature and geometry of the Norwegian Current over the past 600 yr; stable isotope and grain size evidence from the Norwegian margin.  Journal of Quaternary Science 18: 591-602.

Blundell, A. and Barber, K.  2005.  A 2800-year palaeoclimatic record from Tore Hill Moss, Strathspey, Scotland: the need for a multi-proxy approach to peat-based climate reconstructions.  Quaternary Science Reviews 24: 1261-1277.

Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., deMenocal, P., Priore, P., Cullen, H., Hajdas, I. and Bonani, G.  1997.  A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates.  Science 278: 1257-1266.

Broecker, W.S.  1999.  Was a change in thermohaline circulation responsible for the Little Ice Age?  Proceedings of the National Academy of Science of the United States of America Online 4: 1339-1342.

Broecker, W.S.  2001.  Was the Medieval Warm Period global?  Science 291: 1497-1499.

Broecker, W.S., Sutherland, S. and Peng, T.H.  1999.  A possible 20th-century slowdown of Southern Ocean deep water formation.  Science 286: 1132-1135.

Brooks, S.J. and Birks, H.J.B.  2001.  Chironomid-inferred air temperatures from Lateglacial and Holocene sites in north-west Europe: progress and problems.  Quaternary Science Reviews 20: 1723-1741.

Caseldine, C.J.  1985.  The extent of some glaciers in northern Iceland during the Little Ice Age and the nature of recent deglaciation.  The Geographical Journal 151: 215-227.

Casely, A.F. and Dugmore, A.J.  2004.  Climate change and 'anomalous' glacier fluctuations: the southwest outlets of Myrdalsjokull, Iceland.  Boreas 33: 108-122.

Eronen, M., Hyvarinen, H. and Zetterberg, P.  1999.  Holocene humidity changes in northern Finnish Lapland inferred from lake sediments and submerged Scots pines dated by tree-rings.  The Holocene 9: 569-580.

Esper, J., Cook, E.R. and Schweingruber, F.H.  2002.  Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability.  Science 295: 2250-2253.

Jansen, E. and Koc, N.  2000.  Century to decadal scale records of Norwegian sea surface temperature variations of the past 2 millennia.  PAGES Newsletter 8(1): 13-14.

Kreutz, K.J., Mayewski, P.A., Meeker, M.S., Twickler, M.S., Whitlow, S.I. and Pittalwala, I.I.  1997.  Bipolar changes in atmospheric circulation during the Little Ice Age.  Science 277: 1294-1296.

Lewis, J., Dodge, J.D. and Powell, A.J.  1990.  Quaternary dinoflagellate cysts from the upwelling system offshore Peru, Hole 686B, ODP Leg 112.  In: Suess, E., von Huene, R., et al. (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results 112.  Ocean Drilling Program, College Station, TX, pp. 323-328.

Linderholm, H.W. and Gunnarson, B.E.  2005.  Summer temperature variability in central Scandinavia during the last 3600 years.  Geografiska Annaler 87A: 231-241.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1999.  Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations.  Geophysical Research Letters 26: 759-762.

McDermott, F., Mattey, D.P. and Hawkesworth, C.  2001.  Centennial-scale Holocene climate variability revealed by a high-resolution speleothem δ18O record from SW Ireland.  Science 294: 1328-1331.

Nesje, A., Dahl, S.O., Matthews, J.A. and Berrisford, M.S.  2001.  A ~ 4500-yr record of river floods obtained from a sediment core in Lake Atnsjoen, eastern Norway.  Journal of Paleolimnology 25: 329-342.

O'Brian, S.R., Mayewski, P.A., Meeker, I.D., Meese, D.A., Twickler, M.S. and Whitlow, S.I.  1995.  Complexity of Holocene climate as reconstructed from a Greenland ice core.  Science 270: 1962-1964.

Roncaglia, L.  2004.  Palynofacies analysis and organic-walled dinoflagellate cysts as indicators of palaeo-hydrographic changes: an example from Holocene sediments in Skalafjord, Faroe Islands.  Marine Micropaleontology 50: 21-42.

Sangiorgi, F., Capotondi, L. and Brinkhuis, H.  2002.  A centennial scale organic-walled dinoflagellate cyst record of the last deglaciation in the South Adriatic Sea (Central Mediterranean).  Palaeogeography, Palaeoclimatology, Palaeoecology 186: 199-216.

Velle, G.  1998.  A paleoecological study of chironomids (Insecta: Diptera) with special reference to climate.  M.Sc. Thesis, University of Bergen.

Last updated 7 December 2005