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 exercise, 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; and these distinctive periods were even more strongly expressed than were the Medieval Warm Period and Little Ice Age.

A similar pattern of climate change was observed in Iceland: by Jiang et al. (2002), who used diatom assemblages from a high-resolution core extracted from the seabed of the north Icelandic shelf to reconstruct a 4600-year history of mean summer sea surface temperature at that location, and by Olafsdottir et al. (2001), who simulated the spatial relationship between temperature change and potential vegetation cover for Iceland over the period of the Holocene and calibrated their results against palynological and geomorphological data.

Evidence for the Dark Ages Cold Period in Europe was also found in the Mediterranean Sea by Castagnoli et al. (2002), who developed a 1400-year δ¹³C record of the foraminifera Globigerinoides rubber by analyzing a sediment core extracted from the Gallipoli terrace of the Gulf of Taranto.  Starting at the beginning of the record, δ¹³C values increased from about 0.4 per mil around 600 AD to a value of 0.8 per mil by 900 AD; and the researchers suggest that this increase was likely driven by the increase in oceanic productivity that accompanied the climatic transition from the Dark Ages Cold Period to the Medieval Warm Period.

To the west in Iberia, Desprat et al. (2003) conducted a high-resolution pollen analysis of a sediment core retrieved from the central axis of the Ria de Vigo in the south of Galicia.  They determined that over the past 3000 years there was "an alternation of three relatively cold periods with three relatively warm episodes."  In order of their occurrence, these periods are described by Desprat et al. as the "first cold phase of the Subatlantic period (975-250 BC)," which was "followed by the Roman Warm Period (250 BC-450 AD)," which was followed by "a successive cold period (450-950 AD), the Dark Ages," which "was terminated by the onset of the Medieval Warm Period (950-1400 AD)," which was followed by "the Little Ice Age (1400-1850 AD), including the Maunder Minimum (at around 1700 AD)," which "was succeeded by the recent warming (1850 AD to the present)."  Desprat et al. additionally note that these findings from northwest Iberia parallel "global climatic changes recorded in North Atlantic marine records (Bond et al., 1997; Bianchi and McCave, 1999; Chapman and Shackelton, 2000)."

In Germany, Niggemann et al. (2003) analyzed petrographical and geochemical properties of three stalagmites found in a cave in Sauerland from which they developed a climatic history covering the last 17,600 years.  The results, in their words, "resemble records from an Irish stalagmite (McDermott et al., 1999)."  Specifically, they note that their data provide evidence for the existence of the Little Ice Age, the Medieval Warm Period and the Roman Warm Period, which also implies the existence of the Dark Ages Cold Period that separated the Medieval and Roman Warm Periods.

Similar results were obtained in northern Europe by Grudd et al. (2002), who assembled tree-ring widths from 880 living, dead and subfossil northern Swedish pines into a continuous and precisely dated chronology covering the period 5407 BC to AD 1997.  The strong association between these data and summer mean temperatures of the final 129 years of this period enabled them to produce a 7400-year history of summer mean temperature for northern Swedish Lapland.  The most dependable portion of the record, based upon the number of trees that were sampled, were the last two millennia, which Grudd et al. say "display features of century-timescale climatic variation known from other proxy and historical sources, including a warm 'Roman' period in the first centuries AD and a generally cold 'Dark Ages' climate from about AD 500 to about AD 900," after which came the Medieval Warm Period, Little Ice Age and Modern Warm Period.

Off the coast of Europe in the eastern Norwegian Sea, Andersson et al. (2003) reconstructed a 3000-year history of surface conditions above the Voring Plateau from planktic stable isotope and foraminiferal assemblage patterns derived from analyses of two sediment cores.  The temperature history they developed was remarkably similar to the one developed by McDermott et al. (2001) in southwestern Ireland.  Both records began during the end-stage of the long cold period that preceded the Roman Warm Period, both depicted warming from that point in time to the peak of the Roman Warm Period (which occurred about 2000 years BP), and both depicted a subsequent descent into the Dark Ages Cold Period, which held sway until the increase in temperature that produced the Medieval Warm Period.

We conclude this summary with some brief remarks of Berglund (2003) about the impact of the Dark Ages Cold Period on Northwest Europe.  Based on a history of reconstructed climate derived from data pertaining to "insolation, glacier activity, lake and sea levels, bog growth, tree line, and tree growth," this exercise, in his words, revealed "a positive correlation between human impact/land-use and climate change."  Specifically, Berglund reports there was a great "retreat of agriculture" centered on about AD 500, which led to "reforestation in large areas of central Europe and Scandinavia."  He additionally reports 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)."  Following the depression of human activity associated with the Dark Ages Cold Period, however, Berglund says there was a "boom period" that covered "several centuries from AD 700 to 1100," as the region basked in the redeeming climate of the Medieval Warm Period.

In conclusion, the Dark Ages Cold Period has been observed in paleoclimatic data from all parts of Europe, often in long temperature histories that reveal the existence of similar multi-century cold intervals sandwiched between equally significant periods of warmth.  In Europe, as in Asia, there is also evidence that the Dark Ages Cold Period was not a particularly good time for human societies residing in the northern parts of the continent.

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

Bianchi, G.G. and McCave, I.N.  1999.  Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland.  Nature 397: 515-517.

Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., de Menocal, 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.

Castagnoli, G.C., Bonino, G., Taricco, C. and Bernasconi, S.M.  2002.  Solar radiation variability in the last 1400 years recorded in the carbon isotope ratio of a Mediterranean sea core.  Advances in Space Research 29: 1989-1994.

Chapman, M.R. and Shackelton, N.L.  2000.  Evidence of 550-year and 1000-year cyclicities in North Atlantic circulation patterns during the Holocene.  The Holocene 10: 287-291.

Desprat, S., Goñi, M.F.S. and Loutre, M.-F.  2003.  Revealing climatic variability of the last three millennia in northwestern Ibera using pollen influx data.  Earth and Planetary Science Letters 213: 63-78.

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.

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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.

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Niggemann, S., Mangini, A., Richter, D.K. and Wurth, G.  2003.  A paleoclimate record of the last 17,600 years in stalagmites from the B7 cave, Sauerland, Germany.  Quaternary Science Reviews 22: 555-567.

Olafsdottir, R., Schlyter, P. and Haraldsson, H.V.  2001.  Simulating Icelandic vegetation cover during the Holocene: Implications for long-term land degradation.  Geografiska Annaler 83 A:203-215.