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Climate Oscillations (Millennial Variability - Europe) -- Summary
Much of the early evidence for a global millennial-scale oscillation of climate originated in Europe. Newer studies employing a number of different techniques and covering a variety of time spans continue to confirm the existence of this natural phenomenon in diverse parts of the continent, all of which evidence suggests that 20th-century global warming is merely a manifestation of this ubiquitous non-CO2-induced climatic cycle.

McDermott et al. (2001) derived a ğ18O record from a stalagmite found in a cave in southwestern Ireland, the time resolution of which is described by them as being "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." They additionally report that their 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 cave data are the signatures of the earlier Roman Warm Period and Dark Ages Cold Period that comprised the prior such cycle of climate in that region. Commenting on the coherent ğ18O variations in the records from both sides of the North Atlantic, McDermott et al. say they "indicate that many of the subtle multicentury ğ18O variations in the Greenland ice cores reflect regional North Atlantic margin climate signals rather than local effects."

Utilizing a vastly different technique, Dapples et al. (2003) developed a chronology of Holocene landslide events in the Eastern and Western Swiss Alps, wherein the three most recent and best documented periods of landslide activity were determined to be 3500-2100, 1700-1150 and 750-300 years before present (BP). They report that these periods can be related to significant climatic deteriorations associated "with periods of more cold and humid conditions," and we note that these intervals of heightened landslide activity were largely coeval, in reverse order, with the Little Ice Age, the Dark Ages Cold Period, and the long unnamed cold period that preceded the Roman Warm Period.

Desprat et al. (2003) used yet another technique to broach the subject of millennial-scale oscillations of climate in Europe, studying the climatic variability of the last three millennia in northwest Iberia via 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 found, in their words, "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)." They thus declared that "a millennial-scale climatic cyclicity over the last 3000 years is detected for the first time in NW Iberia paralleling global climatic changes recorded in North Atlantic marine records (Bond et al., 1997; Bianchi and McCave, 1999; Chapman and Shackelton, 2000)," additionally stating that the "solar radiative budget and oceanic circulation seem to be the main mechanisms forcing this cyclicity in NW Iberia."

A fourth approach to the subject was employed by Andersson et al. (2003), who 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 spanned a depth interval corresponding to the last three thousand years. The climate history derived from this study is remarkably similar to that derived by McDermott et al. in southwestern Ireland. At the beginning of the 3000-year-long Voring Plateau record, 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. As another point of interest, neither record indicates the existence of much recent warmth; and Andersson et al. report that "surface ocean conditions warmer than present were common during the past 3000 years."

Also working at sea, in this case the Tyrrhenian Sea, Sbaffi et al. (2004) derived proxy temperature records from two sediment cores that provide new insights into the climatic variability of the region encompassing the Mediterranean basin during the termination of the last great ice age and throughout the Holocene. Their work revealed a climatic oscillation with a period of between 1400 and 1700 years; and they note that the timing and intensity of the oscillation is "in good agreement with others previously identified in the Mediterranean basin." Specifically, they report that in both the western and eastern Mediterranean, "evidences of Holocene climate instability have been interpreted as implying 1-2°C variations in sea surface temperatures (Rohling et al., 1997; De Rijk et al., 1999; Cacho et al., 2001; Sbaffi et al., 2001)," and they say that "these fluctuations are considered to be closely linked with the more extended events observed in the north Atlantic Ocean," i.e., "the original 1500 year cycle highlighted in north Atlantic studies of the late 1990s (O'Brien et al., 1995; Bond et al., 1997; Campbell et al., 1998)."

On another research front, Holzhauser et al. (2005) derived high-resolution records of variations in glacier size in the Swiss Alps, which together with lake-level fluctuations in the Jura mountains, the northern French Pre-Alps and the Swiss Plateau were used in developing a 3500-year climate history of west-central Europe, beginning with an in-depth analysis of the Great Aletsch glacier, which is the largest of all glaciers located in the European Alps. Near the beginning of this period, the three researchers determined that "during the late Bronze Age Optimum from 1350 to 1250 BC, the Great Aletsch glacier was approximately 1000 m shorter than it is today," noting that "the period from 1450 to 1250 BC has been recognized as a warm-dry phase in other Alpine and Northern Hemisphere proxies (Tinner et al., 2003)." Then, after an intervening unnamed cold-wet phase, when the glacier grew in both mass and length, they say that "during the Iron/Roman Age Optimum between c. 200 BC and AD 50," which is perhaps better known as the Roman Warm Period, the glacier again retreated and "reached today's extent or was even somewhat shorter than today."

Next came the Dark Ages Cold Period, which Holzhauser et al. say was followed by "the Medieval Warm Period, from around AD 800 to the onset of the Little Ice Age around AD 1300," which latter cold-wet phase was "characterized by three successive [glacier length] peaks: a first maximum after 1369 (in the late 1370s), a second between 1670 and 1680, and a third at 1859/60," following which the glacier began its latest and still-ongoing recession in 1865. In addition, they state that written documents from the 15th century indicate that at some time during that hundred-year interval "the glacier was of a size similar to that of the 1930s," which latter period in many parts of the world was as warm as, or even warmer than, it is today, in harmony with a growing body of evidence which suggests that a "Little" Medieval Warm Period manifested itself during the 15th century within the broader expanse of the Little Ice Age (see Little Medieval Warm Period in our Subject Index).

Data pertaining to the Gorner glacier (the second largest of the Swiss Alps) and the Lower Grindelwald glacier of the Bernese Alps tell much the same story, as Holzhauser et al. report that these glaciers and the Great Aletsch glacier "experienced nearly synchronous advances" throughout the study period.

With respect to what was responsible for the millennial-scale climatic oscillation that produced the alternating periods of cold-wet and warm-dry conditions that fostered the similarly-paced cycle of glacier growth and retreat, the Swiss and French scientists report that "glacier maximums coincided with radiocarbon peaks, i.e., periods of weaker solar activity," which in their estimation "suggests a possible solar origin of the climate oscillations punctuating the last 3500 years in west-central Europe, in agreement with previous studies (Denton and Karlen, 1973; Magny, 1993; van Geel et al., 1996; Bond et al., 2001)." And to underscore this point, they conclude their paper by stating that "a comparison between the fluctuations of the Great Aletsch glacier and the variations in the atmospheric residual 14C records supports the hypothesis that variations in solar activity were a major forcing factor of climate oscillations in west-central Europe during the late Holocene."

Finally, in a study reaching much further back in time, Muller et al. (2005) examined pollen grains found in a sediment core retrieved from a lake in the southwest German alpine foreland, producing a climate history of this region for the penultimate interglacial (126,000 - 110,000 years BP). Their analysis revealed the presence of 11 major cold events having an average recurrence time of approximately 1450 years, which periodicity is essentially identical to that of the millennial-scale oscillation of climate that has prevailed throughout the current interglacial (Bond et al., 1997, 2001; DeMenocal et al., 2000; McDermott et al., 2001; Gupta et al., 2003; Hu et al., 2003), as well as the similar oscillation that has been documented throughout interglacial and glacial periods alike over the past half-million years (McManus et al., 1999) and the equivalent oscillation that was present even before the development of the large 100,000-year ice sheets characteristic of the late Pleistocene (Raymo et al., 1998). As for the cause of the 1450-year cycle, Müller et al. have no definitive answer, but they suggest that it may ultimately be the product of variations in solar activity.

In light of the revelations of these diverse (in space, time and means of acquisition) data sets, plus the similar revelations of many earlier studies, it appears that wherever one turns in Europe, and through whatever investigative glasses one looks in attempting to discern the continent's climatic history, the data that are found all tell essentially the same story, i.e., that the region's current warmth is merely the most recent manifestation of the natural and likely solar-induced millennial-scale oscillation of climate that produced the earlier Medieval and Roman Warm Periods, as well as all of the similarly sized and spaced warm epochs going as far back in time as scientists have been able to probe, which findings suggest that the historical rise in the air's CO2 concentration has had little or nothing to do with 20th-century global warming.

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.

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., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I. and Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science 294: 2130-2136.

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.

Cacho, I., Grimalt, J.O., Canals, M., Sbaffi, L., Shackleton, N.J., Schonfeld, J. and Zahn, R. 2001. Variability of the Western Mediterranean Sea surface temperature during the last 30,000 years and its connection with the northern hemisphere climatic changes. Paleoceanography 16: 40-52.

Campbell, I.D., Campbell, C., Apps, M.J., Rutter, N. and Bush, A.B.G. 1998. Late Holocene ~1500 yr climatic periodicities and their implications. Geology 26: 471-473.

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.

Dapples, F., Oswald, D., Raetzo, H., Lardelli, T. and Zwahlen, P. 2003. New records of Holocene landslide activity in the Western and Eastern Swiss Alps: Implication of climate and vegetation changes. Eclogae geologicae Helvetiae 96: 1-9.

DeMenocal, P., Ortiz, J., Guilderson, T. and Sarnthein, M. 2000. Coherent high- and low-latitude variability during the Holocene warm period. Science 288: 2198-2202.

De Rijk, S., Hayes, A. and Rohling, E.J. 1999. Eastern Mediterranean sapropel SI interruption: an expression of the onset of climatic deterioration around 7 ka B.P. Marine Geology 153: 337-343.

Denton, G.H. and Karlen, W. 1973. Holocene climate variations - their pattern and possible cause. Quaternary Research 3: 155-205.

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.

Gupta, A.K., Anderson, D.M. and Overpeck, J.T. 2003. Abrupt changes in the Asian southwest monsson during the Holocene and their links to the North Atlantic Ocean. Nature 421: 354-356.

Hu, F.S., Kaufman, D., Yoneji, S., Nelson, D., Shemesh, A., Huang, Y., Tian, J., Bond, G., Clegg, B. and Brown, T. 2003. Cyclic variation and solar forcing of Holocene climate in the Alaskan subarctic. Science 301: 1890-1893.

Magny, M. 1993. Solar influences on Holocene climatic changes illustrated by correlations between past lake-level fluctuations and the atmospheric 14C record. Quaternary Research 40: 1-9.

McDermott, F., Mattey, D.P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem ğ18O record from SW Ireland. Science 294: 1328-1331.

McManus, J.F., Oppo, D.W. and Cullen, J.L. 1999. A 0.5-million-year record of millennial-scale climate variability in the North Atlantic. Science 283: 971-974.

Müller, S., Geyh, M.A., Pross, J. and Bond, G.C. 2005. Cyclic climate fluctuations during the last interglacial in central Europe. Geology 33: 449-452.

O'Brien, S.R., Mayewski, A., Meeker, L.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.

Raymo, M.E., Ganley, K., Carter, S., Oppo, D.W. and McManus, J. 1998. Millennial-scale climate instability during the early Pleistocene epoch. Nature 392: 699-702.

Rohling, E.J., Jorissen, F.J. and de Stigter, H.C. 1997. 200 years interruption of Holocene sapropel formation in the Adriatic Sea. Journal of Micropaleontology 16: 9-108.

Sbaffi, L., Wezel, F.C., Curzi, G. and Zoppi, U. 2004. Millennial- to centennial-scale palaeoclimatic variations during Termination I and the Holocene in the central Mediterranean Sea. Global and Planetary Change 40: 201-217.

Sbaffi, L., Wezel, F.C., Kallel, N., Paterne, M., Cacho, I., Ziveri, P. and Shackleton, N. 2001. Response of the pelagic environment to palaeoclimatic changes in the central Mediterranean Sea during the Late Quaternary. Marine Geology 178: 39-62.

Tinner, W., Lotter, A.F., Ammann, B., Condera, M., Hubschmied, P., van Leeuwan, J.F.N. and Wehrli, M. 2003. Climatic change and contemporaneous land-use phases north and south of the Alps 2300 BC to AD 800. Quaternary Science Reviews 22: 1447-1460.

van Geel, B., Buurman, J. and Waterbolk, H.T. 1996. Archaeological and palaeoecological indications of an abrupt climate change in the Netherlands and evidence for climatological teleconnections around 2650 BP. Journal of Quaternary Science 11: 451-460.

Last updated 9 August 2006