The Piora Oscillation was an abrupt cold and wet period in the climate history of the Holocene Epoch; it is roughly dated to c. 3900-3000 BC. Some researchers associate the Piora Oscillation with the end of the Atlantic climate regime, and the start of the Sub-Boreal, in the Blytt–Sernander sequence of Holocene climates.

The spatial extent of the change is unclear; it does not show up as a major, or even identifiable, event in hemispheric temperature reconstructions.

First detection

The phenomenon is named after the Val Piora or Piora Valley in Switzerland, where it was first detected; some of the most dramatic evidence of the Piora Oscillation comes from the region of the Alps.^[1] Glaciers advanced in the Alps, apparently for the first time since the Holocene climatic optimum; the Alpine tree line dropped by 100 meters. In the Middle East, the surface of the Dead Sea rose nearly 100 meters (300 feet), then receded to a more usual level. It also triggered the collapse of the Uruk period, through decreased temperatures and increased rainfall,^[2] which were believed to contribute to Babylonian and Hebrew flood myths.^[3]

Link to horse domestication

The Piora Oscillation has also been linked to the domestication of the horse. In Central Asia, a colder climate favored the use of horses: "The horse, since it was so adept at foraging with snow on the ground, tended to replace cattle and sheep."^[4] The Piora period seems associated with a period of colder drier air over the Western and Eastern Mediterranean, and may have depressed rainfalls as far afield as the Middle East. It is also associated with a sudden onset of drier weather in the central Sahara.

Causes

The cause or causes of the Piora Oscillation are debated. A Greenland ice core, GISP2, shows a sulfate spike and methane trough c. 3250 BCE, suggesting an unusual occurrence — either a volcanic eruption or a meteor or an asteroid impact event. Other authorities associate the Piora Oscillation with other comparable events, like the 8.2 kiloyear event, that recur in climate history, as part of a larger 1500-year climate cycle.

It may also be caused by changes in solar activity and orbital parameters. ^[5]

See also

• Bond event
• 4.2-kiloyear event
• Bølling–Allerød warming
• African humid period
• Older Peron

Notes

References

• Baronia, Carlo; Orombelli, Giuseppe (1996). "The Alpine "Iceman" and Holocene Climatic Change". Quaternary Research. 46 (1): 78–83. Bibcode:1996QuRes..46...78B. doi:10.1006/qres.1996.0046. S2CID 128772817.
• Burroughs, William J. (2003). Climate: Into the 21st Century. Cambridge: Cambridge University Press. ISBN 0-521-79202-9.
• Caseldine, C.; Thompson, G.; Langdon, C.; Hendon, D. (2005). "Evidence for an extreme climatic event on Achill Island, Co. Mayo, Ireland around 5200–5100 cal. yr BP". Journal of Quaternary Science. 20 (2): 169–178. Bibcode:2005JQS....20..169C. doi:10.1002/jqs.901. S2CID 140619228.
• Hou, Mei; Wu, Wen Xiang (5 December 2020). "A review of 6000-5000 cal BP climatic anomalies in China". Quaternary International. 571: 58–72. doi:10.1016/j.quaint.2020.12.004. ISSN 1040-6182.
• Lamb, Hubert H. (1995). Climate, History, and the Modern World. London: Routledge. ISBN 0-415-12735-1.
• Magny, Michel; Haas, Jean Nicolas (2004). "A major widespread climatic change around 5300 cal. yr BP at the time of the Alpine Iceman". Journal of Quaternary Science. 19 (5): 423–430. Bibcode:2004JQS....19..423M. doi:10.1002/jqs.850. S2CID 128697360.
• Matossian, Mary A. K. (1997). Shaping World History: Breakthroughs in Ecology, Technology, Science, and Politics. New York: M. E. Sharpe. ISBN 0-7656-0061-7.
• Wick, Lucia; Tinner, Willy (1997). "Vegetation Changes and Timberline Fluctuations in the Central Alps as Indicators of Holocene Climatic Oscillations". Arctic and Alpine Research. 29 (4): 445–458. doi:10.2307/1551992. JSTOR 1551992.