Piora Oscillation (jan 1, 3900 BC – jan 1, 3000 BC)

Description:

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.

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]