4th millennium BC
(5th millennium BC – 4th millennium BC – 3rd millennium BC - other millennia)
Events Environmental changes Based on studies by glaciologist Lonnie Thompson (professor at Ohio State University and researcher with the Byrd Polar Research Center) [1] a number of indicators shows there were a global change in climate 5,200 years ago: The climate was altered suddenly with severe impacts.Plants buried in the Quelccaya ice cap in the Peruvian Andes demonstrate the climate had shifted suddenly and severely to capture the plants and preserve them until now.A man trapped in an Alpine glacier ("Oetzi") is frozen until his discovery in 1991.Tree rings from Ireland and England show this was their driest period.Ice core records showing the ratio of two oxygen isotopes retrieved from the ice fields atop Africa’s Mount Kilimanjaro, a proxy for atmospheric temperature at the time snow fell. Major changes in plant pollen uncovered from lakebed cores in South America. Record lowest levels of methane retrieved from ice cores from Greenland and Antarctica. Beginning of desertification of Sahara (35th century BC). The shift by the Sahara Desert from a habitable region to a barren desert.
Significant persons
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