(5th millennium BC – 4th millennium BC – 3rd millennium BC - other millennia)
Based on studies by glaciologist Lonnie Thompson (professor at Ohio State University and researcher with the Byrd Polar Research Center)  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.
Inventions, discoveries, introductions