4th Millennium BC - Environmental Changes

Environmental Changes

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 was a global change in climate 5,200 years ago, probably due to a drop in solar energy output as hypothesized by Ohio State University.

• 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 ("Ötzi the Iceman") 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.
• End of the Neolithic Subpluvial, start of desertification of Sahara (35th century BC). North Africa shifts from a habitable region to a barren desert.