What on Earth Happened in 3200 BC?

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For a more technical version of this page, with references, click HERE.

For the latest from the GISP2 team (Jan 96 Science) click HERE (takes 30 sec to load).

What was the climate like at the dawn of organized civilization, 5000 years ago? (3200 BC, or 5200 years BP, Before Present, the age of the unification of Egypt and Mesopotamia) This compilation of recent graphical representations of various paleoclimatic data from ice cores and other sources gives some clues.

a) Sulfate concentration in Greenland ice. Notice the huge spike at 3200 years BC. What caused this? A comet? Volcano? Or just a local swamp? Scientists are still debating the question. There are indications that volcanos can cause a great fog to envelop the world, lowering the temperature several degrees, leaving their marks on the ice cores of the north as well asmethane-producing vegetation at 3200 BC, followed by and explosive growth?

c) Dead Sea levels rose 300 feet at 3200 BC. The Jordan River must have been a tropical paradise.

d) Ice core oxygen isotope ratio; the higher the curve, the warmer the temperature. What was the big freeze-up at 5000 years BP?

e) Greenland Dye 3 oxygen isotope ratio. Minimum value between 2000 and 8000 cal yrs BP occurs just before 5000 yrs BP. Data from National Snow and Ice Data Center. A large acid peak at 3150 BC is suggestive of a volcanic event. For additional ice data from the southern hemisphere click here.

f) Data from Belfast 7272 year oak tree ring chronology; (f) is an index of the tree ring narrowness, corresponding to cold weather in Ireland. The peak in (g) at about 3150 BC followed by the maximum tree and site sample size suggest a major climatic event at this time. Similar sudden increase in swamp oak (mooreichen, still used to make furniture in Germany) shows up at 5100 BP on the Danube. Much of this information comes from the oaks of Ireland.

h) Heavy flooding in Navajo country, the American Southwest, based on paleoflooding studies. The peak at 5K yrs BP represents 8 sites.

i) Arid interval 5010-4860 (+/- 150) Morocco. Corresponding decline in oaks suggests reduced winter precipitation corresponding to cooler sea temperatures in North Atlantic.

Some tentative conclusions: Millennial-scale warming terminates with a period of climatic disturbance (so-called "Piora oscillation") and flooding in the lower latitudes (Nile, Arizona, Morocco, Israel, Mesopotamia), followed by a drought; general, worldwide, climate-driven shock to early societies living in "edenic" geography of plenty with "fertile crescent" survivors organizing into more centrally directed and hierarchical culture based on irrigation. Abrupt cooling at higher latitudes, possibly related to oceanic effects, especially in Northern Europe, corresponding to peak of megalith cultures. Probable oscillation in sea level at 3200 BC followed by 10-15 ft. alluvial deposition in river valleys.