Chaotic Climate; November 1995; Scientific American Magazine; by Broecker; 7 Page(s)

The past 10,000 years are anomalous in the history of our planet. This period, during which civilization developed, was marked by weather more consistent and equable than any similar time span of the past 100 millennia. Cores drilled through several parts of the Greenland ice cap show a series of cold snaps and warm spells-- each lasting 1,000 years or more--that raised or lowered the average winter temperature in northern Europe by as much as 10 degrees Celsius over the course of as little as a decade. The signs of these sudden changes can be read in the records of atmospheric dust, methane content and precipitation preserved in the annual ice layers.

The last millennium-long cold period, known as the Younger Dryas (after a tundra flower whose habitat expanded significantly), ended about 11,000 years ago. Its marks can be found in North Atlantic marine sediments, Scandinavian and Icelandic glacial moraines, and northern European and maritime Canadian lakes and bogs. New England also cooled significantly.