The above graphic, derived from sampling of an ice core in Greenland, shows a

historical tendency for particular regions to experience periods of abrupt cooling

within periods of general warming.1 

The Cooling Event 8,200 Years Ago 

The climate change scenario outlined in this report is modeled on a century-long

climate event that records from an ice core in Greenland indicate occurred 8,200

years ago.  Immediately following an extended period of warming, much like the

phase we appear to be in today, there was a sudden cooling .  Average annual

temperatures in Greenland dropped by roughly 5 degrees Fahrenheit, and

temperature decreases nearly this large are likely to have occurred throughout the

North Atlantic region. During the 8,200 event severe winters in Europe and some

other areas caused glaciers to advance, rivers to freeze, and agricultural lands to be

less productive. Scientific evidence suggests that this event was associated with, and

perhaps caused by, a collapse of the ocean’s conveyor following a period of gradual

warming.

—From “An Abrupt Climate Change Scenario and Its Implications for United States National Security,” by Peter Schwartz and Doug Randall