In three years, the temperature in Greenland fell by ten degrees Celsius.

This happened approximately twelve thousand nine hundred years ago. The evidence is preserved in the layered ice of the Greenland ice sheet, in the GISP2 and GRIP cores extracted by international research teams in the nineteen nineties. The cooling was global. North America dropped three degrees. Europe dropped between two and six. The planet's climate did not slowly degrade. It collapsed.

The event is called the Younger Dryas. It lasted approximately one thousand three hundred years. During that interval, the woolly mammoth, the American mastodon, the saber-toothed tiger, the giant ground sloth, and most of the rest of the Pleistocene megafauna of North America disappeared. The Clovis people, the dominant human culture of the continent, vanished from the archaeological record at the same boundary.

RECOMMENDATION: Maintain active monitoring of the named entities and systems. Refer requests for declassified detail to the Office of Operations. The ice has been waiting twelve thousand nine hundred years to be read.