Roughly 14,700 years ago the weather patterns that bring snow to Greenland shifted from one year to the next—a pattern of abrupt change that was repeated 12,900 years ago and 11,700 years ago when the earth’s climate became the one enjoyed today—according to records preserved in an ice core taken from the northern island. These speedy changes—transitions from warming to cooling and back again—in the absence of changes in greenhouse gas could presage abrupt, catastrophic climate change in our future.

"What made these abrupt climate changes were circulation changes, and these changes took place from one year to the next more or less," says glaciologist Sune Olander Rasmussen of the Centre for Ice and Climate at the University of Copenhagen, who was part of a team that analyzed annual data from ice tubes extracted from as deep as 10,000 feet (3,085 meters) beneath the ice sheet, which were collected by the North Greenland Ice Core Project, a drilling expedition.

Oopsie.