Climate can exhibit abrupt shifts over large regions of the world. As the last glacial period was giving way to the current warm interglacial period, average temperatures in Greenland returned to glacial levels for more than 1,000 years. This unusual period, which is called the Younger Dryas, ended abruptly about 12,000 years ago. Evidence from an ice core drilled in Greenland indicates that temperatures there rose approximately 15°F (8°C) in less than a decade. No Audio.