Short answers, pulled from the story.
Abrupt climate change is defined as a shift into a different mode on a time scale faster than the responsible forcing. This physical definition explains how such changes occur within the climate system.
The Younger Dryas event began 12,800 years ago and moved back into a warm-and-wet climate regime about 11,600 years ago. It is the most recent of the Dansgaard, Oeschger cycles.
The Greenland Sea flushing at 75 degrees north shut down in 1978 and recovered over the next decade. The second-largest flushing site, the Labrador Sea, shut down in 1997 for ten years.
Up to 95 percent of all species became extinct during this period. Life on land took 30 million years to recover from these wide-ranging and severe impacts.
Tropical rainforests were devastated by climate change resulting in a cooler and drier climate. This shift had a severe effect on amphibian biodiversity.