Climate change often isn’t gradual. It’s sudden and ferocious. When it happens, we won’t have time to adjust.

A National Academy of Sciences study published this year, ”Abrupt Climate Change: Inevitable Surprises,” collates a mass of geological evidence showing that the earth’s climate system is a jumpy beast: long, dormant spells are overturned suddenly by drastic events. Instead of smoothly transitioning over 10,000 years from ice age to warm era, the earth jumps from one ”regime” to another in just a few years.

For instance, 11,500-year-old ice cores taken from Greenland show that annual precipitation doubled in three years and that the annual mean temperature jumped 14 degrees in just 10 years. ”That means a third to half of the warming that took place between the last ice age and today all happened in one decade,” says Richard Alley, the Penn State geologist who presided over the study. Two dozen such climate jumps have occurred in the last 100,000 years.