An abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause. (NRC, 2002)

transition of the climate system into a different state (of temperature, rainfall, and other aspects) on a time scale that is faster than the responsible forcing (mechanistic); change of the climate system that is faster than the adaptation time of social and/or ecosystems (impacts).

A change in climate over a widespread area that takes place so rapidly and unexpectedly that human and natural systems have difficulty adapting. Although not considered a high probability, an abrupt climate change occurs on the scale of decades, rather than centuries, and persists for years. Global warming has been suggested as a plausible trigger for abrupt climate change. Atmosphere: The gaseous envelope or layers surrounding the earthâ€(tm)s surface. It contains roughly 78% nitrogen, 21% oxygen and 1% argon, with trace amounts of other gases including the significant greenhouse gases of carbon dioxide, methane and nitrous oxide. The atmosphere absorbs solar radiation and serves to moderate surface temperature and recycles water and other chemicals.