What is Abrupt Climate Change?

Abrupt climate change (ACC) refers to rapid state changes in the climate system that are either transient or persistent, and of variable magnitude.  ACC includes dramatic changes in temperature, atmospheric circulation, and precipitation, and can occur in less than a decade and in some cases in less than 1 – 2 years.  A classic example of ACC is the Younger Dryas period of cold conditions at the end of the Pleistocene.  However, periods of rapid change to cool poles and dry tropics, sustained for 200 to 1,000 years, occurred several times over the past 10,000 years, with civilizations around the world flourishing or failing during these periods. State shifts in the climate system have also occurred during the 20th century, including an upward shift in observed global mean temperatures in the 1970s and increased storm frequency and severity in many regions of the US since 1950.



 “Severe droughts and other past abrupt climate changes have had demonstrable, adverse effects on human societies.  While it is important not to be fatalistic about the threats posed by abrupt climate change, denying the likelihood or downplaying the relevance of past abrupt events could be costly. Increased knowledge is the best way to improve the effectiveness of response; research into the causes, patterns, and likelihood of abrupt climate change can help reduce vulnerabilities and increase our ability to adapt.”

(National Research Council, 2004)