Climate Science: Investigating Climatic and Environmental Processes
Abrupt Climate Change
We have all experienced dramatic changes of weather, as when a sudden storm blows through the region or a shift in the jet stream sends a cold front our way and temperatures plummet. Extreme weather events can include hurricane, flash floods or blizzards.

Abrupt climate change, on the other hand, has very different causes and effects. While climate is often remarkably steady with expected norms of daily and seasonal fluctuations, paleoclimate research has shown that climate can in fact change very quickly, in a matter of seasons and years rather than centuries or millennia as was previously thought.

One example of abrupt climate change is an event that happened some 11,600 years ago at the termination of the Younger Dryas cold event, which was the last blast of cold climate at the end of the last Ice Age some.

Ice core records from Greenland show in less than a decade there was a sudden warming of around 15 degrees Celsius (27^oF) of the annual mean temperature. At the same time a doubling of annual precipitation occurred. Researcher Richard Alley suggests that not only does the climate system have dials that slowly alter climate patterns, there are also switches that can suddenly shift climate in dramatic ways. (Source: Alley, et al. 1993. Graphic above from CLIVAR.) This abrupt event can be found in paleo records from many parts of the world, although not necessarily to such an extreme degree. While the exact causes of abrupt climate changes have yet to be clearly established, one area of research that is receiving a great deal of attention the Thermohaline Circulation system and what role it may play on abrupt climate shifts.

Abrupt changes in climate can occur at many time scales, and while usually they are abrupt warming events, sudden cooling can occur as well. Recent studies such as the National Academy of Science's Abrupt Climate Change: Inevitable Surprises note that it is not a matter if such events will occur in the future but when.

For more on abrupt climate change during the last Ice Age, see Climate History 100,000, and in the Holocene, see Climate Science 10,000. Further back in Earth's history there have also been cataclysmic events that have triggered severe climatic and environmental changes that triggered mass extinctions of species. See Climate Science Beyond for an overview.

Listen to an interview about climate variability on Fresh Air with Paul Mayewski, who led the National Science Foundation's Greenland Ice Sheet Project 2. (Requires Real Audio)