Climate change refers to the changes in average weather conditions that generally occur over long periods of time, usually centuries or longer. Occasionally, these changes can occur more rapidly, in periods as short as decades. Such climate changes are often characterized as "abrupt."

Weather or Climate?

Climate change refers to a change in the average temperature, precipitation, winds, and other aspects of the climate system, in contrast to weather, which describes the constantly changing atmospheric circulation (including storms and the hurricane shown here).

Examining the Paleo Record
Abrupt Climate Change: Past, Present & Future
Mechanisms of Change
Example 1: Glacial-Interglacial transitions
Example 2: Thermohaline Circulation
Example 3: Vegetation Feedbacks

Introduction

Paleoclimate evidence from ice cores, tree rings, and other natural recorders reveals that large changes in climate such as in temperature and precipitation have happened in the past. The changes have occurred over decades to centuries, sometimes affecting small regions and sometimes entire hemispheres. The changes are massive compared to anything we have experienced since people have been keeping records of climate. What if these abrupt climate changes were to occur in the future? Would ecosystems be affected? How would humans adapt? These questions motivate a vigorous research effort to understand the changes of the past, and eventually to predict future abrupt climate change.

Although we have been actively studying the issue and the science is growing rapidly, there is a lot we don't understand and much we need to know before we can make reliable predictions. Even the definition of abrupt climate change is being refined. The scientific literature documenting abrupt change events (including the recent NRC Abrupt Climate Change publication and a four-page overview) is growing rapidly, and new methods are being developed to document and understand abrupt change. Until recently, many scientists studying changes and variations in the climate thought that the climate system was slow to change, and that it took many thousands if not millions of years for ice ages and other major events to occur. Scientists are just beginning to formulate and test hypotheses regarding the causes of abrupt climate change, but only a handful of attempts have been made to model abrupt change using computer models. These efforts are focused not only on past events, but also on abrupt events that might occur in the future as greenhouse gases increase in the atmosphere and temperatures continue to rise.

The following definitions represent two evolving attempts to characterize abrupt climate change:

Mechanistic definition	Impacts-based definition
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.	Change of the climate system that is faster than the adaptation time of social and/or ecosystems.

Abrupt climate change can occur within decades (end of the Younger Dryas) or centuries. Both are abrupt events because they are fast relative to the cause.

Next: Examining the Paleo Record

Acknowledgements

References

Site Map


NOAA > NESDIS > NCDC > NOAA Paleoclimatology > Abrupt Home > The Story

Introduction

Mechanistic definition

Impacts-based definition

Next: Examining the Paleo Record