Illinois State Water Survey - University of Illinois at Urbana-Champaign

State Climatologist Office for Illinois

Glossary of Climate Terms

climate change - Any systematic change in the long-term statistics of climate elements (such as temperature, pressure, or winds) sustained over several decades or longer. Climate change may be due to natural external forcings, such as changes in solar emission or slow changes in the earth's orbital elements; natural internal processes of the climate system; or anthropogenic forcing.

climate variability - The temporal variations of the atmosphere-ocean system around a mean state. Typically, this term is used for timescales longer than those associated with synoptic weather events (i.e., months to millennia and longer). The term "natural climate variability"; is further used to identify climate variations that are not attributable to or influenced by any activity related to humans.

climate - The slowly varying aspects of the atmosphere–hydrosphere–land surface system. It is typically characterized in terms of suitable averages of the climate system over periods of a month or more, taking into consideration the variability in time of these averaged quantities. Climatic classifications include the spatial variation of these time-averaged variables. Beginning with the view of local climate as little more than the annual course of long-term averages of surface temperature and precipitation, the concept of climate has broadened and evolved in recent decades in response to the increased understanding of the underlying processes that determine climate and its variability.

climatic discontinuity - A climate change that consists of a rather abrupt and permanent change during the period of record from one average value (for the early part of the record) to a distinctly different average value (for the later part of the record).

climatic fluctuation—A climatic inconstancy that consists of any form of systematic change, whether regular or irregular, except climatic trend and climatic discontinuity. It is characterized by at least two maxima (or minima) and one minimum (or maximum) including those at the end points of the record.

climatic trend - A climate change characterized by a reasonably smooth, monotonic increase or decrease of the average value of one or more climatic elements during the period of record.

anthropogenic - Human-induced or resulting from human activities; often used to refer to environmental changes, global or local in scale.

climate system - The system, consisting of the atmosphere, hydrosphere, lithosphere, and biosphere, determining the earth's climate as the result of mutual interactions and responses to external influences (forcing). Physical, chemical, and biological processes are involved in the interactions among the components of the climate system.

These terms are from the American Meteorological Society's Glossary of Meteorology

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