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Frequently used terms in Climate Change studies.  The definitions found below also appear throughout the site when whenever one of the terms is used within the text.

100 Year Flood

A one-hundred-year flood is calculated to be the level of flood water expected to be equaled or exceeded every 100 years on average. The 100-year flood is more accurately referred to as the 1% annual exceedance probability flood, since it is a flood that has a 1% chance of being equaled or exceeded in any single year.

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IPCC title for the medium-high emissions scenario. A2 projects continuous population growth and uneven economic and technological growth. The income gap between now-industrialized and developing parts of the world does not narrow. Heat-trapping emissions increase through the 21st century; atmospheric CO2 concentration approximately triples, relative to pre-industrial levels, by 2100.


Adjustments in natural or human systems in response to actual or expected climatic stimuli or their effects, aimed at minimizing harm or taking advantage of beneficial opportunities.


IPCC title for the lower emissions scenario. B1 characterizes a world with high economic growth and a global population that peaks by mid-century and then declines. There is a rapid shift toward less fossil fuel-intensive industries and introduction of clean and resource-efficient technologies. Heat-trapping emissions peak about mid-century and then decline; CO2 concentration approximately doubles, relative to pre-industrial levels, by 2100.


Acronym for Bias-Correction Spatial Disaggregation. BCSD is a method used to downscale lower resolution projections to a higher resolution.


Acronym for Community Climate System Model, version 3.0. CCSM3 is a General Circulation Model (GCM) developed by the National Center for Atmospheric Research (NCAR).  More info »


Acronym for Centre National de Recherches Meteorologiques. CNRM is a General Circulation Model (GCM) developed by the Centre National de Recherches Meteorologiques, Meteo France. More info ».


Acronym for General Circulation Model. A GCM is a global, three-dimensional computer model of the climate system which can be used to simulate human-induced climate change. GCMs are highly complex and they represent the effects of such factors as reflective and absorptive properties of atmospheric water vapor, greenhouse gas concentrations, clouds, annual and daily solar heating, ocean temperatures and ice boundaries. The most recent GCMs include global representations of the atmosphere, oceans, and land surface.


Acronym for Geophysical Fluid Dynamics Laboratory. GFDL is a General Circulation Model (GCM) developed by NOAA's Geophysical Fluid Dynamics Laboratory. More info »


Consequences of climate change on natural and human systems. Depending on the consideration of adaptation, one can distinguish between potentialimpacts and residualimpacts.Potential impacts are thosethat may occur given a projected change in climate, without considering adaptation.


Acronym for Intergovernemtal Panel on Climate Change. IPCC is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. More Info »


Acronym for Parallel Climate Model. PCM1 is a General Circulation Model (GCM) developed by the National Center for Atmospheric Research (NCAR). More info »


The term "projection" is used in two senses in the climate change literature. In general usage, a projection can be regarded as any description of the future and the pathway leading to it. However, a more specific interpretation has been attached to the term "climate projection" by the IPCC when referring to model-derived estimates of future climate.


A georeferenced GIS data format that consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information.


A coherent, internally consistent and plausible description of a possible future state of the world. It is not a forecast; rather, each scenario is one alternative image of how the future can unfold. A set of scenarios is often adopted to reflect, as well as possible, the range of uncertainty in projections. Other terms that have been used as synonyms for scenario are "characterisation", "storyline" and "construction".


Data presented in a table or spreadsheet format.  Tabular data can be read and analyzed using Excel or other speadsheet applications.


Susceptibility to change or harm. The degree to which a system is exposed to, susceptible to, and (un)able to cope with and adapt to, the adverse effects of climate change, including climate variability and extremes.


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