Carbon budget refers to the balance of exchanges (incomes and losses) of carbon between carbon reservoirs or between one specific loop (e.g., atmosphere - biosphere) of the carbon cycle. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for carbon dioxide.

Carbon flux is the net difference between carbon removal and carbon addition to a system. For the atmosphere this refers to carbon removed by plant growth, mineralisation and dissolving the ocean while it is added through plant respiration, fossil-fuel burning and volcanic activity.

A carbon sink is a carbon reservoir that is increasing in size, and is the opposite of a carbon source. Natural sinks include the oceans and plant growth. Sources include burning of fossil fuels, volcanoes and plant respiration.

Climate change refers to the variation in the Earth's global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years.

Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate.

In permafrost soils, cryoturbation, or frost churning, refers to the mixing of materials from various horizons of the soil right down to the bedrock due to freezing and thawing.

Ecosystem models are a development of theoretical ecology that aim to characterise the major dynamics of ecosystems, both to synthesise the understanding of such systems and to allow predictions of their behaviour (in general terms, or in response to particular changes).

There are four basic processes within an ecosystem: water cycle, mineral cycle, energy flow and community dynamics. Ecosystem change will come about if one or more of these processes are perturbed, either naturalyl or by human-induced means

The steady state response of the climate system (or a climate model) to an imposed radiative forcing [IPCC].

The European Union (EU) is a family of democratic European countries, committed to working together for peace and prosperity.

A GCM, or Global Circulation Model, is a numerical model which depicts the climate using a three dimensional grid over the globe, typically having a horizontal resolution of between 250 and 600 km, 10 to 20 vertical layers in the atmosphere and sometimes as many as 30 layers in the oceans.

GIS is an abbreviation for 'Geographic Information System' A GIS is a computer system designed to facilitate the collection, management and analysis of large volumes of spatially referenced information and associated attribute data.

Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades and the projected continuation of rising temperatures.

Greenhouse gases are components of the atmosphere that contribute to the greenhouse effect. Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

The IPCC is a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP). The IPCC was established to provide the decision-makers and others interested in climate change with an objective source of information about climate change.

Patch dynamics is the concept that communities are a mosaic of different areas (patches) within which non-biological disturbances (such as climate) and biological interactions proceed.

Permafrost is ground that stays at or below the freezing point of water (0°C or 32°F) all year round. Most permafrost is located in high latitudes (e.g. North and South poles), but alpine permafrost exists at high altitudes.

Taiga is a biome characterized by coniferous forests. Covering most of inland Alaska, Canada, Sweden, Finland, inland Norway, northern Kazakhstan and Russia (especially Siberia) south of the Arctic treeline.

Althought not karstic in origin, arctic thermokarst is the pitted land surface that results from frost heave and subsequent melting. Larger hummocks may be formed over ice lenses.

The time-dependent response of the climate system or model to a time-varying change of forcing [IPCC].

The tree-line is the edge of the habitat at which trees are capable of growing. Beyond the tree-line, they are unable to grow due to inappropriate environmental conditions. In the case of the Arctic tree-line this is due to extreme cold and short growing season.

Tundra is an area where the tree growth is hindered by low temperatures and short growing seasons. There are three types of tundra: Arctic tundra, Antarctic tundra, and alpine tundra. In all of these types, the dominant vegetation is grasses, mosses, and lichens.