Global Warming Glossary *

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Ecological community - A community of plants and animals characterized by a typical assemblage of species and their abundances. See also ecosystem.

Ecological corridor - A thin strip of vegetation used by wildlife, potentially allowing movement of biotic factors between two areas.

Economies in Transition - Countries with their economies changing from a planned economic system to a market economy.

Economies of scale - The unit cost of an activity declines when the activity is extended (e.g., more units are produced).

Ecophysiological process - Individual organisms respond to environmental variability, such as climate change, through ecophysiological processes which operate continuously, generally at a microscopic or sub-organ scale. Ecophysiological mechanisms underpin individual organism's tolerance to environmental stress, and comprise a broad range of responses defining the absolute tolerance limits of individuals to environmental conditions. Ecophysiological responses may scale up to control species geographic ranges.

Ecosystem - A system of living organisms interacting with each other and their physical environment. The boundaries of what could be called an ecosystem are somewhat arbitrary, depending on the focus of interest or study. Thus, the extent of an ecosystem may range from very small spatial scales to, ultimately, the entire Earth.

Ecosystem function - The processes and interactions that operate within an ecosystem, such as energy flow, nutrient cycling, filtering and buffering of contaminants, and regulation of populations.

Ecosystem services - Ecological processes or functions having monetary or non-monetary value to individuals or society at large. There are (i) supporting services such as productivity or biodiversity maintenance, (ii) provisioning services such as food, fiber, or fish, (iii) regulating services such as climate regulation or carbon sequestration, and (iv) cultural services such as tourism or spiritual and aesthetic appreciation.

Ecotone - Transition area between adjacent ecological communities (e.g., between forests and grasslands).

El Niño-Southern Oscillation (ENSO) - The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with a basin-wide warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere-ocean phenomenon, with preferred time scales of two to about seven years, is collectively known as the El Niño-Southern Oscillation (ENSO). It is often measured by the surface pressure anomaly difference between Darwin and Tahiti and the sea surface temperatures in the central and eastern equatorial Pacific. During an ENSO event, the prevailing trade winds weaken, reducing upwelling and altering ocean currents such that the sea surface temperatures warm, further weakening the trade winds. This event has a great impact on the wind, sea surface temperature and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world, through global teleconnections. The cold phase of ENSO is called La Niña.

Emissions - Emissions of heat-trapping gases (greenhouse gases), greenhouse-gas precursors, and aerosols associated with human activities. These include the burning of fossil fuels, deforestation, land-use changes, livestock, fertilization, etc. that result in a net increase in emissions.

Emissions Direct / Indirect - Direct emissions or "point of emission" are defined at the point in the energy chain where they are released and are attributed to that point in the energy chain, whether a sector, a technology or an activity. For example, emissions from coal-fired power plants are considered direct emissions from the energy supply sector. Indirect emissions or emissions "allocated to the end-use sector" refer to the energy use in end-use sectors and account for the emissions associated with the upstream production of the end-use energy. For example, some emissions associated with electricity generation can be attributed to the buildings sector corresponding to the building sector's use of electricity.

Emission factor - An emission factor is the rate of emission per unit of activity, output or input.

Emission permit - An emission permit is a non-transferable or tradable entitlement allocated by a government to a legal entity (company or other emitter) to emit a specified amount of a substance. A tradable permit is an economic policy instrument under which rights to discharge pollution - in this case an amount of heat-trapping gas (greenhouse gas) emissions - can be exchanged through either a free or a controlled permit-market.

Emission quota - The portion of total allowable emissions assigned to a country or group of countries within a framework of maximum total emissions.

Emission scenario - A plausible representation of the future development of emissions of substances that are potentially radiatively active (e.g., greenhouse gases, aerosols), based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socioeconomic development, technological change) and their key relationships. Concentration scenarios, derived from emission scenarios, are used as input to a climate model to compute climate projections. In IPCC (1992) a set of emission scenarios was presented which were used as a basis for the climate projections in IPCC (1996). These emission scenarios are referred to as the IS92 scenarios. In the IPCC Special Report on Emission Scenarios (Nakićenović and Swart, 2000) new emission scenarios, the so-called SRES scenarios, were published.

Emission standard - A level of emission that by law or by voluntary agreement may not be exceeded. Many standards use emission factors in their prescription and therefore do not impose absolute limits on the emissions.

Emissions trading - A market-based approach to achieving environmental objectives. It allows those reducing heat-trapping (greenhouse gas) emissions below their emission cap to use or trade the excess reductions to offset emissions at another source inside or outside the country. In general, trading can occur at the intra-company, domestic, and international levels. The Second Assessment Report by the IPCC adopted the convention of using permits for domestic trading systems and quotas for international trading systems.

Emission trajectories - These are projections of future emission pathways, or observed emission patterns.

Endemic - Restricted or peculiar to a locality or region. With regard to human health, endemic can refer to a disease or agent present or usually prevalent in a population or geographical area at all times.

Energy - The amount of work or heat delivered. Energy is classified in a variety of types and becomes useful to human ends when it flows from one place to another or is converted from one type into another.   ► Primary energy (also referred to as energy sources) is the energy embodied in natural resources (e.g., coal, crude oil, natural gas, uranium) that has not undergone any human conversion. It is transformed into   ► secondary energy by cleaning (natural gas), refining (oil in oil products) or by conversion into electricity or heat. When the secondary energy is delivered at the end-use facilities it is called   ► final energy (e.g., electricity at the wall outlet), where it becomes   ► usable energy (e.g., light). Daily, the sun supplies large quantities of energy as rainfall, winds, radiation, etc. Some share is stored in biomass or rivers that can be harvested by men. Some share is directly usable such as daylight, ventilation or ambient heat.   ► Renewable energy is obtained from the continuing or repetitive currents of energy occurring in the natural environment and includes non-carbon technologies such as solar energy, hydropower, wind, tide and waves and geothermal heat, as well as carbon-neutral technologies such as biomass.   ► Embodied energy is the energy used to produce a material substance (such as processed metals or building materials), taking into account energy used at the manufacturing facility (zero order), energy used in producing the materials that are used in the manufacturing facility (first order), and so on.

Energy balance - The difference between the total incoming and total outgoing energy. If this balance is positive, warming occurs; if it is negative, cooling occurs. Averaged over the globe and over long time periods, this balance must be zero. Because the climate system derives virtually all its energy from the Sun, zero balance implies that, globally, the amount of incoming solar radiation on average must be equal to the sum of the outgoing reflected solar radiation and the outgoing thermal infrared radiation emitted by the climate system. A perturbation of this global radiation balance, be it human-induced or natural, is called radiative forcing.

Energy efficiency - The ratio of useful energy output of a system, conversion process or activity to its energy input.

Energy intensity - The ratio of energy use to economic output. At the national level, energy intensity is the ratio of total domestic primary energy use or final energy use to Gross Domestic Product. See also specific energy use.

Energy security - The various security measures that a given nation, or the global community as a whole, must carry out to maintain an adequate energy supply.

Ensemble - A group of parallel model simulations used for climate projections. Variation of the results across the ensemble members gives an estimate of uncertainty. Ensembles made with the same model but different initial conditions only characterize the uncertainty associated with internal climate variability, whereas multi-model ensembles including simulations by several models also include the impact of model differences.

Environmentally sustainable technologies - Technologies that are less polluting, use resources in a more sustainable manner, recycle more of their wastes and products, and handle residual wastes in a more acceptable manner than the technologies that they substitute. They are also more compatible with nationally determined socio-economic, cultural and environmental priorities.   ► Evapotranspiration - The sum of water loss into the atmosphere due to evaporation and transpiration.   ► Evaporation is the movement of water from oceans, lakes, rivers, and soils into the atmosphere.   ► Transpiration is the process whereby plants give off water into the atmosphere. Sunlight, temperature, wind speed, and relative humidity influence how much and how fast these two processes occur.

Epidemic - Occurring suddenly in incidence rates clearly in excess of normal expectancy, applied especially to infectious diseases but may also refer to any disease, injury, or other health-related event occurring in such outbreaks.

Equilibrium line - The boundary between the region on a glacier where there is a net annual loss of ice mass (ablation area) and that where there is a net annual gain (accumulation area). The altitude of this boundary is referred to as equilibrium line altitude.

Equivalent carbon dioxide (CO2) emission - The amount of carbon dioxide emission that would cause the same integrated radiative forcing, over a given time horizon, as an emitted amount of a well mixed heat-trapping gas (greenhouse gas) or a mixture of well mixed greenhouse gases. The equivalent carbon dioxide emission is obtained by multiplying the emission of a well mixed greenhouse gas by its Global Warming Potential for the given time horizon. For a mix of greenhouse gases it is obtained by summing the equivalent carbon dioxide emissions of each gas. Equivalent carbon dioxide emission is a standard and useful metric for comparing emissions of different greenhouse gases but does not imply exact equivalence of the corresponding climate change responses.

Erosion - The process of removal and transport of soil and rock by weathering, mass wasting, and the action of streams, glaciers, waves, winds and underground water.

Eustatic sea-level rise - See sea-level rise.

Eutrophication - The process by which a body of water (often shallow) becomes (either naturally or by pollution) rich in dissolved nutrients, with a seasonal deficiency in dissolved oxygen.

Evaporation - The transition process from liquid to gaseous state.

Evapotranspiration - The combined process of evaporation from the Earth's surface and transpiration from vegetation.

External forcing - External forcing refers to a forcing agent outside the climate system causing a change in the climate system. Volcanic eruptions, solar variations and human-induced changes in the composition of the atmosphere and land use change are external forcings.

Externalities - Occur when a change in the production or consumption of one individual or firm affects indirectly the well-being of another individual or firm. Externalities can be positive or negative. The impacts of pollution on ecosystems, water courses or air quality represent classic cases of negative externality.

Extinction - The global disappearance of an entire species.

Extirpation - The disappearance of a species from part of its range; local extinction.

Extreme weather event - An extreme weather event is an event that is rare at a particular place and time of year. Definitions of rare vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile of the observed probability density function. By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. Single extreme events cannot be simply and directly attributed to human-induced climate change, as there is always a finite chance the event in question might have occurred naturally. When a pattern of extreme weather persists for some time, such as a season, it may be classed as an extreme climate event, especially if it yields an average or total that is itself extreme (e.g., drought or heavy rainfall over a season).

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