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GLOSSARY

 
 
SOME HEADLINE FACTS:
1 tonne of carbon = 3.67 tonnes of CO2.
1 tonne of burnt jet fuel emits 3.15 tonnes of CO2.
A Boeing 747-400 fully loaded with 216,389 litres (57,164 U.S. gallons) of fuel is carrying about
175,275 kg or 175.275 tonnes (386,411 lbs) at a fuel density of 0.810 g/mL (6.76 lbs/gal). The Airbus A380 holds about 310,000 litres (81,900 U.S. gallons) of fuel.
A modern aircraft consumes approx. 0.035 litres of fuel per passenger/km.
In 2007, global commercial air transport emitted 672 million tonnes of CO2.
Global commercial air transport is responsible for 2-3% of total anthropogenic CO2 emissions and around 3% of the radiative forcing. According to IPCC, CO2 emissions from the sector will account for up to 5% of the total by 2050.
Carbon emissions from the deforestation that happens every 24 hours equate to flying 25 million people across the Atlantic.
 
 
 
A
 
ACARE (Advisory Council for Aeronautics Research in Europe): This set an industry target for aircraft manufacturers to deliver a 50% reduction in new aircraft fuel consumption between 2000 and 2020, thereby leading to a 50% cut in CO2 emissions per seat kilometre by 2020 relative to 2000. The target is expected to be achieved through airframe, engine and air traffic management improvements. The role of an optimized air traffic management system is substantial with a target contribution of 5-10% lower fuel consumption through reductions in flight delays, route inefficiencies and taxiing times.
AIR CARRIER: An operator (e.g. airline) in the commercial system of air transportation consisting of aircraft that hold certificates to conduct scheduled or non-scheduled flights within the country or abroad.
AIR POLLUTION: One or more chemicals or substances in high enough concentrations in the air to harm humans, other animals, vegetation or materials. Such chemicals or physical conditions (such as excess heat or noise) are called air pollutants.
ALTERNATIVE FUELS: Fuels which are not petroleum-based such as biofuels, as well as gas-to-liquid and coal-to-liquid fuels manufactured through the Fischer-Tropsch process.
ANNEX I COUNTRIES:The group of countries included in Annex I to the UNFCCC, including all the OECD countries and economiesin transition. Under Articles 4.2 (a) and 4.2 (b) of the Convention,Annex I countries committed themselves specifically to the aim ofreturning individually or jointly to their 1990 levels of greenhouse gasemissions by the year 2000. By default, the other countries arereferred to as Non-Annex I countries.
ANNEX II COUNTRIES:The group of countries included in Annex II to the UNFCCC,including all OECD countries. Under Article 4.2 (g) of theConvention, these countries are expected to provide financialresources to assist developing countries to comply with theirobligations, such as preparing national reports. Annex II countriesare also expected to promote the transfer of environmentally soundtechnologies to developing countries.
ANNEX B COUNTRIES:The countries included in Annex B to the Kyoto Protocol that have agreed to a target for their greenhouse gas emissions, including all the Annex I countries (as amended in 1998) except for Turkey and Belarus.
ANTHROPOGENIC: Human made. In the context of greenhouse gases, anthropogenic emissions are produced as the result of human activities.
ATMOSPHERE: The mixture of gases surrounding the Earth. The Earth’s atmosphere consists of about 79.1 per cent nitrogen (by volume), 20.9 per cent oxygen, 0.036 per cent carbon dioxide and trace amounts of other gases. The atmosphere can be divided into a number of layers according to its mixing or chemical characteristics, generally determined by its thermal properties (temperature). The layer nearest the Earth is the troposphere, which reaches up to an altitude of about 8 kilometres (about 5 miles) in the polar regions and up to 17 kilometres (nearly 11 miles) above the equator. The stratosphere, which reaches to an altitude of about 50 kilometres (31miles) lies atop the troposphere. The mesosphere, which extends from 80 to 90 kilometres atop the stratosphere, and finally, the thermosphere, or ionosphere, gradually diminishes and forms a fuzzy border with outer space. There is relatively little mixing of gases between layers.
AVAILABLE SEAT KILOMETRES (ASKs): Measure of passenger capacity calculated by multiplying the number of seats available on a particular flight by the kilometres flown on that flight. (See also REVENUE PASSENGER KILOMETRES.)
AVIATION GASOLINE: All special grades of gasoline for use in aviation reciprocating engines, as cited in the American Society for Testing and Materials (ASTM) specification D 910. Includes all refinery products within the gasoline range that are to be marketed straight or in blends as aviation gasoline without further processing (any refinery operation except mechanical blending). Also included are finished components in the gasoline range, which will be used for blending or compounding into aviation gasoline.
 
B
 
BARREL OF OIL: One barrel of crude oil equals 42 US gallons (or 34.9723 Imperial gallons or 158.9873 litres).
BIOFUEL: Gas or liquid fuel made from plant material (biomass). Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulphite liquors, agricultural waste, straw, tyres, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline.
BIOMASS: Total dry weight of all living organisms that can be supported at each tropic level in a food chain. Also, materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, crops, grasses, tree litter, roots, and animals and animal waste.
BIOMASS ENERGY: Energy produced by combusting biomass materials such as wood. The carbon dioxide emitted from burning biomass will not increase total atmospheric carbon dioxide if this consumption is done on a sustainable basis (i.e. if in a given period of time, re-growth of biomass takes up as much carbon dioxide as is released from biomass combustion). Biomass energy is often suggested as a replacement for fossil fuel combustion.
BUNKER FUEL: Fuel supplied to ships and aircraft for international transportation, irrespective of the flag of the carrier, consisting primarily of residual and distillate fuel oil for ships and jet fuel for aircraft.
 
C
 
CAP: Mandated restraint as an upper limit on emissions. The Kyoto Protocol mandates emissions caps in a scheduled timeframe on the anthropogenic GHG emissions released by Annex B countries. By 2008-2012, for example, the EU must reduce its CO2-equivalent emissions of six greenhouse gases to a level 8% lower than the 1990-level.
CARBON CAPTURE AND STORAGE (CCS):A process consisting of separation of CO2 from industrial andenergy-related sources, transport to a storage location, and long termisolation from the atmosphere.
CARBON CYCLE: All carbon reservoirs and exchanges of carbon from reservoir to reservoir by various chemical, physical, geological and biological processes. Usually thought of as a series of the four main reservoirs of carbon interconnected by pathways of exchange. The four reservoirs, regions of the Earth in which carbon behaves in a systematic manner, are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). Each of these global reservoirs may be subdivided into smaller pools, ranging in size from individual communities or ecosystems to the total of all living organisms (biota).
CARBON DIOXIDE (CO2): A colourless, odourless, non-poisonous gas that is a normal part of the ambient air. Carbon dioxide is a product of fossil fuel combustion. Although carbon dioxide does not directly impair human health, it is a greenhouse gas that traps terrestrial (i.e. infrared) radiation and contributes to the potential for global warming.
CARBON EQUIVALENT (CE) or CARBON DIOXIDE EQUIVALENT: A metric measure used to compare the emissions of the different greenhouse gases based upon their global warming potential (GWP). Greenhouse gas emissions are most commonly expressed as ‘million metric tons (or tonnes) of carbon equivalents’ (MMTCE). Global warming potentials are used to convert greenhouse gases to carbon dioxide equivalents (CO2-eq).
CARBON OFFSETTING: The purchase and cancellation of emission reduction credits generated by projects and activities that reduce carbon emissions.
CARBON OFFSET PROVIDER: A company whose core business is the provision of offsets either directly to the public or as a service provider to another organization (such as an airline) to allow their consumers to offset. A provider may directly fund an offsetting project or it may buy credits from an intermediary such as a broker or another offset provider.
CARBON SEQUESTRATION: The uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned.
CARBON SINKS: Carbon reservoirs and conditions that take-in and store more carbon (i.e. carbon sequestration) than they release. Carbon sinks can serve to partially offset greenhouse gas emissions. Forests and oceans are large carbon sinks.
CERTIFIED EMISSIONS REDUCTIONS (CERs): Tradeable units generated by projects in developing countries (Kyoto Protocol non-Annex 1 Parties) under the Clean Development Mechanism (CDM). They may be counted by Annex 1 Parties towards compliance with their UN and EU emissions target, and are equal to one tonne of carbon dioxide equivalent gases.
CHICAGO CONVENTION: The Convention on International Civil Aviation, popularly known as the Chicago Convention, was signed in December 1944 by 52 countries (or Contracting States) and sets out the framework on which air services operate in order that “international air transport services may be established on the basis of equality of opportunity and operated soundly and economically”. It functioned until April 1947 when it established the formation of the International Civil Aviation Organization (ICAO). There are now around 190 countries that are party to the Convention.  Annex 16 of the Convention covers Environmental Protection (Vol 1: Aircraft noise, Vol II: Aircraft Engine Emissions). Article 24 states that international aircraft fuel shall be exempt from taxes, customs duty, local duties and charges, which has proved controversial. The full text of the original convention can be found at http://www.mcgill.ca/files/iasl/chicago1944a.pdf .
CLEAN DEVELOPMENT MECHANISM (CDM): One of the so-called ‘flexible mechanisms’ under the Kyoto Protocol. The Protocol provides for a CDM in Article 12 as a means for companies to undertake projects in developing countries without a Kyoto target (non-Annex 1 Parties) which reduce their emissions of greenhouse gases and contribute to sustainable development. Such projects are then credited with Certified Emissions Reductions (CERs).
CLIMATE: The average weather, usually taken over a 30-year time period, for a particular region and time period. Climate is not the same as weather but rather it is the average pattern of weather for a particular region. Weather describes the short-term state of the atmosphere. Climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost and hailstorms, and other measures of the weather.
CLIMATE CHANGE: The term ‘climate change’ is sometimes used to refer to all forms of climatic inconsistency, but because the Earth’s climate is never static, the term is more properly used to imply a significant change from one climatic condition to another and that persists for an extended period, typically decades or longer. In some cases, ‘climate change’ has been used synonymously with the term ‘global warming’; scientists, however, sometimes tend to use the term in the wider sense to also include natural changes in climate. Note that UNFCCC, in its Article 1, defines ‘climate change’ as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. The UNFCCC thus makes a distinction between ‘climate change’ attributable to human activities altering the atmospheric composition, and ‘climate variability’ attributable to natural causes.
CO2-EQUIVALENT CONCENTRATION:The concentration of carbon dioxide that would cause the sameamount of radiative forcing as a given mixture of carbon dioxideand other greenhouse gases.
CO2-EQUIVALENT EMISSION:The amount of carbon dioxideemission that would cause the same radiativeforcing as an emitted amount of a well-mixed greenhouse gas, or amixture of well-mixed greenhouse gases, all multiplied with theirrespective Global Warming Potentials to take into account thediffering times they remain in the atmosphere.
CONFERENCE OF THE PARTIES (COP):  The supreme body of the UNFCCC, comprising countries with right to vote that have ratified or acceded to the convention. The first session of the Conference of the Parties (COP-1) was held in Berlin (1995), followed by -2 Geneva (1996), -3 Kyoto (1997), -4 Buenos Aires (1998), -5 Bonn (1999), -6 The Hague/Bonn (2000, 2001), -7 Marrakech (2001), -8 Delhi (2002), -9 Milan (2003), -10 Buenos Aires (2004), -11 Montreal (2005), -12 Nairobi (2006), -13 Bali (2007), -14 Poznan (Dec 2008).
CONTRAIL: Contrails are line-shaped clouds or ‘condensation trails’, composed of ice particles that are visible behind jet aircraft engines, typically at cruise altitudes in the upper atmosphere. Aircraft engines emit water vapour, carbon dioxide (CO2), small amounts of nitrogen oxides (NOx), hydrocarbons, carbon monoxide, sulphur gases, and soot and metal particles formed by the high-temperature combustion of jet fuel during flight. Contrails contribute to radiative forcing and research is ongoing into their climate impact.
CRUDE OIL: A mixture of hydrocarbons that exist in liquid phase in underground reservoirs and remain liquid at atmospheric pressure after passing through surface separating facilities.
 
D
 
DEFORESTATION: Those practices or processes that result in the conversion of forested lands for nonforest uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons: (1) the burning or decomposition of the wood releases carbon dioxide; and (2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present.
DOUBLE COUNTING: When a carbon reduction is counted twice. This can either happen at a project level where credits are sold two or more times and/or at a national level where voluntary reductions are counted against national mandatory targets.
 
E
 
EMISSION FACTOR: The rate at which pollutants are emitted into the atmosphere by one source or a combination of sources.
EMISSION INVENTORY: A list of air pollutants emitted into a community’s, state’s, nation’s, or the Earth’s atmosphere in amounts per some unit time (e.g. day or year) by type of source. An emission inventory has both political and scientific applications.
EMISSION REDUCTION UNITS (ERUs): Tradable units generated by projects in developed countries (Annex 1 Parties). Annex 1 Parties may count them towards compliance with their emissions target. Each ERU is equal to one tonne of carbon dioxide equivalent gases. 
EMISSIONS: Releases of gases to the atmosphere (e.g. the release of carbon dioxide during fuel combustion). Emissions can be either intended or unintended releases.
EMISSIONS COEFFICIENT/FACTOR: A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g. grams of carbon dioxide emitted per barrel of fossil fuel consumed).
EMISSION PERMIT: An emission permit is a non-transferable or tradeable entitlement allocated by a government to a legal entity (company or other emitter) to emit a specified amount of a substance. A tradeable permitis an economic policy instrument under which rights to discharge pollution - in this case an amount of 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.
EMISSIONS REDUCTION UNIT (ERU):Equal to one metric tonne of CO2-equivalent emissions reduced or sequestered arising from a Joint Implementation (defined in Article 6 of the Kyoto Protocol) project. (See also CERTIFIED EMISSIONS REDUCTIONS and EMISSIONS TRADING.)
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 GHG 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. Emissions trading under Article 17 of the Kyoto Protocol is a tradeable quota system based on the assigned amounts calculated from the emission reduction and limitation commitments listed in Annex B of the Protocol.
ENERGY: The capacity for doing work as measured by the capability of doing work (potential energy) or the conversion of this capability to motion (kinetic energy). Energy has several forms, some of which are easily convertible and can be changed to another form useful for work. Most of the world’s convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical or other means in order to accomplish tasks. Electrical energy is often measured in kilowatt-hours (kWh), while heat energy is often measured in British thermal units (Btu).
ENERGY INTENSITY: Ratio between the consumption of energy to a given quantity of output; usually refers to the amount of primary or final energy consumed per unit of gross domestic product.
ENERGY QUALITY: Ability of a form of energy to do useful work. High-temperature heat and the chemical energy in fossil fuels and nuclear fuels are concentrated high quality energy. Low quality energy such as low-temperature heat is dispersed or diluted and cannot do much useful work.
ENERGY-EFFICIENCY: The ratio of the useful output of services from an article of industrial equipment to the energy use by such an article; for example, vehicle miles travelled per gallon of fuel (mpg).
ENHANCED GREENHOUSE EFFECT: The concept that the natural greenhouse effect has been enhanced by anthropogenic emissions of greenhouse gases. Increased concentrations of carbon dioxide, methane, nitrous oxide, CFCs, HFCs, PFCs, SF6, NF3 and other photochemically important gases caused by human activities such as fossil fuel consumption, trap more infra-red radiation, thereby exerting a warming influence on the climate.
ENPLANEMENTS: The number of passengers on departing aircraft.
ETHANOL: Otherwise known as ethyl alcohol, alcohol or grain spirit. A clear, colourless, flammable oxygenated hydrocarbon with a boiling point of 78.5 degrees Celsius in the anhydrous state. In transportation, ethanol is used as a vehicle fuel by itself (E100), blended with petrol (or gasoline) (E85), or as a petrol octane enhancer and oxygenate (10 per cent concentration).
EU ALLOWANCES (EUAs): Units specific to the EU Emissions Trading Scheme (EU ETS) that are equal to one tonne of carbon dioxide equivalent gases. They are traded in the carbon market and their price at the end of June 2008 was just under 30 euros each.
 
F
 
FLUOROCARBONS: Carbon-fluorine compounds that often contain other elements such as hydrogen, chlorine, or bromine. Common fluorocarbons include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).
FORCING MECHANISM: A process that alters the energy balance of the climate system (i.e. changes the relative balance between incoming solar radiation and outgoing infrared radiation from Earth). Such mechanisms include changes in solar irradiance, volcanic eruptions and enhancement of the natural greenhouse effect by emission of carbon dioxide.
FOSSIL FUEL: A general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas or heavy oils by exposure to heat and pressure in the Earth’s crust over hundreds of millions of years.
FREIGHT TONNE KILOMETRES (FTKs): Measure of airfreight traffic calculated by multiplying the number of tonnes of freight by the kilometres flown on a flight.
FUEL CELL: Generates electricity in a direct and continuous way from the controlled electrochemical reaction of hydrogen or another fuel and oxygen. With hydrogen as fuel it emits only water and heat (no CO2) and the heat can be utilized.
 
G
 
GENERAL AVIATION: That portion of civil aviation, which encompasses all facets of aviation except air carriers. It includes any air taxis, commuter air carriers and air travel clubs.
GLOBAL WARMING: The progressive gradual rise of the Earth’s surface temperature thought to be caused by the greenhouse effect and responsible for changes in global climate patterns.
GLOBAL WARMING POTENTIAL (GWP): The index used to translate the level of emissions of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emissions of one kilogram of a greenhouse gas to that from the emission of one kilogram of carbon dioxide over a period of time (usually 100 years). Gases involved in complex atmospheric chemical processes have not been assigned GWPs.
GREENHOUSE EFFECT: Trapping and build-up of heat in the atmosphere (troposphere) near the Earth’s surface. Some of the heat flowing back towards space from the Earth’s surface is absorbed by water vapour, carbon dioxide, ozone and several other gases in the atmosphere and then reradiated back toward the Earth’s surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.
GREENHOUSE GAS (GHG): Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, but are not limited to, water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrochlorofluorocarbons (HCFCs), ozone (O3), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).
 
H
 
HUB AND SPOKE SYSTEM: a hub is an airport on which traffic from a number of peripheral points is concentrated, and which is in turn linked by direct flights to peripheral (spoke) points. Such systems can involve linking a gateway airport to a number of domestic points (common in the US) or can be used in change of gauge operations. (Compare with POINT-TO-POINT.)
HYDROCARBONS: Substances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.
HYDROSPHERE: All the Earth’s liquid water (oceans, smaller bodies of fresh water, and underground aquifers), frozen water (polar ice caps, floating ice, and frozen upper layer of soil known as permafrost), and small amounts of water vapour in the atmosphere.
 
I
 
INFRARED RADIATION: The heat energy that is emitted from all solids, liquids and gases. In the context of the greenhouse issue, the term refers to the heat energy emitted by the Earth’s surface and its atmosphere. Greenhouse gases strongly absorb this radiation in the Earth’s atmosphere and re-radiate some of it back towards the surface, creating the greenhouse effect.
INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC): The IPCC was established jointly by the United Nations Environment Programme and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature related to all significant components of the issue of climate change. The IPCC draws upon hundreds of the world’s expert scientists as authors and thousands as expert reviewers. Leading experts on climate change and environmental, social, and economic sciences from some 60 nations have helped the IPCC to prepare periodic assessments of the scientific underpinnings for understanding global climate change and its consequences. With its capacity for reporting on climate change, its consequences and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official advisory body to the world’s governments on the state of the science of the climate change issue. For example, the IPCC organized the development of internationally accepted methods for conducting national greenhouse gas emission inventories. Link: http://www.ipcc.ch/. In 1999, IPCC published a seminal report, Aviation and the Global Atmosphere (http://www.grida.no/Climate/ipcc/aviation/index.htm).
 
J
 
JET FUEL: There are currently two main grades of turbine fuel in use in civil commercial aviation: Jet A-1 and Jet A, both of which are kerosene type fuels. There is another grade of jet fuel, Jet B which is a wide cut kerosene (a blend of gasoline and kerosene) but it is rarely used except in very cold climates. Jet A-1 is a kerosene grade of fuel suitable for most turbine-engined aircraft. It is produced to a stringent, internationally agreed standard, has a flash point above 38°C (100°F) and a freeze point maximum of -47°C. It is widely available outside the US. Jet A is a similar kerosene type of fuel, produced to an ASTM specification and normally only available in the US. It has the same flash point as Jet A-1 but a higher freeze point maximum (-40°C). Less widely used, Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to Jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. Fuels used in military aviation are graded JP-4, JP-5 and JP-8, the latter the equivalent of Jet A-1 with the addition of corrosion inhibitor and anti-icing additives.
JOINT IMPLEMENTATION (JI):A market-based implementation mechanism defined in Article 6 ofthe Kyoto Protocol, allowing Annex I countries or companies fromthese countries to implement projects jointly that limit or reduceemissions or enhance sinks, and to share the Emissions ReductionUnits. JI activity is also permitted in Article 4.2(a) of the UNFCCC.
 
K
 
KEROSENE: Aviation jet fuel is also known as kerosene (see JET FUEL).
KYOTO COMPLIANCE CREDITS: Internationally recognized carbon credits from the regulated market. These credits can be used for compliance with legal obligations (for instance under the Kyoto Protocol or EU Emissions Trading Scheme) or for voluntary offsetting.
KYOTO PROTOCOL: An international agreement struck by nations attending the Third Conference of Parties (COP) to the United Nations Framework Convention on Climate Change (held in December of 1997 in Kyoto, Japan) to reduce worldwide emissions of greenhouse gases. If ratified and put into force, individual countries have committed to reduce their greenhouse gas emissions by a specified amount. Annex B countries agreed to reduce their anthropogenic GHG emissions (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride) by at least 5% below 1990 levels in the commitment period 2008-2012. The Kyoto Protocol came into force on 16 February 2005.
 
L
 
LANDING AND TAKEOFF CYCLE (LTO): Refers to an aircraft’s landing and takeoff (LTO) cycle. One aircraft LTO is equivalent to two aircraft operations (one landing and one takeoff). The standard LTO cycle begins when the aircraft crosses into the mixing zone as it approaches the airport on its descent from cruising altitude, lands and taxis to the gate. The cycle continues as the aircraft taxis back out to the runway for takeoff and climbout as its heads out of the mixing zone and back up to cruising altitude. The five specific operating modes in a standard LTO are: approach, taxi/idle-in, taxi/idle-out, takeoff, and climbout. Most aircraft go through this sequence during a complete standard operating cycle.
LIFETIME (ATMOSPHERIC): The lifetime of a greenhouse gas refers to the approximate amount of time it would take for the anthropogenic increment to an atmospheric pollutant concentration to return to its natural level (assuming emissions cease) as a result of either being converted to another chemical compound or being taken out of the atmosphere via a sink. This time depends on the pollutant’s sources and sinks as well as its reactivity. The lifetime of a pollutant is often considered in conjunction with the mixing of pollutants in the atmosphere; a long lifetime will allow the pollutant to mix throughout the atmosphere. Average lifetimes can vary from about a week (e.g. sulphate aerosols) to more than a century (e.g. CFCs, carbon dioxide).
LOAD FACTOR (LF): Also called Passenger Load Factor (PLF), it is a measure of airliner capacity utilization expressed as a percentage, calculated by dividing Revenue Passenger Kilometres (RPKs) by Available Seat Kilometres (ASKs) multiplied by 100. The higher the percentage, the fuller the occupancy of passengers on a given flight. An airline’s efficiency can therefore be measured by its load factor – the higher it is, the more economically viable it is likely to be. However, if faced with financial difficulties, an airline might well reduce the number of flights available to passengers in order to increase capacity utilization and save costs. IATA reported that international load factors reached an industry record 77.0% in 2007, up from 76.0% in 2006 and 75.1% in 2005. In January 2008 it said this trend will likely end in 2008 as demand growth is forecast to slow. By February 2008, the global industry Load Factor did indeed fall to 73.3%, the most significant drop for four years, according to IATA.
 
M
 
MEETING OF THE PARTIES (to the Kyoto Protocol) (MOP):The Conference of the Parties (COP) of the UNFCCC serves asthe Meeting of the Parties (MOP), the supreme body of the KyotoProtocol, since the latter entered into force on 16 February 2005.Only parties to the Kyoto Protocol may participate in deliberationsand make decisions.
METHANE (CH4): A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 21. Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The atmospheric concentration of methane has been shown to be increasing at a rate of about 0.6  per cent per year and the concentration of about 1.7 per million by volume (ppmv) is more than twice its pre-industrial value. However, the rate of increase of methane in the atmosphere may be stabilizing.
METRIC TON: Common international measurement for the quantity of greenhouse gas emissions. A metric ton, or tonne, is equal to 1,000 kilograms, 2,204.6 pounds, or 1.1023 short tons.
 
N
 
NATURAL GAS: Underground deposits of gases consisting of 50 to 90 per cent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H4) and butane (C4H10).
NITROGEN OXIDES (NOx): Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced, for example, by the combustion of fossil fuels in aircraft engines, vehicles and electric power plants. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), impair visibility and have health consequences; they are considered serious pollutants. However, they are not one of the six greenhouse gases listed in the Kyoto Protocol, a matter for some dispute. Since NOx formation is controlled by the maximum local temperature reached in an aircraft engine’s combustor, it is determined primarily by engine design and operating conditions. Current engine design trends are intended to ensure more complete combustion more rapidly resulting in more uniform combustion temperatures and thus lowering NOx emissions. NOx emission factors for modern commercial engines are about 4g NOx per kg fuel at idle. A fuel with 20 ppm bound nitrogen will contribute 66 mg NO2 per kg fuel, about 1.5% of the total. As NOx emissions are higher at take off, climb, and cruise conditions, the fuel bound nitrogen contributes an even smaller percentage at these operating conditions.
NON-ANNEX I COUNTRIES/PARTIES:The countries that have ratified or acceded to the UNFCCC but arenot included in Annex I.
 
O
 
OIL SANDS (or Tar Sands): Unconsolidated porous sands containing bituminous material that can be mined and converted to a liquid fuel. There are heavy deposits in Alberta, Canada, with the potential for billions of barrels of oil, but the mining and production process emits far higher – up to three times more – CO2 emissions than conventional crude oil, so is considered environmentally harmful.
OZONE: A colourless gas with a pungent odour, having the molecular form of O3, found in two layers of the atmosphere, the stratosphere and the troposphere. Ozone is a form of oxygen found naturally in the stratosphere that provides a protective layer shielding the Earth from ultraviolet radiation’s harmful health effects on humans and the environment. In the troposphere, ozone is a chemical oxidant and major component of photochemical smog. Ozone can seriously affect the human respiratory system.
OZONE LAYER: Layer of gaseous ozone (O3) in the stratosphere that protects life on Earth by filtering out harmful ultraviolet radiation from the sun.
OZONE PRECURSORS: Chemical compounds, such as carbon monoxide, methane, non-methane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere.
 
P
 
PARTICULATES:Particulates and unburned hydrocarbons are the result of incomplete aircraft engine combustion. If present in high enough concentration, these particulates will be visible as smoke or soot coming out of the engine. Modern jet engine combustors are designed to significantly reduce visible smoke and thus emit fewer particulates than older engines.
PARTS PER BILLION (ppb): Number of parts of a chemical found in one billion parts of a particular gas, liquid or solid mixture.
PARTS PER MILLION (ppm): Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid.
PERFLUOROCARBONS (PFCs): A group of human-made chemicals composed of carbon and fluorine only. These chemicals (predominantly CF4 and C2F6) were introduced as alternatives, along with hydrofluorocarbons, to the ozone-depleting substances. In addition, PFCs are emitted as by-products of industrial processes and are also used in manufacturing. PFCs do not harm the stratospheric ozone layer, but they are powerful greenhouse gases: CF4 has a global warming potential (GWP) of 6,500 and C2F6 has a GWP of 9,200.
PETROLEUM: A generic term applied to oil and oil products in all forms, such as crude oil, lease condensate, unfinished oils, petroleum products, natural gas plant liquids and non-hydrocarbon compounds blended into finished petroleum products.
POINT-TO-POINT: A system whereby an airline’s route network is composed of a number of city pairs, not necessarily linked by hub airports. This system is favoured by low-cost carriers such as Southwest Airlines (in the US), easyJet and Ryanair (in Europe). (Compare with HUB AND SPOKE.)
POLLUTION: A change in the physical, chemical or biological characteristics of the air, water or soil that can affect the health, survival or activities of humans in an unwanted way. Some expand the term to include harmful effects on all forms of life.
 
R
 
RADIATION: Energy emitted in the form of electromagnetic waves. Radiation has differing characteristics depending upon the wavelength. Because the radiation from the Sun is relatively energetic, it has a short wavelength (e.g. ultraviolet, visible, and near infrared) while energy re-radiated from the Earth’s surface and the atmosphere has a longer wavelength (e.g. infrared radiation) because the Earth is cooler than the Sun.
RADIATIVE FORCING: A change in the balance between incoming solar radiation and outgoing infrared (i.e. thermal) radiation. Without any radiative forcing, solar radiation coming to the Earth would continue to be approximately equal to the infrared radiation emitted from the Earth. The addition of greenhouse gases to the atmosphere traps an increased fraction of the infrared radiation, reradiating it back toward the surface of the Earth and thereby creates a warming influence. Measured in Watts per square metre (W/m2).
RENEWABLE ENERGY: Energy obtained from sources that are essentially inexhaustible, unlike, for example, fossil fuels, of which there is a finite supply. Renewable sources of energy include wood, waste, geothermal, wind, photovoltaic, and solar thermal energy.
REVENUE PASSENGER KILOMETRES (RPKs): A measure of passenger traffic calculated by multiplying the number of paying passengers by the kilometres flown on a flight. (See also AVAILABLE SEAT KILOMETRES.)
 
S
 
SHORT TON: Common measurement for a ton in the United States. A short ton is equal to 2,000 lbs. or 0.907 metric tons.
SINK: Any process, activity or mechanism that removes a greenhouse gas or aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.Soil and trees tend to act as natural sinks for carbon.
SOLAR ENERGY: Direct radiant energy from the sun. It also includes indirect forms of energy such as wind, falling or flowing water (hydropower), ocean thermal gradients and biomass, which are produced when direct solar energy interact with the Earth.
SOLAR RADIATION: Energy from the Sun. Also referred to as short-wave radiation. Of importance to the climate system, solar radiation includes ultra-violet radiation, visible radiation, and infrared radiation.
STRATOSPHERE: Second layer of the atmosphere, extending from about 19 to 48 kilometres (12 to 30 miles) above the Earth’s surface. It contains small amounts of gaseous ozone (O3), which filters out about 99 per cent of the incoming harmful ultraviolet (UV) radiation. Most commercial airline flights operate at a cruising altitude in the lower stratosphere.
SUSTAINABLE DEVELOPMENT:  The concept of sustainable development was introduced in the World Conservation Strategy (IUCN 1980) and had its roots in the concept of a sustainable society and in the management of renewable resources. Adopted by the WCED in 1987 and by the Rio Conference in 1992 as a process of change in which the exploitation of resources, the direction of investments, the orientation of technological development and institutional change are all in harmony and enhance both current and future potential to meet human needs and aspirations. It integrates the political, social, economic and environmental dimensions.
SYNTHETIC NATURAL GAS (SNG): A manufactured product chemically similar in most respects to natural gas, resulting from the conversion or reforming of petroleum hydrocarbons. It may easily be substituted for, or interchanged with, pipeline quality natural gas.
 
T
 
TANKERING: The practice of filling aircraft fuel tanks for a series of flights at an airport offering the lowest price, whereas the most environmentally efficient method would be to upload just the required amount for the next flight.
TAR SANDS: (see OIL SANDS)
TRACE GAS:A minor constituent of the atmosphere, next to nitrogen and oxygen that together make up 99% of all volume. The most important trace gases contributing to the greenhouse effect are carbon dioxide, ozone, methane, nitrous oxide, perfluorocarbons, chlorofluorocarbons, hydrofluorocarbons, sulphur hexafluoride and water vapour.
TROPOSPHERE: The lowest layer of the atmosphere and contains about 95 per cent of the mass of air in the Earth’s atmosphere. The troposphere extends from the Earth’s surface up to about 10 to 15 kilometres. All weather processes take place in the troposphere. Ozone that is formed in the troposphere plays a significant role in both the greenhouse gas effect and urban smog.
 
U
 
UNITED NATIONS FRAMEWORK CONVENTION ON CLIMATE CHANGE (UNFCCC): The Convention was adopted on 9 May 1992 in New York and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Economic Community. The convention came into force in March 1994. Under the Convention, parties included in Annex I aimed to return greenhouse gas emission not controlled by the Montreal Protocol to 1990 levels by the year 2000. It is the parent treaty of the 1997 Kyoto Protocol, which has, at April 2008, 178 member Parties. Under the Protocol, 37 States, consisting of highly industrialized countries and countries undergoing the process of transition to a market economy, have legally binding emission limitation and reduction commitments. The ultimate objective of both treaties is to stabilize greenhouse gas concentrations in the atmosphere at a level that will prevent dangerous human interference with the climate system (http://unfccc.int/2860.php).
 
V
 
VERIFIED EMISSIONS REDUCTION UNITS (VERs): Differ from other carbon credits in that they are not recognized by, and do not form part of, the Kyoto Protocol or EU ETS. They are not verifiable in the same way as other carbon credits but they can often be linked to small, non-industrial projects.
VOLATILE ORGANIC COMPOUNDS (VOCs): Organic compounds that evaporate readily into the atmosphere at normal temperatures. VOCs contribute significantly to photochemical smog production and certain health problems.
 
W
 
WATER VAPOUR: The most abundant greenhouse gas; it is the water present in the atmosphere in gaseous form. Water vapour is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapour feedback. In addition to its role as a natural greenhouse gas, water vapour plays an important role in regulating the temperature of the planet because clouds form when excess water vapour in the atmosphere condenses to form ice and water droplets and precipitation.
WEATHER: Weather is the specific condition of the atmosphere at a particular place and time. It is measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. In most places, weather can change from hour-to-hour, day-to-day, and season-to-season. Climate is the average of weather over time and space. A simple way of remembering the difference is that ‘climate’ is what you expect (e.g. cold winters) and ’weather’ is what you get (e.g. a blizzard).


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