IPCC Special Report on Emissions Scenarios

Emissions Scenarios

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Appendix XI: Glossary of Terms

The act or process of establishing a forest, especially on land not previously forested.
Alternative Energy
Energy derived from non-fossil fuel sources.
Anthropogenic Emissions
Emissions of greenhouse gases (GHGs) associated with human activities. These include burning of fossil fuels for energy, deforestation, and land-use changes.
Annex I Countries
Annex I to the Climate Convention (UNFCCC) lists all the countries in the Organization of Economic Cooperation and Development (OECD), plus countries with economies in transition, Central, and Eastern Europe (excluding the former Yugoslavia and Albania). By default the other countries are referred to as Non-Annex I countries. Under Article 4.2 (a&b) of the Convention, Annex I countries commit themselves specifically to the aim of returning individually or jointly to their 1990 levels of GHG emissions by the year 2000.
Annex II Countries
Annex II to the Climate Convention lists all countries in the OECD. Under Article 4.2 (g) of the Convention, these countries are expected to provide financial resources to assist developing countries comply with their obligations such as preparing national reports. Annex II countries are also expected to promote the transfer of environmentally sound technologies to developing countries.
Annex B Countries
Annex B in the Kyoto Protocol lists those developed countries that have agreed to a target for their GHG emissions, including those in the OECD, Central and Eastern Europe, and the Russian Federation. Not quite the same but similar to Annex I, which also includes Turkey and Belarus, while Annex B includes Croatia, Monaco, Liechtenstein, and Slovenia.
A projected level of future emissions against which reductions by project activities could be determined.
Base Year
A common year for calculating emission inventories or to begin model simulations for future scenarios.
A fuel produced from dry organic matter or combustible oils produced by plants. Examples of biofuel include alcohol (from fermented sugar), black liquor from the paper manufacturing process, wood, and soybean oil.
The total dry organic matter or stored energy content of living organisms. Biomass can be used for fuel directly by burning it (e.g., wood), indirectly by fermentation to an alcohol (e.g., sugar), or by extraction of combustible oils (e.g., soybeans).
Carbon Cycle
The natural processes that influence the exchange of carbon (in the form of carbon dioxide (CO2), carbonates and organic compounds, etc.) among the atmosphere, ocean, and terrestrial systems. Major components include photosynthesis, respiration, and decay between atmospheric and terrestrial systems (approximately 100 billion tons/year (gigatons)); thermodynamic invasion and evasion between the ocean and atmosphere, operation of the carbon pump and mixing in the deep ocean (approx. 90 billion tons/year). Deforestation and fossil fuel burning releases approximately 7 Gt into the atmosphere annually. The total carbon in the reservoirs is approximately 2000 Gt in land biota, soil, and detritus, 750 Gt in the atmosphere, and 38,000 Gt in the oceans. (Figures from IPCC WGI Scientific Assessment 1990.)
Carbon Dioxide
A naturally occurring gas, CO2 is also a by-product of burning fossil fuels and biomass, as well as land-use changes and other industrial processes. It is the principal anthropogenic GHG that affects the earth's temperature. It is the reference gas against which other GHGs are measured and therefore has a "Global Warming Potential" (GWP) of 1.
Carbon Sequestration
The long-term storage of carbon or CO2 in the forests, soils, ocean, or underground in depleted oil and gas reservoirs, coal seams, and saline aquifers. Examples include the separation and disposal of CO2 from flue gases or processing fossil fuels to produce H2- and CO2-rich fractions, and the direct removal of CO2 from the atmosphere through land use change, afforestation, reforestation, ocean fertilization, and agricultural practices to enhance soil carbon.
Carbon Sinks
Natural or man-made systems that absorb CO2 from the atmosphere and store them. Trees, plants, and the oceans all absorb CO2 and, therefore, are carbon sinks.
See "Chlorofluorocarbons".
See "Methane".
Chlorofluorocarbons (CFCs) are GHGs covered under the 1987 Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. As they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone. These gases are being replaced by other compounds, including hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), which are GHGs covered under the Kyoto Protocol.
Climate Change (UNFCCC definition)
A change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability over comparable time periods.
Climate Convention
See "UN Framework Convention on Climate Change".
Climate Models
Large and complex computer programs used to mathematically simulate global climate. They are based on mathematical equations derived from our knowledge of the physics that governs the earth­atmosphere system.
The use of waste heat from electric generation, such as exhaust from gas turbines, for either industrial purposes or district heating.
Sequence of actions necessary to achieve market entry and general market competitiveness of new innovative technologies, processes, and products.
Conference of the Parties (COP)
The supreme body of the UN Framework Convention on Climate Change (UNFCCC), comprises countries that have ratified or acceded to the Framework Convention on Climate Change. The first session of the Conference of the Parties (COP-1) was held in Berlin in 1995, COP-2 in Geneva 1996, COP-3 in Kyoto 1997, and COP-4 in Buenos Aires. COP-5 will be held in Bonn.
See "Carbon Dioxide".
A criterion that specifies that a technology or measure delivers a good or service at equal or lower cost than current practice, or the lowest cost alternative for the achievement of a given target.
A decrease in the specific carbon content of primary energy or of fuels.
The removal of forest stands by cutting and burning to provide land for agricultural purposes, residential or industrial building sites, roads, etc., or by harvesting the trees for building materials or fuel.
Demand-Side Management
Policies and programs designed to reduce consumer demand for electricity and other energy sources while maintaining (or even increasing) the services the energy use renders. It helps to reduce the need for constructing new power facilities.
A decrease in the material intensity of economic activity in general, or of individual production processes and end-use applications.
Economic Potential
The portion of technical potential for GHG emissions reductions or energy efficiency improvements that could be achieved cost-effectively in the absence of market barriers. The achievement of market potential requires additional policies and measures to break down market barriers.
The release of GHGs and/or their precursors into the atmosphere over a specified area and period of time.
Emissions Category
The SRES Scenarios are grouped into four categories of cumulative CO2 emissions (all sources) between 1990 and 2100: low, medium-low, medium-high, and high emissions. Each category contains scenarios with a range of different driving forces yet similar cumulative emissions. See also "(Scenario) Category."
Emission Standard
A level of emission that under law may not be exceeded.
Energy Intensity
This is the ratio of energy consumption to economic or physical output. At the national level, energy intensity is the ratio of total domestic primary energy consumption or final energy consumption to gross domestic product or physical output.
See 'UN Framework Convention on Climate Change'.
Final Energy
Energy supplied that is available to the consumer to be converted into useful energy (e.g. electricity at the wall outlet).
Fossil Fuels
Carbon-based fuels, including coal, oil, and natural gas and their derived fuels such as gasoline, synthesis gas from coal, etc.
Fuel Switching
Policy designed to reduce CO2 emissions by requiring electric utilities or consumers to switch from high-carbon to low- carbon fuels (e.g. from coal to gas).
See "Greenhouse Gases".
GHG Reduction Potential
Possible reductions in emissions of greenhouse gasses (quantified in terms of absolute reductions or in percentages of baseline emissions) that could be achieved through the use of technologies and measures.
Global Warming
The hypothesis that the earth's temperature is being increased, in part, because of emissions of GHGs associated with human activities, such as burning fossil fuels, biomass burning, cement manufacture, cow and sheep rearing, deforestation, and other land-use changes.
Global Warming Potential
A measurement technique to define the relative contribution of each GHG to atmospheric warming. A GWP can only be calculated for specified time horizons (e.g. 20 to 500 years) and for given GHG concentration levels (e.g. current). Both direct and indirect effects are considered. (Indirect effects include changes in atmospheric chemistry such as ozone formation and changes in stratospheric water vapor.) CO2 has been assigned a GWP of 1, against which all other GHGs are compared. For example, methane (CH4) has a GWP that is currently estimated to be about 21 times greater than that of CO2 over a 100 year time horizon, and thus CH4 has a GWP of 21. (Note that in the economic literature GWP usually denotes gross world product, referrred to as global GDP in this report.)
Greenhouse Effect
The trapping of heat by an envelope of naturally occurring heat-retaining gases (water vapour, CO2, nitrous oxide (N2O), CH4, and ozone) that keeps the earth about 30°C (60°F) warmer than if these gases did not exist.
Greenhouse Gases
Gases in the earth's atmosphere that absorb and re-emit infrared radiation. These gases occur through both natural and human-influenced processes. The major GHG is water vapour. Other GHGs include CO2, N2O,
CH4, ozone, and CFCs.
The provision of emission or socio-economic activity data in spatially highly explicit form.
See "Global Warming Potential".
See "Hydrofluorocarbons".
A procedure to ease comparability of model results by adopting common (exogenous) input assumptions. Through harmonization, differences in emissions outcomes resulting from differences in model input assumptions (e.g. exogenous population growth) can be separated from differences that arise from different internal model parametrizations (e.g. of the dynamics of technological change). The scenarios reported here can be classified into three categories: "fully harmonized" scenarios share population, GDP, and final energy use assumptions at the level of the four SRES regions (and hence also at the global level) between 1990 and 2100 within prespecified bounds. "Globally harmonized" scenarios share global population and GDP assumptions at the global level for the 1990 to 2100 period within prespecified bounds (deviations in one 10-year interval are not considered). "Other scenarios" have adopted alternative assumptions for population and GDP than the ones suggested for scenario harmonization.
HFCs are among the six GHGs to be curbed under the Kyoto Protocol. They are produced commercially as a substitute for CFCs. HFCs are used largely in refrigeration and semi-conductor manufacturing. Their GWPs range from 1300 to 11,700 times that of CO2 (over a 100 year time horizon), depending on the HFC.
Illustrative Scenario
A scenario that is illustrative for each of the six scenario groups reflected in the Summary for Policymakers of this report. They include four revised "scenario markers" for the scenario groups A1B, A2, B1 and B2, and two additional scenarios for the A1FI and AIT groups. All scenario groups are equally sound. See also "(Scenario) Groups" and "(Scenario) Markers".
Intergovernmental Organization (IGO)
Organizations constituted of governments. Examples include the World Bank, the OECD, and the International Civil Aviation Organization. The UNFCCC allows accreditation of these IGOs to attend the negotiating sessions.
International Energy Agency (IEA)
Paris-based organization formed in 1973 by the major oil-consuming nations to manage future oil supply shortfalls.
International Institute for Applied Systems Analysis (IIASA)
Non-governmental, international, interdisciplinary research institute located in Laxenburg, Austria. IIASA is supported by the Academy of Sciences and similar learned societies from 15 countries. Its research focuses on the human dimensions of global change.
Kyoto Mechanisms (formerly known as Flexibility Mechanisms)
Economic mechanisms based on market principles that Parties to the Kyoto Protocol can use in an attempt to lessen the potential economic impacts of GHG emission-reduction requirements. They include Joint Implementation (Article 6), the Clean Development Mechanisms (Article 12), and Emissions Trading (Article 17).
Kyoto Protocol
The Protocol, drafted during the Berlin Mandate process, that, on entry into force, would require countries listed in its Annex B (developed nations) to meet differentiated reduction targets for their GHG emissions relative to 1990 levels by 2008­2012. It was adopted by all Parties to the Climate Convention in Kyoto, Japan, in December 1997.
Marker (Scenario)
See "(Scenario) Marker".
Market Penetration
The share of a given market that is provided by a particular good or service at a given time.
Market Potential (or Currently Realizable Potential)
The portion of the economic potential for GHG emissions reductions or energy efficiency improvements that could be achieved under existing market conditions, assuming no new policies and measures.
Actions that can be taken by a government or a group of governments, often in conjunction with the private sector, to accelerate the use of technologies or other practices that reduce GHG emissions.
One of the six GHGs to be mitigated under the Kyoto Protocol, it has a relatively short atmospheric lifetime of 10 ± 2 years. Primary sources of CH4 are landfills, coal mines, paddy fields, natural gas systems, and livestock (e.g., cows and sheep). It has a GWP of 21 (100 year
time horizon).
A formal representation of a system that allows quantification of relevant system variables and simulation of systems' behavior, e.g. the implications on future GHG emissions of alternative demographic, economic and technological developments (scenarios).
Montreal Protocol
International agreement under the UN which entered into force in January 1989 to phase out the use of ozone-depleting compounds such as CFCs, methyl chloroform, carbon tetrachloride, and many others.
See "Non-Governmental Organization".
Nitrous Oxide
One of the six GHGs to be curbed under the Kyoto Protocol, N2O is generated by burning fossil fuels and the manufacture of fertilizer. It has a GWP 310 times that of CO2 (100 year time horizon).
Non-Annex I Parties
The countries that have ratified or acceded to the UNFCCC that are not included in Annex I of the Convention.
Non-Annex B Parties
The countries that are not included in the Annex B list of developed nations in the Kyoto Protocol.
Non-Governmental Organization/Observer
Non-Governmental Organization (NGOs) include registered non-profit organizations and associations from business and industry, environmental groups, cities and municipalities, academics, and social and activist organizations.
No Regrets
Actions that result in GHG limitations and abatement, and that also make good environmental and economic sense in their own right.
Ozone (O3) in the troposphere, or lower part of the atmosphere, can be a constituent of smog and acts as a GHG. It is created naturally and also by reactions in the atmosphere that involve gases resulting from human activities, including nitrogen oxides (NOx), from motor vehicles and power plants. The Montreal Protocol seeks to control chemicals that destroy ozone in the stratosphere (upper part of the atmosphere), where the ozone absorbs ultra-violet radiation.
See "Policies and Measures".
Among the six GHGs to be abated under the Kyoto Protocol. Perfluorocarbons (PFCs) are a by-product of aluminum smelting and uranium enrichment. They also are the replacement for CFCs in manufacturing semiconductors. The GWP of PFCs is 6500­9200 times that of CO2 (100 year time horizon).
See 'Perfluorocarbons'.
Policies and Measures
In UNFCCC parlance, policies are actions that can be taken and/or mandated by a government ­ often in conjunction with business and industry within its own country, as well as with other countries ­ to accelerate the application and use of successful measures to curb GHG emissions. Measures are technologies, processes, and practices used to implement policies that, if employed, would reduce GHG emissions below anticipated future levels. Examples might include carbon or other energy taxes, standardized fuel efficiency standards for automobiles, etc. "Common and co-ordinated" or "harmonized" policies refer to those adopted jointly by Parties. (This could be by region, such as the European Union (EU), or by countries that comprise a given classification, for example, all Annex I nations.)
Precautionary Principle
From the UN Framework Convention on Climate Change (Article 3): Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures taking into account that policies and measures to deal with climate change should be cost-effective so as to ensure global benefits at the lowest possible cost.
Primary Energy
Energy embodied in natural resources (e.g., coal, crude oil, sunlight, uranium) that has not undergone any anthropogenic conversion or transformation.
Quantified Emissions Limitations and Reductions Objectives
Abbreviated to QELROs, these are the GHG emissions reduction commitments made by developed countries listed in Annex B of the Protocol. (See also "Targets and Timetables".)
Regulatory Measures
Rules or codes enacted by governments that mandate product specifications or process performance characteristics.
Energy sources that are, within a short timeframe relative to the earth's natural cycles, sustainable, and include non-carbon technologies such as solar energy, hydropower, and wind as well as carbon-neutral technologies such as biomass.
Research, Development, and Demonstration
Scientific/technical research and development of new production processes or products, coupled with analysis and measures that provide information to potential users regarding the application of the new product or process; demonstration tests, and feasibility of applying these products processes via pilot plants and other pre-commercial applications.
A plausible description of how the future may develop, based on a coherent and internally consistent set of assumptions ("scenario logic") about key relationships and driving forces (e.g., rate of technology change, prices). Note that scenarios are neither predictions nor forecasts.
(Scenario) Category
The SRES Scenarios are grouped into four categories of cumulative CO2 emissions (all sources) between 1990 and 2100: low, medium-low, medium-high, and high emissions. Each category contains scenarios with a range of different driving forces yet similar cumulative emissions. See also "Emissions Category".
(Scenario) Family
Scenarios that have a similar demographic, societal, economic and technical-change storyline. Four scenario families comprise the SRES scenario set: A1, A2, B1 and B2.
(Scenario) Group
Scenarios within a family that reflect a consistent variation of the storyline. The A1 scenario family includes four groups designated as A1T, A1C, A1G and A1B that explore alternative structures of future energy systems. In the Summary for Policymakers, the A1C and A1G groups have been combined into one "Fossil Intensive" A1FI scenario group. The other three scenario families consist of one group each. The SRES scenario set reflected in the SPM thus consists of six distinct scenario groups, all of which are equally sound and together capture the range of uncertainties
associated with driving forces and emissions.
(Scenario) Marker
A scenario that was originally posted in draft form on the SRES website to represent a given scenario family. The choice of markers was based on which of the initial quantifications best reflected the storyline, and the features of specific models. Markers are no more likely than other scenarios, but are considered by the SRES writing team as illustrative of a particular storyline. They are included in revised form in this report. These scenarios have received the closest scrutiny of the entire writing team and via the SRES open process. Scenarios have also been selected to illustrate the other two scenario groups (see also "Scenario Group" and "Illustrative Scenario".
(Scenario) Set
A set of scenarios developed using a particular methodologic approach. The SRES scenario set comprises 40 scenarios grouped into four scenario families, seven (six in the SPM) scenario groups and four (cumulative CO2) emissions categories.
(Scenario) Storyline
A narrative description of a scenario (or a family of scenarios) highlighting the main scenario characteristics, relationships between key driving forces and the dynamics of their evolution.
Adopting standardized numerical values to improve model and scenario comparability. In this report, emissions are standardized for the two reporting years 1990 and 2100 across all models and scenarios, and individual scenario differences thereafter are corrected for differences between original model outputs and standardized values ("offsets"). (Base year differences reflect scientific uncertainty in source/sink strengths for many GHGs as well as differences in model calibration and simulation time horizons, e.g. for some models 1990 is a projected year as simulations begin by an earlier base year.
See "Sulfur Hexafluoride".
Sinks (UNFCCC Definition)
Any process or activity or mechanism that removes a GHG, aerosol, or precursor of a GHG into the
Source (UNFCCC Definition)
Any process or activity that releases a GHG, aerosol, or precursor of a GHG into the atmosphere.
Standards/Performance Criteria
Set of rules or codes that mandate or define product performance (e.g., grades, dimensions, characteristics, test methods, rules for use).
Structural Change
Changes, for example, in the relative share of GDP produced by the industrial, agricultural, or services sectors of an economy; or (more generally) systems transformations whereby some components are either replaced or potentially substituted by other ones.
Sulfur Hexafluoride
One of the six GHGs to be curbed under the Kyoto Protocol. Sulfur hexafluoride (SF6) is largely used in heavy industry to insulate high-voltage equipment and to assist in the manufacturing of cable-cooling systems. Its GWP is 23,900 times that of CO2 (100 year time horizon).
Targets and Timetables (see also QELROs)
A target is the reduction of a specific percentage of GHG emissions (e.g., 6%, 7%) from a baseline date (e.g., "below 1990 levels") to be achieved by a set date, or timetable (e.g., 2008­2012). For example, under the Kyoto Protocol's formula, the EU has agreed to reduce its GHG emissions by 8% below 1990 levels by the 2008­2012 commitment period. These targets and timetables are, in effect, a cap on the total amount of GHG emissions that can be emitted by a country or region in a given time period.
Technical Potential
The amount by which it is possible to reduce GHG emissions or improve energy efficiency by using a technology or practice in all applications in which it could technically be adopted, without consideration of its costs or practical feasibility.
A systems of means towards particular ends that includes both hardware and social information, e.g. a piece of equipment or a technique for performing a particular activity.
Trace Gas
A minor constituent of the atmosphere. The most important trace gases that contribute to the greenhouse effect are CO2, ozone, CH4, N2O, ammonia, nitric acid, ethylene, sulfur dioxide (SO2), nitric oxide, CFCs, HFCs
HCFCs, SF6, methyl chloride, carbon monoxide, and carbon tetrachloride.
UN Framework Convention on Climate Change (UNFCCC)
A treaty signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries. Its ultimate objective is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic (human-induced) interference with the climate system". While no legally binding level of emissions is set, the treaty states an aim by Annex I countries to return these emissions to 1990 levels by the year 2000. The treaty took effect in March 1994 upon the ratification of more than 50 countries; a total of some 160 nations have now ratified. In March 1995, the UNFCCC held the first session of the COP, the supreme body of the Convention, in Berlin. Its Secretariat is based in Bonn, Germany. In the biennium 2000­01, its approved budget and staffing level are approximately US$12 million annually with approximately 80 personnel.
Values are based on individual preferences, and the total value of any resource is the sum of the values of the different individuals involved in the use of the resource. The values that are the foundation of the estimation of costs are measured in terms of the willingness to pay (WTP) by individuals to receive the resource or by the willingness of individuals to accept payment (WTA) to part with the resource.
Voluntary Measures

Measures to reduce GHG emissions that are adopted by firms or other actors in the absence of government mandates. Voluntary measures help make climate-friendly products or processes more readily available or encourage consumers to incorporate environmental values in their market choices.

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