Annexes
1249
I
ANNEX
Glossary, Acronyms and
Chemical Symbols
Glossary Editors:
Julian M. Allwood (UK), Valentina Bosetti (Italy), Navroz K. Dubash (India), Luis Gómez-Echeverri
(Austria / Colombia), Christoph von Stechow (Germany)
Glossary Contributors:
Marcio D‘Agosto (Brazil), Giovanno Baiocchi (UK / Italy), John Barrett (UK), John Broome (UK),
Steffen Brunner (Germany), Micheline Cariño Olvera (Mexico), Harry Clark (New Zealand),
Leon Clarke (USA), Heleen C. de Coninck (Netherlands), Esteve Corbera (Spain), Felix Creutzig
(Germany), Gian Carlo Delgado (Mexico), Manfred Fischedick (Germany), Marc Fleurbaey
(France / USA), Don Fullerton (USA), Richard Harper (Australia), Edgar Hertwich (Austria / Norway),
Damon Honnery (Australia), Michael Jakob (Germany), Charles Kolstad (USA), Elmar Kriegler
(Germany), Howard Kunreuther (USA), Andreas Löschel (Germany), Oswaldo Lucon (Brazil), Axel
Michaelowa (Germany / Switzerland), Jan C. Minx (Germany), Luis Mundaca (Chile / Sweden),
Jin Murakami (Japan / China), Jos G.J. Olivier (Netherlands), Michael Rauscher (Germany),
Keywan Riahi (Austria), H.-Holger Rogner (Germany), Steffen Schlömer (Germany), Ralph Sims
(New Zealand), Pete Smith (UK), David I. Stern (Australia), Neil Strachan (UK), Kevin Urama
(Nigeria / UK / Kenya), Diana Ürge-Vorsatz (Hungary), David G. Victor (USA), Elke Weber (USA),
Jonathan Wiener (USA), Mitsutsune Yamaguchi (Japan), Azni Zain Ahmed (Malaysia)
This annex should be cited as:
Allwood J. M., V. Bosetti, N. K. Dubash, L. Gómez-Echeverri, and C. von Stechow, 2014: Glossary. In: Climate Change 2014:
Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental
Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum,
S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cam-
bridge University Press, Cambridge, United Kingdom and New York, NY, USA.
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Contents
Glossary � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 1251
Acronyms and chemical symbols � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 1275
References � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 1278
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Glossary
This glossary defines some specific terms as the Lead Authors
intend them to be interpreted in the context of this report. Glos-
sary
entries (highlighted in bold) are by preference subjects; a
main entry can contain
subentries, in bold and italic, for example,
Primary Energy is defined under the entry Energy. Blue, itali-
cized
words indicate that the term is defined in the Glossary. The
glossary is followed by a list of acronyms and chemical symbols.
Please refer to Annex II for standard units, prefixes, and unit con-
version (Section A.II.1) and for regions and country groupings
(Section A.II.2).
Abrupt climate change: A large-scale change in the climate system
that takes place over a few decades or less, persists (or is anticipated
to persist) for at least a few decades, and causes substantial disrup-
tions in human and natural systems. See also Climate threshold.
Adaptability: See Adaptive capacity.
Adaptation: The process of adjustment to actual or expected climate
and its effects. In human systems, adaptation seeks to moderate or
avoid harm or exploit beneficial opportunities. In some natural sys-
tems, human intervention may facilitate adjustment to expected cli-
mate and its effects.
1
Adaptation Fund: A Fund established under the Kyoto Protocol in
2001 and officially launched in 2007. The Fund finances adaptation
projects and programmes in developing countries that are Parties to
the Kyoto Protocol. Financing comes mainly from sales of Certified
Emissions Reductions (CERs) and a share of proceeds amounting to
2 % of the value of CERs issued each year for Clean Development
Mechanism (CDM) projects. The Adaptation Fund can also receive
funds from government, private sector, and individuals.
Adaptive capacity: The ability of systems, institutions, humans, and
other organisms to adjust to potential damage, to take advantage of
opportunities, or to respond to consequences.
2
Additionality: Mitigation projects (e. g., under the Kyoto Mecha-
nisms), mitigation policies, or climate finance are additional if they go
beyond a business-as-usual level, or baseline. Additionality is required
to guarantee the environmental integrity of project-based offset mech-
anisms, but difficult to establish in practice due to the counterfactual
nature of the baseline.
1
Reflecting progress in science, this glossary entry differs in breadth and focus from
the entry used in the Fourth Assessment Report and other IPCC reports.
2
This glossary entry builds from definitions used in previous IPCC reports and the
Millennium Ecosystem Assessment (MEA, 2005).
Adverse side-effects: The negative effects that a policy or measure
aimed at one objective might have on other objectives, without yet
evaluating the net effect on overall social welfare. Adverse side-effects
are often subject to uncertainty and depend on, among others, local
circumstances and implementation practices. See also Co-benefits,
Risk, and Risk tradeoff.
Aerosol: A suspension of airborne solid or liquid particles, with a
typical size between a few nanometres and 10 μm that reside in the
atmosphere for at least several hours. For convenience the term aero-
sol, which includes both the particles and the suspending gas, is often
used in this report in its plural form to mean aerosol particles. Aerosols
may be of either natural or anthropogenic origin. Aerosols may influ-
ence climate in several ways: directly through scattering and absorbing
radiation, and indirectly by acting as cloud condensation nuclei or ice
nuclei, modifying the optical properties and lifetime of clouds. Atmo-
spheric aerosols, whether natural or anthropogenic, originate from two
different pathways: emissions of primary particulate matter (PM), and
formation of secondary PM from gaseous precursors. The bulk of aero-
sols are of natural origin. Some scientists use group labels that refer
to the chemical composition, namely: sea salt, organic carbon, black
carbon (BC), mineral species (mainly desert dust), sulphate, nitrate, and
ammonium. These labels are, however, imperfect as aerosols combine
particles to create complex mixtures. See also Short-lived climate pol-
lutants (SLCPs).
Afforestation: Planting of new forests on lands that historically have
not contained forests. Afforestation projects are eligible under a num-
ber of schemes including, among others, Joint Implementation (JI) and
the Clean Development Mechanism (CDM) under the Kyoto Protocol
for which particular criteria apply (e. g., proof must be given that the
land was not forested for at least 50 years or converted to alternative
uses before 31 December 1989).
For a discussion of the term forest and related terms such as afforesta-
tion, reforestation and deforestation, see the IPCC Special Report on
Land Use, Land-Use Change and Forestry (IPCC, 2000). See also the
report on Definitions and Methodological Options to Inventory Emis-
sions from Direct Human-induced Degradation of Forests and Deveg-
etation of Other Vegetation Types (IPCC, 2003).
Agreement: In this report, the degree of agreement is the level of con-
currence in the literature on a particular finding as assessed by the
authors. See also Evidence, Confidence, Likelihood, and Uncertainty.
Agricultural emissions: See Emissions.
Agriculture, Forestry and Other Land Use (AFOLU): Agriculture,
Forestry and Other Land Use plays a central role for food security and
sustainable development (SD). The main mitigation options within
AFOLU involve one or more of three strategies: prevention of emis-
sions to the atmosphere by conserving existing carbon pools in soils
or vegetation or by reducing emissions of methane (CH
4
) and nitrous
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oxide (N
2
O); sequestration increasing the size of existing carbon
pools, and thereby extracting carbon dioxide (CO
2
) from the atmo-
sphere; and substitution substituting biological products for fossil
fuels or energy-intensive products, thereby reducing CO
2
emissions.
Demand-side measures (e. g., by reducing losses and wastes of food,
changes in human diet, or changes in wood consumption) may also
play a role. FOLU (Forestry and Other Land Use) also referred to as
LULUCF (Land use, land-use change, and forestry) is the subset of
AFOLU emissions and removals of greenhouse gases (GHGs) result-
ing from direct human-induced land use, land-use change and forestry
activities excluding agricultural emissions.
Albedo: The fraction of solar radiation reflected by a surface or object,
often expressed as a percentage. Snow-covered surfaces have a high
albedo, the albedo of soils ranges from high to low, and vegetation-
covered surfaces and oceans have a low albedo. The earth’s planetary
albedo varies mainly through varying cloudiness, snow, ice, leaf area
and land cover changes.
Alliance of Small Island States (AOSIS): The Alliance of Small Island
States (AOSIS) is a coalition of small islands and low-lying coastal
countries with a membership of 44 states and observers that share
and are active in global debates and negotiations on the environment,
especially those related to their vulnerability to the adverse effects of
climate change. Established in 1990, AOSIS acts as an ad-hoc lobby and
negotiating voice for small island development states (SIDS) within the
United Nations including the United Nations Framework Convention
on Climate Change (UNFCCC) climate change negotiations.
Ancillary benefits: See Co-benefits.
Annex I Parties / countries: The group of countries listed in Annex
I to the United Nations Framework Convention on Climate Change
(UNFCCC). Under Articles 4.2 (a) and 4.2 (b) of the UNFCCC, Annex
I Parties were committed to adopting national policies and measures
with the non-legally binding aim to return their greenhouse gas (GHG)
emissions to 1990 levels by 2000. The group is largely similar to the
Annex B Parties to the Kyoto Protocol that also adopted emissions
reduction targets for 2008 2012. By default, the other countries are
referred to as Non-Annex I Parties.
Annex II Parties / countries: The group of countries listed in Annex
II to the United Nations Framework Convention on Climate Change
(UNFCCC). Under Article 4 of the UNFCCC, these countries have a spe-
cial obligation to provide financial resources to meet the agreed full
incremental costs of implementing measures mentioned under Article
12, paragraph 1. They are also obliged to provide financial resources,
including for the transfer of technology, to meet the agreed incremen-
tal costs of implementing measures covered by Article 12, paragraph
1 and agreed between developing country Parties and international
entities referred to in Article 11 of the UNFCCC. This group of coun-
tries shall also assist countries that are particularly vulnerable to the
adverse effects of climate change.
Annex B Parties / countries: The subset of Annex I Parties that have
accepted greenhouse gas (GHG) emission reduction targets for the
period 2008 2012 under Article 3 of the Kyoto Protocol. By default,
the other countries are referred to as Non-Annex I Parties.
Anthropogenic emissions: See Emissions.
Assigned Amount (AA): Under the Kyoto Protocol, the AA is the
quantity of greenhouse gas (GHG) emissions that an Annex B country
has agreed to as its cap on its emissions in the first five-year commit-
ment period (2008 2012). The AA is the country’s total GHG emissions
in 1990 multiplied by five (for the five-year commitment period) and by
the percentage it agreed to as listed in AnnexB of the Kyoto Protocol
(e. g., 92 % for the EU). See also Assigned Amount Unit (AAU).
Assigned Amount Unit (AAU): An AAU equals 1 tonne (metric ton) of
CO
2
-equivalent emissions calculated using the Global Warming Poten-
tial (GWP). See also Assigned Amount (AA).
Atmosphere: The gaseous envelope surrounding the earth, divided
into five layers — the troposphere which contains half of the earth’s
atmosphere, the stratosphere, the mesosphere, the thermosphere,
and the exosphere, which is the outer limit of the atmosphere. The
dry atmosphere consists almost entirely of nitrogen (78.1 % volume
mixing ratio) and oxygen (20.9 % volume mixing ratio), together
with a number of trace gases, such as argon (0.93 % volume mixing
ratio), helium and radiatively active greenhouse gases (GHGs) such
as carbon dioxide (CO
2
) (0.035 % volume mixing ratio) and ozone
(O
3
). In addition, the atmosphere contains the GHG water vapour
(H
2
O), whose amounts are highly variable but typically around 1 %
volume mixing ratio. The atmosphere also contains clouds and aero-
sols.
Backstop technology: Models estimating mitigation often use an
arbitrary carbon-free technology (often for power generation) that
might become available in the future in unlimited supply over the hori-
zon of the model. This allows modellers to explore the consequences
and importance of a generic solution technology without becoming
enmeshed in picking the actual technology. This ‘backstop’ technology
might be a nuclear technology, fossil technology with Carbon Dioxide
Capture and Storage (CCS), solar energy, or something as yet unimag-
ined. The backstop technology is typically assumed either not to cur-
rently exist, or to exist only at higher costs relative to conventional
alternatives.
Banking (of Assigned Amount Units) : Any transfer of Assigned
Amount Units (AAUs) from an existing period into a future commit-
ment period. According to the Kyoto Protocol [Article 3 (13)], Parties
included in Annex I to the United Nations Framework Convention on
Climate Change (UNFCCC) may save excess AAUs from the first com-
mitment period for compliance with their respective cap in subsequent
commitment periods (post-2012).
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Baseline / reference: The state against which change is measured.
In the context of transformation pathways, the term ‘baseline sce-
narios’ refers to scenarios that are based on the assumption that no
mitigation policies or measures will be implemented beyond those that
are already in force and / or are legislated or planned to be adopted.
Baseline scenarios are not intended to be predictions of the future,
but rather counterfactual constructions that can serve to highlight
the level of emissions that would occur without further policy effort.
Typically, baseline scenarios are then compared to mitigation scenar-
ios that are constructed to meet different goals for greenhouse gas
(GHG) emissions, atmospheric concentrations, or temperature change.
The term ‘baseline scenario’ is used interchangeably with ‘reference
scenario’ and ‘no policy scenario’. In much of the literature the term
is also synonymous with the term ‘business-as-usual (BAU) scenario,’
although the term ‘BAU’ has fallen out of favour because the idea of
‘business-as-usual’ in century-long socioeconomic projections is hard
to fathom. See also Climate scenario, Emission scenario, Representa-
tive concentration pathways (RCPs), Shared socio-economic pathways,
Socio-economic scenarios, SRES scenarios, and Stabilization.
Behaviour: In this report, behaviour refers to human decisions and
actions (and the perceptions and judgments on which they are based)
that directly or indirectly influence mitigation or the effects of poten-
tial climate change impacts (adaptation). Human decisions and actions
are relevant at different levels, from international, national, and sub-
national actors, to NGO, tribe, or firm-level decision makers, to com-
munities, households, and individual citizens and consumers. See also
Behavioural change and Drivers of behaviour.
Behavioural change: In this report, behavioural change refers to
alteration of human decisions and actions in ways that mitigate cli-
mate change and / or reduce negative consequences of climate change
impacts. See also Drivers of behaviour.
Biochar: Biomass stabilization can be an alternative or enhancement
to bioenergy in a land-based mitigation strategy. Heating biomass
with exclusion of air produces a stable carbon-rich co-product (char).
When added to soil a system, char creates a system that has greater
abatement potential than typical bioenergy. The relative benefit of bio-
char systems is increased if changes in crop yield and soil emissions of
methane (CH
4
) and nitrous oxide (N
2
O) are taken into account.
Biochemical oxygen demand (BOD): The amount of dissolved oxy-
gen consumed by micro-organisms (bacteria) in the bio-chemical oxi-
dation of organic and inorganic matter in wastewater. See also Chemi-
cal oxygen demand (COD).
Biodiversity: The variability among living organisms from terrestrial,
marine, and other ecosystems. Biodiversity includes variability at the
genetic, species, and ecosystem levels.
3
3
This glossary entry builds from definitions used in the Global Biodiversity Assess-
ment (Heywood, 1995) and the Millennium Ecosystem Assessment (MEA, 2005).
Bioenergy: Energy derived from any form of biomass such as recently
living organisms or their metabolic by-products.
Bioenergy and Carbon Dioxide Capture and Storage (BECCS):
The application of Carbon Dioxide Capture and Storage (CCS) technol-
ogy to bioenergy conversion processes. Depending on the total life-
cycle emissions, including total marginal consequential effects (from
indirect land use change (iLUC) and other processes), BECCS has the
potential for net carbon dioxide (CO
2
) removal from the atmosphere.
See also Sequestration.
Bioethanol: Ethanol produced from biomass (e. g., sugar cane or
corn). See also Biofuel.
Biofuel: A fuel, generally in liquid form, produced from organic mat-
ter or combustible oils produced by living or recently living plants.
Examples of biofuel include alcohol (bioethanol), black liquor from the
paper-manufacturing process, and soybean oil.
First-generation manufactured biofuel: First-generation manu-
factured biofuel is derived from grains, oilseeds, animal fats, and
waste vegetable oils with mature conversion technologies.
Second-generation biofuel: Second-generation biofuel uses
non-traditional biochemical and thermochemical conversion pro-
cesses and feedstock mostly derived from the lignocellulosic frac-
tions of, for example, agricultural and forestry residues, municipal
solid waste, etc.
Third-generation biofuel: Third-generation biofuel would
be derived from feedstocks such as algae and energy crops by
advanced processes still under development.
These second- and third-generation biofuels produced through new
processes are also referred to as next-generation or advanced biofuels,
or advanced biofuel technologies.
Biomass: The total mass of living organisms in a given area or volume;
dead plant material can be included as dead biomass. In the context of
this report, biomass includes products, by-products, and waste of bio-
logical origin (plants or animal matter), excluding material embedded
in geological formations and transformed to fossil fuels or peat.
Traditional biomass: Traditional biomass refers to the bio-
mass fuelwood, charcoal, agricultural residues, and animal
dung used with the so-called traditional technologies such as
open fires for cooking, rustic kilns and ovens for small industries.
Widely used in developing countries, where about 2.6 billion peo-
ple cook with open wood fires, and hundreds of thousands small-
industries. The use of these rustic technologies leads to high pol-
lution levels and, in specific circumstances, to forest degradation
and deforestation. There are many successful initiatives around
the world to make traditional biomass burned more efficiently
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and cleanly using efficient cookstoves and kilns. This last use of
traditional biomass is sustainable and provides large health and
economic benefits to local populations in developing countries,
particularly in rural and peri-urban areas.
Modern biomass: All biomass used in high efficiency conversion
systems.
Biomass burning: Biomass burning is the burning of living and dead
vegetation.
Biosphere (terrestrial and marine): The part of the earth system
comprising all ecosystems and living organisms, in the atmosphere, on
land (terrestrial biosphere) or in the oceans (marine biosphere), includ-
ing derived dead organic matter, such as litter, soil organic matter and
oceanic detritus.
Black carbon (BC): Operationally defined aerosol species based on
measurement of light absorption and chemical reactivity and / or ther-
mal stability. It is sometimes referred to as soot. BC is mostly formed
by the incomplete combustion of fossil fuels, biofuels, and biomass
but it also occurs naturally. It stays in the atmosphere only for days or
weeks. It is the most strongly light-absorbing component of particu-
late matter (PM) and has a warming effect by absorbing heat into the
atmosphere and reducing the albedo when deposited on ice or snow.
Burden sharing (also referred to as Effort sharing): In the context
of mitigation, burden sharing refers to sharing the effort of reducing
the sources or enhancing the sinks of greenhouse gases (GHGs) from
historical or projected levels, usually allocated by some criteria, as well
as sharing the cost burden across countries.
Business-as-usual (BAU): See Baseline / reference.
Cancún Agreements: A set of decisions adopted at the 16th Session
of the Conference of the Parties (COP) to the United Nations Frame-
work Convention on Climate Change (UNFCCC), including the follow-
ing, among others: the newly established Green Climate Fund (GCF),
a newly established technology mechanism, a process for advancing
discussions on adaptation, a formal process for reporting mitigation
commitments, a goal of limiting global mean surface temperature
increase to 2 °C, and an agreement on MRV Measuring, Reporting
and Verifying for those countries that receive international support for
their mitigation efforts.
Cancún Pledges: During 2010, many countries submitted their exist-
ing plans for controlling greenhouse gas (GHG) emissions to the Cli-
mate Change Secretariat and these proposals have now been formally
acknowledged under the United Nations Framework Convention on
Climate Change (UNFCCC). Developed countries presented their plans
in the shape of economy-wide targets to reduce emissions, mainly
up to 2020, while developing countries proposed ways to limit their
growth of emissions in the shape of plans of action.
Cap, on emissions: Mandated restraint as an upper limit on emis-
sions within a given period. For example, the Kyoto Protocol mandates
emissions caps in a scheduled timeframe on the anthropogenic green-
house gas (GHG) emissions released by Annex B countries.
Carbon budget: The area under a greenhouse gas (GHG) emissions
trajectory that satisfies assumptions about limits on cumulative emis-
sions estimated to avoid a certain level of global mean surface temper-
ature rise. Carbon budgets may be defined at the global level, national,
or sub-national levels.
Carbon credit: See Emission allowance.
Carbon cycle: The term used to describe the flow of carbon (in various
forms, e. g., as carbon dioxide) through the atmosphere, ocean, terres-
trial and marine biosphere and lithosphere. In this report, the reference
unit for the global carbon cycle is GtC or GtCO
2
(1 GtC corresponds
to 3.667 GtCO
2
). Carbon is the major chemical constituent of most
organic matter and is stored in the following major reservoirs: organic
molecules in the biosphere, carbon dioxide (CO
2
) in the atmosphere,
organic matter in the soils, in the lithosphere, and in the oceans.
Carbon dioxide (CO
2
): A naturally occurring gas, also a by-product
of burning fossil fuels from fossil carbon deposits, such as oil, gas and
coal, of burning biomass, of land use changes (LUC) and of industrial
processes (e. g., cement production). It is the principal anthropogenic
greenhouse gas (GHG) that affects the earth’s radiative balance. It is
the reference gas against which other GHGs are measured and there-
fore has a Global Warming Potential (GWP) of 1. See Annex II.9.1 for
GWP values for other GHGs.
Carbon Dioxide Capture and Storage (CCS): A process in which
a relatively pure stream of carbon dioxide (CO
2
) from industrial and
energy-related sources is separated (captured), conditioned, com-
pressed, and transported to a storage location for long-term isolation
from the atmosphere. See also Bioenergy and carbon capture and stor-
age (BECCS), CCS-ready, and Sequestration.
Carbon dioxide fertilization: The enhancement of the growth of
plants as a result of increased atmospheric carbon dioxide (CO
2
) con-
centration.
Carbon Dioxide Removal (CDR): Carbon Dioxide Removal methods
refer to a set of techniques that aim to remove carbon dioxide (CO
2
)
directly from the atmosphere by either (1) increasing natural sinks for
carbon or (2) using chemical engineering to remove the CO
2
, with the
intent of reducing the atmospheric CO
2
concentration. CDR methods
involve the ocean, land, and technical systems, including such meth-
ods as iron fertilization, large-scale afforestation, and direct capture
of CO
2
from the atmosphere using engineered chemical means. Some
CDR methods fall under the category of geoengineering, though this
may not be the case for others, with the distinction being based on
the magnitude, scale, and impact of the particular CDR activities. The
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boundary between CDR and mitigation is not clear and there could be
some overlap between the two given current definitions (IPCC, 2012,
p.2). See also Solar Radiation Management (SRM).
Carbon footprint: Measure of the exclusive total amount of emis-
sions of carbon dioxide (CO
2
) that is directly and indirectly caused by
an activity or is accumulated over the life stages of a product (Wied-
mann and Minx, 2008).
Carbon intensity: The amount of emissions of carbon dioxide (CO
2
)
released per unit of another variable such as gross domestic product
(GDP), output energy use, or transport.
Carbon leakage: See Leakage.
Carbon pool: See Reservoir.
Carbon price: The price for avoided or released carbon dioxide (CO
2
)
or CO
2
-equivalent emissions. This may refer to the rate of a carbon
tax, or the price of emission permits. In many models that are used to
assess the economic costs of mitigation, carbon prices are used as a
proxy to represent the level of effort in mitigation policies.
Carbon sequestration: See Sequestration.
Carbon tax: A levy on the carbon content of fossil fuels. Because vir-
tually all of the carbon in fossil fuels is ultimately emitted as carbon
dioxide (CO
2
), a carbon tax is equivalent to an emission tax on CO
2
emissions.
CCS-ready: New large-scale, stationary carbon dioxide (CO
2
) point
sources intended to be retrofitted with Carbon Dioxide Capture and
Storage (CCS) could be designed and located to be ‘CCS-ready’ by
reserving space for the capture installation, designing the unit for opti-
mal performance when capture is added, and siting the plant to enable
access to storage locations. See also Bioenergy and Carbon Dioxide
Capture and Storage (BECCS).
Certified Emission Reduction Unit (CER): Equal to one metric
tonne of CO
2
-equivalent emissions reduced or of carbon dioxide (CO
2
)
removed from the atmosphere through the Clean Development Mech-
anism (CDM) (defined in Article 12 of the Kyoto Protocol) project, cal-
culated using Global Warming Potentials (GWP). See also Emissions
Reduction Units (ERU) and Emissions trading.
Chemical oxygen demand (COD): The quantity of oxygen required
for the complete oxidation of organic chemical compounds in water;
used as a measure of the level of organic pollutants in natural and
waste waters. See also Biochemical oxygen demand (BOD).
Chlorofluorocarbons (CFCs): A chlorofluorocarbon is an organic
compound that contains chlorine, carbon, hydrogen, and fluorine and
is used for refrigeration, air conditioning, packaging, plastic foam,
insulation, solvents, or aerosol propellants. Because they are not
destroyed in the lower atmosphere, CFCs drift into the upper atmo-
sphere where, given suitable conditions, they break down ozone (O
3
).
It is one of the greenhouse gases (GHGs) covered under the 1987
Montreal Protocol as a result of which manufacturing of these gases
has been phased out and they are being replaced by other compounds,
including hydrofluorocarbons (HFCs) which are GHGs covered under
the Kyoto Protocol.
Clean Development Mechanism (CDM): A mechanism defined
under Article 12 of the Kyoto Protocol through which investors (gov-
ernments or companies) from developed (Annex B) countries may
finance greenhouse gas (GHG) emission reduction or removal projects
in developing (Non-Annex B) countries, and receive Certified Emission
Reduction Units (CERs) for doing so. The CERs can be credited towards
the commitments of the respective developed countries. The CDM is
intended to facilitate the two objectives of promoting sustainable
development (SD) in developing countries and of helping industrial-
ized countries to reach their emissions commitments in a cost-effective
way. See also Kyoto Mechanisms.
Climate: Climate in a narrow sense is usually defined as the average
weather, or more rigorously, as the statistical description in terms of
the mean and variability of relevant quantities over a period of time
ranging from months to thousands or millions of years. The classical
period for averaging these variables is 30 years, as defined by the
World Meteorological Organization. The relevant quantities are most
often surface variables such as temperature, precipitation and wind.
Climate in a wider sense is the state, including a statistical description,
of the climate system.
Climate change: Climate change refers to a change in the state of
the climate that can be identified (e. g., by using statistical tests) by
changes in the mean and / or the variability of its properties, and that
persists for an extended period, typically decades or longer. Climate
change may be due to natural internal processes or external forcings
such as modulations of the solar cycles, volcanic eruptions and persis-
tent anthropogenic changes in the composition of the atmosphere or
in land use. Note that the United Nations Framework Convention on
Climate Change (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 com-
position, and climate variability attributable to natural causes. See also
Climate change commitment.
Climate change commitment: Due to the thermal inertia of the
ocean and slow processes in the cryosphere and land surfaces, the cli-
mate would continue to change even if the atmospheric composition
were held fixed at today’s values. Past change in atmospheric com-
position leads to a committed climate change, which continues for
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as long as a radiative imbalance persists and until all components of
the climate system have adjusted to a new state. The further change
in temperature after the composition of the atmosphere is held con-
stant is referred to as the constant composition temperature commit-
ment or simply committed warming or warming commitment. Climate
change commitment includes other future changes, for example in
the hydrological cycle, in extreme weather events, in extreme climate
events, and in sea level change. The constant emission commitment is
the committed climate change that would result from keeping anthro-
pogenic emissions constant and the zero emission commitment is the
climate change commitment when emissions are set to zero. See also
Climate change.
Climate (change) feedback: An interaction in which a perturbation
in one climate quantity causes a change in a second, and the change
in the second quantity ultimately leads to an additional change in
the first. A negative feedback is one in which the initial perturbation
is weakened by the changes it causes; a positive feedback is one in
which the initial perturbation is enhanced. In this Assessment Report, a
somewhat narrower definition is often used in which the climate quan-
tity that is perturbed is the global mean surface temperature, which in
turn causes changes in the global radiation budget. In either case, the
initial perturbation can either be externally forced or arise as part of
internal variability.
Climate engineering: See Geoengineering.
Climate finance: There is no agreed definition of climate finance.
The term ‘climate finance’ is applied both to the financial resources
devoted to addressing climate change globally and to financial flows
to developing countries to assist them in addressing climate change.
The literature includes several concepts in these categories, among
which the most commonly used include:
Incremental costs: The cost of capital of the incremental invest-
ment and the change of operating and maintenance costs for a
mitigation or adaptation project in comparison to a reference proj-
ect. It can be calculated as the difference of the net present values
of the two projects. See also Additionality.
Incremental investment: The extra capital required for the initial
investment for a mitigation or adaptation project in comparison to
a reference project. See also Additionality.
Total climate finance: All financial flows whose expected effect is
to reduce net greenhouse gas (GHG) emissions and / or to enhance
resilience to the impacts of climate variability and the projected
climate change. This covers private and public funds, domestic and
international flows, expenditures for mitigation and adaptation to
current climate variability as well as future climate change.
Total climate finance flowing to developing countries:The
amount of the total climate finance invested in developing coun-
tries that comes from developed countries. This covers private and
public funds.
Private climate finance flowing to developing countries:
Finance and investment by private actors in / from developed coun-
tries for mitigation and adaptation activities in developing coun-
tries.
Public climate finance flowing to developing countries:
Finance provided by developed countries’ governments and bilat-
eral institutions as well as by multilateral institutions for mitiga-
tion and adaptation activities in developing countries. Most of the
funds provided are concessional loans and grants.
Climate model (spectrum or hierarchy): A numerical representa-
tion of the climate system based on the physical, chemical and biologi-
cal properties of its components, their interactions and feedback pro-
cesses, and accounting for some of its known properties. The climate
system can be represented by models of varying complexity, that is,
for any one component or combination of components a spectrum or
hierarchy of models can be identified, differing in such aspects as the
number of spatial dimensions, the extent to which physical, chemical
or biological processes are explicitly represented, or the level at which
empirical parametrizations are involved. Coupled Atmosphere-Ocean
General Circulation Models (AOGCMs) provide a representation of the
climate system that is near or at the most comprehensive end of the
spectrum currently available. There is an evolution towards more com-
plex models with interactive chemistry and biology. Climate models
are applied as a research tool to study and simulate the climate, and
for operational purposes, including monthly, seasonal and interannual
climate predictions.
Climate prediction: A climate prediction or climate forecast is the
result of an attempt to produce (starting from a particular state of the
climate system) an estimate of the actual evolution of the climate in
the future, for example, at seasonal, interannual, or decadal time scales.
Because the future evolution of the climate system may be highly sen-
sitive to initial conditions, such predictions are usually probabilistic in
nature. See also Climate projection, and Climate scenario.
Climate projection: A climate projection is the simulated response of
the climate system to a scenario of future emission or concentration of
greenhouse gases (GHGs) and aerosols, generally derived using climate
models. Climate projections are distinguished from climate predictions
by their dependence on the emission / concentration / radiative forcing
scenario used, which is in turn based on assumptions concerning, for
example, future socioeconomic and technological developments that
may or may not be realized. See also Climate scenario.
Climate scenario: A plausible and often simplified representation
of the future climate, based on an internally consistent set of clima-
tological relationships that has been constructed for explicit use in
investigating the potential consequences of anthropogenic climate
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change, often serving as input to impact models. Climate projections
often serve as the raw material for constructing climate scenarios,
but climate scenarios usually require additional information such as
the observed current climate. See also Baseline / reference, Emission
scenario, Mitigation scenario, Representative concentration pathways
(RCPs), Scenario, Shared socio-economic pathways, Socio-economic
scenario, SRES scenarios, Stabilization, and Transformation pathway.
Climate sensitivity: In IPCC reports, equilibrium climate sensitivity
(units: °C) refers to the equilibrium (steady state) change in the annual
global mean surface temperature following a doubling of the atmo-
spheric CO
2
-equivalent concentration. Owing to computational con-
straints, the equilibrium climate sensitivity in a climate model is some-
times estimated by running an atmospheric general circulation model
(GCM) coupled to a mixed-layer ocean model, because equilibrium
climate sensitivity is largely determined by atmospheric processes.
Efficient models can be run to equilibrium with a dynamic ocean. The
climate sensitivity parameter (units: °C (W m
– 2
)
– 1
) refers to the equilib-
rium change in the annual global mean surface temperature following
a unit change in radiative forcing.
The effective climate sensitivity (units: °C) is an estimate of the global
mean surface temperature response to doubled carbon dioxide (CO
2
)
concentration that is evaluated from model output or observations for
evolving non-equilibrium conditions. It is a measure of the strengths of
the climate feedbacks at a particular time and may vary with forcing
history and climate state, and therefore may differ from equilibrium
climate sensitivity.
The transient climate response (units: °C) is the change in the global
mean surface temperature, averaged over a 20-year period, centred at
the time of atmospheric CO
2
doubling, in a climate model simulation
in which CO
2
increases at 1 % yr
– 1
. It is a measure of the strength and
rapidity of the surface temperature response to greenhouse gas (GHG)
forcing.
Climate system: The climate system is the highly complex system
consisting of five major components: the atmosphere, the hydrosphere,
the cryosphere, the lithosphere and the biosphere, and the interactions
between them. The climate system evolves in time under the influence
of its own internal dynamics and because of external forcings such as
volcanic eruptions, solar variations and anthropogenic forcings such
as the changing composition of the atmosphere and land use change
(LUC).
Climate threshold: A limit within the climate system that, when
crossed, induces a non-linear response to a given forcing. See also
Abrupt climate change.
Climate variability: Climate variability refers to variations in the
mean state and other statistics (such as standard deviations, the occur-
rence of extremes, etc.) of the climate on all spatial and temporal
scales beyond that of individual weather events. Variability may be due
to natural internal processes within the climate system (internal vari-
ability), or to variations in natural or anthropogenic external forcing
(external variability). See also Climate change.
CO
2
-equivalent concentration: The concentration of carbon dioxide
(CO
2
) that would cause the same radiative forcing as a given mixture
of CO
2
and other forcing components. Those values may consider only
greenhouse gases (GHGs), or a combination of GHGs, aerosols, and
surface albedo changes. CO
2
-equivalent concentration is a metric for
comparing radiative forcing of a mix of different forcing components
at a particular time but does not imply equivalence of the correspond-
ing climate change responses nor future forcing. There is generally
no connection between CO
2
-equivalent emissions and resulting CO
2
-
equivalent concentrations.
CO
2
-equivalent emission: The amount of carbon dioxide (CO
2
) emis-
sion that would cause the same integrated radiative forcing, over a
given time horizon, as an emitted amount of a greenhouse gas (GHG)
or a mixture of GHGs. The CO
2
-equivalent emission is obtained by mul-
tiplying the emission of a GHG by its Global Warming Potential (GWP)
for the given time horizon (see Annex II.9.1 and WGI AR5 Table 8.A.1
for GWP values of the different GHGs). For a mix of GHGs it is obtained
by summing the CO
2
-equivalent emissions of each gas. CO
2
-equivalent
emission is a common scale for comparing emissions of different GHGs
but does not imply equivalence of the corresponding climate change
responses. See also CO
2
-equivalent concentration.
Co-benefits: The positive effects that a policy or measure aimed at
one objective might have on other objectives, without yet evaluating
the net effect on overall social welfare. Co-benefits are often subject
to uncertainty and depend on, among others, local circumstances and
implementation practices. Co-benefits are often referred to as ancil-
lary benefits. See also Adverse side-effect, Risk, and Risk tradeoff.
Cogeneration: Cogeneration (also referred to as combined heat and
power, or CHP) is the simultaneous generation and useful application
of electricity and useful heat.
Combined-cycle gas turbine: A power plant that combines two pro-
cesses for generating electricity. First, fuel combustion drives a gas tur-
bine. Second, exhaust gases from the turbine are used to heat water to
drive a steam turbine.
Combined heat and power (CHP): See Cogeneration.
Computable General Equilibrium (CGE) Model: See Models.
Conference of the Parties (COP): The supreme body of the United
Nations Framework Convention on Climate Change (UNFCCC), com-
prising countries with a right to vote that have ratified or acceded to
the convention. See also Meeting of the Parties (CMP).
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Confidence: The validity of a finding based on the type, amount,
quality, and consistency of evidence (e. g., mechanistic understanding,
theory, data, models, expert judgment) and on the degree of agree-
ment. In this report, confidence is expressed qualitatively (Mastran-
drea etal., 2010). See WGI AR5 Figure 1.11 for the levels of confidence
and WGI AR5 Table 1.2 for the list of likelihood qualifiers. See also
Uncertainty.
Consumption-based accounting: Consumption-based accounting
provides a measure of emissions released to the atmosphere in order
to generate the goods and services consumed by a certain entity (e. g.,
person, firm, country, or region). See also Production-based account-
ing.
Contingent valuation method: An approach to quantitatively
assess values assigned by people in monetary (willingness to pay)
and non-monetary (willingness to contribute with time, resources
etc.) terms. It is a direct method to estimate economic values for
ecosystem and environmental services. In a survey, people are asked
their willingness to pay / contribute for access to, or their willingness
to accept compensation for removal of, a specific environmental ser-
vice, based on a hypothetical scenario and description of the environ-
mental service.
Conventional fuels: See Fossil fuels.
Copenhagen Accord: The political (as opposed to legal) agreement
that emerged at the 15th Session of the Conference of the Parties
(COP) at which delegates ‘agreed to take note’ due to a lack of con-
sensus that an agreement would require. Some of the key elements
include: recognition of the importance of the scientific view on the
need to limit the increase in global mean surface temperature to 2°
C; commitment by Annex I Parties to implement economy-wide emis-
sions targets by 2020 and non-Annex I Parties to implement mitiga-
tion actions; agreement to have emission targets of Annex I Parties
and their delivery of finance for developing countries subject to Mea-
surement, Reporting and Verification (MRV) and actions by developing
countries to be subject to domestic MRV; calls for scaled up financing
including a fast track financing of USD 30 billion and USD 100 billion
by 2020; the establishment of a new Green Climate Fund (GCF); and
the establishment of a new technology mechanism. Some of these ele-
ments were later adopted in the Cancún Agreements.
Cost-benefit analysis (CBA): Monetary measurement of all negative
and positive impacts associated with a given action. Costs and benefits
are compared in terms of their difference and / or ratio as an indicator
of how a given investment or other policy effort pays off seen from the
society’s point of view.
Cost of conserved energy (CCE): See Levelized cost of conserved
energy (LCCE).
Cost-effectiveness: A policy is more cost-effective if it achieves a
goal, such as a given pollution abatement level, at lower cost. A criti-
cal condition for cost-effectiveness is that marginal abatement costs
be equal among obliged parties. Integrated models approximate cost-
effective solutions, unless they are specifically constrained to behave
otherwise. Cost-effective mitigation scenarios are those based on a
stylized implementation approach in which a single price on carbon
dioxide (CO
2
) and other greenhouse gases (GHGs) is applied across the
globe in every sector of every country and that rises over time in a way
that achieves lowest global discounted costs.
Cost-effectiveness analysis (CEA): A tool based on constrained
optimization for comparing policies designed to meet a prespecified
target.
Crediting period, Clean Development Mechanism (CDM): The
time during which a project activity is able to generate Certified Emis-
sion Reduction Units (CERs). Under certain conditions, the crediting
period can be renewed up to two times.
Cropland management: The system of practices on land on which
agricultural crops are grown and on land that is set aside or temporar-
ily not being used for crop production (UNFCCC, 2002).
Decarbonization: The process by which countries or other entities
aim to achieve a low-carbon economy, or by which individuals aim to
reduce their carbon consumption.
Decomposition approach: Decomposition methods disaggregate the
total amount of historical changes of a policy variable into contribu-
tions made by its various determinants.
Deforestation: Conversion of forest to non-forest is one of the major
sources of greenhouse gas (GHG) emissions. Under Article 3.3 of the
Kyoto Protocol, “the net changes in greenhouse gas emissions by
sources and removals by sinks resulting from direct human-induced
land-use change and forestry activities, limited to afforestation,
reforestation and deforestation since 1990, measured as verifiable
changes in carbon stocks in each commitment period, shall be sued
to meet the commitments under this Article of each Party included in
AnnexI”. Reducing emissions from deforestation is not eligible for
Joint Implementation (JI) or Clean Development Mechanism (CDM)
projects but has been introduced in the program of work under REDD
(Reducing Emissions from Deforestation and Forest Degradation)
under the United Nations Framework Convention on Climate Change
(UNFCCC).
For a discussion of the term forest and related terms such as afforesta-
tion, reforestation, and deforestation see the IPCC Special Report on
Land Use, Land-Use Change and Forestry (IPCC, 2000). See also the
report on Definitions and Methodological Options to Inventory Emis-
sions from Direct Human-induced Degradation of Forests and Deveg-
etation of Other Vegetation Types (IPCC, 2003).
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Dematerialization: The ambition to reduce the total material inputs
required to deliver a final service.
Descriptive analysis: Descriptive (also termed positive) approaches to
analysis focus on how the world works or actors behave, not how they
should behave in some idealized world. See also Normative analysis.
Desertification: Land degradation in arid, semi-arid, and dry sub-
humid areas resulting from various factors, including climatic varia-
tions and human activities. Land degradation in arid, semi-arid, and
dry sub-humid areas is a reduction or loss of the biological or eco-
nomic productivity and complexity of rainfed cropland, irrigated crop-
land, or range, pasture, forest, and woodlands resulting from land uses
or from a process or combination of processes, including processes
arising from human activities and habitation patterns, such as (1) soil
erosion caused by wind and / or water; (2) deterioration of the physical,
chemical, biological, or economic properties of soil; and (3) long-term
loss of natural vegetation (UNCCD, 1994).
Designated national authority (DNA): A designated national
authority is a national institution that authorizes and approves Clean
Development Mechansim (CDM) projects in that country. In CDM host
countries, the DNA assesses whether proposed projects assist the host
country in achieving its sustainable development (SD) goals, certifica-
tion of which is a prerequisite for registration of the project by the
CDM Executive Board.
Developed / developing countries: See Industrialized / developing
countries.
Development pathway: An evolution based on an array of techno-
logical, economic, social, institutional, cultural, and biophysical charac-
teristics that determine the interactions between human and natural
systems, including consumption and production patterns in all coun-
tries, over time at a particular scale.
Direct Air Capture (DAC): Chemical process by which a pure carbon
dioxide (CO
2
) stream is produced by capturing CO
2
from the ambient
air.
Direct emissions: See Emissions.
Discounting: A mathematical operation making monetary (or other)
amounts received or expended at different times (years) comparable
across time. The discounter uses a fixed or possibly time-varying dis-
count rate (>0) from year to year that makes future value worth less
today. See also Present value.
Double dividend: The extent to which revenue-generating instru-
ments, such as carbon taxes or auctioned (tradable) emission permits
can (1) contribute to mitigation and (2) offset at least part of the
potential welfare losses of climate policies through recycling the rev-
enue in the economy to reduce other taxes likely to cause distortions.
Drivers of behaviour: Determinants of human decisions and actions,
including peoples’ values and goals and the factors that constrain
action, including economic factors and incentives, information access,
regulatory and technological constraints, cognitive and emotional
processing capacity, and social norms. See also Behaviour and Behav-
ioural change.
Drivers of emissions: Drivers of emissions refer to the processes,
mechanisms and properties that influence emissions through factors.
Factors comprise the terms in a decomposition of emissions. Factors
and drivers may in return affect policies, measures and other drivers.
Economic efficiency: Economic efficiency refers to an economy’s allo-
cation of resources (goods, services, inputs, productive activities). An
allocation is efficient if it is not possible to reallocate resources so as
to make at least one person better off without making someone else
worse off. An allocation is inefficient if such a reallocation is possible.
This is also known as the Pareto Criterion for efficiency. See also Pareto
optimum.
Economies in Transition (EITs): Countries with their economies
changing from a planned economic system to a market economy. See
Annex II.2.1.
Ecosystem: A functional unit consisting of living organisms, their non-
living environment, and the interactions within and between them. The
components included in a given ecosystem and its spatial boundaries
depend on the purpose for which the ecosystem is defined: in some
cases they are relatively sharp, while in others they are diffuse. Ecosys-
tem boundaries can change over time. Ecosystems are nested within
other ecosystems, and their scale can range from very small to the
entire biosphere. In the current era, most ecosystems either contain
people as key organisms, or are influenced by the effects of human
activities in their environment.
Ecosystem services: Ecological processes or functions having mon-
etary or non-monetary value to individuals or society at large. These
are frequently classified as (1) supporting services such as productiv-
ity or biodiversity maintenance, (2) provisioning services such as food,
fiber, or fish, (3) regulating services such as climate regulation or car-
bon sequestration, and (4) cultural services such as tourism or spiritual
and aesthetic appreciation.
Embodied emissions: See Emissions.
Embodied energy: See Energy.
Emission allowance: See Emission permit.
Emission factor / Emissions intensity: The emissions released per
unit of activity. See also Carbon intensity.
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Emission permit: An entitlement allocated by a government to a
legal entity (company or other emitter) to emit a specified amount of a
substance. Emission permits are often used as part of emissions trad-
ing schemes.
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 devel-
opment 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, energy and land use) and their key relationships. Concentra-
tion 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 Emis-
sion Scenarios (Nakićenović and Swart, 2000) emission scenarios,
the so-called SRES scenarios, were published, some of which were
used, among others, as a basis for the climate projections presented
in Chapters 9 to 11 of IPCC (2001) and Chapters 10 and 11 of IPCC
(2007). New emission scenarios for climate change, the four Repre-
sentative Concentration Pathways (RCPs), were developed for, but
independently of, the present IPCC assessment. See also Baseline / ref-
erence, Climate scenario, Mitigation scenario, Shared socio-economic
pathways, Scenario, Socio-economic scenario, Stabilization, and
Transformation pathway.
Emission trajectories: A projected development in time of the emis-
sion of a greenhouse gas (GHG) or group of GHGs, aerosols, and GHG
precursors.
Emissions:
Agricultural emissions: Emissions associated with agricultural
systems — predominantly methane (CH
4
) or nitrous oxide (N
2
O).
These include emissions from enteric fermentation in domestic
livestock, manure management, rice cultivation, prescribed burn-
ing of savannas and grassland, and from soils (IPCC, 2006).
Anthropogenic emissions: Emissions of greenhouse gases
(GHGs), aerosols, and precursors of a GHG or aerosol caused by
human activities. These activities include the burning of fossil fuels,
deforestation, land use changes (LUC), livestock production, fertil-
ization, waste management, and industrial processes.
Direct emissions: Emissions that physically arise from activities
within well-defined boundaries of, for instance, a region, an eco-
nomic sector, a company, or a process.
Embodied emissions: Emissions that arise from the production
and delivery of a good or service or the build-up of infrastructure.
Depending on the chosen system boundaries, upstream emissions
are often included (e. g., emissions resulting from the extraction of
raw materials). See also Lifecycle assessment (LCA).
Indirect emissions: Emissions that are a consequence of the
activities within well-defined boundaries of, for instance, a region,
an economic sector, a company or process, but which occur outside
the specified boundaries. For example, emissions are described as
indirect if they relate to the use of heat but physically arise out-
side the boundaries of the heat user, or to electricity production
but physically arise outside of the boundaries of the power supply
sector.
Scope 1, Scope 2, and Scope 3 emissions: Emissions respon-
sibility as defined by the GHG Protocol, a private sector initiative.
‘Scope 1’ indicates direct greenhouse gas (GHG) emissions that are
from sources owned or controlled by the reporting entity. ‘Scope
2’ indicates indirect GHG emissions associated with the produc-
tion of electricity, heat, or steam purchased by the reporting entity.
‘Scope 3’ indicates all other indirect emissions, i. e., emissions asso-
ciated with the extraction and production of purchased materials,
fuels, and services, including transport in vehicles not owned or
controlled by the reporting entity, outsourced activities, waste dis-
posal, etc. (WBCSD and WRI, 2004).
Territorial emissions: Emissions that take place within the ter-
ritories of a particular jurisdiction.
Emissions Reduction Unit (ERU): Equal to one metric tonne of CO
2
-
equivalent emissions reduced or of carbon dioxide (CO
2
) removed from
the atmosphere through a Joint Implementation (JI) (defined in Arti-
cle 6 of the Kyoto Protocol) project, calculated using Global Warming
Potentials (GWPs). See also Certified Emission Reduction Unit (CER)
and Emissions trading.
Emission standard: An emission level that, by law or by voluntary
agreement, may not be exceeded. Many standards use emission fac-
tors in their prescription and therefore do not impose absolute limits
on the emissions.
Emissions trading: A market-based instrument used to limit emis-
sions. The environmental objective or sum of total allowed emissions is
expressed as an emissions cap. The cap is divided in tradable emission
permits that are allocated either by auctioning or handing out for
free (grandfathering) to entities within the jurisdiction of the trad-
ing scheme. Entities need to surrender emission permits equal to the
amount of their emissions (e. g., tonnes of carbon dioxide). An entity
may sell excess permits. Trading schemes may occur at the intra-com-
pany, domestic, or international level and may apply to carbon dioxide
(CO
2
), other greenhouse gases (GHGs), or other substances. Emissions
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trading is also one of the mechanisms under the Kyoto Protocol. See
also Kyoto Mechanisms.
Energy: The power of ‘doing work’ possessed at any instant by a
body or system of bodies. Energy is classified in a variety of types and
becomes available to human ends when it flows from one place to
another or is converted from one type into another.
Embodied energy: The energy used to produce a material sub-
stance or product (such as processed metals or building materi-
als), taking into account energy used at the manufacturing facility,
energy used in producing the materials that are used in the manu-
facturing facility, and so on.
Final energy: See Primary energy.
Primary energy: Primary energy (also referred to as energy
sources) is the energy stored in natural resources (e. g., coal, crude
oil, natural gas, uranium, and renewable sources). It is defined in
several alternative ways. The International Energy Agency (IEA)
utilizes the physical energy content method, which defines pri-
mary energy as energy that has not undergone any anthropogenic
conversion. The method used in this report is the direct equiva-
lent method (see Annex II.4), which counts one unit of secondary
energy provided from non-combustible sources as one unit of pri-
mary energy, but treats combustion energy as the energy poten-
tial contained in fuels prior to treatment or combustion. Primary
energy is transformed into secondary energy by cleaning (natural
gas), refining (crude oil to oil products) or by conversion into elec-
tricity 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 in supplying energy ser-
vices (e. g., light).
Renewable energy (RE): Any form of energy from solar, geophys-
ical, or biological sources that is replenished by natural processes
at a rate that equals or exceeds its rate of use. For a more detailed
description see Bioenergy, Solar energy, Hydropower, Ocean, Geo-
thermal, and Wind energy.
Secondary energy: See Primary energy.
Energy access: Access to clean, reliable and affordable energy ser-
vices for cooking and heating, lighting, communications, and produc-
tive uses (AGECC, 2010).
Energy carrier: A substance for delivering mechanical work or trans-
fer of heat. Examples of energy carriers include: solid, liquid, or gas-
eous fuels (e. g., biomass, coal, oil, natural gas, hydrogen); pressur-
ized / heated / cooled fluids (air, water, steam); and electric current.
Energy density: The ratio of stored energy to the volume or mass of
a fuel or battery.
Energy efficiency (EE): The ratio of useful energy output of a system,
conversion process, or activity to its energy input. In economics, the
term may describe the ratio of economic output to energy input. See
also Energy intensity.
Energy intensity: The ratio of energy use to economic or physical out-
put.
Energy poverty: A lack of access to modern energy services. See also
Energy access.
Energy security: The goal of a given country, or the global community
as a whole, to maintain an adequate, stable, and predictable energy
supply. Measures encompass safeguarding the sufficiency of energy
resources to meet national energy demand at competitive and stable
prices and the resilience of the energy supply; enabling development
and deployment of technologies; building sufficient infrastructure to
generate, store and transmit energy supplies; and ensuring enforceable
contracts of delivery.
Energy services: An energy service is the benefit received as a result
of energy use.
Energy system: The energy system comprises all components related
to the production, conversion, delivery, and use of energy.
Environmental effectiveness: A policy is environmentally effective
to the extent by which it achieves its expected environmental target
(e. g., greenhouse gas (GHG) emission reduction).
Environmental input-output analysis: An analytical method used
to allocate environmental impacts arising in production to categories
of final consumption, by means of the Leontief inverse of a country’s
economic input-output tables. See also Annex II.6.2.
Environmental Kuznets Curve: The hypothesis that various environ-
mental impacts first increase and then eventually decrease as income
per capita increases.
Evidence: Information indicating the degree to which a belief or prop-
osition is true or valid. In this report, the degree of evidence reflects
the amount, quality, and consistency of scientific / technical information
on which the Lead Authors are basing their findings. See also Agree-
ment, Confidence, Likelihood and Uncertainty.
Externality / external cost / external benefit: Externalities arise from
a human activity when agents responsible for the activity do not take
full account of the activity’s impacts on others’ production and con-
sumption possibilities, and no compensation exists for such impacts.
When the impacts are negative, they are external costs. When the
impacts are positive, they are external benefits. See also Social costs.
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Feed-in tariff (FIT): The price per unit of electricity (heat) that a utility
or power (heat) supplier has to pay for distributed or renewable elec-
tricity (heat) fed into the power grid (heat supply system) by non-utility
generators. A public authority regulates the tariff.
Final energy: See Primary energy.
Flaring: Open air burning of waste gases and volatile liquids, through
a chimney, at oil wells or rigs, in refineries or chemical plants, and at
landfills.
Flexibility Mechanisms: See Kyoto Mechanisms.
Food security: A state that prevails when people have secure access
to sufficient amounts of safe and nutritious food for normal growth,
development, and an active and healthy life.
4
Forest: A vegetation type dominated by trees. Many definitions of the
term forest are in use throughout the world, reflecting wide differences
in biogeophysical conditions, social structure and economics. According
to the 2005 United Nations Framework Convention on Climate Change
(UNFCCC) definition a forest is an area of land of at least 0.05 1 hect-
are, of which more than 10 30 % is covered by tree canopy. Trees must
have a potential to reach a minimum of 25 meters at maturity in situ.
Parties to the Convention can choose to define a forest from within
those ranges. Currently, the definition does not recognize different
biomes, nor do they distinguish natural forests from plantations, an
anomaly being pointed out by many as in need of rectification.
For a discussion of the term forest and related terms such as afforesta-
tion, reforestation and deforestation see the IPCC Report on Land Use,
Land-Use Change and Forestry (IPCC, 2000). See also the Report on
Definitions and Methodological Options to Inventory Emissions from
Direct Human-induced Degradation of Forests and Devegetation of
Other Vegetation Types (IPCC, 2003).
Forest management: A system of practices for stewardship and use
of forest land aimed at fulfilling relevant ecological (including biologi-
cal diversity), economic and social functions of the forest in a sustain-
able manner (UNFCCC, 2002).
Forestry and Other Land Use (FOLU): See Agriculture, Forestry and
Other Land Use (AFOLU).
Fossil fuels: Carbon-based fuels from fossil hydrocarbon deposits,
including coal, peat, oil, and natural gas.
Free Rider: One who benefits from a common good without contrib-
uting to its creation or preservation.
4
This glossary entry builds on definitions used in FAO (2000) and previous IPCC
reports.
Fuel cell: A fuel cell generates electricity in a direct and continu-
ous way from the controlled electrochemical reaction of hydrogen or
another fuel and oxygen. With hydrogen as fuel the cell emits only
water and heat (no carbon dioxide) and the heat can be utilized (see
also Cogeneration).
Fuel poverty: A condition in which a household is unable to guaran-
tee a certain level of consumption of domestic energy services (espe-
cially heating) or suffers disproportionate expenditure burdens to meet
these needs.
Fuel switching: In general, fuel switching refers to substituting fuel A
for fuel B. In the context of mitigation it is implicit that fuel A has lower
carbon content than fuel B, e. g., switching from natural gas to coal.
General circulation (climate) model (GCM): See Climate model.
General equilibrium analysis: General equilibrium analysis consid-
ers simultaneously all the markets and feedback effects among these
markets in an economy leading to market clearance. (Computable)
general equilibrium (CGE) models are the operational tools used to
perform this type of analysis.
Geoengineering: Geoengineering refers to a broad set of methods
and technologies that aim to deliberately alter the climate system
in order to alleviate the impacts of climate change. Most, but not
all, methods seek to either (1) reduce the amount of absorbed solar
energy in the climate system (Solar Radiation Management) or (2)
increase net carbon sinks from the atmosphere at a scale sufficiently
large to alter climate (Carbon Dioxide Removal). Scale and intent
are of central importance. Two key characteristics of geoengineer-
ing methods of particular concern are that they use or affect the cli-
mate system (e. g., atmosphere, land or ocean) globally or regionally
and / or could have substantive unintended effects that cross national
boundaries. Geoengineering is different from weather modification
and ecological engineering, but the boundary can be fuzzy (IPCC,
2012, p.2).
Geothermal energy: Accessible thermal energy stored in the earth’s
interior.
Global Environment Facility (GEF): The Global Environment Facil-
ity, established in 1991, helps developing countries fund projects and
programmes that protect the global environment. GEF grants support
projects related to biodiversity, climate change, international waters,
land degradation, the ozone (O
3
) layer, and persistent organic pollut-
ants.
Global mean surface temperature: An estimate of the global mean
surface air temperature. However, for changes over time, only anoma-
lies, as departures from a climatology, are used, most commonly based
on the area-weighted global average of the sea surface temperature
anomaly and land surface air temperature anomaly.
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Global warming: Global warming refers to the gradual increase,
observed or projected, in global surface temperature, as one of the
consequences of radiative forcing caused by anthropogenic emissions.
Global Warming Potential (GWP): An index, based on radiative
properties of greenhouse gases (GHGs), measuring the radiative forc-
ing following a pulse emission of a unit mass of a given GHG in the
present-day atmosphere integrated over a chosen time horizon, rela-
tive to that of carbon dioxide (CO
2
). The GWP represents the combined
effect of the differing times these gases remain in the atmosphere and
their relative effectiveness in causing radiative forcing. The Kyoto Pro-
tocol is based on GWPs from pulse emissions over a 100-year time
frame. Unless stated otherwise, this report uses GWP values calculated
with a 100-year time horizon which are often derived from the IPCC
Second Assessment Report (see Annex II.9.1 for the GWP values of the
different GHGs).
Governance: A comprehensive and inclusive concept of the full range
of means for deciding, managing, and implementing policies and mea-
sures. Whereas government is defined strictly in terms of the nation-
state, the more inclusive concept of governance recognizes the contri-
butions of various levels of government (global, international, regional,
local) and the contributing roles of the private sector, of nongovern-
mental actors, and of civil society to addressing the many types of
issues facing the global community.
Grazing land management: The system of practices on land used for
livestock production aimed at manipulating the amount and type of
vegetation and livestock produced (UNFCCC, 2002).
Green Climate Fund (GCF): The Green Climate Fund was established
by the 16th Session of the Conference of the Parties (COP) in 2010 as
an operating entity of the financial mechanism of the United Nations
Framework Convention on Climate Change (UNFCCC), in accordance
with Article 11 of the Convention, to support projects, programmes
and policies and other activities in developing country Parties. The
Fund is governed by a Board and will receive guidance of the COP. The
Fund is headquartered in Songdo, Republic of Korea.
Greenhouse effect: The infrared radiative effect of all infrared-
absorbing constituents in the atmosphere. Greenhouse gases (GHGs),
clouds, and (to a small extent) aerosols absorb terrestrial radiation
emitted by the earth’s surface and elsewhere in the atmosphere. These
substances emit infrared radiation in all directions, but, everything else
being equal, the net amount emitted to space is normally less than
would have been emitted in the absence of these absorbers because
of the decline of temperature with altitude in the troposphere and the
consequent weakening of emission. An increase in the concentration
of GHGs increases the magnitude of this effect; the difference is some-
times called the enhanced greenhouse effect. The change in a GHG
concentration because of anthropogenic emissions contributes to an
instantaneous radiative forcing. Surface temperature and troposphere
warm in response to this forcing, gradually restoring the radiative bal-
ance at the top of the atmosphere.
Greenhouse gas (GHG): Greenhouse gases are those gaseous con-
stituents of the atmosphere, both natural and anthropogenic, that
absorb and emit radiation at specific wavelengths within the spectrum
of terrestrial radiation emitted by the earth’s surface, the atmosphere
itself, and by clouds. This property causes the greenhouse effect. Water
vapour (H
2
O), carbon dioxide (CO
2
), nitrous oxide (N
2
O), methane
(CH
4
) and ozone (O
3
) are the primary GHGs in the earth’s atmosphere.
Moreover, there are a number of entirely human-made GHGs in the
atmosphere, such as the halocarbons and other chlorine- and bromine-
containing substances, dealt with under the Montreal Protocol. Beside
CO
2
, N
2
O and CH
4
, the Kyoto Protocol deals with the GHGs sulphur
hexafluoride (SF
6
), hydrofluorocarbons (HFCs) and perfluorocarbons
(PFCs). For a list of well-mixed GHGs, see WGI AR5 Table 2.A.1.
Gross domestic product (GDP): The sum of gross value added, at
purchasers’ prices, by all resident and non-resident producers in the
economy, plus any taxes and minus any subsidies not included in the
value of the products in a country or a geographic region for a given
period, normally one year. GDP is calculated without deducting for
depreciation of fabricated assets or depletion and degradation of natu-
ral resources.
Gross national expenditure (GNE): The total amount of public and
private consumption and capital expenditures of a nation. In general,
national account is balanced such that gross domestic product (GDP) +
import = GNE + export.
Gross national product: The value added from domestic and foreign
sources claimed by residents. GNP comprises gross domestic product
(GDP) plus net receipts of primary income from non-resident income.
Gross world product: An aggregation of the individual country’s
gross domestic products (GDP) to obtain the world or global GDP.
Heat island: The relative warmth of a city compared with surrounding
rural areas, associated with changes in runoff, effects on heat reten-
tion, and changes in surface albedo.
Human Development Index (HDI): The Human Development Index
allows the assessment of countries’ progress regarding social and eco-
nomic development as a composite index of three indicators: (1) health
measured by life expectancy at birth; (2) knowledge as measured by
a combination of the adult literacy rate and the combined primary,
secondary and tertiary school enrolment ratio; and (3) standard of liv-
ing as gross domestic product (GDP) per capita (in purchasing power
parity). The HDI sets a minimum and a maximum for each dimension,
called goalposts, and then shows where each country stands in rela-
tion to these goalposts, expressed as a value between 0 and 1. The
HDI only acts as a broad proxy for some of the key issues of human
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development; for instance, it does not reflect issues such as political
participation or gender inequalities.
Hybrid vehicle: Any vehicle that employs two sources of propulsion,
particularly a vehicle that combines an internal combustion engine
with an electric motor.
Hydrofluorocarbons (HFCs): One of the six types of greenhouse
gases (GHGs) or groups of GHGs to be mitigated under the Kyoto Pro-
tocol. They are produced commercially as a substitute for chlorofluo-
rocarbons (CFCs). HFCs largely are used in refrigeration and semicon-
ductor manufacturing. See also Global Warming Potential (GWP) and
Annex II.9.1 for GWP values.
Hydropower: Power harnessed from the flow of water.
Incremental costs: See Climate finance.
Incremental investment: See Climate finance.
Indigenous peoples: Indigenous peoples and nations are those that,
having a historical continuity with pre-invasion and pre-colonial soci-
eties that developed on their territories, consider themselves distinct
from other sectors of the societies now prevailing on those territories,
or parts of them. They form at present principally non-dominant sectors
of society and are often determined to preserve, develop, and transmit
to future generations their ancestral territories, and their ethnic iden-
tity, as the basis of their continued existence as peoples, in accordance
with their own cultural patterns, social institutions, and common law
system.
5
Indirect emissions: See Emissions.
Indirect land use change (iLUC): See Land use.
Industrial Revolution: A period of rapid industrial growth with far-
reaching social and economic consequences, beginning in Britain dur-
ing the second half of the 18th century and spreading to Europe and
later to other countries including the United States. The invention of
the steam engine was an important trigger of this development. The
industrial revolution marks the beginning of a strong increase in the
use of fossil fuels and emission of, in particular, fossil carbon dioxide.
In this report the terms pre-industrial and industrial refer, somewhat
arbitrarily, to the periods before and after 1750, respectively.
Industrialized countries / developing countries: There are a diver-
sity of approaches for categorizing countries on the basis of their level
of development, and for defining terms such as industrialized, devel-
oped, or developing. Several categorizations are used in this report. (1)
5
This glossary entry builds on the definitions used in Cobo (1987) and previous
IPCC reports.
In the United Nations system, there is no established convention for
designating of developed and developing countries or areas. (2) The
United Nations Statistics Division specifies developed and developing
regions based on common practice. In addition, specific countries are
designated as Least Developed Countries (LCD), landlocked develop-
ing countries, small island developing states, and transition economies.
Many countries appear in more than one of these categories. (3) The
World Bank uses income as the main criterion for classifying countries
as low, lower middle, upper middle, and high income. (4) The UNDP
aggregates indicators for life expectancy, educational attainment, and
income into a single composite Human Development Index (HDI) to
classify countries as low, medium, high, or very high human develop-
ment. See WGII AR5 Box 1 2.
Input-output analysis: See Environmental input-output analysis.
Institution: Institutions are rules and norms held in common by social
actors that guide, constrain and shape human interaction. Institu-
tions can be formal, such as laws and policies, or informal, such as
norms and conventions. Organizations such as parliaments, regula-
tory agencies, private firms, and community bodies develop and act
in response to institutional frameworks and the incentives they frame.
Institutions can guide, constrain and shape human interaction through
direct control, through incentives, and through processes of socializa-
tion.
Institutional feasibility: Institutional feasibility has two key parts: (1)
the extent of administrative workload, both for public authorities and
for regulated entities, and (2) the extent to which the policy is viewed
as legitimate, gains acceptance, is adopted, and is implemented.
Integrated assessment: A method of analysis that combines results
and models from the physical, biological, economic, and social sciences,
and the interactions among these components in a consistent frame-
work to evaluate the status and the consequences of environmental
change and the policy responses to it. See also Integrated Models.
Integrated models: See Models.
IPAT identity: IPAT is the lettering of a formula put forward to describe
the impact of human activity on the environment. Impact (I) is viewed
as the product of population size (P), affluence (A=GDP / person) and
technology (T= impact per GDP unit). In this conceptualization, popu-
lation growth by definition leads to greater environmental impact if A
and T are constant, and likewise higher income leads to more impact
(Ehrlich and Holdren, 1971).
Iron fertilization: Deliberate introduction of iron to the upper ocean
intended to enhance biological productivity which can sequester addi-
tional atmospheric carbon dioxide (CO
2
) into the oceans. See also Geo-
engineering and Carbon Dioxide Removal (CDR).
Jevon’s paradox: See Rebound effect.
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Joint Implementation (JI): A mechanism defined in Article 6 of the
Kyoto Protocol, through which investors (governments or companies)
from developed (Annex B) countries may implement projects jointly
that limit or reduce emissions or enhance sinks, and to share the Emis-
sions Reduction Units (ERU). See also Kyoto Mechanisms.
Kaya identity: In this identity global emissions are equal to the popu-
lation size, multiplied by per capita output (gross world product), mul-
tiplied by the energy intensity of production, multiplied by the carbon
intensity of energy.
Kyoto Mechanisms (also referred to as Flexibility Mechanisms):
Market-based mechanisms that Parties to the Kyoto Protocol can use in
an attempt to lessen the potential economic impacts of their commit-
ment to limit or reduce greenhouse gas (GHG) emissions. They include
Joint Implementation (JI) (Article 6), Clean Development Mechanism
(CDM) (Article 12), and Emissions trading (Article 17).
Kyoto Protocol: The Kyoto Protocol to the United Nations Framework
Convention on Climate Change (UNFCCC) was adopted in 1997 in
Kyoto, Japan, at the Third Session of the Conference of the Parties (COP)
to the UNFCCC. It contains legally binding commitments, in addition to
those included in the UNFCCC. Countries included in Annex B of the
Protocol (most Organisation for Economic Cooperation and Develop-
ment countries and countries with economies in transition) agreed to
reduce their anthropogenic greenhouse gas (GHG) emissions (carbon
dioxide (CO
2
), methane (CH
4
), nitrous oxide (N
2
O), hydrofluorocarbons
(HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF
6
)) by at
least 5 % below 1990 levels in the commitment period 2008 2012.
The Kyoto Protocol entered into force on 16 February 2005.
Land use (change, direct and indirect): Land use refers to the total
of arrangements, activities and inputs undertaken in a certain land
cover type (a set of human actions). The term land use is also used
in the sense of the social and economic purposes for which land is
managed (e. g., grazing, timber extraction and conservation). In urban
settlements it is related to land uses within cities and their hinterlands.
Urban land use has implications on city management, structure, and
form and thus on energy demand, greenhouse gas (GHG) emissions,
and mobility, among other aspects.
Land use change (LUC): Land use change refers to a change in
the use or management of land by humans, which may lead to a
change in land cover. Land cover and LUC may have an impact on
the surface albedo, evapotranspiration, sources and sinks of GHGs,
or other properties of the climate system and may thus give rise to
radiative forcing and / or other impacts on climate, locally or glob-
ally. See also the IPCC Report on Land Use, Land-Use Change, and
Forestry (IPCC, 2000).
Indirect land use change (iLUC): Indirect land use change refers
to shifts in land use induced by a change in the production level of
an agricultural product elsewhere, often mediated by markets or
driven by policies. For example, if agricultural land is diverted to
fuel production, forest clearance may occur elsewhere to replace
the former agricultural production. See also Afforestation, Defores-
tation and Reforestation.
Land use, land use change and forestry (LULUCF): A greenhouse
gas (GHG) inventory sector that covers emissions and removals of
GHGs resulting from direct human-induced land use, land use change
and forestry activities excluding agricultural emissions. See also Agri-
culture, Forestry and Other Land Use (AFOLU).
Land value capture: A financing mechanism usually based around
transit systems, or other infrastructure and services, that captures the
increased value of land due to improved accessibility.
Leakage: Phenomena whereby the reduction in emissions (relative to
a baseline) in a jurisdiction / sector associated with the implementation
of mitigation policy is offset to some degree by an increase outside
the jurisdiction / sector through induced changes in consumption, pro-
duction, prices, land use and / or trade across the jurisdictions / sectors.
Leakage can occur at a number of levels, be it a project, state, province,
nation, or world region. See also Rebound effect.
In the context of Carbon Dioxide Capture and Storage (CCS), ‘CO
2
leak-
age’ refers to the escape of injected carbon dioxide (CO
2
) from the
storage location and eventual release to the atmosphere. In the con-
text of other substances, the term is used more generically, such as
for ‘methane (CH
4
) leakage’ (e. g., from fossil fuel extraction activities),
and ‘hydrofluorocarbon (HFC) leakage’ (e. g., from refrigeration and
air-conditioning systems).
Learning curve / rate: Decreasing cost-prices of technologies shown
as a function of increasing (total or yearly) supplies. The learning rate is
the percent decrease of the cost-price for every doubling of the cumu-
lative supplies (also called progress ratio).
Least Developed Countries (LDCs): A list of countries designated
by the Economic and Social Council of the United Nations (ECOSOC)
as meeting three criteria: (1) a low income criterion below a certain
threshold of gross national income per capita of between USD 750
and USD 900, (2) a human resource weakness based on indicators
of health, education, adult literacy, and (3) an economic vulnerability
weakness based on indicators on instability of agricultural production,
instability of export of goods and services, economic importance of
non-traditional activities, merchandise export concentration, and the
handicap of economic smallness. Countries in this category are eligible
for a number of programmes focused on assisting countries most in
need. These privileges include certain benefits under the articles of the
United Nations Framework Convention on Climate Change (UNFCCC).
See also Industrialized / developing countries.
Levelized cost of conserved carbon (LCCC): See Annex II.3.1.3 for
concepts and definition.
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Levelized cost of conserved energy (LCCE): See Annex II.3.1.2 for
concepts and definition.
Levelized cost of energy (LCOE): See Annex II.3.1.1 for concepts
and definition.
Lifecycle assessment (LCA): A widely used technique defined by ISO
14040 as a “compilation and evaluation of the inputs, outputs and the
potential environmental impacts of a product system throughout its
life cycle”. The results of LCA studies are strongly dependent on the
system boundaries within which they are conducted. The technique is
intended for relative comparison of two similar means to complete a
product. See also Annex II.6.3.
Likelihood: The chance of a specific outcome occurring, where this
might be estimated probabilistically. This is expressed in this report
using a standard terminology (Mastrandrea etal., 2010): virtually cer-
tain 99 100 % probability, very likely 90 100 %, likely 66 100 %,
about as likely as not 33 66 %, unlikely 0 33 %, very unlikely 0 10
%, exceptionally unlikely 0 1 %. Additional terms (more likely than
not > 50 100 %, and more unlikely than likely 0 < 50 %) may also be
used when appropriate. Assessed likelihood is typeset in italics, e. g.,
very likely. See also Agreement, Confidence, Evidence and Uncertainty.
Lock-in: Lock-in occurs when a market is stuck with a standard even
though participants would be better off with an alternative.
Marginal abatement cost (MAC): The cost of one unit of additional
mitigation.
Market barriers: In the context of climate change mitigation, market
barriers are conditions that prevent or impede the diffusion of cost-
effective technologies or practices that would mitigate greenhouse gas
(GHG) emissions.
Market-based mechanisms, GHG emissions: Regulatory approaches
using price mechanisms (e. g., taxes and auctioned emission permits),
among other instruments, to reduce the sources or enhance the sinks
of greenhouse gases (GHGs).
Market exchange rate (MER): The rate at which foreign currencies
are exchanged. Most economies post such rates daily and they vary
little across all the exchanges. For some developing economies, offi-
cial rates and black-market rates may differ significantly and the MER
is difficult to pin down. See also Purchasing power parity (PPP) and
Annex II.1.3 for the monetary conversion process applied throughout
this report.
Market failure: When private decisions are based on market prices
that do not reflect the real scarcity of goods and services but rather
reflect market distortions, they do not generate an efficient allocation
of resources but cause welfare losses. A market distortion is any event
in which a market reaches a market clearing price that is substantially
different from the price that a market would achieve while operating
under conditions of perfect competition and state enforcement of legal
contracts and the ownership of private property. Examples of factors
causing market prices to deviate from real economic scarcity are envi-
ronmental externalities, public goods, monopoly power, information
asymmetry, transaction costs, and non-rational behaviour. See also
Economic efficiency.
Material flow analysis (MFA): A systematic assessment of the flows
and stocks of materials within a system defined in space and time
(Brunner and Rechberger, 2004). See also Annex II.6.1.
Measures: In climate policy, measures are technologies, processes or
practices that contribute to mitigation, for example renewable energy
(RE) technologies, waste minimization processes, public transport com-
muting practices.
Meeting of the Parties (CMP): The Conference of the Parties (COP)
to the United Nations Framework Convention on Climate Change
(UNFCCC) serves as the CMP, the supreme body of the Kyoto Protocol,
since the latter entered into force on 16 February 2005. Only Parties
to the Kyoto Protocol may participate in deliberations and make deci-
sions.
Methane (CH
4
): One of the six greenhouse gases (GHGs) to be miti-
gated under the Kyoto Protocol and is the major component of natural
gas and associated with all hydrocarbon fuels. Significant emissions
occur as a result of animal husbandry and agriculture and their man-
agement represents a major mitigation option. See also Global Warm-
ing Potential (GWP) and Annex II.9.1 for GWP values.
Methane recovery: Any process by which methane (CH
4
) emissions
(e. g., from oil or gas wells, coal beds, peat bogs, gas transmission pipe-
lines, landfills, or anaerobic digesters) are captured and used as a fuel
or for some other economic purpose (e. g., chemical feedstock).
Millennium Development Goals (MDGs): A set of eight time-bound
and measurable goals for combating poverty, hunger, disease, illit-
eracy, discrimination against women and environmental degradation.
These goals were agreed to at the UN Millennium Summit in 2000
together with an action plan to reach the goals.
Mitigation (of climate change): A human intervention to reduce the
sources or enhance the sinks of greenhouse gases (GHGs). This report
also assesses human interventions to reduce the sources of other
substances which may contribute directly or indirectly to limiting cli-
mate change, including, for example, the reduction of particulate mat-
ter (PM) emissions that can directly alter the radiation balance (e. g.,
black carbon) or measures that control emissions of carbon monoxide,
nitrogen oxides (NO
x
), Volatile Organic Compounds (VOCs) and other
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pollutants that can alter the concentration of tropospheric ozone (O
3
)
which has an indirect effect on the climate.
Mitigation capacity: A country’s ability to reduce anthropogenic
greenhouse gas (GHG) emissions or to enhance natural sinks, where
ability refers to skills, competencies, fitness, and proficiencies that a
country has attained and depends on technology, institutions, wealth,
equity, infrastructure, and information. Mitigative capacity is rooted in
a country’s sustainable development (SD) path.
Mitigation scenario: A plausible description of the future that
describes how the (studied) system responds to the implementation
of mitigation policies and measures. See also Baseline / reference,
Climate scenario, Emission scenario, Representative Concentration
Pathways (RCPs), Scenario, Shared socio-economic pathways, Socio-
economic scenarios, SRES scenarios, Stabilization, and Transformation
pathways.
Models: Structured imitations of a system’s attributes and mecha-
nisms to mimic appearance or functioning of systems, for example, the
climate, the economy of a country, or a crop. Mathematical models
assemble (many) variables and relations (often in a computer code) to
simulate system functioning and performance for variations in param-
eters and inputs.
Computable General Equilibrium (CGE) Model: A class of
economic models that use actual economic data (i. e., input / out-
put data), simplify the characterization of economic behaviour,
and solve the whole system numerically. CGE models specify all
economic relationships in mathematical terms and predict the
changes in variables such as prices, output and economic welfare
resulting from a change in economic policies, given information
about technologies and consumer preferences (Hertel, 1997). See
also General equilibrium analysis.
Integrated Model: Integrated models explore the interactions
between multiple sectors of the economy or components of par-
ticular systems, such as the energy system. In the context of trans-
formation pathways, they refer to models that, at a minimum,
include full and disaggregated representations of the energy
system and its linkage to the overall economy that will allow for
consideration of interactions among different elements of that
system. Integrated models may also include representations of the
full economy, land use and land use change (LUC), and the climate
system. See also Integrated assessment.
Sectoral Model: In the context of this report, sectoral models
address only one of the core sectors that are discussed in this
report, such as buildings, industry, transport, energy supply, and
Agriculture, Forestry and Other Land Use (AFOLU).
Montreal Protocol: The Montreal Protocol on Substances that
Deplete the Ozone Layer was adopted in Montreal in 1987, and subse-
quently adjusted and amended in London (1990), Copenhagen (1992),
Vienna (1995), Montreal (1997) and Beijing (1999). It controls the con-
sumption and production of chlorine- and bromine- containing chemi-
cals that destroy stratospheric ozone (O
3
), such as chlorofluorocarbons
(CFCs), methyl chloroform, carbon tetrachloride and many others.
Multi-criteria analysis (MCA): Integrates different decision param-
eters and values without assigning monetary values to all parameters.
Multi-criteria analysis can combine quantitative and qualitative infor-
mation. Also referred to as multi-attribute analysis.
Multi-attribute analysis: See Multi-criteria analysis (MCA).
Multi-gas: Next to carbon dioxide (CO
2
), there are other forcing com-
ponents taken into account in, e. g., achieving reduction for a basket of
greenhouse gas (GHG) emissions (CO
2
, methane (CH
4
), nitrous oxide
(N
2
O), and fluorinated gases) or stabilization of CO
2
-equivalent con-
centrations (multi-gas stabilization, including GHGs and aerosols).
Nationally Appropriate Mitigation Action (NAMA): Nationally
Appropriate Mitigation Actions are a concept for recognizing and
financing emission reductions by developing countries in a post-2012
climate regime achieved through action considered appropriate in a
given national context. The concept was first introduced in the Bali
Action Plan in 2007 and is contained in the Cancún Agreements.
Nitrogen oxides (NO
X
): Any of several oxides of nitrogen.
Nitrous oxide (N
2
O): One of the six greenhouse gases (GHGs) to be
mitigated under the Kyoto Protocol. The main anthropogenic source
of N
2
O is agriculture (soil and animal manure management), but
important contributions also come from sewage treatment, fossil fuel
combustion, and chemical industrial processes. N
2
O is also produced
naturally from a wide variety of biological sources in soil and water,
particularly microbial action in wet tropical forests. See also Global
Warming Potential (GWP) and Annex II.9.1 for GWP values.
Non-Annex I Parties / countries: Non-Annex I Parties are mostly
developing countries. Certain groups of developing countries are
recognized by the Convention as being especially vulnerable to the
adverse impacts of climate change, including countries with low-lying
coastal areas and those prone to desertification and drought. Others,
such as countries that rely heavily on income from fossil fuel produc-
tion and commerce, feel more vulnerable to the potential economic
impacts of climate change response measures. The Convention empha-
sizes activities that promise to answer the special needs and concerns
of these vulnerable countries, such as investment, insurance, and tech-
nology transfer. See also Annex I Parties / countries.
Normative analysis: Analysis in which judgments about the desirabil-
ity of various policies are made. The conclusions rest on value judg-
ments as well as on facts and theories. See also Descriptive analysis.
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Ocean energy: Energy obtained from the ocean via waves, tidal
ranges, tidal and ocean currents, and thermal and saline gradients.
Offset (in climate policy): A unit of CO
2
-equivalent emissions that is
reduced, avoided, or sequestered to compensate for emissions occur-
ring elsewhere.
Oil sands and oil shale: Unconsolidated porous sands, sandstone
rock, and shales containing bituminous material that can be mined
and converted to a liquid fuel. See also Unconventional fuels.
Overshoot pathways: Emissions, concentration, or temperature
pathways in which the metric of interest temporarily exceeds, or ‘over-
shoots’, the long-term goal.
Ozone (O
3
): Ozone, the triatomic form of oxygen (O
3
), is a gaseous
atmospheric constituent. In the troposphere, it is created both naturally
and by photochemical reactions involving gases resulting from human
activities (smog). Tropospheric O
3
acts as a greenhouse gas (GHG). In
the stratosphere, it is created by the interaction between solar ultra-
violet radiation and molecular oxygen (O
2
). Stratospheric O
3
plays a
dominant role in the stratospheric radiative balance. Its concentration
is highest in the O
3
layer.
Paratransit: Denotes flexible passenger transportation, often but not
only in areas with low population density, that does not follow fixed
routes or schedules. Options include minibuses (matatus, marshrutka),
shared taxis and jitneys. Sometimes paratransit is also called commu-
nity transit.
Pareto optimum: A state in which no one’s welfare can be increased
without reducing someone else’s welfare. See also Economic efficiency.
Particulate matter (PM): Very small solid particles emitted during
the combustion of biomass and fossil fuels. PM may consist of a wide
variety of substances. Of greatest concern for health are particulates of
diameter less than or equal to 10 nanometers, usually designated as
PM
10
. See also Aerosol.
Passive design: The word ‘passive’ in this context implies the ideal
target that the only energy required to use the designed product or
service comes from renewable sources.
Path dependence: The generic situation where decisions, events, or
outcomes at one point in time constrain adaptation, mitigation, or
other actions or options at a later point in time.
Payback period: Mostly used in investment appraisal as financial
payback, which is the time needed to repay the initial investment by
the returns of a project. A payback gap exists when, for example, pri-
vate investors and micro-financing schemes require higher profitability
rates from renewable energy (RE) projects than from fossil-fired proj-
ects. Energy payback is the time an energy project needs to deliver as
much energy as had been used for setting the project online. Carbon
payback is the time a renewable energy (RE) project needs to deliver
as much net greenhouse gas (GHG) savings (with respect to the fossil
reference energy system) as its realization has caused GHG emissions
from a perspective of lifecycle assessment (LCA) (including land use
changes (LUC) and loss of terrestrial carbon stocks).
Perfluorocarbons (PFCs): One of the six types of greenhouse gases
(GHGs) or groups of GHGs to be mitigated under the Kyoto Protocol.
PFCs are by-products of aluminium smelting and uranium enrichment.
They also replace chlorofluorocarbons (CFCs) in manufacturing semi-
conductors. See also Global Warming Potential (GWP) and Annex II.9.1
for GWP values.
Photovoltaic cells (PV): Electronic devices that generate electricity
from light energy. See also Solar energy.
Policies (for mitigation of or adaptation to climate change): Poli-
cies are a course of action taken and / or mandated by a government,
e. g., to enhance mitigation and adaptation. Examples of policies aimed
at mitigation are support mechanisms for renewable energy (RE) sup-
plies, carbon or energy taxes, fuel efficiency standards for automobiles.
See also Measures.
Polluter pays principle (PPP): The party causing the pollution is
responsible for paying for remediation or for compensating the damage.
Positive analysis: See Descriptive analysis.
Potential: The possibility of something happening, or of someone
doing something in the future. Different metrics are used throughout
this report for the quantification of different types of potentials, includ-
ing the following:
Technical potential: Technical potential is the amount by which
it is possible to pursue a specific objective through an increase in
deployment of technologies or implementation of processes and
practices that were not previously used or implemented. Quanti-
fication of technical potentials may take into account other than
technical considerations, including social, economic and / or envi-
ronmental considerations.
Precautionary principle: A provision under Article 3 of the United
Nations Framework Convention on Climate Change (UNFCCC), stipu-
lating that the Parties should take precautionary measures to antici-
pate, 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
to postpone such measures, taking into account that policies and mea-
sures to deal with climate change should be cost-effective in order to
ensure global benefits at the lowest possible cost.
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Precursors: Atmospheric compounds that are not greenhouse gases
(GHGs) or aerosols, but that have an effect on GHG or aerosol con-
centrations by taking part in physical or chemical processes regulating
their production or destruction rates.
Pre-industrial: See Industrial Revolution.
Present value: Amounts of money available at different dates in the
future are discounted back to a present value, and summed to get the
present value of a series of future cash flows. See also Discounting.
Primary production: All forms of production accomplished by plants,
also called primary producers.
Primary energy: See Energy.
Private costs: Private costs are carried by individuals, companies or
other private entities that undertake an action, whereas social costs
include additionally the external costs on the environment and on soci-
ety as a whole. Quantitative estimates of both private and social costs
may be incomplete, because of difficulties in measuring all relevant
effects.
Production-based accounting: Production-based accounting pro-
vides a measure of emissions released to the atmosphere for the pro-
duction of goods and services by a certain entity (e. g., person, firm,
country, or region). See also Consumption-based accounting.
Public good: Public goods are non-rivalrous (goods whose consump-
tion by one consumer does not prevent simultaneous consumption by
other consumers) and non-excludable (goods for which it is not pos-
sible to prevent people who have not paid for it from having access
to it).
Purchasing power parity (PPP): The purchasing power of a currency
is expressed using a basket of goods and services that can be bought
with a given amount in the home country. International comparison
of, for example, gross domestic products (GDP) of countries can be
based on the purchasing power of currencies rather than on current
exchange rates. PPP estimates tend to lower per capita GDP in indus-
trialized countries and raise per capita GDP in developing countries.
(PPP is also an acronym for polluter pays principle). See also Market
exchange rate (MER) and Annex II.1.3 for the monetary conversion
process applied throughout this report.
Radiation management: See Solar Radiation Management.
Radiative forcing: Radiative forcing is the change in the net, down-
ward minus upward, radiative flux (expressed in W m
– 2
) at the tropo-
pause or top of atmosphere due to a change in an external driver of
climate change, such as, for example, a change in the concentration of
carbon dioxide (CO
2
) or the output of the sun. For the purposes of this
report, radiative forcing is further defined as the change relative to the
year 1750 and refers to a global and annual average value.
Rebound effect: Phenomena whereby the reduction in energy con-
sumption or emissions (relative to a baseline) associated with the
implementation of mitigation measures in a jurisdiction is offset to
some degree through induced changes in consumption, production,
and prices within the same jurisdiction. The rebound effect is most typ-
ically ascribed to technological energy efficiency (EE) improvements.
See also Leakage.
Reducing Emissions from Deforestation and Forest Degrada-
tion (REDD): An effort to create financial value for the carbon stored
in forests, offering incentives for developing countries to reduce
emissions from forested lands and invest in low-carbon paths to sus-
tainable development (SD). It is therefore a mechanism for mitiga-
tion that results from avoiding deforestation. REDD+ goes beyond
reforestation and forest degradation, and includes the role of con-
servation, sustainable management of forests and enhancement of
forest carbon stocks. The concept was first introduced in 2005 in the
11th Session of the Conference of the Parties (COP) in Montreal and
later given greater recognition in the 13th Session of the COP in 2007
at Bali and inclusion in the Bali Action Plan which called for “pol-
icy approaches and positive incentives on issues relating to reduc-
ing emissions to deforestation and forest degradation in developing
countries (REDD) and the role of conservation, sustainable manage-
ment of forests and enhancement of forest carbon stock in develop-
ing countries”. Since then, support for REDD has increased and has
slowly become a framework for action supported by a number of
countries.
Reference scenario: See Baseline / reference.
Reforestation: Planting of forests on lands that have previously
sustained forests but that have been converted to some other use.
Under the United Nations Framework Convention on Climate Change
(UNFCCC) and the Kyoto Protocol, reforestation is the direct human-
induced conversion of non-forested land to forested land through
planting, seeding, and / or human-induced promotion of natural seed
sources, on land that was previously forested but converted to non-
forested land. For the first commitment period of the Kyoto Protocol,
reforestation activities will be limited to reforestation occurring on
those lands that did not contain forest on 31 December 1989.
For a discussion of the term forest and related terms such as afforesta-
tion, reforestation and deforestation, see the IPCC Report on Land Use,
Land-Use Change and Forestry (IPCC, 2000). See also the Report on
Definitions and Methodological Options to Inventory Emissions from
Direct Human-induced Degradation of Forests and Devegetation of
Other Vegetation Types (IPCC, 2003).
Renewable energy (RE): See Energy.
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Representative Concentration Pathways (RCPs): Scenarios that
include time series of emissions and concentrations of the full suite of
greenhouse gases (GHGs) and aerosols and chemically active gases, as
well as land use / land cover (Moss etal., 2008). The word representa-
tive signifies that each RCP provides only one of many possible scenar-
ios that would lead to the specific radiative forcing characteristics. The
term pathway emphasizes that not only the long-term concentration
levels are of interest, but also the trajectory taken over time to reach
that outcome (Moss etal., 2010).
RCPs usually refer to the portion of the concentration pathway extend-
ing up to 2100, for which Integrated Assessment Models produced
corresponding emission scenarios. Extended Concentration Pathways
(ECPs) describe extensions of the RCPs from 2100 to 2500 that were
calculated using simple rules generated by stakeholder consultations,
and do not represent fully consistent scenarios.
Four RCPs produced from Integrated Assessment Models were selected
from the published literature and are used in the present IPCC Assess-
ment as a basis for the climate predictions and projections presented
in WGI AR5 Chapters 11 to 14:
RCP2.6 One pathway where radiative forcing peaks at approxi-
mately 3 W m
– 2
before 2100 and then declines (the corresponding
ECP assuming constant emissions after 2100);
RCP4.5 and RCP6.0 Two intermediate stabilization pathways in
which radiative forcing is stabilized at approximately 4.5 W m
– 2
and 6.0 W m
– 2
after 2100 (the corresponding ECPs assuming con-
stant concentrations after 2150);
RCP8.5 One high pathway for which radiative forcing reaches
greater than 8.5 W m
– 2
by 2100 and continues to rise for some
amount of time (the corresponding ECP assuming constant emis-
sions after 2100 and constant concentrations after 2250).
For further description of future scenarios, see WGI AR5 Box 1.1. See
also Baseline / reference, Climate prediction, Climate projection, Cli-
mate scenario, Shared socio-economic pathways, Socio-economic sce-
nario, SRES scenarios, and Transformation pathway.
Reservoir: A component of the climate system, other than the atmo-
sphere, which has the capacity to store, accumulate or release a sub-
stance of concern, for example, carbon, a greenhouse gas (GHG) or a
precursor. Oceans, soils and forests are examples of reservoirs of car-
bon. Pool is an equivalent term (note that the definition of pool often
includes the atmosphere). The absolute quantity of the substance of
concern held within a reservoir at a specified time is called the stock.
In the context of Carbon Dioxide Capture and Storage (CCS), this term
is sometimes used to refer to a geological carbon dioxide (CO
2
) stor-
age location. See also Sequestration.
Resilience: The capacity of social, economic, and environmental sys-
tems to cope with a hazardous event or trend or disturbance, respond-
ing or reorganizing in ways that maintain their essential function, iden-
tity, and structure, while also maintaining the capacity for adaptation,
learning, and transformation (Arctic Council, 2013).
Revegetation: A direct human-induced activity to increase carbon
stocks on sites through the establishment of vegetation that covers a
minimum area of 0.05 hectares and does not meet the definitions of
afforestation and reforestation contained here (UNFCCC, 2002).
Risk: In this report, the term risk is often used to refer to the poten-
tial, when the outcome is uncertain, for adverse consequences on lives,
livelihoods, health, ecosystems and species, economic, social and cul-
tural assets, services (including environmental services), and infrastruc-
ture.
Risk assessment: The qualitative and / or quantitative scientific
estimation of risks.
Risk management: The plans, actions, or policies to reduce the
likelihood and / or consequences of a given risk.
Risk perception: The subjective judgment that people make
about the characteristics and severity of a risk.
Risk tradeoff: The change in the portfolio of risks that occurs
when a countervailing risk is generated (knowingly or inadver-
tently) by an intervention to reduce the target risk (Wiener and
Graham, 2009). See also Adverse side-effect, and Co-benefit.
Risk transfer: The practice of formally or informally shifting the
risk of financial consequences for particular negative events from
one party to another.
Scenario: A plausible description of how the future may develop
based on a coherent and internally consistent set of assumptions about
key driving forces (e. g., rate of technological change (TC), prices) and
relationships. Note that scenarios are neither predictions nor forecasts,
but are useful to provide a view of the implications of developments
and actions. See also Baseline / reference, Climate scenario, Emission
scenario, Mitigation scenario, Representative Concentration Pathways
(RCPs), Shared socio-economic pathways, Socioeconomic scenarios,
SRES scenarios, Stabilization, and Transformation pathway.
Scope 1, Scope 2, and Scope 3 emissions: See Emissions.
Secondary energy: See Primary energy.
Sectoral Models: See Models.
Sensitivity analysis: Sensitivity analysis with respect to quantitative
analysis assesses how changing assumptions alters the outcomes. For
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example, one chooses different values for specific parameters and re-
runs a given model to assess the impact of these changes on model
output.
Sequestration: The uptake (i. e., the addition of a substance of con-
cern to a reservoir) of carbon containing substances, in particular car-
bon dioxide (CO
2
), in terrestrial or marine reservoirs. Biological seques-
tration includes direct removal of CO
2
from the atmosphere through
land-use change (LUC), afforestation, reforestation, revegetation, car-
bon storage in landfills, and practices that enhance soil carbon in agri-
culture (cropland management, grazing land management). In parts of
the literature, but not in this report, (carbon) sequestration is used to
refer to Carbon Dioxide Capture and Storage (CCS).
Shadow pricing: Setting prices of goods and services that are not, or
are incompletely, priced by market forces or by administrative regula-
tion, at the height of their social marginal value. This technique is used
in cost-benefit analysis (CBA).
Shared socio-economic pathways (SSPs): Currently, the idea of
SSPs is developed as a basis for new emissions and socio-economic
scenarios. An SSP is one of a collection of pathways that describe
alternative futures of socio-economic development in the absence of
climate policy intervention. The combination of SSP-based socio-eco-
nomic scenarios and Representative Concentration Pathway (RCP)-
based climate projections should provide a useful integrative frame
for climate impact and policy analysis. See also Baseline / reference, Cli-
mate scenario, Emission scenario, Mitigation scenario, Scenario, SRES
scenarios, Stabilization, and Transformation pathway.
Short-lived climate pollutant (SLCP): Pollutant emissions that have
a warming influence on climate and have a relatively short lifetime in
the atmosphere (a few days to a few decades). The main SLCPs are
black carbon (BC) (‘soot’), methane (CH
4
) and some hydroflurorcar-
bons (HFCs) some of which are regulated under the Kyoto Protocol.
Some pollutants of this type, including CH
4
, are also precursors to the
formation of tropospheric ozone (O
3
), a strong warming agent. These
pollutants are of interest for at least two reasons. First, because they
are short-lived, efforts to control them will have prompt effects on
global warming unlike long-lived pollutants that build up in the
atmosphere and respond to changes in emissions at a more sluggish
pace. Second, many of these pollutants also have adverse local impacts
such as on human health.
Sink: Any process, activity or mechanism that removes a greenhouse
gas (GHG), an aerosol, or a precursor of a GHG or aerosol from the
atmosphere.
Smart grids: A smart grid uses information and communications tech-
nology to gather data on the behaviours of suppliers and consumers in
the production, distribution, and use of electricity. Through automated
responses or the provision of price signals, this information can then
be used to improve the efficiency, reliability, economics, and sustain-
ability of the electricity network.
Smart meter: A meter that communicates consumption of electricity
or gas back to the utility provider.
Social cost of carbon (SCC): The net present value of climate dam-
ages (with harmful damages expressed as a positive number) from one
more tonne of carbon in the form of carbon dioxide (CO
2
), conditional
on a global emissions trajectory over time.
Social costs: See Private costs.
Socio-economic scenario: A scenario that describes a possible future
in terms of population, gross domestic product (GDP), and other socio-
economic factors relevant to understanding the implications of climate
change. See also Baseline / reference, Climate scenario, Emission sce-
nario, Mitigation scenario, Representative Concentration Pathways
(RCPs), Scenario, Shared socio-economic pathways, SRES scenarios,
Stabilization, and Transformation pathway.
Solar energy: Energy from the sun. Often the phrase is used to mean
energy that is captured from solar radiation either as heat, as light that
is converted into chemical energy by natural or artificial photosynthe-
sis, or by photovoltaic panels and converted directly into electricity.
Solar Radiation Management (SRM): Solar Radiation Manage-
ment refers to the intentional modification of the earth’s shortwave
radiative budget with the aim to reduce climate change according to a
given metric (e. g., surface temperature, precipitation, regional impacts,
etc.). Artificial injection of stratospheric aerosols and cloud brightening
are two examples of SRM techniques. Methods to modify some fast-
responding elements of the longwave radiative budget (such as cirrus
clouds), although not strictly speaking SRM, can be related to SRM.
SRM techniques do not fall within the usual definitions of mitigation
and adaptation (IPCC, 2012, p.2). See also Carbon Dioxide Removal
(CDR) and Geoengineering.
Source: Any process, activity or mechanism that releases a green-
house gas (GHG), an aerosol or a precursor of a GHG or aerosol into
the atmosphere. Source can also refer to, e. g., an energy source.
Spill-over effect: The effects of domestic or sector mitigation mea-
sures on other countries or sectors. Spill-over effects can be positive
or negative and include effects on trade, (carbon) leakage, transfer of
innovations, and diffusion of environmentally sound technology and
other issues.
SRES scenarios: SRES scenarios are emission scenarios developed by
Nakićenović and Swart (2000) and used, among others, as a basis for
some of the climate projections shown in Chapters 9 to 11 of IPCC
(2001) and Chapters 10 and 11 of IPCC (2007) as well as WGI AR5. The
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following terms are relevant for a better understanding of the structure
and use of the set of SRES scenarios:
Scenario family: Scenarios that have a similar demographic, soci-
etal, economic and technical change storyline. Four scenario fami-
lies comprise the SRES scenario set: A1, A2, B1, and B2.
Illustrative Scenario: A scenario that is illustrative for each of the
six scenario groups reflected in the Summary for Policymakers of
Nakićenović and Swart (2000). They include four revised marker
scenarios for the scenario groups A1B, A2, B1, B2, and two addi-
tional scenarios for the A1FI and A1T groups. All scenario groups
are equally sound.
Marker Scenario: 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 consid-
ered by the SRES writing team as illustrative of a particular sto-
ryline. They are included in revised form in Nakićenović and Swart
(2000). These scenarios received the closest scrutiny of the entire
writing team and via the SRES open process. Scenarios were also
selected to illustrate the other two scenario groups.
Storyline: A narrative description of a scenario (or family of scenar-
ios), highlighting the main scenario characteristics, relationships
between key driving forces and the dynamics of their evolution.
See also Baseline / reference, Climate scenario, Emission scenario,
Mitigation scenario, Representative Concentration Pathways (RCPs),
Shared socio-economic pathways, Socio-economic scenario, Stabiliza-
tion, and Transformation pathway.
Stabilization (of GHG or CO
2
-equivalent concentration): A state
in which the atmospheric concentrations of one greenhouse gas (GHG)
(e. g., carbon dioxide) or of a CO
2
-equivalent basket of GHGs (or a com-
bination of GHGs and aerosols) remains constant over time.
Standards: Set of rules or codes mandating or defining product per