Appendix A

Acronyms, Initialisms, and Glossary

Activity-based (or bottom-up) approach: A bottom-up approach begins with details and works up to the highest conceptual level during a given time period, i.e., the individual technologies leading to emissions. The activity-based approach (typically used for emissions inventory development) involves measuring and/or modeling emissions at the scale of individual emitters, such as emitting equipment within factories, power plants, vehicles, landfills, and then extrapolating those results to similar kinds of sources on regional and national scales. This approach involves use of emission factors, a wide spectrum of activity data, and process-based models. In the simplest form, the emission factor is scaled by the corresponding activity data to estimate emissions. However, it can also include direct flux monitoring, ecosystem modeling, and pollution ratio approaches of varying complexity.

Activity data (AD): Data on the magnitude of a human activity resulting in emissions or removals taking place during a given time period. Data on energy use, population, equipment count, metal production, land area, traffic data, lime and fertilizer use, and waste arisings are examples of activity data (IPCC, 2019a).

Aerosol: A suspension of airborne solid or liquid particles, with a typical size between a few nanometers and 10 μm that reside in the atmosphere for at least several hours. The term aerosol, which includes both the particles and the suspending gas, is often used in its plural form to mean aerosol particles. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: through both interactions that scatter and/or absorb radiation and through interactions with cloud microphysics and other cloud properties, or upon deposition on snow- or ice-covered surfaces thereby altering their albedo and contributing to climate feedback. Atmospheric 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 aerosols are of natural origin. Scientists often use group labels that refer to the chemical composition, namely: sea salt, organic carbon, black carbon, mineral species (mainly desert dust), sulfate, nitrate, and ammonium. These labels are, however, imperfect as aerosols combine particles to create complex mixtures (IPCC, 2019b).

Agriculture, forestry, and other land use (AFOLU): Agriculture, forestry, and other land use plays a central role for food security and sustainable development. The main mitigation options within AFOLU involve one or more of three strategies: prevention of emissions to the atmosphere by conserving existing carbon pools in soils or vegetation or by reducing emissions of methane and N₂O; sequestration—increasing the size of existing carbon pools, and thereby extracting CO₂ from the atmosphere; and substitution—substituting biological products for fossil fuels or energy-intensive products, thereby reducing CO₂ 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 resulting from direct human-induced land use, land-use change, and forestry activities excluding agricultural emissions (Allwood et al., 2014).

Air quality: Generally referred to as air pollution that can have negative effects on human health or plant productivity or built environment due to the introduction into the atmosphere of substances (i.e., gases, aerosols) that have a direct or indirect harmful effect (IPCC, 2021).

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 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 (Allwood et al., 2014).

Anthropogenic emissions: Emissions resulting from human activities of greenhouse gases (GHGs), precursors of GHGs, and aerosols. Building on the definition in IPCC AR6 WGI, these activities include emissions associated with the use of fossil fuels (e.g., extraction, processing, transport, and combustion); industrial processes; and agriculture, forestry, and other land use (AFOLU), including deforestation, land-use and land use changes (LULUC), livestock production, fertilization, as well as emissions from agricultural, industrial, and municipal waste management.

Atmospheric-based (or top-down) approach: A top-down approach to a problem is a situation that begins at the highest conceptual level and works down to the details. The atmospheric-based approach estimates emissions using observations of atmospheric concentrations (e.g., ground stations, tall towers, aircraft, and satellites), typically with models that account for atmospheric transport from the emitter to an observation location.

Biennial Update Report (BUR): Reports to be submitted by non-Annex I Parties, containing updates of national greenhouse gas (GHG) inventories, including a national inventory report and information on mitigation actions, needs and support received. Such reports provide updates on actions undertaken by a Party to implement the Convention, including the status of its GHG emissions and removals by sinks, as well as on the actions to reduce emissions or enhance sinks.

Big data: Complex datasets that contain great variety and volume.

Biomass: (1) Includes above- and below-ground living biomass. (2) Organic matter consisting of or recently derived from living organisms (especially regarded as fuel) excluding peat. Includes products, by-products, and waste derived from such material (IPCC, 2019a).

Biomass burning: Biomass burning is the burning of living and dead vegetation (Allwood et al., 2014).

Capacity: Ability of governments to collect and analyze their own emissions data or utilize datasets generated from other sources to inform action.

Capacity-building Initiative for Transparency (CBIT): Initiative that provides support to developing countries in development of its commitments under the ETF, including development of national inventories.

Carbon dioxide (CO₂): The main anthropogenic sources of CO₂ are as a by-product of burning fossil fuels (such as oil, natural gas, and coal), burning biomass, land use changes and industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas that affects the Earth’s radiative balance (IPCC, 2019a).

Carbon dioxide equivalent (CO₂eq): A metric used to compare the relative warming effect of emissions of various greenhouse gases to CO₂. It is the mass of carbon dioxide that would produce the same estimated radiative forcing as a given mass of another greenhouse gas over a given time period. Carbon dioxide equivalents are computed by multiplying the mass of the gas emitted by its Global warming potential.

Carbon footprint: Total amount of greenhouse gases emitted by an actor or activity during a given period.

Carbon intensity: The amount of emissions of carbon dioxide released per unit of another variable such as gross domestic product, output energy use, or transport (Allwood et al., 2014).

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) (Allwood et al., 2014).

Continuous emissions monitoring system (CEMS): The total equipment necessary for the determination of a gas or particulate matter concentration or emission rate using pollutant analyzer measurements and a conversion equation, graph, or computer program to produce results in units of the applicable emission limitation or standard.

Emission factor: A coefficient that quantifies the emissions or removals of a gas per unit activity. Emission factors are often based on a sample of measurement data, averaged to develop a representative rate of emission for a given activity level under a given set of operating conditions.

Emissions: Sources and sinks affecting the various greenhouse gases (i.e., their emissions and removal processes).

Emissions inventory: A set of estimates of the amount of given pollutants or pollutants emitted into the atmosphere from major mobile, stationary, area-wide, and natural source categories over a specific time period such as a day or a year.

Enhanced Transparency Framework (ETF): Addition to the Paris Agreement that guides countries on reporting their greenhouse gas emissions, progress toward their nationally determined contributions, climate change impacts and adaptation, support provided and mobilized, and support needed and received.

Environmental, social, and governance (ESG) metrics: Performance measures or indicators of performance on environmental, social, and governance issues.

Flaring: All burning of natural gas/vapor streams and hydrocarbon liquids by flares as a waste disposal option rather than for the production of useful heat or power (IPCC, 2019a).

Fugitive emissions (oil and natural gas systems): The intentional or unintentional release of greenhouse gases that occurs during the exploration, processing, and delivery of fossil fuels to the point of final use. This excludes greenhouse gas emissions from fuel combustion for the production of useful heat or power. It encompasses venting, flaring, and leaks (IPCC, 2019a).

Global Environment Facility (GEF): Organization that supports the operationalization of the CBIT supporting 72 countries, including least developed and small island developing states.

Global North: An umbrella term used to refer to countries with high relative power and wealth, generally concentrated in the Northern Hemisphere, but also includes Singapore, Japan, South Korea, Australia, and New Zealand.

Global South: Term used to identify regions within Latin America, Asia, Africa, and Oceania that are considered to have relatively low income and often politically or culturally marginalized.

Global Stocktake: Process for taking stock of the implementation of the Paris Agreement with the aim to assess the world’s collective progress toward achieving the purpose of the agreement and its long-term goals (UNFCCC, n.d.-a).

Good practice: “Good practice” is a key concept for inventory compilers to follow in preparing national greenhouse gas inventories. The key concept does not change in the IPCC 2019 Refinement. The term “good practice” has been defined since 2000, when this concept was introduced, as “a set of procedures intended to ensure that greenhouse gas inventories are accurate in the sense that they are systematically neither over- nor under-estimates so far as can be judged, and

that uncertainties are reduced so far as practicable.” This definition has gained general acceptance among countries as the basis for inventory development and its centrality has been retained for the 2019 Refinement. Certain terms in the definition have been updated based on feedback from the statistics community, such that this definition can be also understood as “a set of procedures intended to ensure that greenhouse gas inventories are accurate in the sense that they are systematically neither over- nor underestimates so far as can be judged, and that they are precise so far as practicable” in the context of refinement of Chapter 3 of Volume 13. Good practice covers choice of estimation methods appropriate to national circumstances, quality assurance and quality control at the national level, quantification of uncertainties, and data archiving and reporting to promote transparency (IPCC, 2019a).

Greenhouse gases (GHGs): Gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapor, CO₂, methane, N₂O, and ozone are the primary GHGs in the Earth’s atmosphere (IPCC, 2022a). Of these, human emissions directly affect the atmospheric concentrations of CO₂, methane, and N₂O. GHGs occurring in the atmosphere mainly because of human activities include sulfur hexafluoride, hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, halons, and perfluorocarbons; several of these also can cause stratospheric ozone depletion (and their production and consumption are regulated under the Montreal Protocol). Short-lived atmospheric gases with major human emissions like carbon monoxide, nitrogen oxides, and non-methane volatile organic compounds are GHG precursors because they can also increase levels of tropospheric ozone.

Halocarbons: A collective term for the group of partially halogenated species, which includes the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), halons, methyl chloride, and methyl bromide. Many of the halocarbons have large global warming potentials (IPCC, 2019a).

Hybrid approach: The hybrid approach derives GHG emissions information through the combination and more complete integration within and between activity-based and atmospheric-based.

In situ measurements: Instrumentation measurements are located directly at the point of interest.

Inverse model: A numerical model for atmospheric processes in which observations are used to infer the values of the parameters characterizing the system under investigation. In top-down analyses, inverse models are used to infer sources and sinks for a greenhouse gas from measurements of the atmospheric or oceanic abundance of that gas.

Isotopic analysis: Identification of abundance of certain stable isotopes of a chemical element.

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 emissions, and mobility, among other aspects (Allwood et al., 2014).

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 globally (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 (Allwood et al., 2014).

Land use, land-use change, and forestry (LULUCF): A greenhouse gas 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 Agriculture, Forestry and Other Land Use (AFOLU) (Allwood et al., 2014).

Least developed countries (LDCs): According to the UN, low-income countries confronting severe structural impediments to sustainable development. They are highly vulnerable to economic and environmental shocks and have low levels of human assets.

Life-cycle analysis (LCA): A cradle-to-grave or cradle-to-cradle analysis technique to assess environmental impacts associated with all the stages of a product’s life, which is from raw material extraction through materials processing, manufacture, distribution, and use (Muralikrishna and Manickam, 2017).

Managed land (vegetation): Land area where human interventions and practices have been applied to perform production, ecological or social functions (IPCC, 2019a).

Methane (CH₄): The main anthropogenic sources of methane, a greenhouse gas, are from three sectors: energy production from fossil fuels, agriculture, and waste (Saunois et al., 2020). Energy production accounts for about 35 percent of anthropogenic methane emissions, agriculture accounts for about 40 percent, and waste accounts for about 20 percent (Saunois et al., 2020; UNEP and CCAC, 2021). Methane is the major component of natural gas and associated with all fossil-based hydrocarbon fuels. Significant anthropogenic emissions also occur as a result of animal husbandry and paddy rice production. Methane is also produced where organic matter decays under anaerobic conditions (IPCC, 2019a), with anthropogenic emissions from landfill waste and wastewater systems. Approximately 35–50 percent of annual methane emissions are from natural sources such as wetlands (Saunois et al., 2020). Under future global warming, there is potential for increased methane emissions from thawing permafrost, wetlands, and subsea gas hydrates.

Mitigation: In the context of climate change, mitigation relates to a human intervention to reduce the sources or enhance the sinks of greenhouse gases. Examples include using fossil fuels more efficiently for industrial processes or electricity generation, switching to solar energy or wind power, improving the insulation of buildings and expanding forests and other “sinks” to remove greater amounts of CO₂ from the atmosphere.

National GHG Inventory Report (NIR): A report containing transparent and detailed information on the inventory. It should include descriptions of the methodologies used in the estimations (including references and sources of information), the data sources, the institutional arrangements for the preparation of the inventory (including quality assurance and control procedures), and recalculations and changes compared with the previous inventory.

Nationally determined contribution (NDC): Submissions by countries that have ratified the Paris Agreement which presents their national efforts to reach the Paris Agreement’s long-term temperature goal of limiting warming to well below 2°C. New or updated NDCs were expected to be submitted in 2020 and should be submitted every 5 years thereafter. NDCs thus represent a country’s current ambition/target for reducing emissions nationally.

Nitrous oxide (N₂O): The main anthropogenic source of N₂O, a greenhouse gas, is agriculture (fertilizer, soil and animal manure management), but important contributions also come from wastewater treatment, fossil fuel combustion, and chemical industrial processes (Allwood et al., 2014). N₂O is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests (Allwood et al., 2014).

Non-Annex I Parties/countries: Non-Annex I Parties are mostly developing countries. Certain groups of developing countries are recognized by the United Nations Framework Convention on Climate Change (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 production and commerce, feel more vulnerable to the potential economic impacts of climate change response measures. The Convention emphasizes activities that promise to answer the special needs and concerns of these vulnerable countries, such as investment, insurance, and technology transfer. See also Annex I Parties/countries (Allwood et al., 2014).

Ozone (O₃): The triatomic form of oxygen, and a gaseous atmospheric constituent. In the troposphere, ozone is created both naturally and by photochemical reactions involving gases resulting from human activities (e.g., smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O₂). Stratospheric ozone plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer.

Particulate matter (PM): Very small particles emitted during the combustion of biomass and fossil fuels or produced through atmospheric chemical interactions. PM may consist of a wide variety of substances. Of greatest concern for health are particulates of diameter less than or equal to 10 μm, usually designated as PM₁₀ (Allwood et al., 2014), especially those less than 2.5 μm (PM_2.5). Also see Aerosols.

Point source: Any single identifiable source of pollution from which pollutants are discharged, such as a pipe, ditch, ship, or factory smokestack.

Precursors: Atmospheric compounds that are not greenhouse gases (GHGs) or aerosols, but that influence GHG or aerosol concentrations by taking part in physical or chemical processes regulating their production or destruction rates (IPCC, 2019a).

Production inventories: Inventories that tie emissions to the geographic location where they enter the atmosphere. This is often also referred to as “Scope 1” emissions, a term that emanates from the scope language routinely used at subnational spatial scales.

Radiative forcing: The change in the net, downward minus upward, radiative flux (expressed in W m^–2) due to a change in an external driver of climate change, such as a change in the concentration of CO₂, the concentration of volcanic aerosols, or in the output of the Sun. The stratospherically adjusted radiative forcing is computed with all tropospheric properties held fixed at their unperturbed values, and after allowing for stratospheric temperatures, if perturbed, to readjust to radiative-dynamical equilibrium. Radiative forcing is called instantaneous if no change in stratospheric temperature is accounted for. The radiative forcing once both stratospheric and tropospheric adjustments are accounted for is termed the effective radiative forcing.

Removals: Removal of greenhouse gases and/or their precursors from the atmosphere by a sink (IPCC, 2019a).

Scope 1, Scope 2, and Scope 3 emissions: Emissions responsibility 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 production of electricity, heat, or steam purchased by the reporting entity. “Scope 3” indicates all other indirect emissions, i.e., emissions associated 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 disposal, etc. (WRI/WBCSD, 2004).

Sector: An emission-producing segment of the economy such as energy; industrial processes and product use; agriculture, forestry, and other land use; and waste (IPCC, 2019a).

Short-lived climate forcers (SLCFs): Following the IPCC definition, chemically reactive compounds with short (relative to CO₂) atmospheric lifetimes (from hours to about two decades) but characterized by different physiochemical properties and environmental effects. Their emission or formation has a significant effect on radiative forcing over a period determined by their respective atmospheric lifetimes. Changes in their emissions can also induce long-term climate effects via, in particular, their interactions with some biogeochemical cycles. SLCFs are classified as direct or indirect, with direct SLCFs exerting climate effects through their radiative forcing and indirect SLCFs being the precursors of other direct climate forcers. Direct SLCFs include methane, ozone, primary aerosols, and some halogenated species. Indirect SLCFs are precursors of ozone or secondary aerosols. SLCFs can be cooling or warming through interactions with radiation and clouds. They are also referred to as near-term climate forcers. Many SLCFs are also air pollutants. A related term “short-lived climate pollutant” is used to denote the set of climate forcers that are warming (methane, black carbon, hydrofluorocarbons, and ozone) and avoid bundling with cooling aerosols (primarily sulfates and nitrates) associated with fossil fuel combustion. Such bundling can lead to coincidental canceling of forcing that leads to the inaccurate perception that emissions of these short-lived species are independent from policies affecting CO₂ emissions from fossil fuel usage.

Sink: Any process, activity or mechanism that removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas from the atmosphere (IPCC, 2019a).

Small Island Developing States (SIDS): A distinct group of 38 Member States and 20 Non-UN Members/Associate Members of United Nations regional commissions that face unique social, economic, and environmental vulnerabilities.

Source: Any process, activity, or mechanism that releases a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol into the atmosphere. Certain activities, such as forestry, can be both a source and a sink of greenhouse gas emissions.

Surrogate (proxy) data: Surrogate data, or so-called proxy data, are data that are used in place of the actual data, where the specific data needed are unobtainable. Often surrogate data are needed to describe changes in an emission source over time, for example population change may be used to approximate change in waste arisings (IPCC, 2019a).

Tier: A tier represents a level of methodological complexity. Usually three tiers are provided. Tier 1 is the basic method, Tier 2 intermediate, and Tier 3 most demanding in terms of complexity and data requirements. Tiers 2 and 3 are sometimes referred to as higher tier methods and are generally considered to be more accurate (IPCC, 2019a).

United Nations Framework Convention on Climate Change (UNFCCC): The Convention was adopted on 9 May 1992 in New York and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Community. Its ultimate objective is the “stabilisation

of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” It contains commitments for all Parties under the principle of “common but differentiated responsibilities.” Under the Convention, Parties included in Annex I aimed to return greenhouse gas emissions not controlled by the Montreal Protocol to 1990 levels by the year 2000. The convention entered in force in March 1994. In 1997, the UNFCCC adopted the Kyoto Protocol (Allwood et al., 2014).

Validation: Validation is the establishment of sound approach and foundation. In the context of emissions inventories, validation involves checking to ensure that the inventory has been compiled correctly in line with reporting instructions and guidelines. It checks the internal consistency of the inventory. The legal use of validation is to give an official confirmation or approval of an act or product (IPCC, 2019a).

Verification: An independent examination of a greenhouse has inventory to help establish whether the actual emissions are consistent with available observations and other analyses.

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