methods could be developed within a few years to independently verify emissions estimates?

The focus of this report is on monitoring and verification of the emissions themselves (see definitions in Box 1.2), rather than on implementation of policies designed to control them. The scales of interest range from national to global and from annual to decades. Although some of the methods described in this report have sufficiently high resolution to be used to audit individual emissions sources, which may be of inter-

BOX 1.2

Definitions of Terms Used in the Report

Activity data—Data on the magnitude of a human activity resulting in emissions or removals during a given period of time. Examples include data on energy use, metal production, management systems, forest clearing, and fertilizer use.

Annex I countries—The 41 countries included in Annex I (as amended in 1998) to the UNFCCC, including industrialized countries that were members of the Organisation for Economic Co-operation and Development in 1992 and many countries with economies in transition. Under the convention, Annex I countries committed to returning individually or jointly to their 1990 levels of greenhouse gas emissions by 2000. By default, the other countries are referred to as non-Annex I countries.

Anthropogenic emissions—Emissions of greenhouse gases, precursors of greenhouse gases, and aerosols resulting from human activities. Because it is difficult to disentangle anthropogenic and natural components of emissions and removals from land use, the UNFCCC considers emissions and removals on managed lands as anthropogenic.

CO2equivalent—The amount of carbon dioxide emission that would cause the same integrated radiative forcing, over a given time horizon, as an emitted amount of a well-mixed greenhouse gas. It is a standard metric for comparing emissions of different greenhouse gases, but does not imply exact equivalence of the corresponding climate change responses. The 100-year global warming potential is used to calculate CO2 equivalents.

Emission factor—The rate of emission per unit of activity, output, or input. For example, a particular fossil-fuel power plant may have a CO2 emission factor of 0.765 kg CO2 kWh–1 generated.

Inventory—An accounting of an item of interest at a specified date.

  • An emissions inventory accounts for the amount of one or more specific greenhouse gases discharged into the atmosphere from all source categories as well as removals by sinks in a certain geographical area and within a specified time span, usually a specific year. Under the UNFCCC, Annex I countries prepare national inventories of anthropogenic greenhouse gas emissions and removals for each calendar year.

  • An ecosystem inventory accounts for the carbon stored in a particular land classification (e.g., forest, peatland) based on ecosystem characteristics that affect carbon storage, such as volume of soil carbon and live and dead above- and belowground biomass, measured from a network of plots. Changes in carbon stock through time (i.e., carbon uptake or release) are measured by differencing two samples from the same plot but separated by 1 to 10 years.

Inverse model—A model in which observations are used to infer the values of the parameters characterizing the system under investigation. In this report, inverse models are used to infer sources and sinks for a greenhouse gas from measurements of the atmospheric or oceanic abundance of that gas.

Monitoring—The observation of emissions or variables correlated with emissions for the purpose of detecting any changes that may occur over time.

Sector—An emission-producing segment of the economy. The Intergovernmental Panel on Climate Change (IPCC) currently specifies four sectors for greenhouse gas reporting: energy; industrial processes and product use; agriculture, forestry, and other land use; and waste.

Sink—Any process, activity, or mechanism that removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere. Removals of greenhouse gases by a sink are conventionally shown as negative emissions.

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.

Survey data—Data from a statistically representative sample.

Tracer-transport model—A model used to predict the movement of greenhouse gases in the atmosphere or dissolved substances in the oceans.

Verification—An independent examination of monitoring data to help establish whether or not a country’s actual emissions are consistent with its obligations under a climate treaty.

SOURCES: Adapted from IPCC glossaries (<>) and UNFCCC resources (<>).

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