How to assess GHG emissions

The FAOSTAT greenhouse gas (GHG) emissions database is compiled using FAO data and applying the simplest, yet robust default Intergovernmental Panel on Climate Change (IPCC) methodology (Tier 1) to calculate the GHG emissions associated with every activity from 1990 to 2010.

What is a tier?

A tier represents a level of methodological complexity to estimate greenhouse gas emissions. Tier 1 methodology, the simplest approach, provides a means to compute national emissions with default coefficients, often applicable globally or at regional level. Tier 1 estimates can be used when detailed information on the dynamic processes underlying emissions and their spatial characteristics are poorly defined or even not available to the country. Tier 3 methodology, the most complex in terms of capturing dynamic processes and their sub-national scale details, allows for precise estimation of emissions, yet require significant data and model capacity. Tier 2 methodologies are intermediate between Tiers 1 and Tier 3, often providing a bit more detail of  the underlying processes with some regional specificities, with respect to a Tier 1 estimation.

Activity data

Activity data describe the magnitude of a human activity resulting in emissions or removals of greenhouse gases, taking place during a given period of time and a specified area. Data on livestock type and numbers, area extent of managed agriculture, pastures, forests and associated  changes, amount of synthetic or organic fertilizer applied, are all examples of activity data relevant to computing emissions from agriculture, forestry and other land use changes.

Emission factors

Emission factors are coefficients that quantify the emissions or removals of a gas per unit activity data. Emission factors are based on samples of measurements, averaged at various levels of detail depending on the Tier methodology used, to develop a representative rate of emission for a given activity level under a given set of operating conditions. We often refer to Tier 1, 2 or 3 emission factors.

Regardless of the Tier approach chosen, GHG emissions can always be expressed as the multiplication of an emission factor times the associated activity data:

GHG Emissions = Emission Factor * Activity Data

Metadata and methodology

Brief metadata and methodology descriptions of GHG emissions are available below.


Emissions - Agriculture

- Enteric fermentation
- Manure management
- Rice cultivation
- Agricultural soil
   Synthetic fertilizers
   Manure applied to soils
   Manure left on pasture
   Crop residues
   Cultivation of organic soils
- Burning - Crop residues
- Burning - Savanna
- Energy Use


Emissions - Land Use

- Forest Land
- Cropland
- Grassland
- Burning - Biomass

last updated:  Tuesday, July 22, 2014