|The Global Greenhouse Regime. Who Pays? (UNU, 1993, 382 p.)|
|Part I Measuring responsibility|
|3 Assessing emissions: five approaches compared|
This Appendix summarizes the sources and methods used for calculating emissions listed above.
Cumulative CO2, energy
Carbon dioxide emissions from fossil fuel combustion between 1860 and 1986 rely on Marland et al. (1988) for the 1950-1986 period, and Subak and Clark (1990) for emissions between 1860 and 1949. The cumulative estimates do not take into account the proportion of trace gas removed from the atmosphere. Energy consumption data used in Subak and Clark (1990) are based on Mitchell's (1981, 1982, and 1983) International Historical Statistics series. Global emissions factors were derived from Marland et al. (1988) and weighted by carbon density estimates by nation published in the United Nations 1986 Energy Statistics Yearbook (1988). In cases where political borders have changed since 1860, emissions were assigned to countries based on estimated energy use share. For example, fossil fuel consumption in the Indian States was assigned as follows: India, 80 per cent; Pakistan, 15 per cent; and Bangladesh, 5 per cent.
Cumulative CO2, energy and biota
Emissions of CO2 between 1860 and 1986 are based on the fossil fuel data set described above and the Richards et al. (1983) database on CO2 release from forest conversion to agricultural purposes. The Richards et al. data set for the 1860-1978 period is based on historical agricultural censuses and FAO land use surveys completed in 1950. To update the database to 1986, we used the FAO 1986 Production Yearbook (FAO 1987). As forest conversion to non-agricultural uses was not included, this database is not intended to be a comprehensive survey of CO2 emissions from land use changes.
Current CO2, energy
Current CO2 emissions from fossil fuel combustion are calculated at the Stockholm Environment Institute (don Hippel et al. 1992) based on 1988 energy consumption data published by the OECD/IEA, (1990a, 1990b). Carbon dioxide emissions from oil flaring were taken from the Marland et al (1990) compendium. As in the cumulative CO2 inventories, emissions from renewables, that is, fuelwood, are assumed to be in a steady-state, with no net CO2 emissions.
Partial CH4 and CO2
Methane emissions from coal mining are derived from ICF (1990b) and natural gas transportation and distribution from OECD/IEA, (1990a, 1990b) CO2 release from deforestation is based on land clearing estimates from FAO (1990), Fearnside et al. (1990), FAO (1988b) and Myers (1989), biomass levels by Brown et al. (1989) and carbon soil emission rates by Houghton (1991). Afforestation rates are primarily from ECE/FAO (1985) and FAO (1988b). The landfill CH4 source is based on a methodology outlined by Bingemer and Crutzen (1987) and waste generation, landfilling and waste composition information is compiled from disparate sources.
The current emissions are expressed in CO2 equivalent units, which compare the relative warming contribution of the trace gases. The CO2 equivalents are based on each trace gas Global Warming Potential (GWP), an index that includes the immediate radiative effect of the gases and the potential warming effect over the time the trace gas resides in the atmosphere. The GWP used in this study is calculated by the Intergovernmental Panel on Climate Change (IPCC) and corresponds to a 100 year time horizon.
To estimate methane emissions from livestock production, emission factors (Crutzen et al. 1986) were applied to FAO livestock population estimates (1990b), and Casada and Safely's (1990) study of CH4 release from animals wastes was used. Methane emissions from rice cultivation are derived from emission factors (Schuetz et al. 1989) and rice cultivation area (FAO 1990b). Emissions of N2O from fertilizer consumption was calculated using the mid-range of Eichner's (1990) emission factors and data from the FAO Fertilizer Yearbook (1988a). Halocarbon emissions were calculated using ICF's (1990) methodology for converting from UNEP's (1990) production figures to emissions. Release of CO2 from cement manufacturing was derived using emission factors from Marland et al. 1988. Biomass burning estimates were taken from Crutzen and Andreae (1990), and adjusted to avoid double counting with the fuelwood and deforestation emissions.