Population Growth and Greenhouse Gas Emissions
By utilizing World Bank categories of actual economic growth experience and projected population growth rates, the scenarios for population, per capita income, CO2 emissions, and family planning (FP) effect are computed and reported in Table N.1. Each group of countries is indexed to 1.00 in 1990. Thus numbers reported for the years 2020, 2050, and 2100 are multiples of the 1990 base.
The rules for calculations include the following:
1. Population is projected for the 1990 to 2020 period by using World Bank projections for 1987 to 2000 for each group. The growth rates (as shown in Table N.1) are from the World Development Report, Table 6. For 2020 to 2050, each group is expected to achieve the population projection for the next highest group in the 1990 to 2020 period (except for the NIEs, who remain at the 1987 to 2000 level). The situation is similar for 2050 to 2100, except that the NIEs have stationary growth.
2. As shown in Table N.1, per capita income for 1990 to 2020 is projected to grow at actual 1965 to 1987 rates (World Bank, 1989, Table 1), except that the NIEs maintain their high growth rates only for 1990 to 2020 and then revert to the upper-middle-income economy growth rates after 2020.
3. Annual CO2 emissions are calculated from population and income projections. It is assumed that CO2 emissions increase proportionately with population for all income levels. For low income levels (i.e., multiples below 5), it is assumed that CO2 emissions additionally increase proportionately with per capita income growth. For higher incomes, CO2 emissions increase less than proportionately with per capita income growth (i.e., at 0.8 for income multiples between 5 and 10, 0.7 for multiples between 10 and 30, and 0.6 for higher multiples). These estimates are based on World Bank Estimates (Siddayo, 1987).
TABLE N.1 Relationship Between Population and Greenhouse Gas Emissions
4. The cumulative CO2 emissions simply sum up annual emissions to the period indicated.
5. "Family planning" effects are calculated as the difference in population between a given group and the next lower group, multiplied by the income multiples of the group. Thus they represent the amount of increased emissions if the population were as large as it would be with the next lower group's population. For the lowest-income economies, the family planning effect is presumed to be the difference between the actual 2.8 percent growth rate over the 1965 to 1987 period and the 2.6 percent projected for 1987 to 2000.
These calculations are based on actual evidence to a considerable extent. A number of countries in the low-income category are actually experiencing no per capita income growth, and many are experiencing population growth more rapid than 2.6 percent. Construction of scenarios for these cases would not be very realistic.
The major points of this exercise are that family planning impacts on greenhouse gas emissions are important at all levels of development. It is probably not feasible to achieve low population growth rates without moving up the development scale. The reduced population growth associated with higher-income growth (and to a small degree with lower-income elasticities as income rises) offsets in large part the higher greenhouse gas emissions associated with faster economic growth.
The family planning effects indicate that as of the year 2020, carbon emissions will be about 15 percent lower for the lower-middle- and upper-middle-income countries than they would be without family planning. Strong family planning programs are in the interests of all countries for greenhouse gas concerns as well as for broader welfare concerns.
Siddayo, C. 1987. Petroleum resources in the Pacific rim: The roles played by governments in their development and trade. In The Pacific Rim: Investment, Development, and Trade, P. Nemetz, ed. Vancouver, B.C.: University of British Columbia Press.
World Bank. 1989. 1989 World Development Report. Washington, D.C.: World Bank.