Scale, composition and technology

Three aspects of an economy are important determinants of its environmental impact: its scale, the composition of GDP in terms of goods and services, and technology. These aspects are incorporated in the IPAT equation (impact = population _ affluence _ technology). Making Room, a simulation model based on a variation of this equation, is described in which countries are categorized as high income, and middle and low income. The population, GDP per capita, energy use and GHG per unit energy of these groups of countries are used to calculate greenhouse gas emissions. It is shown that if past trends are projected into the future, GHG emissions will increase dramatically. It is also shown that the extent of changes required in both categories of countries to achieve a substantial reduction in GHG emissions is considerable. Managing without economic growth in high-income countries will help but much of the required changes will have to occur in low and middle-income countries.