The key conclusion of the new finding is to shift the focus from production to consumption patterns. This implies three shifts. First, the current objection to the use of fossil fuels for the generation of electricity ignores the fact that levels of energy use depend on urban design, type of infrastructure and consumption patterns. In industrialized countries, two-thirds of the electricity generated is used in buildings. Second, in land-use systems, which also cause a quarter of total global emissions, half the emissions are generated subsequent to agricultural production in storage, preparation and transport. If urban eating habits change, global GHG emissions from agriculture can come down to below 1990 levels, even though the demand for food goes up by one-third during the next 20 years. Third, transportation emissions may equal half of global emissions in 2050. These are the fastest growing emissions and are linked to economic growth and wealth and not population, and continue to increase in industrialized countries.

Settlement patterns largely shape electricity demand, transportation use and consumption patterns. Spatial organization, density and lifestyle choices determine natural resource use. As the Chinese and Indian societies are now defining their lifestyles, spending patterns and markets with significant impact on global trends, they should not adopt the structures, technologies and practices of industrialized countries in designing their urban transition.

A carbon budget approach will show that industrialized countries, with 15 percent of the global population, are likely to account for one-third to one-quarter of total global energy use in 2100. This will shift the international debate from apportioning responsibility to acting collectively in the face of uncertain threats for sharing prosperity.

How the ecological limits are approached will prompt a debate on how to move away from the historical patterns of resource use pioneered by the industrialized countries and design new structures for well-being. It should also lead us to examine the preferences of individuals and the realization that high consumption does not guarantee happiness.

The author is a former advisor to the United Nations Environment Programme.