Countries with larger populations tend to emit more GHG emissions (IPCC 2007 WGIII). It is not especially valuable, however, to simply measure total contribution to climate change when that contribution is largely based on population size. Thus, a more useful comparison across countries is to measure environmental performance by carbon dioxide emissions per person:
GHG Emissions, 2005 (metric tons carbon dioxide equivalent) / Total Population, 2005
A country that achieves a smaller ratio for this indicator will have lower relative contributions to climate change per person. Countries in the developing world generally have the lowest per capita emissions due to small industrial sectors and lifestyles that have relatively low energy intensities.
The EPI uses a target value of 50% below 1990 levels by 2050 as the basis for the per capita emissions reduction target. Since the Emissions per Capita indicator represents emissions against population, it is also necessary to set a “target” population value. While population growth has major environmental implications, we chose to apply the median global population projection to 2050 across all countries, since population reductions are not easily achieved through climate policy.
