Accounting for Climate in Ranking Countries’ Carbon Dioxide Emissions
A system that includes the variable of local climate provides a fairer measure of carbon dioxide emissions
The Approach in Action
To attain a measure of emissions that incorporates climate, we used three variables for each of 157 countries: carbon dioxide emissions per capita, GDP per capita (adjusted for differences in purchasing power between countries) and a population-weighted average of the total heating and cooling degree days. For the first two variables, we used data from 2008; the third is based on average annual heating and cooling degree days calculated for various recent time periods. These variables allowed us to calculate rankings of carbon dioxide emissions based on three measures: per capita; per capita and GDP; and per capita, GDP, and heating and cooling degree day.
The 15 lowest and highest emitters on each measure are shown in the figure at right. Using emissions per capita, GDP, and heating and cooling degree day, the 10 lowest emitters (in ascending order) are Chad, Afghanistan, Mali, Niger, Burkina Faso, Burundi, the Central African Republic, Kiribati, Sweden and Iceland. Six of these countries are in Africa, two in Europe and one each in Asia and Oceania. The 10 biggest emitters (in descending order) are South Africa, Uzbekistan, the Republic of Trinidad and Tobago, Turkmenistan, Bosnia and Herzegovina, Iraq, Australia, Syria, Jordan and Kazakhstan. Six of these countries are in Asia, and one each is in Africa, the Caribbean, Europe and Oceania.
Taking climate into account improves emissions rankings for countries with relatively high heating and cooling degree days. For example, the United States moves from the 110th spot (when only population size and economic output are included) to the 100th spot (when climate demands are considered as well); the United Kingdom moves from 63 to 58, Germany from 75 to 55, Sweden from 27 to 9, China from 149 to 147 and India from 125 to 116. But not everyone comes out for the better under the new approach. Countries with relatively low heating and cooling degree days get a less favorable ranking when climate is added into the equation. Among the countries with a substantial worsening are Australia (which goes from 126 to 151), Brazil (52 to 75), Israel (48 to 76) and Mexico (93 to 117). Changes in ranking for the seven countries with the largest improvement in ranking, the seven with the largest worsening, and seven additional countries of general interest are shown in the figure at left.
Comparing different countries’ respective emissions yields intriguing differences. South Africa (the highest emitter) produces about 61 times more emissions per capita, GDP, and heating and cooling degree day than does Chad (the lowest emitter). This range is comparable to the range of emissions per capita and GDP: Using the latter measure, the highest emitter, Uzbekistan, produces 55 times more emissions than does the lowest emitter, Afghanistan. Both of these ranges are substantially smaller than the range considering population alone: The highest emitter, Qatar, produces 2,397 times more emissions per capita than does the lowest emitter, Burundi.
Our results suggest that taking climate into account makes a significant difference in how countries fare in carbon dioxide emissions rankings. Because people respond to the climate they live in by heating and cooling indoor spaces, an index that incorporates climate provides a fairer yardstick than an index that does not. We hope that our approach will stimulate others to further refine this index to reflect even better the complexities involved in ranking countries on emissions.
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