Yale has just released its 2008 Environmental Performance Index (EPI). The EPI ranks countries based on their ostensible environmental performance and has made headlines by giving poor marks to the U.S. But as with so many supposedly dispassionate environmental analyses, Yale’s EPI is an exercise in make-believe, cloaked in a thin scientific veneer.
The EPI is a score between zero and 100 for each country, based on a weighted average of more than a dozen individual factors. Human health-related factors — water quality, air quality, and the environmental burden of disease — form the “Environmental Health” (EH) index, which accounts for half of the overall EPI. The other half is an “Ecosystem Vitality” (EV) index that includes water quality and availability, regional air pollution (for its ecological effects), biodiversity, productivity of natural resources, and climate change.
The U.S. scored 81 on the overall EPI, putting it 39th out of 149 countries. The U.S. scored worse than such environmental edens as Russia, Albania, Croatia, and the Dominican Republic, and barely edged out Cuba, Mexico, and Poland. That alone gives you an idea of the EPI’s tenuous relationship to the real environment. But let’s dig into the numbers a bit deeper to see how the Yale scientists played their game of let’s pretend.
Two words: climate change. Carbon dioxide emissions account for half of the Ecosystem Vitality score and 25 percent of the overall EPI score. The U.S. scored 56 out of 100 on climate change, and that is the main reason for America’s low overall EPI. If you look only at the Environmental Health index — in other words, the factors that directly affect people’s health — the U.S. scored 98.5 out of 100. In fact, virtually all the world’s wealthy countries scored above 95 on this measure.While the Yale researchers style their EPI as a valid measure of a country’s overall environmental performance, only one factor — greenhouse gas emissions — accounts for most of the variation in developed countries’ EPI scores.
Yale’s EPI is misleading in other ways. For example, ozone levels account for 3.75 percent of the overall EPI index score. But according to Yale’s report, the score was based on data for 2000 rather than current data. Ozone has dropped considerably in the U.S. since 2000. Fifty-four percent of the nation violated the federal eight-hour ozone standard in 2000. But the violation rate had dropped to 15 percent by the end of 2006. The average number of days per year exceeding the eight-hour standard declined 65 percent over the same period.
In any case, the ozone score isn’t even based on measured values, but on the output of a global atmospheric chemistry model whose predictions have little relationship to actual ozone levels across the country. U.S. air quality is among the best in the world. Nevertheless, in a New York Times story, one of the Yale researchers claimed that the U.S. “is at the bottom of the world right now” on regional smog.
The EPI’s air quality score also includes sulfur dioxide (SO2). But the score is based on SO2 emissions per unit of populated land (which doesn’t appear to be defined in the report), rather than on actual SO2 levels in the air. The U.S. scores poorly here (88 vs. 100 for most countries) even though U.S. SO2 levels are only a fraction of the federal health standard virtually everywhere in the U.S.
Even on its own terms, the EPI’s climate score is incoherent. It is based on three equally weighted factors: CO2 emissions per capita, CO2 emissions per unit of electricity generation, and industrial carbon intensity. But for climate change, only the first of these three matters. The other two are subsets of the first and vary from country to country based on their particular energy mix, wealth, and technological advancement. The result is that some countries with high CO2 emissions per capita nevertheless get a good score on climate change, while some countries with low CO2 per capita get a poor score.
For example, Canada’s CO2 per capita (23.1 tons per year) is similar to that of the U.S. (24.9 tons per year), but Canada’s climate index score is 69.3 vs. 56.1 for the U.S. Thus, even though Canada and the U.S. have similar per capita CO2 emissions — and therefore similar per-capita impacts on the Earth’s climate — Canada’s better climate score adds 3.3 points to its overall EPI relative to the U.S. If the U.S. got the same climate score as Canada, it would move from an EPI rank of 39 up to 23. On the other hand, China has relatively low CO2 emissions per capita — only 5.7 tons per year — but its climate index score is only 53, because of its relatively high industrial carbon intensity and high CO2 emissions per unit of electricity.
Yale’s EPI doesn’t tell you much about countries’ real environmental quality. But it does show that you can manufacture just about any results you want through shrewd analytical choices and assumptions.