Iceland leads the list of the greenest nations. The US fell 22 places in the 2010 Environment Performance Index, but the study's researchers say that "murky" data makes the list imperfect.
The top five greenest nations on the planet:
3. Costa Rica
And the US?
But take this scorecard with a grain of sodium chloride, the researchers say.
Compiled biannually by Yale and Columbia University researchers, the 2010 Environment Performance Index ranks Iceland the greenest country in the world for reducing carbon emissions and planting new forests, along with plentiful hydropower and geothermal energy.