Common Wealth Economics for a Crowded Planet By Jeffrey D. Sachs 386 pages. $27.95. The Penguin Press.

Iceland Prime Minister Geir Haarde, who since 2006 has presided over this small country that derives 80 percent of its energy needs from renewable sources, has been named the greenest political leader by NEWSWEEK. Iceland's happy status

The tiny island nation can teach the United States valuable lessons about energy policy.