Getty Images Oil drilling rig in The Gulfof Mexico.

In his 2006 State of the Union address, President George W. Bush declared that the U.S. is a nation “addicted to oil” and vowed to take steps to reduce Middle Eastern imports by 75 percent by 2025. After a summer of $3-plus gasoline, most of us would see this as a good idea. But it may be too late. According to a growing cadre of petroleum geologists, the days of cheap oil are over.

Some of the world's best evidence of global warming was buried under 18 feet of snow in the Sierra Nevada last winter, and Connie Millar was determined to dig it out. Millar, a veteran field scientist for the U.S. Forest Service, sweated uphill with three colleagues on a July morning, headed deep into Lundy Canyon, just north of Mono Lake, one of the few access points to the Sierra crest along its rugged eastern flank.