Age: 68
Occupation: Physicist
Muller, a prize-winning physicist, was a climate-change skeptic's dream: a respected scientist who publicly doubted the consensus on global warming. So when he undertook a study of global climate data that was partly bankrolled by a foundation connected to global-warming deniers, the conclusion seemed preordained. But in a Wall Street Journal column last year, Muller announced that his review convinced him that the planet is indeed warming, dealing a blow to skeptics — and proving that a true scientist will change his mind when confronted by good data.