USA Today: Not every crazy idea, say dropping out of Harvard to start a software firm, is a bad one. But you don’t have to be Bill Gates to place your bets that way. Consider atmospheric geoengineering — pumping reflective particles into the stratosphere to reflect sunlight — seen as a way to cut the effects of global warming. In 1991, the eruption of Mt. Pinatubo in the Philippines cooled the atmosphere’s average temperature worldwide almost one degree Fahrenheit, a kind of “global dimming,” …