Sulfur 'umbrella' to save world against warming

Crazy-sounding ideas for saving the planet are getting a serious look from top scientists, a sign of their fears about global warming and the desire for an insurance policy in case things get worse.

How crazy?

There's the man-made volcano that shoots gigatons of sulfur high into the air. The space "sun shade" made of trillions of little reflectors between Earth and sun, slightly lowering the planet's temperature.