In this talk, energy guru Amory Lovins lays out his plan for weaning the US off oil and revitalizing the economy in the process. It’s the subject of his book Winning the Oil Endgame, and he makes it sound fairly simple: On one hand, the deadly risks of continued dependency, and on the other, some win-win solutions.

Environmental scientist David Keith talks about a cheap, effective, shocking solution to climate change: What if we injected a huge cloud of ash into the atmosphere, to deflect sunlight and heat? As an emergency measure to slow a melting ice cap, it could work. Keith discusses why it’s a good idea, why it’s a terrible one — and who, despite the cost, might be tempted to use it.