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.

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http://www.ted.com/talks/view/id/192