HKS Professor David Keith describes both the promise and peril involved with using geo-engineering to mitigate the effects of climate change. Solar radiation management (SRM) could conceivably cool the earth by placing particles in the upper atmosphere that reflect sunlight away. It's an idea that goes back as far as the Johnson administration, but has long been seen as too risky to be worth serious study. But Professor Keith says that's now changing.

The study of SRM evokes a tremendous number of questions - scientific, moral, and even psychological - all of which we touch on in this episode.