Does geoengineering offer a Plan B if nations at the U.N. climate meeting can't reduce carbon emissions? The Glasgow meeting has been called “the last best chance” to take measures to slow down global heating.  But we're nowhere near to achieving the emission reductions necessary to stave off a hothouse planet. We consider both the promise and the perils of geoengineering, and ask who decides about experimenting with Earth’s climate. Guests: Elizabeth Kolbert – Staff Writer at The New Yorker, Pulitzer Prize-winning author of “The Sixth Extinction,” and, most recently, of “Under a White Sky: The Nature of the Future.” David Keith – Professor of public policy and applied physics at Harvard University who also participates in the Stratospheric Controlled Perturbation Experiment (SCoPex) geoengineering project. Kim Cobb – Professor of earth and atmospheric sciences at Georgia Tech, and the director of its Global Change Program.