Geoengineering: "The Horrifying Idea Whose Time Has Come"?

In Washington, D.C., this morning, the New America Foundation (in partnership with Arizona State University and Slate) is holding a “Future Tense Event” called “Geoengineering: The Horrifying Idea Whose Time Has Come?” Past blog posts on the topic can be found here.
Discussants at the event include Congressman Bart Gordon (D.-Tenn.), David Keith, Brad Allenby, Jeff Goodell, Thomas Schelling and Stewart Brand. A preview:

Is it time for humanity to go on offense against global warming? Can we? Should we? Curtailing economic activity, altering lifestyles and well-intentioned talk in Copenhagen has not accomplished much. That’s why serious people are now considering Plan B, to intentionally tinker with the planet’s climate to correct for industrialization-induced warming. The hubris of “hacking the planet” is astounding, as are the implications for everything from military strategy to agriculture.
The subject is unsettling, almost taboo in certain environmental advocacy circles.? And yet nations and entrepreneurs are proceeding with geoengineering research and experiments. Join us in assessing the state of these efforts and in considering the politics and ethics of playing God with the climate.

Meanwhile, Slate has published a special issue on the topic, addressing the history of geoengineering, the politics and policy implications.
(HT: Daniel Lippman)