Everyone who has thought about industrially driven climate change has at some point, however briefly, wondered why we can’t solve the problem by pulling the unwanted carbon dioxide back out of the air. Surely, if burning fossil fuels can blast so much extra carbon dioxide into the atmosphere, some other act of chemistry on an equally gargantuan scale ought to be able to recapture the gas. That's the possibility I explore in a pair of columns for SmartPlanet. "Why not scrub CO2 from the sky?" reviews several ideas for using innovative materials to recapture carbon dioxide released by industrial processes and then safely cache it where it can't contribute to climate change—in theory. "Throwing rocks at CO2" looks at the related concept of using naturally occurring minerals to accelerate the removal of CO2 from the air.