Perhaps we could couple it to mechanical air capture, increasing the carbon content of soils, and reforestation, depending upon how quickly we need to hit the break. Boyd says the following in the Q&A on ieee spectrum:

IEEE Spectrum: Q&A With: Ecologist and Geoengineering Expert Philip Boyd

Spectrum: Which schemes are the most promising and why?

PB: The one I favor the most is atmospheric carbon capture. That is the direct capture of carbon dioxide using some sort of scrubbing system. There have been proposals from U.S. researchers where they've described a medium-sized water-tower structure with a turbine system. As the wind blows through, there is a scrubbing device, which has a chemical absorbent that absorbs the carbon dioxide. Then the carbon dioxide can be converted into a solid and stored so that it can't impact climate. And with these towers, it is possible that they could be incorporated with wind turbines, so you're actually generating power to help drive the process.

The reason that one gets a vote is, although it's one of the more expensive ideas, it is much lower risk. In terms of an emergency stop, it can be shut down quickly, and you can verify how much carbon is being removed.