Recommended reading: "Why not scrub CO2 from the sky?" by John Rennie, whom I know from freelancing at Scientific American when he was editor in chief there. Taking proactive measures to engineer the planet, such as getting rid of some of the carbon that's been emitted, is an issue that is on a distant horizon today but is going to cause massive political turmoil and realignments in time. The fear of moral hazard -- that people will see such potential solutions as a license to emit -- constrains advocacy of such engineering at present, as do concerns about the unanticipated consequences (and recognition of the limits of what engineering can do, eg, how do you de-acidify the ocean?). Left-leaning science advocates such as Rennie are careful to bracket ideas about planetary engineering with cautions that it can't be a substitute for reducing emissions. I can imagine various environmentalists never warming up to such engineering, and various conservatives now in denial about the problem coming around to the idea that we have to do something as long as it's not about cutting emissions.
UPDATE: Also of interest: "Climate Proposal Puts Practicality Ahead of Sacrifice."