If "geoengineering" is truly becoming a mainstream concept, as suggested by Chris Mooney at the Intersection (based on a recent mention in Time magazine), then we are truly on a dangerous path.
Time writes, "Geoengineering has long been the province of kooks, but as the difficulty of reducing greenhouse-gas emissions has become harder to ignore, it is slowly emerging as an option of last resort."
Are we already reduced to thinking about last resorts? If we ever reach the point that we have to say, Let's purposefully try to mess up our planet's extremely complicated climate system in order to restore a poorly understood equilibrium that we lost a while back," then we are truly f****d.
We don't have a planet to practice on. We've never done anything like that before. What are the odds it would work as intended?
If we reach that point, it's far worse than the equivalent of a Hail Mary pass at the end of a football game, or pulling the goalie at the end of a hockey game. After all, those strategies have been tried before and we know they can work, if rarely. In the case of geongineering, it won't work. To even think of attempting it is to think that we're doomed anyway so we might as well have some fun on the way out.
We're not there yet, thankfully, so let's send the talk of geoengineering back to the science fiction books where it belongs.