Brad DeLong links to an interview with Ken Caldeira. It includes this:

e360: Right. Well, a lot of people think of geoengineering as a quick and cheap fix for global warming. Is it?

Caldeira: Let’s pretend for a moment that putting dust in the stratosphere is easy to do and works reasonably well… and that China or India then went into a decade or two of deep drought. Whether the system caused that drought or not, I think the Chinese or the Indians would rightly suspect that the reason they have this drought and ensuing famines might be due to this system that was put up by these other countries. And you could easily imagine that there would be a great amount of political tension…. Then, of course, the system is not going to work perfectly… not going to address… ocean acidification… not going to perfectly offset global warming…. [G]eoengineering options [are] something we would only want to consider if our backs were really up against the wall… because the alternatives look so frightening.

e360: I know that some scientists have suggested that there should be some kind of taboo on geoengineering research. But I know that you’ve been outspoken in the need for a federally-funded geoengineering research program. Can you explain that?

Caldeira: Yes, I think we don’t know right now whether these kinds of approaches have the potential to reduce risk or not. In our climate models, the amount of climate change can be reduced by these kinds of approaches, but the climate models are an imperfect reflection of reality…. Let’s say geoengineering doesn’t work, and that it would add to risk. It seems to me it would be worth having a research program to demonstrate that beyond a reasonable doubt so we can all forget about this and move on. On the other hand, if these options do have the potential to reduce risk, then it seems to me that we would like to have the option to reduce that risk should a time come where that would seem necessary. I kind of think of these geoengineering options as seeing, “Well, can we invent some kind of seatbelts for our climate system?” We need to drive the climate system carefully, we need to greatly reduce emissions. But even if we’re driving carefully we still run the risk of getting into an accident. And seatbelts can potentially reduce the damage when we’re in an accident…. I’m much in favor of a very broad-spectrum approach…. [T]hinking of geoengineering as a substitute for emissions reduction is analogous to saying, “Now that I’ve got the seatbelts on, I can’t just take my hands off the wheel and turn around and talk to people in the back seat.” It’s crazy.

Indeed.