I think there are some valid concerns. But I think there is also a certain amount of reaction, in some circles, against the idea that we should be able to hack

I think there are some valid concerns. But I think there is also a certain amount of reaction, in some circles, against the idea that we should be able to hack our way out of global warming without actually reducing our carbon emissions. I'm all for reducing carbon emissions as fast as we reasonably can, but it takes time. I don't think we should reject geoengineering out of hand, at least as a stopgap. Whether it becomes something that we wind up doing hundreds of years into the future, and what the costs of that will be if we do, remain to be seen. I'm actually surprised we haven't started experimenting with adding sulfur to jet fuel. Nature puts sulfur in the stratosphere itself on occasion, so we have a pretty good idea that it works. The half-life is on the order of a few months, so if we overdo it a bit, all we have to do is stop. I saw a long list of objections to the use of sulfur aerosols, and the only one that seemed strong to me was that it doesn't help at all with ocean acidification. Well, okay; but iron fertilization would work for that. Maybe using these (and possibly other) techniques in concert would mitigate the downside that each would have if you tried to solve the whole problem with it.