I forget where I found this, but there’s a good piece on Environmental Research Web about the moral aspects of geoengineering.
The author, UW prof Steve Gardiner, raises several concerns, but for my money, this is the most telling:
It is not silly to think that substantial investment in geoengineering will itself encourage political inertia on mitigation and adaptation, and also facilitate the actual deployment of geoengineering “solutions”. In short, Crutzen treats the decision to do research and the decision to deploy as if they were causally isolated. But it is not clear what justifies this assumption — indeed, the history of technological innovation suggests otherwise.
If you’re into slightly academic ethics discussions — and who isn’t — read the whole thing.