Although I fully accept that the moral hazards is alive and well, and it is vital we worry about (and prevent) any action undermining efforts to reduce carbon use, the argument used against geoengineering that relies on casting the Earth as some sort of precious, pristine system to be ruined by 'mad scientists' is a fallacy. Precious it is, pristine it ain't.
More than that however, is that this idea leads us towards the moral hazard. If the Earth in 2011 is so in danger of being ruined by geoengineering, why change the status quo? Where's the need for environmental change if Ecotopia is where we are now?
I do genuinely sympathise with the deep greens, it must be odd drifting towards being allies with the climate sceptics.