We've been doing unintentional geoengineering for hundreds of years now, why would some intentional geoengineering be so bad?
Because it might allow us to continue with global trade, industrial capitalism and rising prosperity.
Show me any practical, proven technology whose wide-spread deployment would significantly reduce GHG emissions and I will show you a green activist group vehemently opposed to it.
And of course Nuclear: http://www.nationaljournal.com...
Some people will claim that green activists aren't opposed to all these (and other) technologies per se but rather to these specific projects... and yet there is in fact opposition to every single specific project of sufficient scale or scope to make a difference, so that is clearly false. It is simply not plausible that every single project regardless of technology just happens to be so bad for the Earth it is worthy of vigorous opposition, unless you're against industrial capitalism, global trade and rising prosperity regardless, in which case you should just be honest and say so, and stop with all the irrelevant distractions about the climate.
Green activists are like anti-contraception activists: they believe their target activity (industrial capitalism/sex) is bad in and of itself, and cannot ever be made good, but they disingenuously and dishonestly claim that they are opposed to it because of its potential negative consequences... and then do everything they can to prevent anyone from ameliorating those consequences.
GA: "Global warming is bad! We must shut down industrial capitalism!"
Technologist: "Hey, I can fix things so industrial capitalism wouldn't cause global warming."
GA: "We must not do that!:
Tech: "Why not?"
GA: "Because industrial capitalism is bad!"
Tech: "How come?"
GA: "Because it causes global warming!"
Tech: "But I just showed you how we can avoid that."
GA: "We can't! You're lying! It's a trap! Industrial capitalism can't be made good because it's bad!"
Tech: "Fuck you. I'm going to go ahead anyway."
GA: goes away muttering, waving copy of Malthus...