Interesting post it is. I think a global trade in emissions would be the most effective. It allows to pose a hard limit on the amount of produced greenhouse gasses and it can be lowered year after year to reach targets. I think it is also a better approach since consumers won't criticize the government again for taxing products for their benefit (although higher prices are a result nonetheless). It also leads to a balance where reducing pollution can be more cost effective than buying emission rights. But aren't they already doing this? Or is this not on a global scale yet?

Carbon taxes are indeed way easier to implement but I don't think it offers a lot of control on the total amount of emissions.

And of course, geoengineering could be potentially very dangerous as you and @snowyknight already mentioned. Treating the symptoms rather than the cause is not the way to go, but could it be a last resort, in case all else fails? I think it would be even more dangerous than climate change itself.
Because an important thing to note is that climate change doesn't kill species or disrupt societies, It is the speed at which it changes that can be so destructive. So geoengineering in timescales of only a few years could even be more disastrous.

ps. snowpiercer sounds like I film I definitely want to see! :D