Massive changes do happen. But - the changes are through economics and culture, not through politics. Culture guides the long term behaviours in a civilization, economics play key part in what resources they have to use, politics only guide the short term effects generally.

I agree, it's unlikely a massive change can happen through a political shift (which happen only generally in revolutions and civil wars). A cultural change, however, is completely feasible.

If Facebook for instance turned into a zero-carbon marketing machine I'm pretty sure they could convince the planet to shift gears in consumption. Is the any plausible scenario where they would do this? I suppose if the global catastrophe could be computed as certainly as a trajectory of a asteroid that was about to hit earth - maybe.