We've always got Nuclear energy and that will scale pretty much to the moon - old generation reactors have all sorts of fatal flaws including requiring a fuel that we have trouble acquiring, but that problems mostly been solved.

Nah - I think your gut reaction is mostly just decades of propaganda painting fossil fuels as a necessary evil.

On the topic of pure renewables - hydro definitely can't scale, we can get a lot more out of it then we currently are but it's comparatively not clean and most locations don't have unlimited options for power harnessing - wind and solar scale up pretty ridiculously and in most parts of the world one or the other is going to be quite accessible and, we've also got geothermal and some other options that we can look at.

Beyond that we can look into demand reduction, the dead simplist of these is insulation/passive cooling requirements on housing and taxing private transportation to encourage ride-sharing especially in the commercial realm.

We've got some great options to look at if only the coal barons would STFU and go away.