Is there any good fiction or movie about a slow, completely foreseeable apocalypse, unfolding over say 50 years? Everything I can think of seems to imagine a sharp cliff over days or weeks, but decades is what seems likely.
There's Kim Stanley Robinson's 40 Signs of Rain trilogy and Ministry for the Future, both deal with real climate change, not quite sure if they cover the timescale you are after but they definitely are about a slow-moving catastrophe.