Humans ruined everything. They bred too much and choked the life out of the land, air and sea. And so they must be vaporized by half, or attacked by towering monsters, or vanquished by irate dwellers from the oceans’ polluted depths. Barring that, they face hardscrabble, desperate lives on a once verdant Earth now consumed by ice or drought. That is how many recent superhero and sci-fi movies — among them the latest Avengers and Godzilla pictures as well as “Aquaman,” “Snowpiercer,” “Blade Runner 2049,” “Interstellar” and “Mad Max: Fury Road” — have invoked the climate crisis. They imagine postapocalyptic...