The setting for the post-apocalyptic film Snowpiercer is a future Earth that has fallen into a barren ice age after scientists try to fight global warming by pumping chemicals into the atmosphere. Meanwhile, in the real world, scientists are studying whether to fight global warming by … pumping chemicals into the atmosphere.

To be fair, nobody thinks the kind of geoengineering under consideration would turn the planet into a frozen graveyard. But the reality of what could happen if we use this shortcut is still troubling enough to make us think twice.