Global warming was not the cause of Earth falling into an apocalypse. Nor the nuclear fallout throughout the fertile surface where we grow crops for food.
The world was invaded by monsters through spacial cracks. Solar flares from the sun cause distortions that can fold space where high energies of particles reflect or hit. Who would have known that nuclear fallout in large concentrations had high enough density to stabilize spatial cracks.
It was not until a month later that the information that our planet was being invaded was publicly known. It was initially thought that local wildlife was mutating due to the fallout.
Towns and Cities started planning ways to reduce panic, redistribute resources, and getting through the crisis. City A, offered cryogenic freezing pods for the rich, the plan was to wake up when it was all over. There was options, like waking up in intervals every 3 to 10 years.
A janitor, named Mason, volunteered himself for a short freeze to prove to others the technology was safe. He was originally planned to be kept frozen for only a month, but due a paperwork oversight and the death of one of the lead technicians; Mason was forgotten about.