Science fiction is replete with stories about humanity uniting, putting aside the ubiquitous violence among nations and ideologies, upon the arrival of alien invaders. The entire concept of “us” and “them” is turned upside down.
Aliens will not be visiting, but climate change will create an existential threat and cataclysmic hardship for humans and all other living things. I acknowledge that climate change is an inexact science, and the exact timing and sequence of disasters is not knowable. But, barring major changes, the coming apocalypse is beyond our worst expectations.
The nearly 8 billion people on earth will not be foregoing, under any circumstances, the essential and/or desired aspects of modern life, including hospitals, computers, electronic communication, rapid transportation and heating and cooling.