The emergence of heat and humidity too severe for human tolerance (2020)
Kim Stanley Robinson's recent book The Ministry For the Future starts with a very disturbing scenario: A heatwave  with a "web bulb" temperature of 35 Celsius.It turns out, in those temperatures, even young and healthy people can't survive. Combined with power outages, as happens in the book, everyone living under such a heat wave will likely die.It's looking increasingly likely that such heatwaves are possible in the future, and possibly quite deadly. This could result in the mass deaths of many people, especially in poor tropical countries that don't have a stable infrastructure to cool most people during such a heatwave. I hope a mass death event from a "web bulb" 35C heatwave never happens, but I'm losing hope, especially with the increasing global temperatures, and the very lackluster progress being made on carbon output.