2c seems pretty bad. I guess 5 means no coral reefs, smaller rivers, smaller Antarctica. Permanent northwest passage is a consolation prize, I guess.
On any given day, absent technology, this will kill you in a matter of hours.
Indonesia (100+ million people) is a climate area that would experience this).
I myself have been camping in the Mojave for several days at a time with temperatures high above 100 degrees Fahrenheit.
Are you implying that the combination of heat and humidity is the deadly combination? If so, can you provide some evidence?