My immediate family has a plan of a survivalist camp. More than outdoor survivalist things, but planning to survive modern potential catastrophes. Not finding one on-line like it I attempt here to describe our objectives.
Changes, certainly, but not the end of humanity. Desert area may expand, for various reasons, but this just pushes people to the cities. Those who can't move might die out, but such is not the sum of humanity.
Survival in the cities may get tougher as power, water and housing get scarce. Some may consider personal farms outside the cities. Grow just enough to feed your family and sell a bit. Survival one generation at a time.