I used to be a glaciologist, specifically. People don't grow significant crops in those hot deserts. Afganistan has hot summers, but not horrifically hot compar

I used to be a glaciologist, specifically. People don't grow significant crops in those hot deserts. Afganistan has hot summers, but not horrifically hot compared to some areas. Afganistan also has low humidity, which is key for our ability to perspire. The worst-hit areas are humid tropical climates. Middle eastern populations in the hottest and humidest areas usually have AC. Most other places aren't quite so bad, due to lower humidity if not lower temperature. Traditional populations lived in stone or mud brick houses that can withstand the midday heat better. There has been several occasions recently where the heat index has gotten near fatal in Rajasthan and Punjab, which caused quite a few deaths. Greenhouses aren't that hot, usually not more than 30C. Not many plants like it super hot. Even plants in hot climates will do better if its a bit cooler. With hotter climates, plants (at least the ones people rely on) undergo more heat stress and have shorter growing seasons. Much of Africa is drying, especially the Sahel. Similar situations will occur in many parts of S. America and Asia. A big distinciton here is timeframe and how much mitigation happens. We are more or less locked into a 3C rise, which is really bad. And that's our effective best-case scenario. However, if mitigation fails, and it has thus far, a 7C rise by the end of the century is not out of the question. That will lead to a total civilizational collapse and probably eventual human extinction. We wouldn't be able to maintain an industrial civilization in such an environment, and we'd have to fall back on localized, less industrial production. But, the environment would be so degraded that non-intensive agriculture probably couldn't provide enough food to stave off continual population declines.