Mankind is adrift.
Only few millions of people survived, they are struggling to stay alive. Food is hard to find and plants do not grow (mostly). Water cannot be found on surface, the only way to get it is to find an underground river/lake.
The world is hot, dry, there are almost no clouds and rain is replaced by dust storms. After years, there are no oceans, only salt deserts.
Q: What event/series of events could possibly cause this environment?
The cause should:
- Not kill most of the people - people should starve to death or kill each other for food
- Kill most of the flora
- Make the planet hotter and dry
- Generate no radiation or contamination of food/water
- Be plausible as today. No near-future and no magic.
- BONUS: on areas directly exposed to the sun: burn the skin, causing burns on exposed parts. (This is totally optional)
My initial thought was some kind of pathogen agent that kills most of the flora, but I really don't know if it would cause earth to become an almost desert world.
I also considered a Coronal Mass Ejection, but I don't like the fact that it would kill a lot of people and could contaminate water/food. I'd like a slow apocalypse.
Edit: Heat, dust, no water... this is what the outcome should be, not how the process should behave. You could just frezee the entire world if you can explain that, after an Ice age, the earth would be an almost desert world.