if you live in a city in the northern hemisphere then likely you'd die quickly, but a lot of the world will die as an indirect result. firstly all of the trade around the world will end, and besides everything just fubar when it comes to agriculture and trade, also ports are all getting nuked around the developed world so even if somehow there was some semblance of effort to try and export grain somehow - you're just going to starve. pretty much all humans who survive the first few months are then going to starve. also of course all the billions of livestock won't have grain and they won't be able to graze because of the fallout. then you have the factor of nuclear winter, which is debated how bad it could be, but realistically all nuclear weapons are going to be fired and it will be bad. all the cities burning will produce large amounts of smoke which will fill the atmosphere and quickly cover the whole world and block out the sun, and people miss that nuclear war isn't just all the cities getting nuked but it's largely just russia piling thousands of nuclear warheads into the middle of america and america piling thousands of nuclear warheads into the middle of russia, which will result in much of vegetation in russia and america burning up.  and extreme version of nuclear winter could result in much of the life in the world dying as all of the food chain comes back to the sun. all it takes is 1 nuke on london and you can get a chain reaction leading to mass extinction event far beyond just humans.
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