@Saptarshi With global warming, the virus, nuclear power, bioweapons.. -humans would be eradicated. Worrying and wild speculation is uncalled for, but it would be prudent to keep a close eye on the situation from as many news streams as we can handle.
I don't think WWIII would take place any time soon, because with the advent of such powerful weapons, world leaders would ponder over it for a thousand times before pressing the button.