You may want to read books on history. It is more likely that an environmental disaster will occur rather than WWIII. You can watch a clip from Ken Burns on the "dust bowl" drought on BBC or perhaps look up E.O. Wilson and you can watch his interview with Bill Moyers on the Bill Moyers Journal.
Throughout history there have been many wars, revolutions, rampant poverty etc and it is a part of the world we live in. Until we take responsibility for our own actions instead of leaving it up to the "will of god (whatever deity you believe in, god, gods, goddesses etc.) we will not be able to become truly civilized. We need to take care of each other and develop an understanding for one another through compassion instead of fearing and hating that which we do not understand. Educating yourself is the best way to ease your concerns over any disasters or crisis of the future.
WWIII will not happen.