A great way to start this essay would be to identify or discuss all of the 'end of the world' hype. Much focus and debate centers around this topic. Countless movies like 2012, Armageddon, Deep Impact,have been made; people are obsessed about this topic right now. With the Mayan calendar prophecy looming in the future, shows on television like Doomsday Preppers and Doomsday Bunkers exploit people's genuine concerns about end of the world.
After you explored the hype, then you could lead in with a strong thesis statement introducing your own opinion to complete your introduction.