Create a time machine and hopefully get some travelers who wish to help save the world....or I'll build a time machine and let the people who'll destroy Lavos in the future when the time is right. Or they could just find me. Anyways, I'll be all "Well this sure isn't our day" once it launches its laser barrage that rains own from the heavens across the planet. Also, there wouldn't be wars which would be great, however there would be famine which would suck. Wait, don't those Norwegians have those doomsday seeds up in some underground vault just to help fertilize the earth again if something happens? Unless, the electricity burns out and the seeds start to rot....oh dear. Find a way to survive and create domes and find survivors.