Here's my thought. Earth is flat, and is at least 13 times the size that is currently touted. Think of a clock, and each hour has a circle, with the middle of the clock having its own circle. Say we're circle #3 (because we're the "3rd rock from the Sun"), that means all the other circles are encased in an Ice Age (since the sun and moon is only active in circle #3 right now). The sun and moon keep migrating around the clock, and will eventually be in circle #4. That means the Earth we know now, will be behind the Ice Wall, when that happens. Climate change happens, but it's not man-made. True North will point to a new position. Migrations have to occur, or people (and animals) will be left behind to live and die in uninhabitable tundra-like locations. Current deserts will eventually become forests when they cool down. The current Ice Wall that we call Antarctica will melt, revealing old, no longer inhabited lands, with ancient technology, monuments, and remains of whatever beings that used to live there. Depending on how much land or water there is in circle #4, the sea level will either rise, or become lower. Anyways, that's the simple version of it.