I actually had a campaign idea based around a similar event: the world begins going through a monumental change. Do you let the world continue along its preordained natural course, or do you try to stop it, even if it flies in the face of prophecy?
The Coming of the Four
The four elemental forces have ordained the way the world would grow, change, and develop.
Eons ago, as the world was first created, Dragons flew in from the north, bringing with them their servants, the Kobolds, Lizardmen, and Troglodytes. With the Dragons came the Age of Air. Air comes first because it has the power of Ubiquity: where there is nothing, there is still air. The servants created huge empires, great societies, wondrous palaces, and fascinating magic.
Yet eventually, all ages come to an end. From the mountains and forests to the west, the Spirits emerged, bringing with them Dwarves, Elves, and Halflings. The People of Air fought, but with Earth comes the power of Stability, and just as the wind cannot easily push the stone, the Spirits' servants conquered the land. The Age of Earth began, and large expansive empires of stone halls, sacred groves, and lasting bonds covered the land. Broken, the People of Air hid where they could, and fit as best they could into the new age.
Yet eventually, all ages come to an end. Ships arrived from the seas to the east, bearing Giants, and their servants, the Humans, Gnomes, and Orcs. The Empires of Earth were strong, but with Water comes the power of Fluidity. The Empires, set in their ways, could not understand how to battle a constantly adapting, moving foe. New technology, new tactics, and quick growth meant that wherever they were stopped, the People of Water only appeared somewhere else. The People of Water conquered the land and carved out new empires, just as the river carves the canyon.
The Age of Water is the present age. Empires of humans, gnomes, and orcs are the norm. Great cities are built, and trade based on the rivers and seas is the standard. The People of Air have all but retreated to the furthest, most inhospitable reaches of the world. The People of Earth content themselves to survive the best they can in a world where their way of life is dying.
Yet eventually, all ages come to an end. From the deserts to the south, there are rumors of a new race of beings, Goblins, who burn everything they find to the ground.
(Okay, so it's not exactly humorous, but I've been toying with this, and it reminds me of global warming, kinda. Fire and all.)
