I don't like the odds.
Yukio Isozaki of the University of Tokyo suggests that a weakening magnetic field allowed increasing amounts of cosmic radiation to reach the Earth, breaking nitrogen atoms into ions that formed seeds to create huge cloud masses and massive global cooling. This catastrophe was put in motion by "a plume of super-hot material" that began rising from the Earth's core. It was the movement of this plume toward the surface weakened the Earth's magnetic field, according to the article.
When the plume reached the surface, it became three supervolcanoes. From the article:
On their own they were too small to do much harm, but together Isozaki thinks they cooled the climate even further, launching an extinction as bad as the one that would kill the dinosaurs 185 million years later.This didn't happen overnight: The sequence so far took around five million years to complete. The really massive die-off came 10 million years later. Isozaki thinks this, too, was a consequence of the plume.
Other scientists disagree. According to the Discover News article, Gregory Retallack of the University of Oregon agrees that the first extinction event was bad -- killing as many as two-thirds of all species -- but thinks there was a recovery before the really massive die-off. The apparent recovery between the two events apparently diminishes the likelihood that the extinction events are causally linked.
I'm not at all sure that's comforting.
Anyway, the deterioration of the Earth's magnetic field was not a one-time-only event. Wikipedia's article on geomagnetic reversal suggests that the field is deteriorating right now, and the rate of deterioration has accelerated in recent years. On the other hand, "The rate of decrease and the current strength are within the normal range of variation, as shown by the record of past magnetic fields recorded in rocks." Also, the Earth's magnetic field "has gone up and down in the past with no apparent rhyme or reason."
Ah, well. The point is, Al Gore can make us curb all our hydrocarbon emissions but if the Earth's magnetic field flips on us, we all might die anyway. It's flipped before and will flip again.
Life on Earth has only a precarious hold. As large as our home planet is, it is still a speck in the cosmic order of things. And our planet changes over time -- always has, always will. Who are we smug humans to think we can arrest the planet's natural course? Why our we so arrogant to assume that our pollution will cause more than a blip in the natural course of the planet?
As a species, we really should be thinking about Plan B, don't you think? We need to start boldly going: In nature, dispersal is recognized as a really good survival strategy.