And when I say "uninhabitable," I mean take a look at Venus, our nearest neighbor. Its current state (much hotter than a pizza oven) is the result of a naturally occurring runaway greenhouse effect (we assume that it was natural) that took place millions or billions of years ago. Planetologists believe that it started out to be much like earth, but the same volcanic activity that happened on earth in its early stages, combined with its proximity to the sun, precipitated Venus's current state, uninhabitable by any life-form anywhere near similar to life as we understand it.

That could be us sometime in the not too far distant future.

Don't think it could happen here? That's a comforting self-deception. But eco-systems are far more delicately balanced than most people believe. We've been pretty lucky so far. But we could very easily screw up big time!

Don Firth