Ars Technica: The earth sciences have described a number of processes that are decidedly unpleasant for any living organisms unlucky enough to experience them, from volcanic eruptions to mass extinctions. Climatic tipping points are one of those scary processes. You can think of them along the lines of a kid who accidentally crests a steep hill on an old bike with no brakes--he wont be stopping before the bottom of the hill (or he wipes out, whichever comes first). Crossing a tipping point in the climate system...