Do Global Climate Tipping Points Exist?

In Scientific American this week - An academic debate ponders whether Earth's climate could change precipitously, and how unmitigated regional stressors could irrevocably alter the planet
Is there a chance that human intervention—rising temperatures, massive land-use changes, biodiversity loss and so on—could “tip” the entire world into a new climatic state? And if so, does that change what we should do about it?

“You’re pushing an egg toward the end of the table,” says Tony Barnosky, a professor at the University of California, Berkeley. At first, he says, “not much happens. Then it goes off the edge and it breaks. That egg is now in a fundamentally different state, you can’t get it back to what it was.”

“If there is plausibility to one of these tipping points, which I think there is, then it’s an even more urgent matter to act to slow all of these individual stressors down,” Barnosky says, “because the outcomes could be more surprising and more disruptive to society, and happen faster than we have time to react…. I’d much rather err on the side of precaution then ignore the possibility of tipping points and then be unpleasantly surprised when they happen.