I mentioned the possibility on a thread some time back and was told that I was a raving alarmist, totally insane, and full of bovine excrement, not just by the global warming doubters and self-appointed debunkers, but by some folks who are concerned about it and should have known better, but still told me that I was being ridiculously excessive.

Nevertheless, more than one astronomer and planetologist whose writings I have read have ventured the opinion that, even though it's a remote possibility, it is nevertheless possible that, between natural cycles and human activity, a runaway greenhouse effect could be precipitated here on earth—the same planetary catastrophe that made Venus the way it is:   hotter than a pizza oven and uninhabitable by earth-type critters. And when and if a runaway greenhouse effect gets started, there is no way of reversing it. That's what's meant by "runaway."

And here's the fun part:   nobody knows for certain just where that tipping-point might be, but knowledgible planetologists have opined that it is quite probably much earlier than most people would assume.

Don Firth