of these permafrost methane events in the past that led to runaway green house warming? Or is there some kind of buffering mechanism that eventually kicks in and counteracts the effect?

I've always assumed that the unbroken history of life on earth guaranteed that the global climate might oscillate wildly, but that it would remain between certain extremes. Could this methane release initiate a runaway greenhouse effect, like Venus? And if it could, why hasn't it happened in the past? Or has it? Ice ages are runaway excursions in the other direction, but the world can recover from them. I don't think it could reverse a Venus-type excursion.

How about it, Podrock? Can you shed any light on this?