A new paper published appearing Thursday in the prestigious scientific journal Nature presents the worst-case scenario for runaway climate change that could leave the Earth entirely ice-free within a generation.

If global temperatures continue to rise, massive amounts of methane gas could be released from the 10,000 gigaton reserves of frozen methane that are currently locked in the world's deep oceans and permafrost. Passing this climate tipping point would result in global warming that would be far worse and more rapid than scientists' current estimates.

The new paper suggests that exactly this type of cascading release of methane reserves rapidly warmed the Earth 635 million years ago, replacing an Ice Age with a period of tropical heat. The study's lead author suggests it could happen again, and fast -- not over thousands or millions of years, but possibly within a century.

This is a few months old now but I don't remember seeing it at the time.