During the 1990s there were warnings from scientists that rising global temperatures could trigger the release of vast amounts of the greenhouse gas methane from melting of frozen bogs in Siberia and other arctic areas. This would create a global warming feedback mechanism as methane would cause increased global temperatures which in turn would release more methane and so on. Unfortunately for us it appears that this very worrisome situation may be happening. The latest evidence comes a group of scientists who detected increased amounts of methane being released from a thawing lake in Siberia. In their September 7th article in the journal Nature they reported that methane was being released at five times the rate of previous estimates.
The good news about methane is that methane molecules tend to last for a much shorter time in the atmosphere than carbon dioxide molecules. The bad news about methane is that methane molecules trap much more heat than carbon dioxide molecules. If this positive feedback mechanism has really been triggered then that's very bad news.