Scientists find new global warming threat

As the Earth warms, greenhouse gases once stuck in the long-frozen soil are bubbling into the atmosphere in much larger amounts than previously anticipated, according to a study in Thursday's journal Nature.

Methane trapped in a special type of permafrost is bubbling up at a rate five times faster than originally measured, the journal said.

Scientists are fretting about a global warming vicious cycle that had not been part of their already gloomy climate forecasts: Warming already underway thaws permafrost, soil that had been continuously frozen for thousands of years.

Thawed permafrost releases methane and carbon dioxide. Those gases reach the atmosphere and help trap heat on Earth in the greenhouse effect. The trapped heat thaws more permafrost, and so on...