Behind the mysterious holes in Siberia

Aired: 8/20/2014 | 0:06:52 | Clip
When holes opened up in the earth recently in Siberia, a wave of speculation was set off as to their cause. Scientists are now pinpointing a dramatic increase in arctic thawing, which may have released methane once trapped below the frozen ground. For a better understanding, Judy Woodruff talks to Tom Wagner of NASA.

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