The climate is changing faster than many scientists expected. Among the worrisome indicators: more than 4 million square miles of carbon-rich frozen soil in and around the Arctic.
It's been frozen for hundreds, maybe thousands, of years. But in some places, it's beginning to thaw.
Reporter Daniel Grossman visited Alaska and talked with two scientists who say if that trend continues, the outcome could be catastrophic. Listen to the audio of his report above.
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