"We're Scarily Close to the Permafrost Tipping Point"
"Permafrost—the ground that stays frozen for two or more consecutive years—is a ticking time bomb of climate change. Some 24 percent of Northern Hemisphere land is permafrost. That's 9 million square miles (23 million square kilometers) found mostly in Siberia, the Tibetan Plateau, Alaska, the Canadian Arctic, and other higher mountain regions."