One of the world's last great wildernesses, the Yamal peninsula in Arctic Russia is under heavy strain from global warming. Scientists say there is unmistakable evidence that Yamal's ancient permafrost is melting, which could catastrophically release billions of tonnes of carbon dioxide and the potent greenhouse gas methane, which were previously trapped in frozen soil. The survival of the indigenous Nenets people is under grave threat as they contend with a tundra made increasingly unpredictable by the changing climate