Age: THE blanket of permafrost covering a fifth of the world’s land mass traps twice as much greenhouse gas as previously thought — and is therefore much more likely to trigger rapid climate change as it melts, research says. A paper published in the journal Bioscience estimates that more than 1500 billion tonnes of carbon dioxide and methane is locked in frozen vegetation at high latitudes. This is more than double the amount of greenhouse gas now in the atmosphere. CSIRO …