Agence France-Presse: Ice unearthed in Canada that stayed frozen for 700,000 years, even in warmer times, should allay fears of melting permafrost venting its vast carbon stores to hasten global warming, a study said Friday. Permafrost, or subsoil that remains frozen year-round, underlies a quarter of the land in the Northern Hemisphere and is estimated to hold twice as much carbon as is in the atmosphere. When it melts, some experts fear it will quicken the pace of global warming …