Permafrost warming in parts of Alaska 'is accelerating'

One of the world's leading experts on permafrost has told BBC News that the recent rate of warming of this frozen layer of earth is "unbelievable".

Prof Vladimir Romanovsky said that he expected permafrost in parts of Alaska would start to thaw by 2070.

Researchers worry that methane frozen within the permafrost will be released, exacerbating climate change

The professor said a rise in permafrost temperatures in the past four years convinced him warming was real.