Scientists have identified thousands of sites in the Arctic where methane that has been stored for many millennia is bubbling into the atmosphere.This article is a good link to Edexcel Unit 1 World at Risk to show the possible impacts of global warming and positive feedback mechanisms...
http://www.bbc.co.uk/news/science-environment-18120093
http://www.bbc.co.uk/news/science-environment-18120093