Permafrost is permanently frozen soil, and occurs mostly in high latitudes. Permafrost comprises 24% of the land in the Northern Hemisphere, and stores massive amounts of carbon. As a result of climate change, permafrost is at risk of melting, releasing the stored carbon in the form of carbon dioxide and methane, which are powerful heat-trapping gases.

In addition, permafrost is structurally important, and its melting has been known to cause erosion, disappearance of lakes, landslides, and ground subsidence. It will also cause changes in plant species composition at high latitudes.

Estimates of the total area of alpine permafrost vary. Bockheim and Munroe[18] combined three sources and made the tabulated estimates by region, totaling 3,560,000 km2 (1,370,000 sq mi).

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https://en.wikipedia.org/wiki/Arctic_methane_emissions

https://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/oct/13/methane-release-fr...

http://siberiantimes.com/ecology/casestudy/news/n0681-now-the-proof-permafrost-bubbles-are-leaking-m...

https://www.google.sk/search?q=methane+clathrate&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwijx67luY...: