It represents 20% of the surface of the planet. Permafrost refers to a set of terrestrial layers whose temperature is maintained below 0°C for at least two years. This geological phenomenon is mainly present in Russia, Canada, Greenland, and Alaska. Unfortunately, in recent years, global warming has caused permafrost to melt. The danger is that these ice layers contain nearly 40 billion tonnes of carbon, double the amount stored in all of Europe's forests.