There is a concern with the carbon stored in the form of frozen partially decomposed vegetation in the vast tundra of the north. When the permafrost melts, it may releases carbon in the form of carbon dioxide and methane, both of which are greenhouse gases. The amount of greenhouse gases which will be released from the Arctic’s stockpile of carbon may be more secure than scientists thought. In a 20-year experiment that warmed patches of chilly ground, tundra soil kept its stored carbon, researchers report. Almost half of the world’s soil carbon is stored at high latitude, in the form of dead and decaying organisms.