When organic matter thaws from the ice, microbial action generates methane and other greenhouse gases, which ultimately get pushed into the atmosphere. This activity is a source of carbon that can rival the burning of fossil fuels by humans. Within the permafrost is one of the largest carbon reservoirs on the planet. By some estimates there is more than twice the carbon locked within permafrost than there is in the atmosphere. Changing permafrost sets off another feedback loop—melting ice and permafrost release carbon into the atmosphere, which, in turn, causes more warming.
