There is a growing concern that increased thawing of permafrost due to warming temperatures in the Arctic has the potential to release large amounts of carbon dioxide and methane into the atmosphere. A recent estimate suggests that Arctic permafrost contains twice as much carbon as the entire atmosphere. If significant amounts of these greenhouse gases are released, it could cause a positive feedback, intensifying global warming. Methane, in particular, is an especially efficient greenhouse gas, and its potential release is of even more concern to scientists than the carbon dioxide that would be released simultaneously. Preliminary projections suggest that Arctic permafrost could eventually become an annual source of carbon, contributing an amount equivalent to 15-35% of current annual greenhouse gas emissions from human activities. However, it is believed that if emissions are brought under control now, contributions from thawing permafrost could potentially be much less. Scientists have declared the need to understand this problem as a major priority, recognizing the large amount of uncertainty that still exists. Experts’ most significant worry at this point is that once the carbon in permafrost begins to break down, it will be impossible to stop.