As the Arctic warms, greenhouse gases will be released from thawing permafrost faster and at significantly higher levels than previous estimates, according to new results. Permafrost thaw will release approximately the same amount of carbon as deforestation. However, the effect of thawing permafrost on climate will be 2.5 times greater because emissions include methane, a more powerful greenhouse gas than carbon dioxide.

Source: Abrupt permafrost thaw increases climate threat