As global warming thaws perpetually frozen Arctic land called permafrost (pictured), the greenhouse gases trapped within will escape, ramping up climate change’s economic toll by trillions of dollars, a new study finds. To make the calculations, researchers first determined how much carbon dioxide and methane the permafrost would release as the world warms. They used a model that estimates how climate factors like temperature affect absorption and release of these gases by land, plants, and microbes. They then fed the results from that model into a different model that estimates economic damages based on future greenhouse gas emissions. The model assumed that human activities by themselves would boost carbon dioxide levels 75% from today to 2100. Total damages without the permafrost emissions would be $326 trillion globally, the researchers found. With permafrost-related emissions included, however, additional damages ranged from $3 trillion to $166 trillion, depending on how much human emissions warmed the Arctic, the team reports online today in Nature Climate Change; the average value was $43 trillion. Aggressive cuts in human emissions could reduce that average price tag to around $6 trillion, the researchers suggest.