The warming Arctic tundra will make it harder for the world to curb climate change, as thawing permafrost and wildfires release greenhouse gases not fully accounted for in global emissions agreements, according to a study published Monday.

As temperatures rise and permafrost thaws, carbon dioxide and methane trapped in the long-frozen soil are released. The deeper the thaw, the more gas is released.

That threatens to create a feedback loop that contributes to even more warming of the atmosphere, scientists warn in a study published in the journal Proceedings of the National Academy of Sciences.