This article discusses the impact that climate change is having on the permafrost, which covers about a fifth of the Northern Hemisphere. Permafrost refers to ground that has been mostly frozen for half a million years or more. It is thawing out accelerated rates, and we may soon approach a point of no return, where the feedback loop is exacerbating the thawing.
Why is this bad? Permafrost contains organic matter, and thawing will enable bacterial decomposition that will release methane as a byproduct of anaerobic respiration. Thawing will accelerate the amount of methane gas being released into the atmosphere, and methane is one of the most potent GHGs, as much as 86 times more potent that CO2.