The land around the Arctic Circle is covered in a layer of permafrost - effectively, permanently frozen soil. That permafrost is one of the world's great reservoirs of carbon, holding an estimated 1,600 gigatonnes, much of it in the form of methane. And its melting:
Scientists have recorded a massive spike in the amount of a powerful greenhouse gas seeping from Arctic permafrost, in a discovery that highlights the risks of a dangerous climate tipping point.In other words, a vicious positive-feedback cycle. They don't think we're at the tipping-point yet, but its close, and dangerous. And with the arctic getting warmer every year (thanks in part to its own positive feedback cycle, in which less ice equals more warming equals less ice), there's a real danger that this could run away on us.Experts say methane emissions from the Arctic have risen by almost one-third in just five years, and that sharply rising temperatures are to blame.
[...]
They fear the warming caused by increased methane emissions will itself release yet more methane and lock the region into a destructive cycle that forces temperatures to rise faster than predicted.