How much carbon will permafrost thaw actually release this century, and how much of it will come from abrupt rather than gradual thaw?

Permafrost holds an estimated 1,400 to 1,650 billion tons of organic carbon. Even under a high-warming scenario, only an estimated 5 to 15 percent of it is expected to be lost over decades and centuries through gradual thaw, but abrupt thaw processes (thermokarst collapse, thaw slumps) release proportionally more methane, accounting for an estimated 40 to 70 percent of the total warming impact from permafrost carbon, and abrupt thaw remains far harder to model and quantify than gradual thaw. Vegetation regrowth is very unlikely to offset the emissions either way. The range between the gradual-thaw and abrupt-thaw estimates is wide enough that the century-scale climate impact is not yet pinned down.