The problems affect a fairly narrow band of latitudes; specifically, those where the average long-term temperature was just below freezing i.e. the southern mar

The problems affect a fairly narrow band of latitudes; specifically, those where the average long-term temperature was just below freezing i.e. the southern margin of the permafrost. 1-2F is indeed within natural variation, but historically a warm year or two was followed by a harsh winter to refreeze the surface so that the deep layer stayed frozen. Now, the average temperature is just above freezing or close enough to it that the heating effect of the asphalt pushes the local average temperature above freezing. This means that deep layers are now thawing for the first time in thousands of years; they will stabilize eventually, but in the meantime they're going to be near impossible to build roads on. And the thaw line continues to march north, year by year.