Arnold also writes:

Pearce himself said, and I agree, that skepticism about climate models should increase one’s concern about both tails. That is, the models may under-predict global warming. In fact, that is my number one concern with the issue. His book, which I bought, is a litany of potential disaster scenarios, from peat bogs dissolving and releasing massive amounts of methane to ice sheets quickly breaking loose into the ocean. Even though these scenarios are not in the scientific consensus represented by Dr. McCracken, I think they are the right things to worry about.

I’ve got to disagree. As I’ve argued before, all predictions of severe disaster should be treated with utmost skepticism, because they are almost always wrong.

Yes, this too is a defeasible presumption. But in light of the track record of doomsayers through the ages, it’s reasonable to expect overwhelming evidence before we abandon this presumption.