Predictions and ad Hominem Attacks

Eric S. Raymond's recent post on "Eight Warning Signs of Junk Science" (written in the context of climate science, but applicable more generally) is recommended, but the best bits are in the comments. First, from Raymond himself, a distinction between ad hominem and not really ad hominem attacks:

There is an important difference between saying “I think person X is lying about global warming because person X has often been caught lying before in similar circumstances” and saying “I think person X is lying about global warming because he likes to bugger sheep.” In the latter case, the claim that X likes to bugger sheep is probably irrelevant to X’s truthfulness about global warming; in the former, the specific claim about a pattern of lying is relevant. The latter is ad hominem; the [former] is not.

A handy one to keep in the arsenal.

Second, from commenter Contemplationist, an answer to the important question, How can a layperson evaluate the accuracy of claims made by scientists:

A lay man need not know anything about a scientific field to intelligently evaluate it other than whether the humility (or lack thereof) of the practitioners of the field calibrate with the success (or failure) of their models’ predictions.

According to the data I've seen, climate scientists's prediction record is poor indeed.