You might be a junk scientist if:

You prophesy disaster in some remote future. It is safest to choose a date in the long run, when we’re all dead, but even the less judicious have little to worry about: by the time D-Day rolls around people will have forgotten what you said. If someone does happen to remember, you can either issue a new report revising your predictions, or, as a last gasp, maintain that you were right in general, even as your every specific prediction has been falsified. Or both.

You deal in poorly-understood, multi-causal phenomena, traditional playgrounds for the scientific crank. Cancer and climatology are especially popular.

You have trouble with extrapolation, like Ralph Hingson of the Boston University School of Health, who concluded that college drinking causes 1,400 deaths annually, by taking the total number of alcohol-related deaths among people 18-24 and multiplying by, uh, the percentage of them in college. (Note that this is supposed to establish that college drinking is especially dangerous.) Social science: it’s easy!

You are famous for work outside your field, like Paul Ehrlich, a bug man best-known for speculation on overpopulation and global cooling (yes, cooling); Barry Commoner, the cancer-biologist-cum-nuclear-testing-authority-cum-geneticist; Rachel Carson, an expert on chemicals by virtue of her master’s in marine biology; and Stephen Jay Gould, another genetics authority, trained in paleontology. The press, notwithstanding, can be relied on to refer to you as “Dr.,” “Ph.D.,” or “distinguished scientist.”

You do a lot of testifying for plaintiffs in class-action suits. Extra credit if this is how you make your living.