When questioned in 1998, OISM's Arthur Robinson admitted that only 2,100 signers of the Oregon Petition had identified themselves as physicists, geophysicists, climatologists, or meteorologists, "and of those the greatest number are physicists." This grouping of fields concealed the fact that only a few dozen, at most, of the signatories were drawn from the core disciplines of climate science - such as meteorology, oceanography, and glaciology - and almost none were climate specialists. The names of the signers are available on the OISM's website, but without listing any institutional affiliations or even city of residence, making it very difficult to determine their credentials or even whether they exist at all. When the Oregon Petition first circulated, in fact, environmental activists successfully added the names of several fictional characters and celebrities to the list, including John Grisham, Michael J. Fox, Drs. Frank Burns, B. J. Honeycutt, and Benjamin Pierce (from the TV show M*A*S*H), an individual by the name of "Dr. Red Wine," and Geraldine Halliwell, formerly known as pop singer Ginger Spice of the Spice Girls. Halliwell's field of scientific specialization was listed as "biology." Even in 2003, the list was loaded with misspellings, duplications, name and title fragments, and names of non-persons, such as company names.

OISM has refused to release info on the number of mailings it made. From comments in Nature:

"Virtually every scientist in every field got it," says Robert Park, a professor of physics at the University of Maryland at College Park and spokesman for the American Physical Society. "That's a big mailing." According to the National Science Foundation, there are more than half a million science or engineering PhDs in the United States, and ten million individuals with first degrees in science or engineering.