Johnathan Wolff publishing in the Guardian cites the case of Naomi Oreskes as to why the equal time idea of journalism doesn't work for science:

I learned to shut my mouth on the topic after hearing a lecture from a San Diego philosopher of science, Naomi Oreskes, who reported the results of a review of the scientific literature on global warming. Not one peer-reviewed scientific article, of the hundreds she surveyed, denied that the earth was warming or that human action was at least partially responsible. The sceptics, she argued, were largely members of independent thinktanks, often sponsored by companies with vested interests, publishing their own reports without external review.

A little later, Oreskes published her findings in the leading journal Science, and was immediately shot down by bloggers, journalists and thinktankers, who mixed insults about her honesty with more plausible-sounding complaints about her methodology. Oreskes replied, with great restraint, that she would wait for the peer-reviewed criticisms.

But if Oreskes is right, why do so many people think there is an active scientific debate? One reason is that few people appreciate the difference between peer-reviewed journals and thinktank reports. But even worse, she argued, is the influence of the media: you knew that was coming, didn't you?

In fact, she makes an excellent point. Journalistic ethics require balance. In reporting political arguments, each claim must be countered so that a lively debate can take place and readers come to their own views (well, that's the theory). Oreskes suggests that journalists have mistakenly applied the same ethical code to scientific reporting. Whenever a story on climate change is produced, a maverick nay-sayer is rolled out for the sake of balance. But this misleads the public into thinking that a few lone voices have equal weight to the scientific orthodoxy.

The same thing happened when a scientific consensus was forming around the theory that HIV causes Aids. A small number of scientists questioned the hypothesis and received a disproportionate share of attention. The false appearance of wide scientific disagreement gave policy-makers in some countries an excuse to delay the introduction of prevention and treatment programmes, with tragic results.

How well equipped are we non-scientists to understand scientific discussions? We all study science for a few years, but learn - or at least remember - very little about methodology. Science is presented as a body of known truths. As adults, though, we need to know not the atomic number of chlorine, but how to assess evidence for or against a theory. (Emphasis mine.)

1) I agree with Wolff that science possesses no strong impulse to equal time, and that this is probably good. We don't do equal time because scientific debate is conducted through the screen of peer review. A system where all ideas would receive equal weight would lack such a filter.

Though some people would argue that this screen out dissonant views, this has not been my experience with the system in practice. What the system in practice screens out is views without evidence or views that require ad hominem attacks to make them sound reasonable. I have never heard of a paper that was denied access to a journal on the grounds that the evidence it showed was unfortunate -- most of those papers get fast-tracked to the best journals because everyone likes the publicity.

Someone might respond: what about papers denying evolution and advocating intelligent design? An argument based on the absence of evidence is not equivalent to an argument based on the presence of evidence. To get in a journal you have to propose counter-evidence, not just a counter-argument.

2) Non-scientists often seemed bewildered by the difference between scientific and journalistic discourse, but I have always found them very easy to distinguish. It is not done -- as some have suggested -- by looking at the origin of the information because some scientists do spout nonsense that isn't science from time to time and some journalists make scientific arguments. And, even though I noted above that the process is intrinsic to science, peer-review is not always a perfect guide to scientific validity (although it is a pretty good one)

From a practical point of view, here are two handy principles by which a scientific argument is identified:

• 1) A scientific argument is based on evidence and only evidence. By evidence, I mean experiment, derivation of conclusions from experiments, or explication of mathematical or logical principles derived from experiment.
• 2) A scientific argument is never based on evaluation of the merits of the speaker, the ideological background of the institution where the speaker works, or the social history of the field.

If you find an argument that violates either of those two principles, it is not a scientific one -- even if it is being spoken by a scientist.

(Incidentally, I have never read Oreskes article, so I cannot say anything about the validity of that particular example.)

Hat-tip: Peer-to-Peer