Science is a collective, multi-layered process consisting of three steps. First is the individual scientist testing hypotheses according to the norms of their field. Second, the results of the individual scientist undergo peer-review and are published for the community to evaluate. At this point a result may be considered preliminary, but not proven.
Third, important claims are then re-tested in the “crucible of science” — they are either reproduced by independent scientific groups or they have their implications tested to insure consistency with the existing body of scientific knowledge. After enough tests/reproductions, a consensus emerges that the idea is correct.
In the end, claims that are repeatedly verified by the scientific community (e.g., the earth is warming, DNA is a double-helix, CFCs destroy ozone) eventually come to be accepted as true.
The key point here is the importance of repeated testing. After an idea is sufficiently well tested, people accept it and move on. While such a scientific consensus might turn out to be wrong, for important and well-tested ideas (e.g., smoking causes cancer, the earth is warming), it’s exceedingly unlikely.
Similarly, claims that have not been repeatedly verified must be viewed with caution. Why? Because they might turn out to be wrong.
A great example of this is unfolding right now. A recent analysis of the latest ocean observations (2003 to 2005) showed a decrease in the ocean heat content over those years. This result is puzzling and suggests that much of what we think should be happening to our climate due to the build-up of greenhouse gases is wrong.
Roger Pielke Sr.’s blog, for example, featured this result seemingly daily in his quixotic quest to cast doubt on the IPCC’s interpretation of the science.
Recently, however, this statement was posted on Pielke Sr.’s site:
We have been informed today, however, that a correction will be completed soon on this paper in which the recent cooling trend will be removed.
In other words, the problematic cooling trend looks to be wrong.
I’m not an expert on these data, and I don’t know whether the trend will turn out to be correct or not (though I suspect the smart money is on “not”). The important point is this: a new result that seems to overturn a confident conclusion of the scientific community is probably wrong.
For example, we should be skeptical of a new study that shows smoking does not cause cancer. And we should be similarly skeptical of new studies that suggest that the earth is not really warming.
Such studies might eventually turn out to be correct, but the odds are long. Before you accept a claim from such a study, you should wait for the result to be verified a few times. You’ll probably be waiting for a long, long time.