Several things we thought we knew about the PDO we do not, in fact, know at all. The unprecedented great Pacific climate shift of the late 1970s linked to global warming was, in fact, precedented and unrelated to global warming. And the useful predictability of the PDO for predicting west coast drought may not be useful at all, since the PDO will, apparently on a whim, suddenly become non-periodic for centuries at a time (unrelated to global warming).I point to this commentary, not so much because I agree with the basic analysis, but because I think it may be worthwhile to consider how we should approach incorporating science into political debate of alternative public policies.
The biggest problem with all of these somewhat cyclical climate shifts is that no one knows for sure that a shift has actually taken place until many years AFTER the event, when it's too late to be useful. So be wary of global warming psychics warning us of unprecedented climate shifts -- in most cases, they are only unprecedented because of the short life span of most scientists. Remember one of the absolutely fundamental and too-often unstated tenets of science -- there's little point in studying anything that doesn't vary during a scientist's lifetime.
Consider Davis's comment: "Several things we thought we knew about the PDO we do not, in fact, know at all." As I understand scientific method, science is best at finding out what we don't know. In order to be good at identifying what is not true, science recognizes by its very methodology that it is not able to identify what is true. Instead, science proceeds by the process of scientists thinking up hypotheses, making predictions, measuring the reality of interest, and comparing the measured reality against the predictions. If there is sufficient consistency, then the hypothesis is PROVISIONALLY accepted. The provisional acceptance of the hypothesis and theory continues until it is discovered that the theory is wrong. Of course it may never be discovered that the theory is wrong. In such an event would we conclude that the theory was, as a matter of fact, true? I don't think so. We simply continue to use the theory as long as it works for us. I don't think it is at all surprising, looking historically, that there are things science thinks it knew but later discovered it did not know. I think this is merely an inherent characteristic of science.
The question is, given this is an inherent characteristic of science, how should we utilize science when we discuss public policy issues that rely on what scientists think they know about something? It seems to me that most of our political debate in such cases proceeds as though science is telling us what is factually true. Isn't such a presumption inaccurate, and therefore, isn't relying on such a presumption a poor way to approach public policy debate?