As a follow-up to the last post, sometimes people who ask me about global warming say, “there was a some document issued by National Academy of Sciences (or Intergovernmental Panel on Climate Change, etc.) that global warming is real, so it must be real, right?”

Well, actually, if anything, the fact that there is a consensus statement or a policy document from a scientific body on global warming is a pretty good indicator that the issue is NOT settled.

There is little need for a consensus statement when scientists are in agreement. We don’t see the National Academy of Sciences issuing a document stating that the Earth revolves around the Sun, or that gravity exists. Only when the data is not clear is there a document issued.

And such documents are not scientific document. Scientific doesn’t work by majority vote.

The document is issued by scientists, but it’s not an act of science. It’s a political or social document. Scientific documents, such as scientific journal articles, are a product of science, where the data and logic drive the conclusions. Regardless of whether the reviewer agrees or disagrees with the conclusions, if the data supports the conclusion, it is published. Consensus documents like the ones produced by scientific bodies are a product of negotiation and voting. They’re produced by committees where people horse trade one position for another, to come up with a document that everyone can live with. This is not how real science is done. The validity of the Theory of Gravity is unaffected by how many scientists vote for or against it. Its basis is rooted in data.

This is not to say that the documents are not important, or that they are wrong. It just that the documents are not scientific documents and do little to affect the validity of the theories in and of themselves.

Similarly, when American Heart Association issues guidelines for how high cholesterol should be treated, the fact that there is a guideline is an indicator that the scientific data is not clear-cut. There is no guideline about whether someone who’s had a perforated appendix should receive surgery (though there are guidelines about what kind of surgery). That’s because the evidence is clear-cut. Medicine is chock-full of guidelines precisely because the best course of action is often unclear.

So, the take away is that consensus statements and guidelines are helpful, but should be seen as a political or social document, not a scientific one, and is typically an indicator that the scientific question is not yet settled.