Email 239, Oct 2003, John Holdren defends Michael Mann's alarmism by stressing Mann's careful weasel wording

Email 239

Regarding extravagant claims, you continue to argue that Mann et al. have been guilty of this, but the formulation of theirs that you offer as evidence is not evidence of this at all. You quote them from the NYT in 1998, referring to a study Mann and co-authors published in that year, as saying

"Our conclusion was that the warming of the past few decades appears to be closely tied to emission of greenhouse gases by humans and not any of the natural factors."

and you ask "Does that seem to be careful in the nature of a claim?" My answer is: Yes, absolutely, their formulation is careful and appropriate. Please note that they did NOT say "Global warming is closely tied to emission of greenhouse gases by humans and not any of the natural factors." They said that THEIR CONCLUSION (from a particular, specified study, published in NATURE) was that the warming of THE PAST FEW DECADES (that is, a particular, specified part of the historical record) APPEARS (from the evidence adduced in the specified study) to be closely tied... This is a carefully specified, multiply bounded statement, which accurately reflects what they looked at and what they found. And it is appropriately contingent --"APPEARS to be closely tied" -- allowing for the possibility that further analysis or new data could later lead to a different perspective on what appears to be true. With respect, it does not require a PhD in science to notice the appropriate boundedness and contingency in the Mann et al. formulation. It only requires an open mind, a careful reading, and a degree of understanding of the character of scientific claims and the wording appropriate to convey them that is accessible to any thoughtful citizen. That is why I'm an optimist.