The comment thread is, for the most part, intelligent and points to more evidence and counter-evidence. In it, I hit this: Crichton's Caltech Michelin Lecture, aka "Aliens Cause Global Warming." He lambasts scientist for being Bad for making public appearances intended to sway policy-making and mixing specious conclusions in with Things That Can Be Proven and Are Therefore Appropriately Scientific. Yeah, ok, in many respects he's probably right to offer the reminders; but he's a poor social scientist himself to overlook the role of peer networks in doing research (and don't forget even peer review can allow bad results to get published!), the necessity of relying on second hand reports to keep oneself informed, and the lack of time a scientist has to prove everything from first principles for her own satisfaction or otherwise keep mum about it.