Mark Hertsgaard displays an embarrassing lack of self-awareness with that statement. But then perhaps leftists such as Hertsgaard have lost the ability to feel embarrassment, when the alternative is paying attention to facts that call leftist dogma into question.
First he decries the supposed intransigence of the authorities (as represented by the RCC) that refused to listen to the arguments of Galileo ("the denier"), while lionizing Galileo's efforts. Then in the next breath he uses a "reference to authority" argument to prop up his assertions of impending man-made climate-change doom and to damn all of those pesky deniers (Galileo excluded, of course). He's playing a game of "good denier, bad denier" without even realizing what he's doing. Talk about cluelessness...
Hint to Hertsgaard: "Major scientific organizations" are political animals that follow the money, the orthodoxy, and the crowd - they are not actually organizations that follow the scientific method to arrive at their pronouncements. The leadership of such societies have often taken sides on issues without adequately polling their membership. For example, do some research about the controversy within the APS (American Physical Society) wherein actual scientists took strong issue with the official position of the APS leadership that climate science was settled science.
It would be a good idea for bandwagon jumpers such as Hertsgaard to do some reflection on the meaning of the oft-repeated caution that "science advances one funeral at a time"...
Lefties - you're gonna have to come up with another magic bullet to impose communism on us. We're not buying this one.