Speech codes are rare in the industrialized, Western democracies. In Germany and Austria, for instance, it is forbidden to proselytize Nazi ideology or trivialize the Holocaust. Given those countries' recent histories, that is a restraint on free expression we can live with.

More curious are our own taboos on the subject of global warming. I sat in a roomful of journalists 10 years ago while Stanford climatologist Stephen Schneider lectured us on a big problem in our profession: soliciting opposing points of view. In the debate over climate change, Schneider said, there simply was no legitimate opposing view to the scientific consensus that man - made carbon emissions drive global warming. To suggest or report otherwise, he said, was irresponsible.

Indeed. I attended a week's worth of lectures on global warming at the Chautauqua Institution last month. Al Gore delivered the kickoff lecture, and, 10 years later, he reiterated Schneider's directive. There is no science on the other side, Gore inveighed, more than once. Again, the same message: If you hear tales of doubt, ignore them. They are simply untrue.

I ask you: Are these convincing arguments? And directed at journalists, who are natural questioners and skeptics, of all people? What happens when you are told not to eat the apple, not to read that book, not to date that girl? Your interest is piqued, of course. What am I not supposed to know?

Here's the kind of information the ``scientific consensus" types don't want you to read. MIT's Alfred P. Sloan professor of meteorology Richard Lindzen recently complained about the ``shrill alarmism" of Gore's movie ``An Inconvenient Truth." Lindzen acknowledges that global warming is real, and he acknowledges that increased carbon emissions might be causing the warming -- but they also might not.

``We do not understand the natural internal variability of climate change" is one of Lindzen's many heresies, along with such zingers as ``the Arctic was as warm or warmer in 1940," ``the evidence so far suggests that the Greenland ice sheet is actually growing on average," and ``Alpine glaciers have been retreating since the early 19th century, and were advancing for several centuries before that. Since about 1970, many of the glaciers have stopped retreating and some are now advancing again. And, frankly, we don't know why."

When Lindzen published similar views in The Wall Street Journal this spring, environmentalist Laurie David, the wife of comedian Larry David, immediately branded him a ``shill." She resurrected a shopworn slur first directed against Lindzen by former Globe writer Ross Gelbspan, who called Lindzen a ``hood ornament" for the fossil fuels industry in a 1995 article in Harper's Magazine.

I decided to check out Lindzen for myself. He wasn't hard to find on the 16th floor of MIT's I.M. Pei-designed Building 54, and he answered as many questions as I had time to ask. He's no big fan of Gore's, having suffered through what he calls a ``Star Chamber" Congressional inquisition by the then senator . He said he accepted $10,000 in expenses and expert witness fees from fossil- fuel types in the 1990s, and has taken none of their money since.

He's smart. He's an effective debater. No wonder the Steve Schneiders and Al Gores of the world don't want you to hear from him. It's easier to call someone a shill and accuse him of corruption than to debate him on the merits.

While vacationing in Canada, I spotted a newspaper story that I hadn't seen in the United States. For no apparent reason, the state of California, Environmental Defense, and the Natural Resources Defense Council have dragged Lindzen and about 15 other global- warming skeptics into a lawsuit over auto- emissions standards. California et al . have asked the auto companies to cough up any and all communications they have had with Lindzen and his colleagues, whose research has been cited in court documents.

``We know that General Motors has been paying for this fake science exactly as the tobacco companies did," says ED attorney Jim Marston. If Marston has a scintilla of evidence that Lindzen has been trafficking in fake science, he should present it to the MIT provost's office. Otherwise, he should shut up.

``This is the criminalization of opposition to global warming," says Lindzen, who adds he has never communicated with the auto companies involved in the lawsuit. Of course Lindzen isn't a fake scientist, he's an inconvenient scientist. No wonder you're not supposed to listen to him.

Alex Beam is a Globe columnist. His e-dress is beam@globe.com.

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