Late last month Senator James M. Inhofe, Republican of Oklahoma, brandished a snowball on the Senate floor, suggesting that the ugly winter weather afflicting the Eastern Seaboard was evidence that global warming is a hoax. This moment of political theater was widely ridiculed (by Jon Stewart and others), but “Merchants of Doubt,” Robert Kenner’s informative and infuriating new documentary, ought to remind us that the denial of climate change is hardly a joke.

And those who promote it — in the news media, in political discourse, in serious-looking reports published by dubious think tanks — are anything but fools. “Merchants of Doubt,” based on Naomi Oreskes and Erik M. Conway’s book of the same title, examines the history of corporate-financed public relations efforts to sow confusion and skepticism about scientific research. The filmmakers interview scientists, activists and whistle-blowers who have tried to expose such activities, as well as some of its perpetrators, repentant and otherwise.

“If you can ‘do tobacco,’ ” one of the perpetrators is quoted as saying, “you can do just about anything in public relations.” The reference is to the long campaign to obfuscate and undermine attempts to make the public aware of the dangers of cigarettes. As early as the 1950s, tobacco companies were aware — thanks to their own research — that their products were hazardous and habit forming, but they waged a prolonged and frequently successful campaign to suppress and blur the facts. Their tactics included sending dubiously credentialed experts out into the world to disguise dishonesty as reasonable doubt. “We just don’t know.” “The science is complicated.” “We need more research.”

The pro-tobacco strategy also called for smearing critics and invoking noble ideals like personal freedom against inconvenient facts like nicotine addiction. Thanks to thousands of pages of documents leaked to Stanton A. Glantz, a doctor and anti-tobacco crusader, the scale and the details of the deception are well known. The image of tobacco company executives taking an oath at a congressional hearing and proceeding to lie about what they knew is part of the collective memory. It also opened the door to lawsuits that led, in 1998, to the Tobacco Master Settlement Agreement.