She published that finding in a short paper in the journal Science in 2004, and the reaction was electric. Advocates of climate action seized on it as proof of a level of scientific consensus that most of them had not fully perceived. Just as suddenly, Dr. Oreskes found herself under political attack.

Some of the voices criticizing her — scientists like Dr. Singer and groups like the George C. Marshall Institute in Washington — were barely known to her at the time, Dr. Oreskes said in an interview. Just who were they?

Image A scene from the documentary “Merchants of Doubt.” Credit... Sony Pictures Classics

She had connected by then with Dr. Conway, an official NASA historian who, working on his own time, helped her dig into some important archives. It did not take them long to document that this group, which included prominent Cold War scientists, had been attacking environmental research for decades, challenging the science of the ozone layer and acid rain, even the finding that breathing secondhand tobacco smoke was harmful. Trying to undermine climate science was simply the latest project.

Dr. Oreskes and Dr. Conway came to believe that the attacks were patterned on the strategy employed by the tobacco industry when evidence of health risks first emerged. Documents pried loose by lawyers showed that the industry had paid certain scientists to contrive dubious research, had intimidated reputable scientists, and had cherry-picked evidence to present a misleading picture.

The tobacco industry had used these tactics in defense of profits. But Dr. Oreskes and Dr. Conway wrote that the so-called merchants of doubt had adopted them for a deep ideological reason: contempt for government regulation. The insight gave climate scientists a new way of understanding the politics that had engulfed their field.

Following Dr. Oreskes’s cue, researchers have in recent years developed a cottage industry of counting scientific papers and polling scientists. The results typically show that about 97 percent of working climate scientists accept that global warming is happening, that humans are largely responsible, and that the situation poses long-term risks, though the severity of those risks is not entirely clear. That wave of evidence has prompted many national news organizations to stop portraying the field as split evenly between scientists who are convinced and unconvinced.