Leaked documents suggest that an organization known for attacking climate science is planning a new push to undermine the teaching of global warming in public schools, the latest indication that climate change is becoming a part of the nation’s culture wars.

The documents, from a nonprofit organization in Chicago called the Heartland Institute, outline plans to promote a curriculum that would cast doubt on the scientific finding that fossil fuel emissions endanger the long-term welfare of the planet. “Principals and teachers are heavily biased toward the alarmist perspective,” one document said.

While the documents offer a rare glimpse of the internal thinking motivating the campaign against climate science, defenders of science education were preparing for battle even before the leak. Efforts to undermine climate-science instruction are beginning to spread across the country, they said, and they fear a long fight similar to that over the teaching of evolution in public schools.

In a statement, the Heartland Institute acknowledged that some of its internal documents had been stolen. But it said its president had not had time to read the versions being circulated on the Internet on Tuesday and Wednesday and was therefore not in a position to say whether they had been altered.