The inner workings of a libertarian thinktank working to discredit the established science on climate change have been exposed by a leak of confidential documents detailing its strategy and fundraising networks.

DeSmogBlog, which broke the story, said it had received the confidential documents from an "insider" at the Heartland Institute, which is based in Chicago. The blog monitors industry efforts to discredit climate science.

The scheme includes spending $100,000 for spreading the message in K-12 schools that "the topic of climate change is controversial and uncertain - two key points that are effective at dissuading teachers from teaching science", said the documents.

It was not possible to immediately verify the authenticity of the documents, although Heartland issued a statement on Wednesday claiming at least one document was fake, and that it was the victim of theft and forgery. However, Anthony Watts, a weather-caster who runs one of the most prominent anti-science blogs, Watts Up With That?, acknowledged Heartland was helping him with $90,000 for a new project. He added: "They do not regularly fund me nor (sic) my WUWT website, I take no salary from them of any kind."

Watts, in an email, did not mention the entire cost of his temperature station initiative but said: "Heartland simply helped me find a donor for funding a special project."