Leading climate scientists have told the controversial Heartland Institute to take a long hard look at itself, after a damning set of documents purported to be from the think tank were leaked online.

The free-market Heartland Institute has mounted “a systematic attack on mainstream climate science”, in the words of Nature’s Jeff Tollefson, who profiled the organization in a Nature News feature last year.

Now several documents — the veracity of which is disputed by the institute — surfaced earlier this week on the DeSmogBlog, allegedly showing its budget, fund-raising plan and strategy outline.

Today, an open letter from seven researchers whose e-mails featured in the stolen ‘climate-gate’ documents that were posted online in 2009 and 2011 says that “although we can agree that stealing documents and posting them online is not an acceptable practice, we would be remiss if we did not point out that the Heartland Institute has had no qualms about utilizing and distorting e-mails stolen from scientists”.

Researchers including Michael Mann of Pennsylvania State University in University Park, and Gavin Schmidt of NASA, say that Heartland was one of the groups that attacked scientists on the basis of the stolen e-mails, which were purloined from the University of East Anglia’s climate-research unit.

“We hope the Heartland Institute will begin to play a more constructive role in the policy debate. Refraining from misleading attacks on climate science and climate researchers would be a welcome first step toward having an honest, fact-based debate about the policy responses to climate change,” they say in a letter published in The Guardian newspaper.

The Heartland Institute says that the documents released this week amount to ‘an online mugging’, and that one is a fake. Others were “stolen”, it says, by someone pretending to be a Heartland board member who persuaded a staff member to send them to a new e-mail address.

It has asked “all activists, bloggers, and other journalists” to remove the documents and any quotations from them from the internet and other publications and said it plans to “pursue charges and collect payment for damages” from people who commented on the documents.

The document that Heartland says is fake states that the group is considering developing material for use in classrooms that would provide a “curriculum that shows that the topic of climate change is controversial and uncertain — two key points that are effective at dissuading teachers from teaching science”. This document also notes that a “key Anonymous Donor” provided US$1.7 million in 2010 and $979,000 in 2011 for “climate work” and that the Charles G. Koch Foundation — also a controversial body — gave $200,000 in 2011.