Climate scientist Michael Mann has been challenged time and time again for the research he's done to prove the existence and severity of global warming. And time and time again, he has been exonerated of any wrongdoing.

Yet the witch hunt against him continues--this time, by the American Tradition Institute, which has issued a subponea to cull information on work Mann did at the University of Virginia.

Like Mann's other attackers, ATI has strong ties to global warming denalism. Its executive director previously worked for the Heartland Institute, an Exxon-supported organization that sponsors an annual climate change denialism summit. And its senior litigator has written such books as Red Hot Lies: How Global Warming Alarmists Use Threats, Fraud and Deception to Keep You Misinformed.

A group with such obvious bias should not be allowed to drag a climate scientist through the mud, especially one who has already been exonerated multiple times. The University of Virginia has bravely fought back against unfounded efforts to bring down Mann before. Let's tell them to fight back again.