Ron Johnson LCV screenshot

A screenshot from the League of Conservation Voters' ad attacking Sen. Ron Johnson for his views on climate change.

Upon hearing news earlier this week that the League of Conservation Voters planned to release an ad criticizing his views on climate change, Sen. Ron Johnson claimed to know little about the organization.

“It doesn’t really concern me at all,” Johnson said in an interview with the Milwaukee Journal Sentinel published Tuesday.

But his tone changed Wednesday as he attempted to use the attack to raise money. In an email sent to supporters, Johnson described the LCV effort as an “environmental jihad.”

"The League of Conservation Voters is one of the many attack dog groups used by President Obama, the Democrats and the extreme left to weaken, defeat and silence conservatives," Johnson wrote in the email. "They use TV ads — filled with smears — because they work."

The LCV responded by issuing a release playing up the ad, which hasn't even begun to run on TV yet.

"Ron Johnson must be nervous about this ad because he’s responded with inflammatory rhetoric without even seeing it first," said Jeff Gohringer, National Press Secretary for the League of Conservation Voters.

The ad targeting Johnson, just released by the LCV on YouTube Wednesday morning, is relatively mild compared to those directed at three House Republicans. But it was produced with a style similar to those the organization ran in Wisconsin during the 2012 U.S. Senate race between Tammy Baldwin and Tommy Thompson. The LCV spent a lot of money late in that race to support Baldwin and blast Thompson.

The new ads are part of a strong effort on the part of LCV, President Barack Obama and Organizing for Action to confront members of Congress who have been climate change skeptics.

Johnson was quoted in 2010 calling theories linking human activity to climate change "crazy" and "lunacy."

"It's far more likely that it's just sunspot activity or just something in the geologic eons of time," he said in his Senate campaign against then-Sen. Russ Feingold.

The LCV ad attacking Johnson:

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Jason Joyce has lived in Madison for over 30 years, starting as a student at UW-Madison. After working at Isthmus for 15 years, where he oversaw digital operations and wrote a sports column, he took over as news editor at The Capital Times in 2013.