Rep. Cory Gardner, the Republican challenger to Sen. Mark Udall of Colorado, declined in a debate on Tuesday to state definitively whether humans contribute to climate change. His hands-in-the-air response marked the third position Gardner has held on climate change this week.

Gardner, who’s running neck-and-neck with Udall in the polls, began the week a firm climate denier. During his 2010 congressional campaign, Gardner asserted that humans are not “causing [climate] change to the extent that’s been in the news,” and he voted against an amendment this year affirming that climate change is occurring.

Advertisement:

The congressman naturally made headlines, then, after he conceded in a Monday debate that climate change is happening and that “pollution contributes” to it. His admission seemed like political posturing aimed at attracting more moderate voters to his campaign, for even as Gardner acknowledged humans’ role in climate change, he attacked Udall over his support for policies to actually address the problem. But Gardner’s statement represented a change nonetheless.

But just a day later, Gardner adopted the GOP’s “I’m not a scientist” tack on the issue. As the Huffington Post’s Elise Foley reports, Gardner refused to give a yes-or-no answer in Tuesday’s debate after moderator Cuck Plunkett of the Denver Post asked if humans contribute to climate change.

"I believe that the climate is changing, I disagree to the extent that [humans’ role] been in the news," Gardner replied.

Advertisement:

Pressed to give a yes-or-no answer, Gardner challenged Plunkett.

“This is a serious debate,” the congressman said, “we're both running for the United States Senate, and this is a serious issue. And I don't think we should shortchange serious issues with yes or no answers without being able to talk about them now."

Ninety seven percent of climate scientists have answered Plunkett’s question with a simple “yes.”

Advertisement:

Watch Gardner's stumbling response here: