New Hampshire Senate candidate Scott Brown has added his name to the list of Republicans who have dismissed the science behind climate change, despite previously stating that global warming is real.

During a GOP primary debate on Saturday, Brown was asked if he believed that "the theory of man-made climate change has been scientifically proven." The former Massachusetts senator, who hopes to challenge Sen. Jeanne Shaheen (D-N.H.), responded, "Uh, no."

Watch Brown's answer in the video above.

Brown's response, posted in a video Monday by the Democratic opposition research firm American Bridge, is at odds with the position he held while defending his seat in the 2012 Massachusetts Senate race. Back then, Brown said he did believe in climate change during a debate with Sen. Elizabeth Warren, the Democrat who eventually defeated him.

"Yes, yes I do," he said. "I absolutely believe that climate change is real and I believe there's a combination between man-made and natural."

When asked for comment Monday, Brown's campaign offered a response that more closely resembled his remarks in 2012.

"Scott Brown believes that the climate is changing by a combination of natural and manmade causes," Elizabeth Guyton, a spokeswoman for the campaign, told The Huffington Post. "The real issue is whether we are going to impose a new national energy tax on carbon. Scott Brown says no and Jeanne Shaheen says yes."

Though Brown is expected to win the primary on Sept. 9, he has adopted a more conservative stance on some issues to garner support from the right. He has recently pounded Shaheen's record on immigration, despite voting, while serving as a state senator in Massachusetts, for one of the same reforms he criticized her for backing.

Shaheen hit Brown for his comments on climate change, calling them "disappointing" and an effort to "appease the Big Oil special interests who fund his campaigns."

"Scott Brown is wrong," Shaheen said. "Climate change is very real and here in New Hampshire we are already seeing consequences. In order to protect the people and environment in New Hampshire, we’ve got to take action now to reduce pollution, reduce our reliance on foreign oil, and encourage clean energy investments that create jobs and lower energy costs."

NextGen Climate, a group backed by billionaire financier and climate activist Tom Steyer working to elect Democrats, said Brown "can’t make up his mind about what he believes" on climate change, immigration, health care or women's rights.

"New Hampshire voters see Scott Brown for what he is: someone more interested in his own political career than in the issues that matter to Granite State voters," said Pete Kavanaugh, the New Hampshire director for NextGen.