calling for mandatory carbon caps.

"I didn't go out and crow as Gov. Romney did when he was governor of Massachusetts about imposing the first CO2 cap, the first CO2 cap in the country," Santorum continued. "Both of them say, 'Yeah, we have to do something about man-made global warming.'"

"We don't need somebody who changes when the climate changes," the candidate remarked. "We need somebody who looks at science with a clear head and a level eye."

In their quest to woo GOP voters, both Gingrich and Romney have tempered their support for climate change legislation in the past year.

Late last year, Gingrich admitted that appearing in the ad with Pelosi was "the dumbest single thing I’ve done in the last few years."

In October, Romney told voters in Pittsburgh that "the idea of spending trillions and trillions of dollars to try to reduce CO2 emissions is not the right course for us."

Santorum, however, has said he never believed the global warming "hoax."

"I've never supported even the hoax of global warming," he insisted last month, adding that Gingrich and Romney "bought into the science of man-made global warming, and they bought into the remedy, both of which are bogus."