President Obama used a commencement speech over the weekend to hit hard at skepticism about climate change, calling it comparable to the belief that the moon is made of cheese.

He made this comparison - a variation on his standard line comparing climate change skeptics to members of the Flat Earth Society - during a commencement address to graduates of the University of California at Irvine on Saturday.

Although the president claimed he was not there to deliver “a policy speech,” there was no mistaking the address’s heavy focus on policy. More than 2,000 words of the 4,000-word address concerned climate change.

The address's political tinge was likewise unmistakable. The White House has aggressively promoted the Environmental Protection Agency's new regulations to cut carbon emissions by 30 percent of their 2005 levels in 15 years.

In the speech, Obama drew a comparison between his climate efforts and the decade-long moon shot announced by President John F. Kennedy. According to Obama, while some critics opposed Kennedy's project as too risky or expensive, “I don't remember anybody saying that the moon wasn't there or that it was made of cheese.”

The comparison is inaccurate in at least one sense, as no prominent climate change skeptic claims the climate “is not there."

Critics will concede that Obama’s climate policy is similar to Kennedy’s space policy in at least one regard, however: Both were embarked upon for symbolic, rather than substantial, reasons.

Former Vice President Al Gore said as much during a commencement address at Princeton University in which he praised the EPA's coal regulations for reestablishing “the moral authority of the United States” even though they will have a negligible effect on global carbon emissions - a reduction in warming of 0.02 degrees Celsius by 2100, to be precise. No wonder Democrats are more interested in touting the rules' health impact than its climate impact.

Nevertheless, Obama sternly criticized his Republican opponents as “deniers” beholden to the radical right.

“... [W]hen they’re asked about climate change, they say, ‘Hey, look, I’m not a scientist,’ ” Obama said. “And I’ll translate that for you. What that really means is, ‘I know that manmade climate change really is happening, but if I admit it, I’ll be run out of town by a radical fringe that thinks climate science is a liberal plot, so I’m not going to admit it.’ ”

The line is an indirect shot at Republican Sen. Marco Rubio, the presidential hopeful who recently expressed doubt about how much humans contribute to climate change.

To the contrary, Obama cited that 97 percent of scientists have “put the debate” on climate change “to rest,” a common argument with a dubious pedigree. Secretary of State John Kerry said the same thing in a Boston College commencement address last month.

Obama received "three standing ovations" from the crowd of 30,000 during his address in Anaheim, Calif.