From the remarks by President Obama at University of California-Irvine Commencement Ceremony, Angel Stadium Anaheim, California, June 14, 2014, 12:10 P.M. PDT.
Part of what’s unique about climate change, though, is the nature of some of the opposition to action. It’s pretty rare that you’ll encounter somebody who says the problem you’re trying to solve simply doesn’t exist. When President Kennedy set us on a course for the moon, there were a number of people who made a serious case that it wouldn’t be worth it; it was going to be too expensive, it was going to be too hard, it would take too long. But nobody ignored the science. I don’t remember anybody saying that the moon wasn’t there or that it was made of cheese.
Official transcript of the remarks: The White House Office of the Press Secretary