Despite the release of a White House report detailing the devastating effects of global warming already underway, many Republicans are unwavering in their belief that humans play no role in climate change.

Sen. Marco Rubio (R-Fla.), for instance, told ABC News on Sunday that he does not "believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it." And last month, Sen. Rand Paul (R-Ky.) claimed the global warming debate had become "dumbed down," before making claims on historic temperatures that stand in stark contrast to the work of climate scientists.

Former vice president Al Gore says he sees the true motivation behind these remarks: currying favor with Republican megadonors like Charles and David Koch.

Speaking at the University of Chicago's Institute of Politics on Monday, Gore noted that Republicans like John McCain and Mitt Romney had acknowledged and taken steps toward solving the issue before it became politicized by the right.

"I don't think it's particularly complicated why they have all cowed into abandoning that position," Gore said. "They will face primary opponents financed by the Koch Brothers, and others who are part of their group, if they even breathe the slightest breath of sympathy for the truth about climate science. It's not really that complicated."

Gore continued: "And of course, Sen. Paul is from a coal state, but even if he were not, anyone who wants to set his or her aspirations on the Republican nomination for the presidency in 2016 already knows that they can't possibly cross the Koch brothers and the others that are part of that group, the large carbon polluters and ideological anti-statists who are really terrified that the government will do anything new, so as Grover Norquist said famously years ago, they want to shrink the government to where it can be drowned in a bathtub."