The Republican presidential contenders regard global warming as a hoax or, at best, underplay its importance. The most vocal denier is Rick Perry, the Texas governor and longtime friend of the oil industry, who insists that climate change is an unproven theory created by “a substantial number of scientists who have manipulated data so that they will have dollars rolling into their projects.”

Never mind that nearly all the world’s scientists regard global warming as a serious threat to the planet, with human activities like the burning of fossil fuels a major cause. Never mind that multiple investigations have found no evidence of scientific manipulation. Never mind that America needs a national policy. Mr. Perry has a big soapbox, and what he says, however fallacious, reaches a bigger audience than any scientist can command.

With one exception — make that one-and-one-half — the rest of the Republican presidential field also rejects the scientific consensus. The exception is Jon Huntsman Jr., a former ambassador to China and former governor of Utah, who recently wrote on Twitter: “I believe in evolution and trust scientists on global warming. Call me crazy.” The one-half exception is Mitt Romney, who accepted the science when he was governor of Massachusetts and argued for reducing emissions. Lately, he’s retreated into mush: “Do I think the world’s getting hotter? Yeah, I don’t know that, but I think that it is.” As for the human contribution: “It could be a little. It could be a lot.”

The others flatly repudiate the science. Ron Paul of Texas calls global warming “the greatest hoax I think that has been around for many, many years.” Michele Bachmann of Minnesota once said that carbon dioxide was nothing to fear because it is a “natural byproduct of nature” and has complained of “manufactured science.” Rick Santorum, a former senator from Pennsylvania, has called climate change “a beautifully concocted scheme” that is “just an excuse for more government control of your life.”