Some voters may think the Republican presidential candidates all agree with each other on climate change, but they'd be wrong. It's more accurate to say they hold varying degrees of skepticism about it.
The Republican candidates who will be debating on CNBC on Oct. 28 have mixed — and sometimes unclear — views on global climate change. To understand each of their positions, it's helpful to look at their answers to four questions: 1) Is the planet's climate changing? 2) Are humans behind that change? 3) Is that something to worry about? and 4) What can or should be done about it?
A look at previous statements by the presidential hopefuls yields clues to where they stand on those questions, even if it doesn't always reveal clear positions on each.
Former HP CEO Carly Fiorina seems to accept the scientific evidence for climate change, but she appeared to disagree with "the scientists" whose conclusions call for "a three-decade global effort costing trillions of dollars." Instead, she said that "the only answer is innovation."
Ohio Gov. John Kasich said in a recent interview on "Meet the Press" that he believes in climate change but opposes a fix that hurts the economy. "Man absolutely affects the environment," he said, adding that "of course we have to be sensitive to it, but we don't want to destroy people's jobs based on some theory that's not proven."
Then there's U.S. Sen. Ted Cruz of Texas, who seems to feel that there is no scientific consensus on climate change. He argued with Sierra Club President Aaron Mair during a Senate hearing about climate change and global warming, questioning whether the overwhelming majority of scientists — Mair put it at 97 percent — was valid.
Sen. Marco Rubio, Republican of Florida, frames the issue in purely political terms. He takes issue with the conclusion that "the left wants us to make," as he said at the last Republican debate.
"Here's what we should be skeptical of: We should be skeptical of decisions the left wants us to make," Rubio said. "They will not do a thing to lower the rise of the sea, they will not do a thing for the drought here in California, but what they will do is make America a more expensive place to create jobs."
New Jersey Gov. Chris Christie, in general, tends to accept that evidence of climate change exists and that humans contribute to it. But he holds reservations about what action, if any, the United States should take.
In May, for example, Christie said, "I think global warming is real. I don't think that's deniable. And I do think human activity contributes to it." He implied, however, that the United States can't fix the problem by itself.
Like Cruz, political outsider Ben Carson makes the claim that there is no scientific consensus on the existence of climate change. He said in November of last year. "There's always going to be either cooling or warming going on. As far as I'm concerned, that's irrelevant. What is relevant is that we have an obligation and a responsibility to protect our environment."
Carson's career in neurosurgery has led to interest in views on various issues in science. He told the San Francisco Chronicle, "I know there are a lot of people who say 'overwhelming science,' but then when you ask them to show the overwhelming science, they never can show it. There is no overwhelming science that the things that are going on are man-caused and not naturally caused." California Gov. Jerry Brown responded to Carson's statement by sending him a copy of a 2014 report from the United Nations on climate change.
Carson later mocked the press coverage of the incident, and said, "I don't need any education about the environment," according to The Des Moines Register.
Donald Trump is less equivocal than most. He seems to favor regulating air pollution but has openly said that he rejects the idea that the planet is warming: "I believe in clean air. Immaculate air," Trump said. "But I don't believe in climate change."
In his typical style, Trump has also tweeted that he thinks global warming is a "very expensive hoax," and that it's a conspiracy designed to make U.S. manufacturing less competitive with China.
Coverage of Sen. Rand Paul's views suggests he is wary of the evidence for climate change, and warier still of attempts to regulate industry based on that evidence. Notably, however, Paul has spoken of the need to control pollution.
Former New York State Gov. George Pataki is a bit more open to addressing global warming than the other GOP candidates. Pataki co-chaired a task force for the Council on Foreign Relations on "Confronting Climate Change" with former Iowa Gov. and current Secretary of Agriculture Tom Vilsack. The task force concluded that climate change is real, and humans are contributing to it. Among other things, it recommends a cap-and-trade system for carbon emissions "designed in a way that avoids shocks to the economy and that does not impose undue burden on any particular part of society."
The CFR task force recommended that the United States should secure commitments from other major polluting nations before passing restrictive legislation at home.
Former Sen. Rick Santorum from Pennsylvania has said in the past that he's bothered by "the idea that the science is settled." Recently, he has suggested that the United States can cut global carbon emissions by moving manufacturing jobs out of China — the world's largest carbon polluter — and back to the United States.
Louisiana Gov. Bobby Jindal acknowledges the existence of climate change but has expressed reservations, common among Republicans, about making commitments to curbing greenhouse gases that are not matched by emerging economies, according to his campaign website.
Former Arkansas Gov. Mike Huckabee has said that "stewardship of the environment" is humankind's responsibility, but he told "Meet the Press" in June that the "science is not as settled on [climate change] as it is on some things."
Sen. Lindsey Graham of South Carolina appears to agree with climate science and encourages the GOP to start proposing solutions. On "Meet the Press," he said, "I believe man-made emissions are hurting the environment. The best way for a Republican to fight on this is the solution, not argue with the science. I think the science is sound. And at the end of the day, ask my competitors what is the environmental policy of the Republican Party?"
Former Florida Gov. Jeb Bush has expressed skepticism about climate science and frustration that he and his fellow skeptics are the targets of their opponents' "intellectual arrogance." Speaking at an event in New Hampshire in July, he said: "Clearly there is some influence. We are living on a planet and we kind of dominate the planet. Man-made climate change is part of this. But there is also natural changes and so why do we have to have a debate where people that may have some doubts about this are considered Neanderthals?"
"I don't think the science is clear of what percentage is man-made and what percentage is natural. It's convoluted," he said, again according to The Hill. "For the people to say the science is decided on this is really arrogant, to be honest with you," he said. "It's this intellectual arrogance that now you can't have a conversation about it, even."
The candidates may not feel a need to express any view on climate change, because it doesn't matter to most Republican voters, according to a study that came out in January.
A Pew Research survey showed that just 15 percent of Republicans think addressing global warming is a top priority, compared with 54 percent of Democrats and 39 percent of independents. Pew Research numbers show a wide ideological divide over climate change, with conservatives generally skeptical of either the scientific evidence, or skeptical of regulation.
Jon Krosnick, a researcher at Stanford, has been studying public opinion on climate change since the 1990s. He told CNBC that his surveys have consistently shown that Americans are overwhelmingly accepting of climate change science, and are even willing to accept the costs of some regulation, if those regulations stand to mitigate the effects of warming.
"When we started back in the mid-90s I was really surprised to see huge majorities of Americans accepting positions that natural scientists and their research would suggest," Krosnick told CNBC. "As a political scientist, I am used to watching public opinion on issues and seeing the kind of 50-50ish splits that you are used to."
Krosnick said that that majority has not changed much, despite the occurrence of events he thought might have moved opinion in either direction, such as major hurricanes, or the criticism of either the validity of the science or of the economic effects of regulation.
It's worth noting that Krosnick's surveys show greater agreement among Americans than do surveys by Pew Research or Gallup, but Krosnick attributes that to the differences in how each survey asks questions.
Krosnick said that this consensus among the general public is obscured by what he calls the "issue public" — the relatively small portion of the population that feels very strongly about the issue either way and engages in activism, fundraising or other activities.