Climate change, more than many other issues, lays bare a stark divide between the two parties: Democrats warn of the grave threat posed by global warming, stressing the need to reduce carbon emissions to prevent a catastrophe. Republicans, including most of the GOP's 2016 presidential candidates, either don't acknowledge climate change is happening, or they question whether it's caused by human activity.

As far as President Obama is concerned, the matter is settled: climate change is real, it's caused largely by humans, and anyone who says otherwise is living in a dangerous state of denial.

"On this issue - of all issues - there is such a thing as being too late," Mr. Obama said Monday during a speech at an Arctic climate summit in Alaska. "And that moment is almost upon us." Failure to act, he added, would "condemn our children to a planet beyond their capacity to repair."

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On Tuesday, the president will visit one of the state's shrinking glaciers and visit communities in Alaska's Arctic region that are threatened by rising sea levels.

Republicans, though, have long seen the president's environmental policies as an overreach of federal power and a danger to the economy. Nearly any Republican who succeeds him in the White House in 2016 can be expected to try to roll back some of the climate regulations he has instituted through executive order. Only some of the GOP candidates for president believe that climate change is real, and even fewer think humans are responsible. Hardly any say the U.S. should take steps to address it.

Here's a look at how the GOP candidates view global warming:

Jeb Bush: Count Bush among those who acknowledge climate change but won't weigh in on its cause. He said recently, "The climate is changing," but, he added, "I don't think the science is clear on what percentage is man-made and...what percentage is natural. It's convoluted. And for the people to say the science is decided on this is just really arrogant."

He believes the U.S. needs to adapt, and he wants countries that have increased carbon emissions to cut back. But, he said, "We're not one of them," thanks to the increase in U.S. natural gas production from fracking.

Ben Carson: Carson actually volunteered his position on climate change in Iowa earlier this year without being asked.

"I'll tell you what I think about climate change. The temperature's either going up or down at any point in time, so it really is not a big deal," he told a group of Republicans in Des Moines, Iowa in May, according to the Des Moines Register. "What is a big deal is that the environment is under our control. We do have a responsibility to pass it on to those behind us in at least as good a condition as we found it, hopefully an improved condition."

Chris Christie: "I think global warming is real. I don't think that's deniable. And I do think human activity contributes to it," Christie said at Republican dinner in Keene, New Hampshire in May. "The degree to which it contributes to it is what we need to have a discussion about."

But he doesn't believe that programs intended to limit carbon emissions like cap and trade are effective. He called for a "global solution," rather than unilateral cuts by the U.S.

Ted Cruz: At an event sponsored by billionaire industrialist brothers Charles and David Koch in August, Cruz denied the existence of climate change.

"If you look to the satellite data in the last 18 years there has been zero recorded warming. Now the global warming alarmists, that's a problem for their theories. Their computer models show massive warming the satellite says it ain't happening. We've discovered that NOAA, the federal government agencies are cooking the books," he said.

In an interview with the Texas Tribune in March, he said, "the global warming alarmists are the equivalent of flat-Earthers," recalling that Galileo was once branded a "denier" for saying the Earth was round when contemporary scientific wisdom held that it was flat.

Carly Fiorina: "There's a lot of consensus among scientists that climate change is real," Fiorina said at an event in New Hampshire earlier this year. But she also disputes that the U.S. can do anything about it.

"[E]very one of the scientists that tell us that climate change is real and being caused by man-made activity also tells us that a single nation acting alone can make no difference at all," she told Yahoo News in an interview earlier this summer.

Jim Gilmore: Speaking to WMUR in June, Gilmore said that if he were president he "would look at this group of scientists and say, 'Do they have an ax to grind?' and make sure that they're objective." Pressed on whether he is convinced climate change is caused by man, he said, "I would like it to be shown that it's man-made, and if it is, then at that point I think that we have to address how we deal with it."

Lindsey Graham: Graham has called out members of his party who dismiss climate change.

"When it comes to climate change being real, people of my party are all over the board. There was several resolutions," Graham said after a recent Council on Foreign Relations event. "I said that it's real, that man has contributed to it in a substantial way."

Mike Huckabee: On NBC's "Meet the Press" in June, Huckabee said, "Whether it's man-made or not, I know that when I was in college I was being taught that if we didn't act very quickly, that we were going to entering a global freezing. And, you know, go back and look at the covers of Time and Newsweek from the early '70s. And we were told that if we didn't do something by 1980, we'd be popsicles. Now we're told that we're all burning up. Science is not as settled on that as it is on some things," he said.

Bobby Jindal: "I'm sure human activity is having an impact on the climate," Jindal told reporters at a Christian Science Monitor breakfast in September 2014. "But I would leave it to the scientists to decide how much, what that means, what are the consequences." He argues that the Obama administration policies have hurt the environment and the economy and has said Louisiana won't comply with the administration's Clean Power Plan, which aims to curb carbon emissions from power plants.

John Kasich:The Ohio governor has in the past said he's concerned about climate change, telling a conference in 2012, "I happen to believe there is a problem with climate change. I don't want to overreact to it, I can't measure it all, but I respect the creation that the Lord has given us and I want to make sure we protect it."

He's also taken steps to this end, telling NBC's Meet the Press in August that in Ohio, "[W]e preciously take care of Lake Erie. We've reduced emissions by 30 percent over the last 10 years. We believe in alternative energy." But, he continued, "We don't want to destroy people's jobs based on some theory that's not proven." His campaign later modified that statement, reiterating that he believes that climate change is real and that something needs to be done.

Still, most of Ohio's electricity - about two thirds - is generated by coal-burning power plants. Kasich has been a proponent of clean coal, and he said at the 2012 conference, "we are going to dig it, we are going to clean it, and we are going to burn it in Ohio, and we are not going to apologize for it."

George Pataki:For years, since the 1990s, George Pataki believed that climate change is scientifically proven. Unlike most of his GOP opponents, he has supported reductions in greenhouse gases since 1998. He even co-chaired an independent commission on climate change that released a report recommending a market-friendly cap-and-trade system that aimed to cut emissions by 60-80 percent from 1990 levels by 2050. He has not, however, expressed a position on climate change since he announced his presidential candidacy, and there appears not to be any mention of climate change on his campaign website.

Rand Paul:Paul has a mixed voting record on climate change. He voted for an amendment in January that said that climate change is real and humans contribute to it, but then in March cast a vote against a bill that would cut carbon emissions.

This is a sensitive issue for Paul's home state of Kentucky, which keeps the lights on with electricity almost exclusively powered by coal and which is also the third-largest coal producing state in the U.S.

Paul doesn't talk much about the global warming. When he spoke with former top Obama adviser David Axelrod at the University of Chicago Institute of Politics a year and a half ago, he said, that the "earth goes through periods of time when the climate changes, but he's 'not sure anybody exactly knows why,'" according to The Hill.

Rick Perry: In his 2010 book, "Fed Up!" Perry called global warming a "contrived, phony mess" and he has accused scientists of manipulating data to win research funding. At a June 2014 Christian Science Monitor breakfast, he suggested that there's no action that should be taken to curb global warming because "I don't believe that we have the settled science, by any sense of the imagination."

The Environmental Protection Agency is also the department he famously forgot he would cut during a 2011 presidential debate.

Marco Rubio: "I believe climate is changing because there's never been a moment where the climate is not changing," Rubio said in CBS' "Face the Nation" in April. In an interview with ABC's "This Week" in May 2014, he said, "Our climate is always changing. And what they have chosen to do is take a handful of decades of research and say that this is now evidence of a longer-term trend that's directly and almost solely attributable to manmade activity. I do not agree with that."

Rick Santorum: What rankles Santorum about the debate over climate change is the idea that the science is settled. In June, on "Fox News Sunday," he said,

"Any time you hear a scientist say the science is settled, that's political science, not real science, because no scientists in their right mind would say ever the science is settled," he said.

As far as he's concerned, the idea that man is responsible for the warming and cooling of the earth is "just patently absurd," he told Rush Limbaugh in 2011, and "just an excuse for more government control of your life."

Donald Trump: Although Trump has yet to take a formal position, it's probably fair to say he's not a believer in global warming. His commentary on the topic over Twitter goes back a few years, and that largely denies climate change, especially when the weather is cold.

This very expensive GLOBAL WARMING bullshit has got to stop. Our planet is freezing, record low temps,and our GW scientists are stuck in ice — Donald J. Trump (@realDonaldTrump) January 2, 2014

He goes further than most climate change deniers, saying, in fact, that he thinks it's a hoax.

Ice storm rolls from Texas to Tennessee - I'm in Los Angeles and it's freezing. Global warming is a total, and very expensive, hoax! — Donald J. Trump (@realDonaldTrump) December 6, 2013

And Trump thinks he knows exactly who's behind that hoax.

The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive. — Donald J. Trump (@realDonaldTrump) November 6, 2012

Scott Walker: Walker has dodged questions about whether climate change is caused by man, but his campaign spokeswoman AshLee Strong said, he "believes facts have shown that there has not been any measurable warming in the last 15 or 20 years." He has also given a speech at the Heartland Institute, a group that challenges climate change.

Walker has signaled that he plans to block Wisconsin from implementing to administration's Clean Power Plan, which aims to curb carbon emissions from power plants.