Democratic presidential candidate Sen. Bernie Sanders has been contending that all of his Republican opponents are climate change deniers.

The matter came up during the Feb. 4 Democratic debate in New Hampshire when Sanders talked about the way money and influence are leveraged to sway political positions.

"Let's talk about climate change," he said. "Do you think there's a reason why not one Republican has the guts to recognize that climate change is real, and that we need to transform our energy system? Do you think it has anything to do with the Koch brothers and ExxonMobil pouring huge amounts of money into the political system? That is what goes on in America."

Not one Republican recognizes that climate change is real? We decided to look at the positions of the GOP candidates who were in the race when Sanders made his statement.

The climate change question has several elements. Some candidates acknowledge that Earth's climate has changed in recent decades but insist that natural forces — not human activity — are responsible.

Some acknowledge that humans are playing a significant role in climate change but argue that there's little the United States can do by itself to reverse the global warming trend.

Others are pushing for specific proposals to address the issue.

So where do the Republican candidates stand?

Last August , NPR produced a chart showing how all the candidates viewed the various aspects of the climate question. In addition, we repeatedly emailed all the candidates' campaigns to see if that chart was still accurate and whether there were additional nuances that had surfaced in the intervening six months.

We heard from the Chris Christie, Carly Fiorina and John Kasich campaigns. Spokespeople for Jeb Bush, Ben Carson, Ted Cruz, Marco Rubio and Donald Trump didn't respond. We also checked their campaign websites for updated information on how they felt about the climate change question.

On the issue of whether climate has been changing significantly in recent decades, Bush, Christie, Fiorina, Kasich and Rubio say that it has.

Bush, Christie, Fiorina and Kasich say it's man made. Rubio says it's not.

Bush, Christie, Fiorina and Kasich have called for some degree of action to combat it.

For example, Christie's campaign sent us comments from an April town hall meeting in Exeter, N.H., where the candidate said, "I don’t believe we can do this on our own. We have to have cooperation with the rest of the world. If America changes its behavior and puts up with the economic ramifications that will happen from changing that behavior in the short term, the rest of the world has to engage in it with us."

Fiorina's campaign made a similar point, quoting the candidate on CNBC in September as saying that innovation would be the key: "That's how you're going to solve an intractable problem. It's always the way you solve an intractable problem. Not with regulation — with innovation." She made the same point during a Nov. 16 town hall meeting.

Bush in July said humans have contributed to climate change.

"The climate is changing; I don’t think anybody can argue it’s not," Bush told Bloomberg. "Human activity has contributed to it. I think we have a responsibility to adapt to what the possibilities are without destroying our economy, without hollowing out our industrial core."

So clearly, some GOP candidates are not denying the problem at all.

During the debate, Sanders referred to "Republicans," not the GOP presidential candidates. But two days earlier, at an event in Keene, N.H., he specifically said, "We do not have one Republican candidate for president acknowledging this (climate change) reality."

Even if he was referring to party supporters in general, a 2013 Pew poll found that 23 percent of people who lean Republican say there is solid evidence that Earth is warming and human activity is responsible. And a 2013 bipartisan poll found that 53 percent of Republican voters under age 35 picked either "crazy," "ignorant" or "out of touch" to describe someone who denies that climate change is happening.

Since those polls, the evidence for warming has only gotten stronger, with NASA and the National Oceanic and Atmospheric Administration saying that Earth’s 2015 surface temperatures were the warmest since modern record keeping began in 1880.

When we asked the Sanders campaign about the claim, policy director Warren Gunnels said, "The reality is that none of the Republicans have introduced a plan to solve climate change in a way that would transform our energy system. ... Go look at all of their websites. None of them have a plan."

Actually, some of the GOP candidates have posted plans that deal with energy issues, although they don't go in the direction that Sanders and scientists concerned about climate change might like.

Bush's website, for example, calls for the repeal or reform of the Carbon Rule , which is President Barack Obama's executive order requiring coal-fired power plants to dramatically reduce their carbon dioxide emissions by 2030.

Rubio wants to get rid of some anti-pollution rules and use the free market , not government regulation, to encourage "environmental conservation, fuel efficiency and energy diversity."

Others say little if anything on the issue. Christie's website seems to be silent on the matter. The " climate change " section of Kasich's website has a video saying that he cares about the environment. Carson's website simply says , "Earth is in a constantly cycle of warming or cooling,"

Some are downright hostile.

Cruz's website belittles climate change activists and calls for an end to the regulation of carbon dioxide emissions from power plants and all other sources and an end to the "regulation of greenhouse gas emissions from vehicles."

And Trump's issues page bluntly declares, "Climate change: It is a hoax," a claim worthy of a Pants on Fire .

Our ruling

Sanders said, "Not one Republican has the guts to recognize that climate change is real."

In fact, we found four GOP presidential candidates who have said it is real, it's man-made, and they have offered support for actions to deal with it.

Whether their proposed actions — or the actions proposed by Sanders — are the best way of tackling the problem is a matter for debate.

We rate Sanders' assertion as False.