The Republican Party, long a stronghold of fervid global warming disbelief, has lately begun to temper its denial — but the emergence of true GOP leadership on climate change is still a long way off.

Exhibit A in the case for Republican evolution is the phrase "I'm not a scientist," recently deployed by party leaders including John Boehner, Mitch McConnell, and Marco Rubio to dodge questions about the veracity of climate science. That tepid deflection is a far cry from supporting the dramatic reductions in carbon dioxide pollution that scientists say are needed to avert warming's worst effects. Nonetheless, some observers suggest the line signals tentative progress.

"We all think that political orthodoxies are fixed but they're actually very fluid," former South Carolina Rep. Bob Inglis told VICE News. "Some people are basically backing away from climate atheism to climate agnosticism, and may be on their way back to climate faith."

Inglis would know. In 2010, he lost his Congressional seat to primary challenger Trey Gowdy, an avowed climate skeptic with Tea Party support. Inglis later attributed his defeat to having committed the "heresy" of acknowledging climate change. Just four years later, Inglis, now the executive director of the Energy and Enterprise Initiative, says the picture within his party is considerably different.

"We're coming out of the Dark Ages," he told VICE News.

Of course, rabid deniers still have a home within the GOP. Look no further than Oklahoma Senator James Inhofe, author of a 2012 book titled The Greatest Hoax: How the Global Warming Conspiracy Threatens Your Future. Much to environmentalists' horror, Inhofe may soon chair the Senate Environment and Public Works Committee.

Still, for all Inhofe's prominence, such radicalism is increasingly isolated within the GOP's most extreme factions. One recent study by researchers at the University of New Hampshire found that non-Tea Party Republicans are closer to Independents in their views on science and the environment than they are to Tea Party supporters.

If you squint, you can see signs of changing attitudes within the party's rank and file. Senator John Thune of North Dakota recently told Fox News that humans were responsible for at least some warming. And in the 2014 Showtime documentary "Years of Living Dangerously," New York Congressman Michael Grimm, whose Staten Island district was hammered by Hurricane Sandy, came to accept the reality of climate change. "The mass majority of respected scientists say that it's conclusive, the evidence is clear," Grimm admitted.

To Inglis's mind, changing Republican mantras reflect growing concern among the electorate. Some two-thirds of the country now believes in global warming, swayed by bouts of extreme weather and steadily rising temperatures.

"Experience is a harsh but effective teacher, and we're being taught," Inglis said.

Another possible factor is the political muscle of groups like Tom Steyer's NextGen Climate political action committee (PAC), which spent around $100 million to defeat candidates in the midterm elections who were opposed to action on climate change.

"Climate activists on the Democrat side are beginning to make it politically toxic to deny climate science entirely," RL Miller, founder of the PAC Climate Hawks Vote, told VICE News.

But while outright denial is in retreat, real action has so far proven a step too far. One of the few Republicans to have introduced climate legislation is Senator Susan Collins of Maine, whose lifetime 67 percent score from the League of Conservation Voters (LCV) makes her the most environmentally friendly GOPer in the Senate. In 2009, Collins cosponsored a cap and dividend bill, a proposal that would have reduced greenhouse gas emissions by auctioning off pollution permits and returning the proceeds to consumers and renewable energy programs.

This summer, Collins and Senator Chris Murphy, a Connecticut Democrat, introduced a proposal to cut short-lived climate pollutants like black carbon and hydrofluorocarbons.

"She has on a couple of occasions been the only Republican in the entire Senate to defend the EPA's ability to cut carbon under the Clean Air Act," Tiernan Sittenfeld, LCV's Senior Vice President of Government Affairs, told VICE News. Sittenfeld's group endorsed Collins in her race this fall.

Yet the fact that Collins passes for an environmental leader is an indication of the GOP's low bar. She's a longtime supporter of the Keystone XL pipeline and twice voted that no further environmental review should stand in the way of its construction. Her 2009 cap and dividend bill drew criticism for neither cutting emissions forcefully enough nor doing enough to jumpstart clean energy. On Miller's Climate Hawks scorecard, which compiles a variety of climate leadership metrics, Collins scores a dismal minus-13.

"Her score is equivalent to the 7th-worst House Democrat," Miller told VICE News.

At the moment, then, it seems the GOP is a party without a genuine climate champion. That the overwhelming majority of political donations from the oil and gas and coal industries go to Republicans surely contributes to that fact.

Nonetheless, Inglis expects a conservative leader to emerge soon, likely in support of a carbon tax. Though many environmental groups favor fighting global warming via cap and trade, which sets a hard limit on emissions, conservative politicians and economists generally prefer carbon taxes for their comparative simplicity and price certainty — and because a carbon tax could theoretically replace other levies, like payroll taxes or corporate taxes, that Republicans want to see slashed.

"If you combined a carbon tax with a total tax reform package, it might be more palatable to politicians," Aparna Mathur, an economist with the American Enterprise Institute, told VICE News.

At least for now, however, Republican leadership — or even cooperation — on climate legislation seems to be a pipe dream.

"I'm not going to say that action is imminent," Inglis told VICE News. "But at some point a conservative will step forward and say, 'you bet we have an answer to this problem: to make all fuels fully accountable for all their costs and to eliminate all the subsidies.' Surely that's bedrock conservatism."