In an address on energy Thursday, Donald Trump laid out a new breed of climate skepticism taking hold among conservatives.

He pledged to deregulate the American fossil-fuel industry, he decried the cost of renewable energy, and he promised American energy independence to an enthusiastic crowd of oil executives. But he steered clear of climate change entirely.

It is not that Republicans have changed their position on climate change. Some 56 percent of Republicans in the 114th Congress denied or questioned climate science, according to the liberal website ThinkProgress.

But public opinion has begun to shift around them – even among Republicans – pushing them toward an increasingly delicate balancing act.

Not surprisingly, 90 percent of Democrats believe global warming is happening, according to a national survey conducted in March. But 56 percent Republicans do, as well, including 47 percent of conservative Republicans. Those figures have increased significantly in recent years, especially among conservative Republicans.

To be sure, climate remains a partisan issue – and has become, if anything, more polarized. But the expression of that partisanship, particularly on the Republican side, is evolving.

Like Mr. Trump, mainstream Republicans are now either not talking about climate change or saying that addressing it would be an economic risk they’re not willing to take.

“That’s sort of the Republican framing,” says Geoffrey Skelley, a spokesman for the University of Virginia Center for Politics. “Some may believe there’s evidence of global warming, but does that mean we should spend government money to address this, or pay more in taxes? Probably not.”

While Trump had, until Thursday, remained vague on his energy and climate policies, his Republican rivals voiced these sentiments earlier in the campaign. Ted Cruz called climate change a “pseudoscientific theory” in February, and Marco Rubio said in January that he does not believe “that we have to destroy our economy in order to protect our environment.”

Indeed, even as 7 in 10 Americans say there’s solid evidence of global warming, partisan lines among conservatives have hardened, says Barry Rabe, director of the Center for Local, State, and Urban Policy at the University of Michigan, who conducted a poll last October.

“There has really been a partisan shift on an issue that eight to 10 years ago was a little less polarized,” he says.

In 2008, both Barack Obama and John McCain supported reducing greenhouse gas emissions and investing in renewable energy. In the 2012 election, amid a struggling domestic economy, climate change was barely mentioned.

Again this election, climate change has been mostly ignored, with Hillary Clinton and Bernie Sanders resorting to bringing it up themselves in debates. Before Thursday, Republicans who did address the issue had been a bit clearer than Trump.

But Trump took a position similar to theirs Thursday.

“We’re going to be energy independent, we’re going to have all sorts of energy, we’re going to have everything you can think of,” he said on Thursday.

He specifically included wind and solar power in his speech, but questioned their economic viability.

“The problem with solar is it’s very expensive,” he said. “Wind is a problem,” he added. “It’s very, very expensive, and it doesn’t work without subsidy.”

“But despite that, I’m into all types of energy.”

Climate change is unlikely to be high-profile issue in the general election. As a global issue with effects still mostly confined to the future, it has been subordinate to more immediate concerns such as the economy and national security.

But Trump appears to be using the issue to convince Republicans of his conservative bona fides, adopting positions that could appeal to the variety of conservative opinions that now exist.

“You have a significant subset of electorate that does believe that climate change is emerging and playing out, but then argues that, for whatever reason, there’s nothing we can do,” says Professor Rabe.

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Trump hasn’t chosen to question climate science as openly as Senator Cruz, or dismiss it as economically destructive, like Senator Rubio. Instead, he appears to be trying to unite them, becoming the spokesperson for a new hybrid climate skepticism.

“We’re still not sure exactly where he stands,” says Rabe. “I think he’s trying to appeal to all of those groups.”