During his 2018 run for governor, Ron DeSantis not only pledged to protect Florida’s Everglades and waterways, he also acknowledged that humans played a role in exacerbating the climate change that threatened them.

“I think that humans contribute to what goes on around us,” Mr. DeSantis told the editorial board of The Florida Times-Union, a Jacksonville newspaper, according to a recording obtained by The New York Times.

“The resiliency and some of the sea-level rise, we have to deal with that,” he added, although he pointedly said he was “not Al Gore,” referring to the former Democratic vice president who reinvented himself as a climate change activist.

Now running for president five years later, the Florida governor no longer repeats his previous view that humans affect the climate, even as scientists say that the hurricanes battering his state are being intensified by man-made global warming. Those storms include Hurricane Idalia, which killed three people this month, and last year’s catastrophic Hurricane Ian, which killed 150 Floridians.

On the debate stage last month, Mr. DeSantis declined to raise his hand when a moderator asked the Republican candidates if they thought human behavior was causing climate change. His campaign and the governor’s office did not respond to requests for comment about his views.

Instead, Mr. DeSantis has seemingly reverted to an old Republican Party line that climate change is happening naturally, without being accelerated by human behavior like the burning of fossil fuels. Decades of scientific research contradict that position. And it is also out of step with what polling shows many Americans believe.

On the 2024 campaign trail, Mr. DeSantis has promised to ramp up domestic oil and gas production and fight against mandates on the introduction of electric vehicles — the kinds of steps that could worsen the sea-level rise that is flooding coastal cities in Florida and around the world. Mr. DeSantis says he is simply being realistic about the country’s economic and national security needs.

Asked to describe his climate plan in an interview on Fox Business last month, Mr. DeSantis said: “It’s going to be to rip up Joe Biden’s Green New Deal.” (Mr. Biden’s policies do not actually go as far as the so-called Green New Deal, a wide-ranging climate proposal from progressives in Congress.)

As the governor of a traditionally purple state on the front lines of climate change, Mr. DeSantis has been confronted with clear evidence that the environment is changing. But he has largely tried to treat global warming’s symptoms — funding local projects to address flooding and storm surge, for instance — rather than take steps to address what climate scientists say are the human-made underlying causes, such as by cutting back on the use of fossil fuels.

Mr. DeSantis has also cast himself as a conservationist in the Teddy Roosevelt mold, embracing a brand of environmentally friendly outdoor-ism long pushed by Republicans in Florida — where swimming, boating, fishing and hunting are popular and profitable — as well as in Western states. That philosophy led him, especially early in his tenure, to attack the state’s powerful sugar industry, which contributes to water and air pollution.

“In terms of environment, what I care about is the environment people enjoy,” Mr. DeSantis said in a radio interview this year. “I want to conserve Florida, leave it to God better than we found it.”

More recently, however, he rejected roughly $350 million in federal funding for energy efficiency initiatives. And in a nod to the nation’s culture wars, he gave tax breaks to people who bought gas stoves.

Florida environmentalists describe Mr. DeSantis’s mixed record as one that gave them optimism early on in his administration but has since left them feeling somewhat disappointed. Mr. DeSantis’s narrow but intense focus on Everglades restoration felt “very hopeful out of the gate,” said Eve Samples, executive director of Friends of the Everglades, a nonprofit advocacy group. “But the follow-through has been problematic and lacking.”

The governor created a toxic algae task force, she noted, but the group’s scientific recommendations had mostly been ignored. And projects to lessen climate change’s impact have not taken a comprehensive approach, she said.

“‘Resilience’ has become a euphemism for installing diesel-powered pumps at the shoreline to keep developed areas dry,” she said. “That approach is not going to serve Florida in the long term.”

At the first Republican debate last month, Mr. DeSantis reacted angrily when a Fox News moderator asked the candidates onstage to raise their hands if they thought human behavior was causing climate change.

“We’re not school children,” Mr. DeSantis said. “Let’s have the debate.”

But he did not answer the question, instead jumping into an attack on the “corporate media” and President Biden’s response to the wildfires in Maui. One of the moderators, Bret Baier, followed up: “Is that a yes? Is that a hand raise?”

Mr. DeSantis stared at the camera without speaking, allowing another candidate, Vivek Ramaswamy, to jump in. “I think it was a hand raise for him,” Mr. Ramaswamy said.

“No, no, no,” Mr. DeSantis replied. “I didn’t raise a hand.”

In contrast, nearly half of Americans believe that climate change is “mostly” caused by human activity, according to a poll by Ipsos released in May. Roughly a quarter said climate change was mostly caused by natural patterns. (Smaller percentages said that it was “not really happening” or that they did not know its cause.)

There is a clear partisan divide, however. Among Republicans, only 22 percent of people said climate change was mostly caused by human activity, compared with 75 percent of Democrats.

Mr. Biden seemed to weigh in last weekend during a visit to Florida after Idalia. “Nobody intelligent can deny the impact of the climate crisis anymore,” he said.

In an interview with Fox News that aired on Wednesday, Mr. DeSantis shot back. “The idea that we’ve not had powerful storms until recently, that’s just not factually true,” he said, adding that Democrats were trying to “politicize the weather.”

But scientists say that climate change is making hurricanes more powerful, though not more frequent, as warmer ocean waters strengthen and sustain those storms. The proportion of the most severe storms — Categories 4 and 5 — has increased since 1980, when satellite imagery began reliably tracking hurricanes.

When Mr. DeSantis ran for governor in 2018, relations between Florida Republicans and environmentalists had hit a low point. Under Rick Scott, the Republican governor at the time, state officials said they had been warned against even using the phrases “climate change” or “global warming.” (Mr. Scott said there was no policy banning those terms.) Toxic algae blooms were choking many of Florida’s beautiful bays, canals and rivers.

Mr. DeSantis made improving water quality one of his top campaign issues. Other Republicans, including Representatives Vern Buchanan and Brian J. Mast, whose districts were being harmed by the harmful algae, also campaigned on water quality. The G.O.P. had used the issue to attract independent and crossover Democratic voters at a time when Florida was still a true political battleground.

The message, said Jacob Perry, who ran Mr. Mast’s 2016 campaign, was intended to be: “This isn’t your father’s Republican Party.”

Mr. DeSantis appeared to embrace a similar approach.

“The environment was a big reason he won that race,” said Stephen Lawson, Mr. DeSantis’s 2018 communications director, who added that it was one of the top reasons, if not the leading one, that he was able to appeal to swing voters.

As a candidate in the 2018 Republican primary for governor, he criticized his party’s close ties to the sugar industry, which had supported his opponent. He said he backed “resiliency” but did not want to be a climate “alarmist.” Once elected, he seemed to relish signing off on billions of dollars to restore state waterways and the Everglades.

During his first year in office, his environmental policies gave Mr. DeSantis the veneer of a center-right governor. He appointed the state’s first chief science officer and hired a “chief resilience officer,” whose job description included a mandate to prepare the state for the “impacts of climate change, especially sea-level rise.”

He signed the first bill passed by the Republican-held Legislature that directly addressed climate change, after what a Republican state senator acknowledged had been a “lost decade” of inaction. This year, Mr. DeSantis vetoed legislation that would have allowed electric utilities to impose fees on property owners who install solar panels.

But Mr. DeSantis has made other decisions that let down conservationists during his governorship. He limited local governments from making stringent environmental regulations. He backed the building of new rural highways known as the “roads to nowhere.”

On the campaign trail, Mr. DeSantis does not often talk about what his environmental policies would be as president. But he has suggested in broad terms that reducing fossil fuel emissions would be a good thing, while saying that the free market is a more appropriate tool for doing so than government intervention.

At a barbecue in New Hampshire last month, he laid out some of his positions on climate change in response to a voter’s question, taking the opportunity to criticize Democrats for pushing renewable energy in the United States while China and India continue to rely on oil and gas.

“They’ve taken this position that you can never burn a fossil fuel,” Mr. DeSantis said. “That is not going to work for our economy.”

But in a reflection of how divisive climate change — and science more generally — has become for Republicans, the governor almost did not get to answer the question. The man who asked it was bombarded with boos and catcalls from other members of the audience until the event’s host, former Senator Scott Brown of Massachusetts, asked for civility.

“Science!” one woman in the crowd jeered sarcastically. “Facts!”