By LIVIA ALBECK-RIPKA. Illustrations by LOUISA BERTMAN. FEB. 21, 2018

The Rev. Richard Cizik used to believe climate change was a myth. The science had to be rigged, he thought; those who believed in it were just tree-huggers. But in 2002, a friend convinced Mr. Cizik to go to a conference about climate change, and there, he said, “the scales came off my eyes.”

Nearly 70 percent of Americans now say that climate change is caused mainly by human activity, the highest percentage since Gallup began tracking it two decades ago. The number of Americans who say they worry “a great deal” about climate change has risen by about 20 percentage points.

But people don’t change their minds easily about controversial issues. So what is behind this trend?

Anthony Leiserowitz, the director of the Yale Program on Climate Change Communication, said Americans’ opinions about global warming have fluctuated over the years, shifting along with partisan fissures, extreme weather events and messages from political and religious figures. But the overall upward trend in opinion, he said, was strongly tied to the fact that more people are beginning to relate to climate change as a personal issue.

There are certainly many Americans who remain undecided or doubtful. Toby Wilder, a salesman from Seattle, said he found it hard to imagine that human-caused climate change was anything but a hoax propagated by elites who fly private jets. “If they are wasting more fuel in a month than I do in my lifetime, then how can I believe it?” he asked.

Greg Sandmeyer, a social studies teacher at Timberline High School in Boise, Idaho, is also unconvinced. “It’s one thing to say it’s happening, but it’s another to make laws that will affect me,” he said.

But the broader shift in public opinion, however gradual, has moved toward acceptance of human-caused global warming. In order to learn more about the attitudes that are fueling this change, we spoke with dozens of people. Here are six of their stories.

The Meteorologist

Jennifer Rukavina, 38, Paducah, Ky.

When Jennifer Rukavina became a television meteorologist, she noticed her colleagues were divided into two camps: believers and nonbelievers. Ms. Rukavina didn’t know at first which camp she fell into, but she certainly wasn’t “convinced” about climate change.

As a group, meteorologists are no more or less likely than the general public to say that humans are the primary cause of climate change. In the early 2000s, when Ms. Rukavina began her career, Al Gore, the former vice president and climate change activist, had just released his film “An Inconvenient Truth.” The split among her colleagues, Ms. Rukavina said, was largely focused around the political “theater” surrounding the film, which experts often describe as a flash point in the deepening partisan divide on climate change.

“I decided that I needed to educate myself, because the meteorologist is often viewed as the station scientist,” Ms. Rukavina said. In 2008, she attended her first Glen Gerberg Weather and Climate Summit — a meeting of weathercasters and climate scientists — in Colorado. After hearing from the scientists themselves, Ms. Rukavina said, she changed her mind.

“I am a registered Republican, but I don’t let politics dictate what good science is to me,” she said. Every year since, Ms. Rukavina has briefed her WPSD viewers live from the conference. “It really doesn’t matter to me what my viewers think of climate change,” she said. “What matters to me most is being able to prepare them for the changes that lie ahead.”

The Retired Coal Miner

Stanley Sturgill, 72, Harlan County, Ky.

When Stanley Sturgill first learned about global warming in the early 1990s, he was working as a federal coal mine inspector in Lynch, Ky. Mr. Sturgill, who worked 41 years in the coal mines before retiring in 2009, said he was “disheartened and sickened” when he understood the full extent to which human beings were damaging the environment. But he kept quiet on the issue, for fear of losing his job.

“That’s why I got into trying to stop it just as quick as I retired,” he said. “You can hold your nose and do a lot of things, and that’s what I had to do.”

Late last year, Mr. Sturgill, who now describes himself as a climate change activist, testified at a public hearing held by the Environmental Protection Agency in Charleston, W.Va. He also spoke at the 2014 People’s Climate March in New York.

Mr. Sturgill now has black lung and chronic obstructive pulmonary disease from his years spent in the mines, he said. “I knew we were polluting the Earth, but it took time to have a full understanding that what goes around comes around,” he said.

The Community Organizer

Valencia Gunder, 33, Miami

Growing up in Liberty City, Valencia Gunder never thought about climate change. The neighborhood, one of the poorest in Miami, had other “social ills” to deal with, she said.

“You wouldn’t hear anybody talking about climate change,” Ms. Gunder said. “Not at all.”

But in recent years, Liberty City — roughly two miles from the coast and on higher ground than other parts of Miami — has become more attractive to developers, who talk about the neighborhood as “future beachfront property,” Ms. Gunder said. “They’re coming in, putting in multimillion-dollar investments. We’re like a candy shop.”

It wasn’t until a community meeting in 2016, however, that Ms. Gunder first heard the term “climate gentrification.” Something clicked, she said. “Climate change and sea level rise is causing individuals to have to abandon their shorefront homes in more affluent communities and go inland, and the communities inland are lower-income communities,” she said. “That was like, ‘Oh my goodness, wait a minute.’”

After that meeting, Ms. Gunder trained to speak on behalf of a local climate activism group, the CLEO Institute, and has since run more than a dozen workshops educating some of Miami’s lowest-income communities about the ways climate change could affect them personally. Ms. Gunder often finds herself speaking to a room full of people who may have never heard about climate change. “Their minds are always blown,” she said.

The Evangelical Leader

Richard Cizik, 66, Fredericksburg, Va.

In 2002, the Rev. Richard Cizik would have described himself as “a faithful member of the religious right,” he said. So when the Rev. Jim Ball, a founder of the Evangelical Environmental Network, invited him to a climate change conference that year, Mr. Cizik was hesitant.

“I heard the evidence over four days, did a fist to the forehead and thought, ‘Oh my gosh, if this is true, everything has changed,’” said Mr. Cizik, who was then vice president for government affairs at the National Association of Evangelicals. “I liken it to a religious conversion, and not just because I saw something I’d never seen before — I felt a deep sense of repentance.”

But a few years later, when Mr. Cizik began encouraging his fellow evangelicals to learn more about climate change, he was ostracized. Dozens of community leaders signed a petition for his firing. “Ostensibly it was over my supporting civil unions, but the real reality was that the right didn’t like my position on climate change,” Mr. Cizik said. “The entire religious right just attacked me. It was pretty aggressive.”

Mr. Cizik and his wife sold a car, started recycling and modified parts of their home to be more environmentally friendly, he said. They began to do what they thought God was calling them to do: change their minds. “If you’ve never changed your mind about something, pinch yourself, you may be dead,” Mr. Cizik said. “If we don’t change our mind about this subject, we will die.”

The Charter Fleet Owner

Lynne Foster, 70, Hatteras Island, N.C.

For 25 years, Lynne Foster and her husband, Ernie, have run the Albatross Fleet, a charter fishing operation on Hatteras Island in North Carolina’s Outer Banks, trolling the Gulf Stream for mahi-mahi, yellowfin tuna and wahoo.

“We live in a very dynamic natural environment and things are constantly changing,” Ms. Foster said. But when the roads in Hatteras began to flood more often, the coast began to erode and uprooted trees floated down Pamlico Sound, Ms. Foster knew something was different, she said.

Watching the southern end of Hatteras Island all but “float away,” she said, changed her mind about climate change. “It’s hard to live here, and watch so many natural changes take place, and not blame human activity.”

In recent years, rising seas have ravaged the Outer Banks, but Ms. Foster said many people in her community still don’t discuss why. “There are some who do not believe it on principle, even though they can see it with their own eyes,” she said, “but they don’t put a name to it.”

The Mayor

Tomás Regalado, 70, Miami

When Tomás Regalado, a Republican, was elected mayor of Miami in November 2009, climate change was not on his agenda. At the time Mr. Regalado thought that sea level rise was “a very distant future possibility,” and that talking about it was a waste of time, he said.

But Mr. Regalado’s son Jose had his own agenda. Early one morning during his father’s second term as mayor, he made him a cup of coffee and sat him down, with a map, to talk about climate change. “I realized that if this was happening somewhere in the Pacific, well, it could happen here,” Mr. Regalado said.

When Hurricane Irma hit Miami, Mr. Regalado witnessed the vulnerability of his city firsthand. “I think I really understood when I saw people trying to get to their cars, and their cars were flooded,” he said. “They were stranded.”

Late last year, as Mr. Regalado was leaving office, Miami voters supported his idea for a $400 million bond, half of which is dedicated to protecting the city from sea level rise and climate change. “I think it’s a clear message to Washington that the majority of people in Miami at least understand and see this as a nonpartisan issue,” Mr. Regalado said.