Scientists have warned for the last 30 years about the dangers of climate change — more droughts, forest fires and catastrophic weather — as the Earth continues to warm from fossil fuel pollution.

But climate has never been a major issue in a presidential campaign. This year, however, as the dire predictions increasingly become reality, that seems to be changing.

Every major Democratic candidate running against President Trump next fall has issued a detailed climate plan to dramatically increase renewable energy, electric vehicles and energy efficiency. Young environmental activists are demanding a Democratic debate on climate change and protesting at Democratic events. So far they haven’t succeeded, but on Wednesday from 2 p.m. to 9 p.m., CNN will host a live town hall on climate change, with the 10 major Democratic candidates answering questions from a studio audience and a moderator.

“It has become a top-tier issue,” said Larry Sabato, director of the Center for Politics at the University of Virginia. “How could anyone who reads the headlines not recognize that this is not just a problem, it’s a crisis?”

The politics are still evolving. But the science is clear. The 10 hottest years since 1880, when modern temperature records began, all have occurred since 1998, according to NASA and NOAA. July was the hottest month ever recorded globally back to 1880. Record heat waves have gripped Europe this summer. Hurricane Dorian has battered the Bahamas and Florida, its category 5 peak strength driven in part by warmer-than-normal water temperatures that scientists say make hurricanes stronger. Large fires have charred millions of acres across Alaska and Siberia in recent months. And on Aug. 2, Greenland lost 12.5 billion tons of ice to melting, the largest single-day loss in recorded history.

The public is noticing.

A CBS News poll in July of Democratic voters in early primary states found that 78% said climate change was “very important” to them, second only to health care — which scored 88% — and ranking higher than guns, immigration, jobs and income inequality.

At the same time, a massive partisan divide remains.

A survey in July by the Pew Research Center found that 57% of Americans say climate change is a major threat to the United States, up from 40% six years ago. But nearly all of that increase is due to Democrats. While 84% of Democrats described climate change as a major threat in the poll, only 27% of Republicans agreed. And despite California’s record on reducing emissions, polls suggest that voters in the state break down in a similar way by party.

“Climate change offers a wonderful opportunity for Democratic candidates,” said Jon Krosnick, a professor of political science at Stanford University who has run polls on climate change for 20 years. “If they take clear, coherent positions on the issue, that offers an advantage in the primary.”

But, said Krosnick, Stanford’s surveys show only about 20% of voters see climate as the central issue when they vote. That’s up from 9 percent in 1997, but it’s still only 1 in 5.

He noted that Washington Gov. Jay Inslee, who made climate change the centerpiece of his campaign, never climbed in the polls and dropped out last month after failing to qualify for upcoming debates.

“Why did Jay Inslee’s campaign go down in flames?” Krosnick said. “Because 80% of the country yawned at what he was saying. The gun control people say ‘Look at these shootings. How many people have to die?’ Right to life people say ‘What could be more important than that?’ ”

To be sure, climate change has to compete with other issues — health care, the economy, guns, immigration — for the attention of voters. In some key states, notably coal-rich Pennsylvania and Michigan, home of the U.S. auto industry, the issue could become a liability for Democrats, as Hillary Clinton found out in 2016.

Then, a comment she made in Columbus, Ohio — “We’re going to put a lot of coal miners and coal companies out of business” was used against her by the Trump campaign to claim Trump better understood the concerns of blue-collar voters. She later wrote in her post-election memoir, “What Happened,” that the remark, although quickly followed up with her plan for re-training miners, was the one “I regret the most.”

Michael Brune, national executive director of the Sierra Club, said this year’s Democratic candidates have more detailed climate plans that “Obama did, or even Al Gore did.” To reduce the risk of Trump turning the issue on them, Democrats should emphasize that acting on climate creates jobs in renewable energy industries, improves the U.S. competitiveness against other countries, and reduces air and water pollution by burning fewer fossil fuels, all of which are popular issues in both parties, he said.

“The nominee needs to talk about the benefits of the transition to clean energy and how the Democrats will take care of workers employed in the fossil fuel industries,” Brune said. “Just about every climate platform out there talks about how we can and should work with those communities in the Gulf of Mexico and in Appalachia to make sure nobody is left behind.”

Why there is such a chasm between Republicans and Democrats on the issue remains up for debate. Some experts say it is because many of the solutions to climate change — which often involve more government regulations, taxes and treaties with other countries — counter longtime core principles of Republicans.

Others say the issue is simple tribalism. Climate change was identified as “Democratic” for many Republicans because former Vice President Al Gore became its chief spokesman. Others say contributions from fossil fuel companies to Republicans, the fact that most oil and coal producing states — such as Texas, Oklahoma, Kentucky and the Dakotas — are Republican and that GOP leaders so far have ignored the issue also are to blame.

“Parties are a reflection of the leaders of the party,” said Bill Whalen, a former speechwriter for Republican California Gov. Pete Wilson and the Bush-Quayle campaign. “And Donald Trump does not talk about climate change other than to deny it.”

“For the Republican Party to change on this, you are going to have to point them to race after race where Republicans lost” because of the issue, said Whalen, now a fellow at the Hoover Institution at Stanford. “Until they get hit by a two-by-four and lose a race in Arizona or Florida, you are just not going to see Republicans come around on this.”

The most energized voters on climate, polls show, are young people. A Quinnipiac University poll released Aug. 29 found that the younger that people were, the more concerned they were about climate change. In the survey, 74% of Americans ages 18 to 34 said climate change was an emergency, while 52% of people age 65 described it as an emergency.

“For people in their teens and 20s, every year has been the hottest on record for our entire lives,” said Garrett Blad, a spokesman for the Sunrise Movement, an environmental group advocating for sweeping action on climate that on its website describes itself as “an army of young people.”

“We see the world heading off a cliff at an accelerating pace,” he said.

Asked whether a Democratic climate debate, which his organization is seeking, might provide fodder for negative attacks on Democrats in Trump TV commercials, especially in the Midwest, Blad disagreed.

“We are not going to address this by being fearful of losing elections,” he said. “We are going to have to be courageous.”

Whalen noted there is still a long time until election day.

“The goal for Democrats is to kick Donald Trump out of office,” he said, noting that there is a temptation to focus on other issues such as health care, which worked in the 2018 mid-terms.

And if the economy slumps, Whalen said, “the Democratic nominee is going to be on the attack about economic misery now rather than global apocalypse in 50 or 100 years.”