There’s perhaps no topic that more starkly divides Democratic hopefuls and President Donald Trump than the debate on climate change.

Democrats writ large see global warming as an existential crisis, while Trump has dismissed the issue. He has incorrectly suggested wind turbines cause cancer, while arguing that his rivals' plans would throw the U.S. economy into a funk.

Yet, until this week, global warming has remained largely a back-burner issue in an internal Democratic debate that’s largely focused on who is best equipped to take on Trump in the general election and whether pursuing Medicare for All is the best way to fix health care in America.

That could be changing.

Capped with Wednesday's CNN's climate town hall – coming as Hurricane Dorian bears down on the southeastern United States – top Democratic hopefuls this week tried to demonstrate how they would approach turning the tide on global warming should they become the next commander in chief.

“We see that now with Hurricane Dorian,” said former Housing and Urban Development Secretary Julian Castro, who was among 10 leading Democrats invited by CNN to talk part in marathon climate forum and was among five Democrats this week to unveil a climate agenda. “The Arctic ice caps melting. The Amazon on fire. We don’t need climate scientists to tell us what we see with our eyes.”

To be certain, there is little disagreement among Democratic hopefuls that climate change is a mounting catastrophe that Washington and the world need to take immediate action on. But candidates are trying to highlight their credentials as true champions on the issue, which polls show is among the highest priorities of likely Democratic primary and caucus voters.

The issue is particularly salient with young people – voters 18 to 23 are projected to make up one in 10 eligible voters in 2020. A Harvard University poll published in March found that 74% of likely voters ages 18 to 29 disapprove of Trump's handling of climate issues, and 53% of likely voters agree that the government should do more to curb climate change even at the expense of economic growth.

Human-induced warming reached approximately 1°C above pre-industrial levels, according to a 2017 United Nation's Intergovernmental Plan on Climate Change. Scientists project dire consequences should the planet warm by 2°C above the pre-industrial levels.

"Heat waves would last around a third longer, rain storms would be about a third more intense, the increase in sea level would be approximately that much higher and the percentage of tropical coral reefs at risk of severe degradation would be roughly that much greater," according to NASA.

Where the candidates stand

Castro on Wednesday said he would set a goal of pushing the country to end its reliance on carbon-fueled energy by 2045. He said his first act, should he be elected, would be to take executive action declaring to recommit to the Paris climate agreement, an international pact to reduce greenhouse gas emissions that Trump notified fellow signatories the U.S. would officially leave in November 2020.

Sen. Elizabeth Warren said she would spend $3 trillion on research and investment to cut carbon emissions. Her agenda includes making sure that new cars, buses and many trucks run on clean energy – instead of gasoline or diesel – by 2030 and that all the country’s electricity comes from solar, wind and other renewable, carbon-free sources by 2035.

"We have a chance to turn this around in 2020, but we're running out of time," Warren said.

Sen. Bernie Sanders, who has unveiled a $16.3 trillion climate plan that he says would create 20 million jobs, end private utilities and ban hydraulic fracking, pushed back against the notion the nation can't afford his agenda.

"Maybe, just maybe, instead of spending a trillion and a half dollars every single year on weapons of destruction designed to kill each other, maybe we pool those resources and we work together against our common enemy, which is climate change,” Sanders said.

Sen. Kamala Harris said she would move to ban hydraulic fracking and consider getting rid of the legislative filibuster in the Senate in order to pass the Green New Deal. The far-reaching proposed climate legislation championed by liberal lawmakers Rep. Alexandria Ocasio-Cortez and Sen. Ed Markey, and derided by Trump as economic flimflam, aims to tackle climate change. By ending the filibuster, the legislation could be passed with a simple majority in the upper chamber instead of the 60-vote threshold currently needed for legislation.

She has also pitched a $10 trillion spending plan that sets out for the United States to reach the goal of 100% carbon-neutral electricity by 2030. She vowed to end fossil fuel production on public lands and end federal subsidies for fossil fuels.

Harris said from Day 1 as president, if she's elected, she will make clear to the scientists in the U.S. government that her administration "will back you up" as it changes government approach to fighting rising global temperatures.

"Let's just be really clear: Donald Trump, he's got everyone excited by those crazy tweets," Harris said. "Meanwhile, with this hand he's quietly undoing regulations that were built over years, including incredible stuff the Obama administration did. Everybody is distracted by the crazy tweet. Meanwhile, he's completely deregulating industry."

Biden faces criticism over backer's ties:Biden says he will rethink fundraiser hosted by fossil fuel company co-founder

Democratic front-runner Joe Biden has floated a more modest $1.7 trillion agenda for clean energy spending over 10 years and set the goal of eliminating the country’s net carbon emissions by 2050. He pushed back on a question by CNN moderator Anderson Cooper about whether his plan is not aggressive enough – a notion that has been repeated by some environmental activists as well as rivals for the nomination.

"I think it is aggressive enough, and it's got good reviews from most of the environmental community," Biden said. "Science and technology are going to change, and as it charges, we learn more and can do more."

Biden, who was one of 18 candidates to pledge to reject campaign contributions from the fossil fuel industry, also found himself facing some pointed questioning from the CNN audience about his ties to it.

Isaac Larkin, a Northwestern University doctoral student, questioned the former vice president on why he should be trusted to be a environmental champion when he was allowing Andrew Goldman, a former Senate aide who later founded the natural gas production and transportation company Western LNG, to hold a fundraiser for him Thursday.

Biden and his campaign countered that Goldman, who now is the managing director of an investment firm, doesn't have day-to-day involvement in Western LNG.

"If you look at the SEC filings, he's not listed as one of those executives.” Biden said. "I've kept that pledge. Period."

South Bend, Indiana, Mayor Pete Buttigieg said that solving the climate crisis is perhaps the greatest challenge that humanity has faced since World War II. The mayor, who this week introduced a $1.5 trillion climate plan that he said would create 3 million clean energy and infrastructure jobs, went on to say failure to act was akin to sin, wondering out loud about what God thinks as the environment is destroyed.

"I also frankly think of it more selfishly when we talk about hitting this target of 2050 for decarbonizing our economy," said Buttigieg, the youngest of White House hopefuls at 37. "Lord willing, I plan to be here – I would be in my 60s by the time we know whether we have succeeded and can look back and be proud of what we did to getting on the right tack or realize we are the ones that blew it."

The climate forum didn't go unnoticed by Trump. The president took to Twitter to blast Democrats’ "destructive" proposals that he predicted would raise energy bills and prices at the pump.

"Don't the Democrats care about fighting American poverty?" Trump offered as a part of stream of tweets that served as a prebuttal.

On Wednesday, the Trump administration also announced it was rolling back Energy Department requirements to make commonly used bulbs more efficient.

The new standards were included in energy legislation implemented under President George W. Bush and finalized under the Obama administration. The news standards, which would have gradually phased out incandescent and halogen bulbs, were set to go into effect in January 2020.

"I think he’s just messing with CNN on that," entrepreneur and longshot candidate Andrew Yang joked.

Sen. Amy Klobuchar of Minnesota noted at the town hall that the Ojibwe tribe underscores the need to think about the impact their decisions will have on seven generations.

"We have a president that can’t make a decision about seven minutes from now," Klobuchar said.

Until Wednesday, the Democratic presidential field had hardly pressed on the issue. Washington Gov. Jay Inslee, who ended his presidential run last month after he failed to qualify for the September debate in Houston, was the outspoken climate candidate, making stemming global warming the central theme of his candidacy.

Several candidates who participated in the climate forum poured praise on him for making the issue central part of the campaign.

"I proudly adopted many of @JayInslee’s plans – you go anywhere where there are good plans," Warren posted on Twitter after stepping off stage at the climate forum. "The only way we’re going to make change is by looking everywhere."