Climate change -- a hot-button topic for years -- has taken on renewed significance ahead of the 2020 presidential election, with wildfires decimating the West, tropical storms pounding the Gulf Coast and year after year of record temperatures.

Both Trump and Biden largely toe their respective party lines when it comes to issues pertaining to environmental policy.

Throughout his presidency, Trump reversed many American commitments to mitigating climate change, most notably pulling out of the Paris Agreement, removing clean water protections and seeking to fast track environmental reviews of dozens of major energy and infrastructure projects, such as drilling, fuel pipelines and wind farms.

Biden has countered the Trump administration's policies by promising to protect the environment with a proposed a $5 trillion plan.

Here is where each candidate stands on the issues

Trump responded to a question on the impact of his language on racial conflict in the country by touting his work on criminal and prison reform as well as opportunity zones.

"It makes me sad, because I am, I am the least racist person," Trump said. "I can't even see the audience because it's so dark, but I don't care who's in the audience, I'm the least racist person in this room."

Biden responded by saying that the president "pours fuel on every single racist fire, every single one."

When asked about his previous support for crime bills in the 1980s and 1990s, Biden said again that his support was "a mistake."

"I've been trying to change it since then, particularly the portion on cocaine," he said. "That's why I've been arguing that, in fact, we should not send anyone to jail for a pure drug offense. They should be going into treatment across the board."

Trump asked why Biden couldn't change those policies during his time as vice president.

"Why didn't you get it done? See? It's all talk, no action with these politicians," he said. "Why didn't he get it done? That's what I'm going to do when I become president -- you were vice president along with Obama as your president, your leader, for eight years. Why didn't you get it done?

Biden brought up the Obama administration's work to release 38,000 federal prisoners and grant clemency. After continuing pressing from Trump, Biden said they couldn't get more done because "we had a Republican congress."

The final topic of the night was climate change with Welker first asking each candidate how he would combat climate change and support job growth at the same time as president. Trump answered first.

"So we have the trillion trees program. We have so many different programs. I do love the environment, but what I want is the cleanest, crystal clear water, the cleanest air," Trump said, taking credit for the country's reduced carbon emission last year.

He went on to slam other counties air-quality and tout the U.S. by comparison.

"Look at China, how filthy it is. Look at Russia. Look at India. It's filthy. The air is filthy. The Paris Accord, I took us out because we were going to have to spend trillions of dollars, and we were treated very unfairly," Trump said, closing his two minutes by saying his administration has done an incredible job "environmentally."

When it was Biden's turn, he pivoted to the existential threat he says global warming poses to humanity and said the U.S. has a moral obligation to "deal with it" -- but said climate change also creates a prime opportunity for new jobs.

"Here's where we have a great opportunity. I was able to get both all the environmental organizations as well as labor, the people worried about jobs, to support my climate plan. Because what it does -- it will create millions of new good-paying jobs," Biden said. "Wall Street firms indicated that my plan -- my plan will, in fact, create 18.6 million jobs, 7 million more than his. This is from Wall Street. And I'll create $1 trillion more in economic growth than his proposal does. Not on climate, just on the economy."

Trump slammed Biden's response, claiming the former vice president's plan would cause a massive economic depression and deeming it a "pipe dream," before raising Biden's stance on fracking.

In the face of Trump's criticisms, Welker asked Biden directly, "Would you rule out banning fracking?"

"I do rule out banning fracking," Biden said. "We need other industries to transition to get to ultimately a complete zero emissions by 2025. What I will do with fracking over time is make sure we can capture the emissions from the fracking, capture the emissions from gas. We can do that and we can do that by investing money. It's a transition to that."

"Excuse me," Trump interrupted. "He was against fracking. He said it. I will show that to you tomorrow."

"Fracking on federal land, I said," Biden responded. "No fracking and/or oil on federal land."

To open the section on race in America, Welker described "the talk" to the candidates -- when parents of color, regardless of class or income, prepare their children for the chance that they could be targeted by police for no reason other than the color of their skin -- giving the first question to Biden.

"I would like you to speak directly to these families," Welker said. "Do you understand why these parents fear for the children?"

"Yes, I do," said Biden. "The fact of the matter is there is institutional racism in America. We have always said, we've never lived up to it, that we hold these truths to be self-evident, all men and women are created equal. Guess what? We have never, ever lived up to it."

"We have to provide better economic opportunity, better education, better health care, better access to schooling, better access to borrow money to start businesses," Biden continued. "And I've laid out a clear plan as to how to do those things just to give people a shot. It's about accumulating the ability to have wealth as well as it is to be free from violence."

When the same question was posed to Trump, the president raised Biden's controversial 1994 crime bill and again said no one has done more for the Black community than Trump -- other than President Abraham Lincoln.

"Yes, I do," Trump said, before launching an attack on Biden. "And again, he's been in government 47 years. He never did a thing, except in 1994, when he did such harm to the Black community."

"Nobody has done more for the Black community than Donald Trump. And if you look, with the exception of Abraham Lincoln, possible exception, but the exception of Abraham Lincoln, nobody has done what I've done," he added.

Trump went on to rail against Biden for not making the changes he's pushing when he was in office and said he ran for office as a direct response to Obama and Biden.

"Joe, I ran because of you. I ran because of Barack Obama. Because you did a poor job. If I thought you did a good job, I would have never run," Trump said. "I ran because of you."

TRUMP'S CLAIM: "We have a vaccine that's coming. It's ready. It's going to be announced within weeks. And it's going to be delivered." ... "Johnson & Johnson is doing very well. Moderna is doing very well. Pfizer is doing very well. And we have numerous others."

FACT CHECK: A COVID-19 vaccine isn't ready right now. But it is true that two companies -- Pfizer and Moderna -- could seek emergency use authorization in November or December.

Like Pfizer and Moderna, Johnson & Johnson's vaccine is also in late-stage studies, but Johnson & Johnson paused its trial earlier this month to investigate an unexplained illness.

As the chief adviser to the government vaccine distribution initiative Operation Warp Speed, Dr. Moncef Slaoui told ABC’s Bob Woodruff this week that if a vaccine is authorized before the end of the year approximately 20 million to 40 million doses of it will be stockpiled and ready for distribution for a limited population. At first, only high priority Americans, like those over 65, will have access, but by the springtime more Americans should have access.

Slaoui said that vaccine trials are going as fast as it’s safe to go, pledging to resign if he felt undue pressure from the White House. Slaoui said that by June 2021, it's possible "everybody" in the United States could have been immunized.

-ABC News' Sony Salzman and Sasha Pezenik