CNN's climate crisis town hall

Massachusetts Sen. Elizabeth Warren said Wednesday that she would oppose nuclear energy as a way to combat climate change should she be elected president in 2020.

“We’re not going to build any nuclear power plants and we’re going to start weaning ourselves off nuclear energy and replacing it with renewable fuels,” Warren said, adding that she hopes to phase out nuclear power by 2035.

Warren said that while nuclear energy is not carbon-based – and therefore cleaner than some energy sources – there is a clear danger with storage.

“It has a lot of risks associated with it,” Warren said.

Massachusetts Sen. Elizabeth Warren just took the stage at CNN's climate crisis town hall.

She's one of 10 Democratic candidates participating in the 7-hour event event.

Bernie Sanders has put forth a series of plans -- on health care, student debt cancellation and the Green New Deal -- that, taken separately, would each represent a generational change to American domestic policy.

So what is his top priority?

Asked on Wednesday night which policy he would push first if elected, Sanders did not put one before any of the others.

“I have the radical idea that a sane Congress can walk and chew bubble gum at the same time,” Sanders said.

The way to make it all happen, he argued, is to elect lawmakers that support his platform.

“To my mind, it’s not prioritizing this over that. It is finally having a government which represents working families and the middle class, rather than wealthy campaign contributors,” Sanders said. “When you do that, things fall into place.”

Sen. Bernie Sanders was asked if he'd make curbing population growth through birth control a key part of his climate plan.

"The planet cannot sustain this growth," the voter said while asking the question.

Sanders said he would, and turned the conversation to women's rights.

"Women in the United States of Americas, by the way, have a right to control their own bodies and make reproductive decisions," he said.

Sanders continued:

Vermont Sen. Bernie Sanders was asked on Wednesday whether he would roll back Trump administration plans to overturn requirements on energy saving lightbulbs. He delivered an emphatic answer.

“Duh,” the senator explained with a slight smile.

Donald Trump’s administration lifted energy efficiency regulations for several common types of light bulbs on Wednesday, which critics believe is the administration’s latest assault on efforts to combat climate change and energy use.

Sanders pivoted from the lighthearted answer and made the case for making climate change an international issue.

“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.

Vermont Sen. Bernie Sanders is now taking questions from voters about the climate crisis.

He's the sixth Democratic candidiate tonight to participate in the 7-hour event.

Former Vice President Joe Biden said he's been a "champion" for rail and mass transit.

Biden added that in order for new rail lines to be successful, they have to be as fast and as cost efficient as driving.

"It would literally take millions of vehicles off the road. But you have to have a rail system that makes people say, 'If I get on that rail, I will get there as fast as I would have gotten had I driven and I can afford to do it relative to the coast of my driving.'"

Former Vice President Joe Biden said he would not support a nationwide fracking ban on Wednesday -- in part because he doesn’t believe any measure banning fracking could pass -- but the Delaware Democrat said he does support stopping all “oil drilling or gas drilling on federal lands.”

Biden’s position is the most common Democratic position, but other candidates in the race -- like Vermont Sen. Bernie Sanders and New Jersey Sen. Cory Booker -- have pushed for a nationwide fracking ban.

Biden, in response to a question about fracking in Pennsylvania, said on Wednesday that the federal government has “less latitude in what we say we can and cannot do” on state lands.

“I think we should in fact be looking at what exists now and making a judgment whether or not the those in fact that are there, those wells that are there, whether or not they are dangerous, whether or not they have already done the damage,” Biden said.

Biden said the federal government “could pass national legislation” but that he doesn’t believe there are enough votes “to get it done.”

Former Vice President Joe Biden suggested he might reconsider a fundraiser scheduled for Thursday after being confronted and told about its host's connections to the energy industry.

Andrew Goldman is a co-founder of Western LNG, a company whose biggest project is a floating liquefaction facility for natural gas off the coast of British Columbia, Canada. He does not have day-to-day responsibilities with the company, but an audience member asked Biden if his willingness to accept Goldman’s help would compromise his pledge to fight climate change.

Goldman also worked a Biden adviser before the former vice president took that office in 2009.

"I didn't realize he does that," Biden said after being asked initially about Goldman’s role and said, citing SEC filings, that he did not believe attending the fundraiser would be in violation of a pledge to refuse fossil fuel energy executive donations. "I'm going to look at what you just told me and find out if that's accurate."

Immediately after the exchange, Biden spokeswoman Symone Sanders disputed the description of Goldman, claiming he "isn't a fossil fuel executive. He's not involved in the day to day operation. He's not on the board of the company, nor the board of the portfolio company."

She also echoed Biden, in a subsequent tweet, denying that the former vice president has not violated his pledge to reject donations from fossil fuel executives.

“What I was told by my staff is that he did not have any responsibility related to the company,” Biden said later. “He was not on the board, he was not involved at all in the operation of the company at all.

But he said his campaign would review its information to be sure.

“If that turns out to be true, then I will not in any way accept his help,” Biden said. “We go through every contribution make sure that we are not accepting money from people we said we wouldn't, or we shouldn’t.”