Climate change has been a central focus in the Democratic presidential primary, with a vocal coalition keeping the issue in the spotlight and the pressure on the candidates.
The young activists with the Sunrise Movement, often found demonstrating on Capitol Hill, Rep. Alexandria Ocasio-Cortez (D-Bronx), co-sponsor of the Green New Deal, and Washington Gov. Jay Inslee, who had staked his White House bid almost entirely on combating climate change, all have underscored the urgency of the threat.
The top-polling White House hopefuls have detailed policies to stave off the effects of the crisis. Some have commended and adopted parts of the platform proposed by Inslee, who bowed out of the race last month.
“It must be a top priority of the next administration,” Inslee tweeted last week. “And it’s the key to beating Trump.”
Many Republicans, meanwhile, say the Democrats are exaggerating the threat. Trump has labeled climate change a "hoax" invented by China.
The president last week posted several criticisms, including: “The Democrats’ destructive ‘environmental’ proposals will raise your energy bill and prices at the pump.”
The tweet came during the seven hours of back-to-back town halls on climate change hosted by CNN and featuring the 10 highest-polling Democratic candidates, the same ones who qualified for the third official debate this week. Another nationally televised climate change forum, this one stretched over two days and airing later this month on MSNBC, will feature several Democratic hopefuls who weren't among the 10 as well as Republican candidate Bill Weld.
Democratic candidates have drawn contrasts not just with Trump but with each other.
The top-polling contenders agree on the goal of reaching net-zero greenhouse gas emissions by 2050 at the latest, rejoining the Paris climate accord from which Trump withdrew in 2017 and prohibiting new fossil-fuel extraction on federal lands.
Nearly all at the CNN forum cited a need for "climate justice," or solutions that address the racial and economic disparities made worse by global warming.
But there is daylight among the candidates on other measures. Here’s a look at where they differ:
The candidates say a big government investment is necessary to confront a big global crisis, but they disagree on how big.
Sen. Bernie Sanders (I-Vt.) has proposed the most ambitious and most expensive plan. He calls for a $16.3 trillion investment over 15 years, “in line with the mobilization of resources made during the New Deal and WWII” but with the inclusion of black, indigenous and other minority communities, according to his campaign website.
“We have a moral responsibility to act and act boldly, and to do that, yes, it is going to be expensive,” Sanders said at the CNN town hall.
By contrast, former Vice President Joe Biden has proposed spending $1.7 trillion over 10 years, or a total of about $5 trillion with investment from the private sector and from local and state governments. Sen. Elizabeth Warren (D-Mass.) has a $3 trillion price tag on her vision.
A tax or fee on carbon dioxide emissions historically has been viewed as a political third rail because it would lead to higher fuel costs for consumers.
But several candidates embraced it, including Biden, Sen. Cory Booker (D-N.J.), Mayor Pete Buttigieg of South Bend, Indiana, and Sen. Kamala Harris (D-Calif.).
“I know that you’re not supposed use the T-word in politics,” Buttigieg said at the town hall.
Sanders and Warren didn't include carbon pricing in their official platforms, but Sanders has supported it. Warren at the CNN event responded “yes” when asked if she would back it.
Entrepreneur Andrew Yang has proposed a carbon-fee-and-dividend approach and former Rep. Beto O'Rourke (D-Texas) favors a cap-and-trade system.
About 20 percent of the country’s electricity is generated by nuclear plants.
Sanders called for an outright ban, citing radioactive waste as a risk. Warren said she would phase the country away from nuclear power. Booker and Biden signaled that they support the use of nuclear power as part of the energy mix.
Booker said the energy source can be improved, citing at the town hall "next-generation nuclear" solutions. “Right now, nuclear is more than 50 percent of our non-carbon causing energy,” he said. “So people who think that we can get there without nuclear being part of the blend just aren't looking at the facts.”
Sanders and Harris say they support a ban on hydraulic fracturing, commonly called fracking, a drilling technique that uses a high-pressure water mixture to release gas or oil from rock. The practice can contaminate drinking water and lead to air pollution, among other risks.
“There’s no question I’m in favor of banning fracking,” Harris said at the CNN town hall, adding that she would prohibit the practice on public lands via executive action on day one then work with Congress to ban it on private land.
Biden, Booker, former U.S. Housing Secretary Julián Castro and Sen. Amy Klobuchar (D-Minn.) at the town hall pushed for better regulation, or the phasing out, of fracking.
Eliminating the filibuster
A crucial element to Inslee’s plan to move aggressively and immediately on climate change is to scrap the Senate filibuster, so a simple majority of 51 can pass legislation to address the crisis without being blocked by Republicans.
Warren also has supported the elimination of the filibuster.
Harris endorsed the concept at the CNN town hall, saying that as president, she is “prepared to get rid of the filibuster to pass a Green New Deal.”
Sanders doesn't back eliminating the filibuster. He said at the town hall that Democrats could attach climate change legislation to a must-pass budget measure.
“There are ways to get that through the Budget Reconciliation Act, which will require 51 votes, and that's the method we will use,” Sanders said.