This article originally appeared on VICE US.

Joe Biden backed one of the first climate bills in US history, has a relatively strong score from the League of Conservation Voters, and calls fighting global temperature rise “a matter of survival.” The former vice president—who became the frontrunner for the Democratic presidential nomination shortly after entering the race last month—has the profile, on paper, of someone who should be able to tout his bona fides on climate change and the environment.

But Biden appears to be running as a moderate on these issues. On Friday, Reuters reported that while he would support re-joining the Paris climate agreement, he was also open to boosting natural gas and technologies to capture and bury emissions from industrial facilities. That was alarming to some climate activists, who already didn’t trust him on the issue—and that might be putting it mildly.

It’s difficult to find many climate thinkers or activists these days who are all that excited about Biden’s entry into the Democratic primaries—and some interviewed for this story worry that if he wins he could actually slow down progress at a time when the planet is least able to afford it.

“This is an existential threat that we are talking about for all life on Earth, all Americans,” said Leah Stokes, a political scientist at the University of California, Santa Barbara, who closely follows the politics of climate change and energy. “I don’t trust him at all… I think he’s got some explaining to do about what exactly his plan is to deal with the climate crisis.”

Biden’s campaign website contains only three sentences about the greatest crisis ever to face humankind, and these are located midway down a secondary page. “We must turbocharge our efforts to address climate change and ensure that every American has access to clean drinking water, clean air, and an environment free from pollutants,” the site reads. His campaign did not respond to VICE’s request for more details on the actual policies this would entail.

There are virtually no specifics about how Biden plans to cut emissions in half by 2030—which is what United Nation scientists calculated is required to stabilize the world at or below 1.5 degrees Celsius of warming and keep cities like Houston, London, Shanghai, Jakarta, Bangkok, Lagos, Manila and Dhaka above water.

But the Reuters story sheds light on what a Biden presidency might include when it comes to climate—a return to Barack Obama’s policies of regulating emissions and working with the international community, but not the kind of aggressive action favored by experts and advocates. One of the sources for the Reuters article, Heather Zichal, previously advised Obama on climate change and is now an informal advisor to Biden. She is affiliated with Cheniere Energy, a major liquefied natural gas producer based in Houston.

Unsurprisingly, activists were alarmed by this news.

“A ‘middle ground’ policy that's supportive of more fossil fuel development is a death sentence for our generation and the millions of people on the frontlines of the climate crisis,” Varshini Prakash, co-founder of the Sunrise Movement, which has been leading the push for a Green New Deal, said in a statement.

Even before the Reuters story, there were plenty of reasons for people like Prakash to be skeptical of Biden on climate. When he launched his campaign for president on April 29 in Pittsburgh he didn’t mention climate change once. Instead, he gave a lengthy shout-out to union leaders in the audience, promising to “restore,” “rebuild,” and “unify” America after four years under Donald Trump. Buried deep in his 40-minute speech, Biden made a passing reference to low-carbon growth, pledging his support for “rebuilding America’s clean, renewable energy.” He went on to brag that “North American energy makes us independent,” a phrase often used in reference to oil and gas production.

Ed Fallon, a former Iowa legislator turned radio talk show host and climate activist who once played a game of pool with Biden, wasn’t impressed. He found the former vice-president to be “an eloquent speaker and an all-around likable guy.” But with Iowa recovering from two months of historic flooding linked in part to global carbon emissions, and Democrat supporters rating climate change as a top concern, Fallon wanted to know how seriously Biden takes human survival on our planet.

So when Biden spoke in Des Moines on May 2, Fallon and 11 others put on penguin masks and stood directly in front of Biden’s podium holding signs that read “Climate is a crisis.” Biden addressed Fallon’s group directly. “Don’t worry, I’ll get to climate change,” he said, adding, “I introduced climate legislation way, way back in 1987,” a reference to a bill he’d pushed urging President Ronald Reagan to back a task force studying global warming. “You’re preaching to the choir,” Biden said.

But Fallon isn’t so sure. Biden at one point told the crowd that “the United States is soon going to be the largest producer of energy of any nation in the world by the end of the 2020s. My lord, what are we so afraid of?” Biden appeared to be referring to the fact that US oil production has rocketed over recent years to 12.1 million barrels per day, surpassing the output of Saudi Arabia and Russia.

“He’s proud of that,” Fallon told VICE. “Joe’s boasting about being the biggest oil producer. You can’t be proud of that and fight climate change.”

Several days later Biden travelled to Los Angeles to speak at some of his campaign’s first fundraising events. At the home of UCLA School of Medicine faculty member Cynthia Telles and media executive Joe Waz, Biden discussed global warming “in passing,” according to notes emailed to reporters from his campaign. Notes from an event at the Jonathan Club, a private Los Angeles social club, don’t mention climate change at all.

“This is not a second-tier problem,” Stokes said. “This is not something we can pretend will be easy to do and we’ll talk about later, this is a fundamental conversation that has to be happening.”

Biden has at times seemed willing to discuss climate change with the urgency it requires. Earlier this year he told the Conference of Mayors that the US could easily quadruple the wind power it generates and that half of electricity in North America should come “from non-polluting sources” with six years. If rising seas force millions of people out of their homes, he said, “that’s how wars start.”

Biden received an 83 percent score from the League of Conservation Voters for his support of environmental policy as a US senator, a score that may have been higher if he hadn’t missed votes while several times competing in Democratic presidential primaries, said Tiernan Sittenfeld, the group’s senior vice president for government affairs.

But she said with the impacts of climate change becoming clearer and more deadly all the time, “all candidates who are serious about running for president need to make climate change an absolute top-tier priority.” They must prove every day to voters, Sittenfeld went on, that they’ll “move forward in ambitious ways on combating climate change starting on day one in the Oval Office.” The world as we know it could literally be depending on it.