Politics 2016: DiCaprio and Obama at White House First South by South lawn Event

Star and producer DiCaprio moderated a panel at the White House’s first South by South Lawn event on Monday. He took a swipe at politicians–Donald Trump–who deny that climate change is real, claiming that “they should not be able to hold public office.”

Donald Trump has said that climate change is a “hoax,” even though he denied saying that when Hillary Clinton brought it up at last week’s debate.

DiCaprio moderated a panel with President Obama and Katharine Hayhoe, a climate scientist at Texas Tech University. It was tied to a screening of DiCaprio’s new documentary “Before the Flood,” which airs on National Geographic Channel on Oct. 30.

“If you do not believe in climate change, you do not believe in facts or science or empirical truths, and in my opinion you should not be allowed to hold public office,” DiCaprio said.

Part of the panel was devoted to Obama and his administration’s accomplishments on curbing climate change, including the international agreement reached in Paris in December. But he also warned that “climate change is happening at a faster rate than what was predicted even five or ten years ago.”

“We’re in a race against time,” Obama said.

But Obama also tried to give hope that actions like a carbon tax or switch to alternative energy will be meaningful. He cited past efforts to solve environmental damage, like the reduction of acid rain and the recent signs of restoration of the ozone layer. The latter, Obama said, came about because “all it took was people not using aerosol deodorant…it was also a few other things.”

He also recalled his first year of college in Los Angeles in 1979, when he thought that the sunsets were “spectacular” and looked almost “psychedelic.” But that was because of the heavy smoke, which has since been substantially reduced.

DiCaprio noted that in this “unusual election year, to say the least,” environmental concerns rank low in polling on issues top on the minds of voters.

Obama said that climate change was “almost perversely designed to be really hard to solve politically.” When it comes to communicating the issue, “We have to make it visual and make it vivid in ways that people understand.”

Hayhoe also said that too often assumptions are made about who will care about the issue. “One of the most insidious myths is, ‘I have to be a certain type of person to care about climate change.’” She cited the huge growth in wind energy in Texas, including small towns that are fast moving to new energy resources.

The South by South Lawn event was modeled on South by Southwest, where Obama spoke in March. It features panels featuring artists, tech entrepreneurs, and filmmakers.