Leonardo DiCaprio Peppers President Obama With Climate Questions at SXSL

The Hollywood Reporter

Oscar-winning actor Leonardo DiCaprio on Monday didn't pull any punches when talking climate change with President Barack Obama on the White House lawn during the South by South Lawn festival.

In a conversation with the president and Texas Tech atmospheric scientist Katharine Hayhoe, the star of The Revenant??and Titanic??struck the urgent tone of his upcoming documentary on the dangers of climate change,??Before the Flood, which??DiCaprio??was at the White House to promote. The film premiered at the Toronto International Film Festival in September.

"If you do not believe in climate change, you do not believe in facts or in science or empirical truths," DiCaprio said in his opening remarks, "and therefore, in my humble opinion, you should not be allowed to hold public office."

Read more: Watch the Trailer for Leonardo DiCaprio's Climate Change Doc 'Before the Flood'

The actor kept the pressure on while moderating the discussion: "Does our planet have the ability to regenerate if we do the right things? Or has there been enough lasting damage that can never be undone?"

He also called out the "corporate greed of the oil and gas industries," asking for tips on how politicians can wrangle big corporations into curtailing their profitable policies.

Obama sounded hopeful in his repartee with the movie star, but hit upon several harsh realities.

"We're on the more pessimistic end of what was possible," the president acknowledged, referring to recent scientific findings about levels of carbon dioxide in the atmosphere. He added that "the likelihood of an immediate carbon tax," which some experts view as the only public policy capable of curbing carbon emissions, "is a ways away."

Last week, data came in from one of the world's best facilities for studying the climate that confirmed carbon dioxide now makes up 400 parts per million of the atmosphere, a milestone that scientists had long been wary of. The report said the levels would persist "for the indefinite future."

The conversation was part of South by South Lawn, a DC adaptation of the annual Austin, Tex.-based film, music and media festival South by Southwest. The day-long event included a presentation from the 3rd Annual White House Student Film Festival, a partner of the American Film Institute.

In March, President Obama appeared at South by Southwest to discuss civic engagement in the digital age with Texas Tribune editor-in-chief Evan Smith.