Back to the Future is a classic film trilogy, and actor Christopher Lloyd would love to make a fourth movie as Dr. Emmett ‘Doc’ Brown about an issue like climate change.

SlashFilm senior writer Ben Pearson wrote July 7 that Lloyd told the Niagara Falls Comic Con in June he still supports the idea of a Back to the Future 4. He indicated a sequel would need to include a supposedly “universal message” such as climate change.

“I think somehow it needs to kind of convey a message about something that’s important to everyone, universally, like climate change,” Lloyd said. He acknowledged making a sequel to the beloved films would be a “tricky, tricky deal,” and warned against it if it would disappoint fans.

However, it’s been quite “tricky” to make climate change films popular. Former Vice President Al Gore’s 2017 documentary An Inconvenient Sequel: Truth to Power drew outrage from climatologist Dr. Roy Spencer for promoting “bad science, bad policy, and factual errors.”

It also bombed at the box office.

Of course, Lloyd’s attitude about climate change having a universal urgency ignores skeptics and critics of liberal views about a climate catastrophe. In fact, the U.S. today is still significantly divided on whether climate change is a natural phenomenon or caused by man, according to Forbes.

According to SlashFilm, it wasn’t the first time Lloyd suggested a Back to the Future movie based on climate change. In a 2015 interview with USA Today, he also said a sequel would need to be “momentous and current” and have a “real urgency to it.” He suggested “dealing with ISIS or climate change or something radical.”

A sequel (climate related or not) is unlikely, since Lloyd indicated he would be happy to star in a fourth film only if co-writers Robert Zemeckis and Bob Gale were interested. In 2018, Zemeckis soundly refused.