Former Vice President Al Gore on Sunday offered Chicagoans a playbook on how to proselytize about a warming planet in the face of doubters.

“Give them the gift of your attention and let them feel as if they’re being heard. Ask them ‘What part of the scientific consensus troubles you?’ and then try to zero in on that particular part,” Gore told a nearly packed Harris Theater, where he was a speaker at the Chicago Humanities Festival.

“With some, you get the feeling that they’re reading off an internal teleprompter from Fox News and maybe they’re not willing to listen to you, in which case, be kind and say ‘Well, I’ve enjoyed talking to you’ and try to direct your efforts on people who are willing to listen.”

Gore has had firsthand experience in such failure.

“I tried to convince Donald Trump. I’ve had many conversations with him after the election, after he went into the White House, and I thought he would come to his senses, but I was wrong.”

He said of Trump and Environmental Protection Agency chief Scott Pruitt: “There’s zero chance, in my opinion, of changing their minds.”

But his message wasn’t all doom and gloom.

“We’re going to win this regardless of what he tweets,” Gore said of Trump and his support of the fossil fuels industry that contributes to global warming.

“Investors are shifting assets towards renewables,” he said. “This is now embedded in the business plans of the vast majority of companies.”

Gore feigned crying for a moment, to the delight of the audience, when former Chicago Public Radio host Alison Cuddy, who moderated the discussion, told Gore he showed “incredible character” by accepting the Supreme Court’s decision in 2000 that handed the presidential election to George W. Bush.

She then asked if he would have done the same if Trump was his Republican opponent.

Gore didn’t answer the question directly.

“I actually consulted the Constitution after the court’s decision and found that there’s no intermediate step between a final Supreme Court decision and violent revolution,” he said with a laugh. “I won’t say I briefly considered the latter, but . . . .”

“All I did was something reflected in Winston Churchill’s famous quotation about the United States of America. He said ‘The United States generally does the right thing after first exhausting every available alternative.’ That’s really all I did.”

Cuddy also asked if Gore thought the Trump administration was far worse than previous administrations in regard to environmental protection?

Gore’s sarcastic reply: “Ya think?”

Gore’s book, “An Inconvenient Sequel: Truth to Power” was on sale outside the theater. Gore was not paid for the speaking engagement, Nick Conger, a spokesman for Gore said Sunday.