Former Vice President Al Gore said he was incorrect about President Donald Trump's stance on climate change issues and staying in the Paris climate accord with other nations.

"I thought there was a chance he would come to his senses, but I was wrong," Gore said Monday on CBS' "The Late Show With Stephen Colbert."

Gore told Colbert he discussed the accord with Trump after the election and had been optimistic about the chances of Trump keeping the U.S. in it. However, Trump later announced the U.S. would pull out of the agreement.

Some positive actions have come despite Trump's exit from the agreement, Gore said.

"I worried that it would be a disastrous move, but immediately after that, all the other countries in the world doubled down, and said we're going to do even more. And here in the U.S., a lot of our most important governors, and mayors, and business leaders said, ‘We're still in the Paris agreement and we're going to meet the commitments of the country regardless of what Donald Trump tweets," Gore said.

Gore has been warning about climate change issues since his failed run as Democratic presidential nominee in 2000. He appeared on "The Late Show" to promote "An Inconvenient Sequel: Truth to Power," which comes out July 28.

Those who are concerned about climate change issues should address it with candidates, Gore said.

"When candidates ask you for your support, tell them, 'This is important to me,' and depending on what their position is, tell them you'll either be for them or you'll do everything in your power to defeat them."

Also Monday, Gore said on NBC's "Today" that there have been positive developments about climate change issues.

"The good news is that solar electricity and wind electricity have come down so far in price, in many areas it's much cheaper than burning electricity from fossil fuels," Gore said.