When former Vice President Al Gore met with then-President-elect Donald Trump at Trump Tower to discuss climate change a month after the 2016 election, he said was initially optimistic Trump would "come to his senses."

But after Trump announced the withdrawal from the Paris Climate Agreement on June 1, Gore realized he was wrong, he told Willie Geist Monday on TODAY.

"Our country is going through a challenging time for sure, we've never had a president who has deliberately made decisions, the effect of which is to tear down America's standing in the world, starting with the withdrawal from the Paris Agreement," Gore said. "The climate crisis is by far the most serious challenge we face, but he's also undermined our alliances, such as NATO, and hurt our standing in the world in many ways."

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Gore, who starred in and wrote the screenplay for the Academy Award-winning documentary "An Inconvenient Truth," and is in the upcoming "An Inconvenient Sequel," is a staunch environmentalist and has been one of the most prominent voices calling for climate change solutions.

The Paris Agreement — sometimes called the Paris Climate Accord — is an international coalition intended to curb emissions that contribute to climate change. Two nations — Syria, which is torn by civil war, and Nicaragua, which felt the agreement didn't go far enough to protect the climate — did not sign on to the agreement.

Gore said he hasn't spoken with Trump since the president's decision to withdraw the United States from the Paris Agreement, but said he's been troubled by other controversies plaguing the administration.

The former vice president said the "unprecedented assault on our democracy directed by Russia" has created the lens through which the 2016 election must be viewed.

Additionally, Gore said he thinks more disclosures, like emails released by Donald Trump Jr. revealing he met with a Russian lawyer in the midst of the 2016 election, are bound to be revealed.

"John McCain, and by the way I wish him very well in his recovery, he said it's another shoe dropping from the centipede. There's going to be a lot more disclosures ahead if it follows the pattern of all these leaks from apparently inside the White House."

Related: Trump Jr.'s Meeting With Russians Brings Meddling Inquiry to 'New Level,' Sen. Warner Says

Gore said he has complete confidence in Robert Mueller, the special counsel who is overseeing the investigation into possible ties between Russia and the Trump campaign.

"I have so much confidence, as I think everybody does, in Bob Mueller, the independent counsel. It's great our country has a man like him that everybody can rely on [and] whatever they find out, I think people are going to have confidence in it," Gore said.

CORRECTION (July 17, 12:05 p.m.): An earlier version of this article misstated the last name of the special counsel in one reference. It is Bob Mueller, not Muller.