Jill Stein, the Green Party's 2016 presidential nominee, challenged climate change activist Al Gore Albert (Al) Arnold GoreCruz says Senate Republicans likely have votes to confirm Trump Supreme Court nominee 4 inconclusive Electoral College results that challenged our democracy Fox's Napolitano: 2000 election will look like 'child's play' compared to 2020 legal battles MORE to step up his efforts.

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Gore, who served as vice president under Bill Clinton William (Bill) Jefferson ClintonChelsea Clinton: Trump isn't building public confidence in a vaccine Hillary Clinton launching podcast this month GOP brushes back charges of hypocrisy in Supreme Court fight MORE, met with President-elect Donald Trump Monday in New York City.

"I'd like to see Al Gore, for that matter, step up to what we really require, which is 100 percent renewable energy, clean renewable energy by 2030," Stein said in an interview Monday on CNN.

Gore, who previously warned that a President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE would lead to a climate catastrophe described his meeting with the president-elect as "sincere" and "productive."

He also met with Ivanka Trump, and said in an MSNBC interview Monday night that she appears to be committed to the climate.

“It's no secret that Ivanka Trump is very committed to having a climate policy that makes sense for our country and for our world," Gore told Chris Hayes on "All In."

"And that was certainly evident in the conversation that I had with her before the conversation with the President-Elect. And I'm — you know, I appreciate the fact that she is very concerned about this.”