David Letterman transforms into a more overtly environmentally conscious (and beardier) television personality by tackling clean energy in the National Geographic Channel’s docu-series “Years of Living Dangerously.”

The project is Letterman’s first on-air showing since he left Late Night in 2015.

The series, now in its second season, features celebrity hosts who are dedicated to fighting global warming. Producers of the series David Gelber and Joel Bach said they sought out Letterman because they could see his enthusiasm talking about clean energy and felt “he’s definitely invested in this issue.”

In his episode, Letterman will travel to meet with India’s Prime Minister Narendra Modi and other important figures to talk about making clean energy a reality.

“My goal here is a conversation. Containing several points both personal and with regard to environmental issues and climate change,” Letterman said in a behind-the-scenes video, as he prepares to interview.

“If the world helps me with technology, helps me with resources, I will be the very first person to switch over to clean energy completely,” Modi said after Letterman asked how he could bring solar power to millions of people in India without it.

Other Season 2 guests of the Emmy-award-winning show include America Ferrera, Sigourney Weaver, Ian Somerhalder and Don Cheadle.

The episode featuring David Letterman, titled “Into The Light,” will air Oct. 30.