David Letterman is back, baby, and just in time, because we cannot stop ruining our air and water. The former Late Show host returned to television for the first time this year to interview India’s prime minister, Narendra Modi, about clean energy for the National Geographic Channel’s Years of Living Dangerously. The second season of the docuseries features Letterman, among other celebrity hosts like Sigourney Weaver and Don Cheadle, throwing his wry humor and seasoned interview skills behind the fight against global warming. Letterman’s episode on solar energy, titled “Into the Light,” airs October 30. And hey, if nothing else, even if humankind fails in its attempt to stop the planet’s slow slide into oblivion: Free sandwiches.