WHAT IT’S ABOUT Last winter, David Letterman and a production crew went to the Indian state of Uttar Pradesh — population 204 million — to produce a story on India’s growing reliance on coal and attempts to also expand renewable energy. He interviews, among others, the prime minister of India, Narendra Modi, who says that India needs international assistance if his renewable energy mandate is to be achieved. Meanwhile, Letterman learns of a plan to bring electricity to 300 million Indians currently without power. In this second-season premiere of NatGeo’s series on climate change, Cecily Strong of “Saturday Night Live” also reports on solar energy in Nevada.

This is Letterman’s first official TV project since leaving “Late Show.”

MY SAY A year and change ago, David Letterman fell off the grid, then grew a flowing white beard which indicated he had fallen a little further off the grid, and finally flew to remote parts of India to report on — guesses? any guesses? — the grid.

Which simply goes to prove: Second acts can sometimes have their own confoundingly strange and unpredictable logic. That Letterman’s did almost makes perfect sense.

Not that this is full-fledged “second act” just yet. For all we — or Letterman — know, this could just be the intermission. But in a recent interview with The New York Times, he indicated he wants to do more pedagogic-like TV in this vein, so let’s go ahead and call this the likely beginning of the second act.

As a neophyte reporter he brings the right — if not yet fully sharpened — tools to the task. He’s curious, lively, compassionate and displays the familiar and well-practiced skill of wasting no one’s time by getting straight to the point. After patiently listening to the prime minister of India cite Gandhi in explaining why it is his spiritual duty to bring renewable energy to India, Dave asks: “Does it bother you spiritually that coal will be used to electrify the entire country?”

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Walking through the almost surreally packed streets of an Uttar Pradesh city, Letterman seems to float above the fray — for all appearances, a celebrity sadhu, or holy man, with flowing beard and quips as opposed to epigrams. “Could you go a little faster?” he jokes to his rickshaw driver, who is momentarily startled by his hirsute passenger.

Later, talking to a child by candlelight in a town without electricity, the quips are gone. Instead: “I never imagine kids breathing in toxic fumes just to do their homework. But there are 300 million people here with no access to electricity.”

For his first venture into nonfiction TV, Letterman has tackled among the biggest of subjects — third-world energy consumption — but this particular subject is an elephant. The economic, political, geopolitical and demographic components of Indian energy policy aren’t touched upon, and there’s no mention of wind or hydroelectric power. Dave does seem to capture the essence of India’s Catch-22 — the country’s decaying electric grid “bleeds” out so much power, that more coal burning is needed just to keep pace — but you may begin to wonder if that’s the whole story, or simply only the tail of the elephant.

NatGeo’s “Years of Living Dangerously” is a variant of citizen journalism known as celebrity-citizen journalism — including Strong, other “reporters” this season will include Jack Black, Gisele Bündchen, Ty Burrell and Joshua Jackson. No one’s expecting a treatise when they watch this, but rather an earnest, eye-level, passionate and human — or at least human-celebrity — glance at a vitally important issue, global warming.

So, mission accomplished, Dave. Now, what’s next?

BOTTOM LINE Former late-night talk show guy goes to India, reports on global warming, cracks occasional jokes. Also makes a plausible case for a second career act.