TWO NIGHTS later, Steger is back on the party circuit. This time it's a mellow gathering at Diane Isaacs's art-filled home in Brentwood. Looking refreshed after a three-hour hike in the Santa Monica Mountains, Steger mingles with early arrivals while Diane's husband, Greg, an athletic trainer from South Africa, shows a few digital photos of Lance Armstrong training for the New York City Marathon. Greg was his coach.

Isaacs has assembled an impressive group. On hand for margaritas and homemade paella are Lew Coleman, president of DreamWorks Animation; Lloyd Phillips, a producer from Sony; Beau St. Clair, Pierce Brosnan's production partner; Richard Bangs, an explorer and entrepreneur; and Bangs's girlfriend, Laura Hubber, a reporter for the BBC.

Just before everyone sits down to eat, Peter Guber, the producer of The Color Purple, Gorillas in the Mist, and other blockbusters, rolls in with his wife, Tara, a redhaired fireball who's heavily into yoga and the environment. She's toting a copy of Contact: The Yoga of Relationships, a book she co-wrote. After hearing about Steger's exploits from her friend Isaacs, she insisted that her husband meet him.

Peter Guber skips the buffet and sits next to Theo and Steger, who listen silently as Bangs quizzes Guber about movies. "What do you think is the most impactful film you've ever made?" he says.

"Gorillas in the Mist made a huge impact," Guber says, shaking the ice in an empty Starbucks cup. "Movies are an emotional issue, just like the environment. But in the end, it all comes down to the pocketbook. It's the same with global warming—it's market-driven."

After dinner, guests migrate to the living room for Steger's slide show, while Guber self-mockingly vents about the type of Hollywood environmentalist who owns both a hybrid and an Aston Martin—like he does. "I had a friend who bought a car that ran on French-fry oil," he jokes, "but it always made him hungry!"

Steger, who kept mum during dinner, starts clicking through slides of receding polar ice, mixed with charts and graphs. After 20 minutes, he turns the floor over to Theo, who tells it like it is.

"I was born in an igloo. We had no electricity. We lived nomadically and traveled by dogsled to visit relatives," he says. "My culture has been the same for 8,000 years. But it's changed drastically in the last 30 years. Who knows what'll happen in the next five?"

Soon, the lights come on and the group sits in silence. Bangs tries to lighten the mood. "I have a dumb question," he says to Theo. "Why can't we just put polar bears in Antarctica and penguins in the Arctic?"

"I don't think they'd adapt very well," Theo replies.