“There is no contradiction between being smart on the environment and having a strong economy, and we've got to keep it going,” Obama said.
“The fact is that it's man-made,” he said. “It's not, 'We think it's man-made.’ It's not, ‘A lot of people are saying it's man-made.’”
Protecting the environment, he said, won’t happen “if we pretend a snowball in winter means nothing’s wrong...if we boast about how we’re going to scrap international treaties.”
"The light Harry lit shines bright as ever [on Lake Tahoe]," he said.
The outgoing president also promised to return to the lake after leaving the White House.
"This is really nice, I will be coming here more often," he said. "My transportation won't be as nice, but I'll be spending more time here."
Obama said the visit reminded him of "The Godfather II," and a scene in the film where Fredo Corleone, one of the main characters, is killed while fishing on Lake Tahoe.
"'The Godfather' II is maybe my favorite movie. As I was flying over the lake I was thinking about Fredo," he said, to laughter. "It's tough."
The Nevada Democrat praised Obama for protecting more than 260 million acres of public land and waters. Republicans have criticized Obama for using executive authority to create national monuments, a cornerstone of his environmental legacy.