Jack Johnson doesn't agree with his image as a mellow guy, but that's cool.

"I never thought of myself as mellow," says the surfer-turned-music-star. "But I don't mind — it's not a bad thing to be called."

The 33-year-old singer/songwriter with the breezy baritone and casual style, who often plays to thousands of fans wearing faded T-shirts and baggy board shorts, has become the icon of laid-back celebrity. With album sales of almost 10 million, including 1.3 million of his latest, "Sleep Through the Static," according to Nielsen SoundScan, he's big enough to be targeted by "Saturday Night Live," which spoofed him in a skit in April featuring Andy Samberg as the host of "The Mellow Show."

Still, he prefers to shun the spotlight. "If you do too many interviews, you start to believe your own press, and eventually you're in danger of becoming a caricature of yourself," he says. "When you're always talking about yourself in interviews, it's hard to find a balance between your public image and yourself."

On tour through August — on Saturday, he headlined the Virgin Mobile Festival in Baltimore — Johnson dutifully boards buses and planes to perform at venues around the world. But every month, he heads home to O'ahu's North Shore, where he spends time with Kim, his wife of eight years, and their two sons. Once home, he trades in his guitar for a surfboard.

"At a certain point, being around a lot of people and playing shows isn't healthy for me," he says. "I need to get off of the tour periodically; I can't be away from home for long periods of time. A lot of the songs get written while I'm in the ocean because I have time to think out there. There's a connection to nature, and for me, it's not a struggle to write the music when I'm surfing."

Another thing Johnson's not mellow about: the environment.

Though he understands that touring is a necessary part of his success, concerts leave a deep carbon footprint. "We wanted to more than just lessen our impact, but actually make a positive one," he says.

His musical success has afforded him the ability to stipulate the conditions under which he'll perform. Johnson's contracts require that event organizers compost and recycle at least 50 percent of the show's waste and purchase carbon-dioxide offsets covering the show's energy use.