“No god? … No problem!” reads the advertisement featuring the smiling faces of people wearing Santa Claus hats. “Be good for goodness’ sake.”

Over the next two weeks, 270 of the ads will go up on city buses and trains in the Washington area as part of the holiday kickoff to campaigns sponsored by secular groups in cities around the country and abroad. If last year was any indication, the signs are likely to spark a theological war of words.

“We don’t intend to rain on anyone’s parade, but secular people celebrate the holidays, too, and we’re just trying to reach out to our people,” said Roy Speckhardt, the executive director of the American Humanist Association. “To the degree that we are reaching out to the godly, it’s just to say that you can be good without god…”

Elsewhere, this year’s secular signs vary in tone.

In Seattle, this year’s signs say “Millions are good without God.” In Las Vegas, signs to be put up this week will say “Reasons Greetings” and “Yes, Virginia … there is no God…”

The campaigns come against a backdrop of a growing number of nonbelievers. Fifteen percent of Americans identified themselves as having “no religion” in a 2008, up from 8 percent in 1990, according to a study by the Program on Public Values at Trinity College in Hartford.

Overdue.