LIMASSOL, Cyprus -- A remarkable event occurred this week in California -- one that should cheer environmentalists around the world who were angered by the Bush administration's rejection of the Kyoto treaty on global warming.

California's Democratic governor, Gray Davis, signed a bill that for the first time mandates reductions in greenhouse gases coughed out of the tailpipes of all passenger vehicles sold in America's most populous state. This will cut not the vapors that cause smog -- these are already regulated -- but the invisible emissions that cause global warming.

The decision is not an isolated one. What goes for California goes for the rest of the United States. The Golden State, with its sprawling metropolises and cloverleaf freeway exchanges, is home to 10 percent of Americans and an even larger portion of the nation's automobiles. As Davis noted, it boasts the world's largest fleet of cars, SUVs and pickups. And so California has effectively bypassed Washington and forced car manufacturers in every state to curtail the gases that cause global warming.