In most parts of the world, climate change is a worrying subject. Not so in California. At a recent gathering of green luminaries--in a film star’s house, naturally, for that is how seriousness is often established in Los Angeles--the dominant note was self-satisfaction at what the state has already achieved. And perhaps nobody is more complacent than Arnold Schwarzenegger. Unlike A1 Gore, a presidential candidate turned prophet of environmental doom, California’s governor sounds cheerful when talking about climate change. As well he might: it has made his political career.

Although California has long been an environmentally-conscious state, until recently greens were concerned above all with smog and redwood trees. "Coast of Dreams", Kevin Starr’s authoritative history of contemporary California, published in 2004, does not mention climate change. In that year, though, the newly-elected Mr. Schwarzenegger made his first tentative call for western states to seek alternatives to fossil fuels. Gradually he noticed that his efforts to tackle climate change met with less resistance, and more acclaim, than just about all his other policies. These days it can seem as though he works on nothing else.

Mr. Schwarzenegger’s transformation from screen warrior to eco-warrior was completed last year when he signed a bill imposing legally-enforceable limits on greenhouse--gas emissions--a first for America. Thanks mostly to its lack of coal and heavy industry, California is a relatively clean state. If it were a country it would be the world’s eighth- biggest economy, but only its 16th-biggest polluter. Its big problem is transport--meaning, mostly, cars and trucks, which account for more than 40% of its greenhouse-gas emissions compared with 32% in America as a whole. The state wants to ratchet down emissions limits on new vehicles, beginning in 2009. Mr. Schwarzenegger has also ordered that, by 2020, vehicle fuel must produce 10% less carbon: in the production as well as the burning, so a simple switch to corn-based ethanol is probably out.

Thanks in part to California’s example, most of the western states have adopted climate action plans. When it comes to setting emission targets, the scene can resemble a posedown at a Mr. Olympia contest. Arizona’s climate-change scholars decided to set a target of cutting the state’s emissions to 2000 levels by 2020. But Janet Napolitano, the governor, was determined not to be out-muscled by California. She has declared that Arizona will try to return to 2000 emission levels by 2012.

California has not just inspired other states; it has created a vanguard that ought to be able to prod the federal government into per national standards than it would otherwise consider. But California is finding it easier to export its policies than to put them into practice at home. In one way, California’s self-confidence is fully justified. It has done more than any other state--let alone the federal government--to fix America’s attention on climate change. It has also made it seem as though the problem can be solved. Which is why failure would be such bad news. At the moment California is a beacon to other states. If it fails, it will become an excuse for inaction.

Corn-based ethanol might not be chosen as an alternative because（）

A. carbon reduction in both fuel production and burning might be hard

B. California also intends to cut down emissions from new vehicles

C. it is almost impossible for vehicle fuel to produce 10% less carbon

D. California’s corns are chiefly transported by cars and trucks