It's been four-plus years since California passed the nation's first law ordering the slashing of greenhouse-gas emissions from cars and trucks. And, depending on the outcome of the automakers' lawsuit challenging the law and the regulations it spawned, new vehicles will have to do their part to combat climate change starting with model year 2009.

By 2016, new-car emissions of carbon dioxide, methane and other gases that act like a blanket and trap the planet's heat will have to be 30 percent lower than they are today.

With 2009 models a year and a half away from rolling out, a special-interest group, the SUV Owners of America, apparently is getting anxious. The organization last week launched an advertising campaign criticizing California's law as misguided, costly and impractical.

In a statement, group spokesman Ron DeFore said: "This is absurd. Even if you were to eliminate all vehicles in California, it would reduce worldwide greenhouse gases by only one-tenth of 1 percent. So this law will have no effect on global temperatures."

In an accompanying "fact sheet," the organization adds: "There is no device, no converter or trap that can be bolted to a vehicle to capture carbon dioxide emissions. The only way to produce less carbon dioxide is to drive less or drive a smaller car."

Well, yes and no.

"They're absolutely correct. There is no catalytic converter for carbon dioxide," said Jerry Martin, spokesman for the California Air Resources Board that wrote the regulations. "But that's only about 10 percent of the story."

There are dozens of ways to reduce carbon emissions, such as better design and building more gas-electric hybrids, Martin said.

It is not true, he said, that the only way to curb emissions is to improve fuel economy.

And Martin said the sport utility vehicle group erred in estimating California cars' contribution to global warming.

Given the United States is responsible for a quarter of all greenhouse-gas emissions and that vehicles account for 40 percent of California's, Golden State cars contribute more like 1 percent of the worldwide total, he said.

I'm not sure the group has any business whining about the regs. Clearly, it's not just the power plants that are to blame for climate change, and if something is to be done about it, we commuters have got to help.

And besides, what's wrong with driving a smaller car?

It's about time this insane craving for monster vehicles come to an end, anyway.

Readers are encouraged to ask questions and submit ideas for commuter columns. Staff writer Dave Downey may be reached at (760) 740-5442 or ddowney@nctimes.com. For the latest traffic conditions, or to comment on this column, go to nctimes.com.