California is fighting mightily to impose its own carbon-dioxide emission standards on the auto industry. You have to wonder why the state is in such a mad rush.

First off, climate experts say it will take until the end of this century to reverse the effects of man-made global warming. Yet, California insists its emission regulations must be met by 2016.

The state says it will reduce greenhouse gases by 33 million tons (30 million t) by 2020 and 55 million tons (50 million t) by 2050. Pretty impressive numbers, until you put them in perspective.

Cars and light trucks account for only 18% of total CO2 emissions in the U.S. In car-crazy California, they account for 27%, according to California Air Resources Board data. Even if the state eliminated all automotive CO2, that still leaves 73% of other man-made sources untouched. Yet it's the automotive industry in the crosshairs.

Even more telling, California only accounts for 1% of global CO2 emissions. So is it really fixing anything? Besides, it has plenty of greenhouse gases blowing in from India, China and other points in Asia. What's California going to do about that?

You can't blame the state for trying, but you can blame it for trying something that's unworkable. California set a CO2 standard that requires a fleet average of 35 mpg (6.7 L/100 km) by 2016. That translates into an average of roughly 43 mpg (5.5 L/100 km) for cars and 26 mpg (9 L/100 km) for trucks. By 2020, cars will have to average about 49 mpg (4.8 L/100 km), and trucks will have to average 33 mpg (7 L/100 km).

Today, only one car can meet that 43 mpg standard, and that's the Toyota Prius. Even the Honda Civic hybrid falls short. Not one truck even comes close to the target. And remember, that standard is what the entire fleet has to average.

About 16 other states want to adopt California's regulations. I don't see how the auto industry is going to meet them. It's not a question of foot-dragging, a lack of technology or even money. It simply is not physically possible to retool the entire fleet in that time-frame. Even meeting the less stringent federal corporate average fuel economy standard by 2020 will be a stretch.

Amazingly, any auto maker selling fewer than 60,000 vehicles in the state doesn't have to meet the rules. This exempts every auto maker, except the Detroit Three, Toyota, Honda and Nissan. Giant auto makers such as Volkswagen, BMW and Daimler get a free ride. Is that fair?

It's pretty clear what's going to happen. The auto makers forced to meet the standard will have to restrict what they sell in California. Everyone else will shoot for big gains in sales that deliberately fall just short of the 60,000 limit.

I'm tempted to say, “Here we go again,” recalling the state's disastrous attempt at energy deregulation and its failed electric-vehicle mandate.

Not only is California's standard unfair, it risks a big consumer backlash when car buyers discover their choices are limited. To say it in a way most environmentalists will understand, this mandate is not sustainable.

John McElroy is editorial director of Blue Sky Productions and producer of “Autoline” for WTVS-Channel 56, Detroit.