Similar benefits are predicted from rules requiring people to keep their tires properly inflated and for tougher regulations on the manufacture of semiconductors.

Requiring trucking companies to make their rigs more aerodynamic will net a little more than 1 MMT. And capturing more methane from landfills could knock out 2 to 4 MMT of greenhouse gases.

Altogether, CARB is proposing 44 different regulations just to cobble together that 24 percent. And any one of these regulations could lead to a political fight. Each regulation affects a particular industry or a particular part of the California lifestyle.

Let's see: 17 percent plus 24 percent ... that leaves 59 percent of the CO2 pie still to be accounted for. CARB only has until the end of 2008 to figure out where those remaining reductions will come from.

Some of the rules are on the drawing board already. The state's Low-Carbon Fuel Standard, called for in an executive order from Schwarzenegger earlier this year, could reduce California's total emissions by 10 to 20 MMT a year. State laws requiring California to use more renewable energy should also contribute to the reduction.

After all that, you'd still end up putting just as much CO2 into the air in 2020 as you did a generation earlier. But you would also be the first generation to force the line on the graph measuring global-warming pollution to go down, not up. And that's a good thing.