No one at the Air Resources Board is claiming that its new regulation requiring auto windows to do a better job reflecting and absorbing the sun's rays will dramatically slash California's greenhouse gas emissions, the historic goal that AB 32 mandated when it became law in 2006.

But as the state gears up for the epic challenge of meeting the law's requirement to cut greenhouse gas emissions 30 percent by 2020 – and by much more later – the window regulation serves as a reminder that small changes in individual behavior help pave the way for immense changes in the broader economy.

The new window rules adopted by the ARB last week are one of several "early action measures" that the agency has already approved to curb the gases that cause global warming. These measures are, in the words of an ARB official, "low-hanging fruit" that can be quickly – and sometimes easily – plucked before the law's more daunting challenges are confronted.

The other early-action measures involving cars and trucks that have been OK'd include requiring tire-pressure checks during maintenance and cutting greenhouse gas emissions from refrigerant cans used by do-it-yourselfers when they fix air conditioning systems. The ARB also approved a more complex early-action measure cutting the carbon content of vehicle fuels.

The window regulation will resonate with anyone who has lived through a Sacramento summer. The hotter vehicle interiors get, the harder air-conditioning systems have to work to cool them down, and keep them comfortable. The new regulation requires that beginning in 2012, new cars sold in California have windows that block more of the sun's energy. If things go as planned, that will mean cooler interiors, less demand on air conditioners, and fewer greenhouse gas emissions.

The cost will be about $70 per vehicle for the standard mandated for 2012, and $250 for the tougher limits set for 2016. Those investments, the ARB says, will take so much carbon dioxide out of the atmosphere that by 2020, it will be comparable to removing 140,000 cars from the road.

Would that mean the polar ice caps are now safe? Hardly. To keep things in perspective, a rough calculation suggests that the state window regulations will have about one-tenth of 1 percent the impact on greenhouse gas emissions as the new vehicle-mileage standards President Barack Obama announced in May.

But that doesn't mean that the new window rules, and the early-action measures generally, are insignificant. It's true that the big battles in the war against climate change will be fought over the major policy changes mandated by AB 32 – sharp improvements in vehicle emissions, alternative energy use, building conservation, and the establishment of a "cap and trade" system for emission permits.

But even if these policies deliver on their promised cuts in greenhouse gases at an affordable price – and the jury remains out on whether they can – they won't by themselves be able to fashion the new energy culture we'll almost certainly need in the decades ahead.

That will require smaller, more personal changes in the way we live – from the cars and appliances and power sources we choose, to the way we use them. More efficient windows are a part of this cultural shift. It may be a small step, but it's one that's well worth taking.