Obama addressed his bill calling for a National Low-Carbon Fuel Standard Tuesday.

ATLANTA, Georgia (CNN) – While campaigning in Los Angeles, California Tuesday, Senator Barack Obama, D-Illinois, stopped at a gas station that offered alternative fuel to address his bill calling for a National Low-Carbon Fuel Standard.

The White House contender showed up at the gas station – the second in California in the process of offering E85, ethanol-based fuel – in a government car without a flexible fuel tank that can run on ethanol, but he stressed that if president, he would make sure things change, including the type of cars federal employees drive.

“The debate about whether or not climate change is a man-made disaster is over. The question now is what we do about it,” said Obama. “We know that transportation fuels account for a third of America’s global warming pollution. And we know there are fuels available that emit less carbon-dioxide into the atmosphere – fuels like biodiesel and ethanol.”

Modeled in part after California’s proposed Low-Carbon Fuel Standard, Senator Obama introduced the legislation last month with Senator Tom Harkin, D-Iowa. The federal proposal would require that all transportation fuels sold in the U.S. contain 5 percent less carbon by 2015 and 10 percent less carbon by 2020. He also asked that automakers more than double the fuel efficiency of U.S.

Obama added the importance of California as a “trend setting state. Demographically [California] reflects where America is moving. We need to speak to the issues that are so important to California.”

Last January, by executive order, California Gov. Arnold Schwarzenegger established a Low-Carbon Fuel Standard statewide with the intent of sparking research in alternatives to oil and to reduce greenhouse gas emissions.

– CNN’s Political Assignment Editor Marissa Muller