Texas would rank seventh in the world in carbon emissions if it were its own country, according to the most recent figures from the U.S. Energy Information Administration.

Texas, the second most populous state, behind California, has 23.5 million people and more than 20 million registered vehicles, about one in four of them a pickup truck. California has a population of 36.5 million and 33 million registered vehicles.

Transportation accounted for 28 percent of Texas' carbon emissions in 2003.

The number of hybrid vehicles registered in Texas more than doubled last year, to 48,550. Still, that's only a fraction of 1 percent of all vehicles registered in the state.

"As more hybrids are added on, particularly hybrids that are trucks, you see a spike in those," said Kim Sue Lia Perkes, a spokeswoman for the Texas Department of Transportation title and registration division. "You might not get Texans out of their trucks, but they will buy their hybrid trucks."

For more on Pollution and Texas check out this AP story: Texas Is Biggest Carbon Polluter.