(Host) The automobile industry is fighting Vermont's efforts to limit greenhouse gas pollution.

But the state and environmental groups have an important ally in their court case.

A leading NASA researcher on climate change has testified in the case.

He says it's important to cut pollution from cars if the world is going to make any headway against global warming.

VPR's John Dillon reports:

(Dillon) Vermont and other states have followed the lead of California. The new rules require a gradual reduction in carbon dioxide pollution from cars.

Beginning with the 2009 model year, car companies would have to reduce CO-2 emissions by 2%. The rules are designed to lead to a 30% reduction by 2016.

But the industry has challenged the rules in federal court in California, Rhode Island and Vermont.

As part of the court process, the states and environmental groups have provided experts witnesses. And one of the main experts defending the rule is Scientist James Hansen director of NASA Goddard Institute for Space Studies.

(Valentinetti) "He is probably one of the most credible scientists out there dealing with the issue of climate change and global warming."

(Dillon) Richard Valentinetti directs the state's air quality division. He says Hansen makes the direct link between vehicle emissions and climate change.

(Valentinetti) "The tailpipe emissions and the ability to reduce emissions from automobiles seems to be a key component to reducing greenhouse gases."

(Dillon) Hansen has worked on climate research for 40 years. He's not getting paid for his testimony, and he makes clear in court documents that he's speaking as a private citizen, not as a government scientist.

Last winter, his outspokenness caught the attention of the Bush Administration. Officials told Hansen that they would review his lectures, Internet postings and public statements.

In his written testimony, Hansen says motor vehicle emissions are the fastest growing source of carbon-dioxide. He says controlling CO-2 from cars is a needed first step for the planet to avoid catastrophic warming.

Anthony Iarropino, a lawyer for the Conservation law Foundation, says it's significant that the scientist chose to get involved in the court case.

(Iarropino) "I think him going to that length is a demonstration that this greatly transcends politics for him and just as a scientist and a private citizen he feels very strongly that this program is a step in the right direction and is something that should happen."

(Dillon) The car companies have argued in court documents that the states don't have the authority to issue the new regulations. They say that by placing limits on CO-2 the states are actually regulating fuel economy, which only the federal government can do.

The industry also says that the new emission controls would be expensive, and that consumers would have to pay about $3,000 more per vehicle.

For Vermont Public Radio, I'm John Dillon.