SAN FRANCISCO - A federal judge in San Francisco has thrown out a lawsuit that the state attorney general filed against the six largest automakers, in what had been billed as a novel attempt to hold the companies financially liable for global warming.

The suit alleged that carmakers have damaged the state’s natural resources and created a public nuisance by producing “millions of vehicles that collectively emit massive quantities of carbon dioxide.” Those emissions required major expenses in firefighting and other areas, the suit said.

But in a 24-page decision Monday, U.S. District Judge Martin Jenkins said it would be inappropriate for the court to wade into the “global warming thicket” as it pertained to interstate commerce and foreign policy - matters he said should be left to the political branches of government.

“In this case, by seeking to impose damages for the defendant automakers’ lawful worldwide sale of automobiles, plaintiff’s nuisance claims sufficiently implicate the political branches’ powers over interstate commerce and foreign policy,” Jenkins wrote.

The automakers aren’t the only companies responsible for global warming, he said.

“In this case, there are multiple worldwide sources of atmospheric warming across myriad industries and multiple countries,” Jenkins wrote.

The suit was filed in September 2006 by then-state Attorney General Bill Lockyer against General Motors, Toyota, Ford Motor Co., Honda North America, Chrysler Motors Corp. and Nissan North America.

Theodore Boutrous, a Los Angeles attorney representing the automakers, said his clients were pleased that the lawsuit was tossed.

“Our bottom-line point is that global warming presents exceedingly complex policy issues that must be addressed at the national level by Congress and the president, not through lawsuits seeking damages in the federal courts,” he said.

In announcing the suit last year, Lockyer noted that cars produce about 30 percent of the carbon dioxide emitted in California. “It is time to hold these companies responsible for their contribution to the (global warming) crisis,” he said.

“Global warming is harming California, its environment, its economy and the health and well-being of its citizens,” said the suit, which Attorney General Jerry Brown took over in January.

In his ruling, Jenkins said the state had not proved that there was a sound framework by which global-warming nuisance damages could be assessed.

At a hearing earlier this year, Jenkins said it could be difficult for a judge or jury to determine how much California residents were being harmed by one industry’s contribution to a global problem.

Ken Alex, a supervising deputy attorney general, said the decision was disappointing.

“But we’ll take some time to carefully review the decision and see what next steps are appropriate and whether it’s appropriate to take an appeal,” he said.

Alex said he recognized that the judge was reluctant to “jump into the middle of the global-warming dispute. On the other hand, we think it’s such an important issue that it may be appropriate to ask the court to do just that.”

The suit sought unspecified damages for the harm to state lands, waters and the air, as well as the state’s costs in planning and prevention. Global warming can kill trees and habitat and change the state’s annual precipitation. Rising sea levels will probably inundate roads and other infrastructure like sewage-treatment plants and public buildings.

Another federal judge is considering automakers’ challenge to a California law that requires vehicles to limit emissions of greenhouse gases starting in 2009.

“When it comes to solving global warming, the eyes of the world are still on California,” said Jeremy Symons of the National Wildlife Federation. “If the Bush administration will not lead on global warming, they need to get out of the way and let California pave the way forward.”

© 2007 San Francisco Chronicle