It's not much of a stretch to say global warming policy will be on trial at the U.S. Supreme Court today.

Twelve states are squaring off against the U.S. Environmental Protection Agency, which they say has failed to do its job by refusing to limit emissions of carbon dioxide, a heat-trapping greenhouse gas.

But in Texas, where the state climatologist says global warming is a pressing concern and scientists say the Gulf Coast could be flooded within the century, the attorney general has joined a smaller coalition of states that sides with the EPA, which says the gas is not a dangerous air pollutant.

The Texas attorney general's office did not even consult the state's environmental agency before signing onto the legal brief submitted to the high court, according to one of the agency's commissioners.

"The State of Texas' intervention in this case wasn't derived from any formal request" from the Texas Commission on Environmental Quality, said Larry Soward, one of three members of the commission. "This agency did not ask the attorney general to intervene in the lawsuit on our behalf, nor have we been involved.

"It's routine or common course for the agency with regulatory authority to be integrally involved. And that hasn't been the case."

The attorney general's office and the governor's office refused to comment on the case.

Texas is the No. 1 emitter of carbon dioxide nationally, with roughly a third coming from tailpipes, a third from industries and a third from utilities.

"The states signing up on different sides reflects realities in the states," said Jared Snyder, a lawyer with the New York attorney general's office who has worked on the case. "We in the Northeast are trying to ratchet down carbon dioxide."

The case, Massachusetts v. EPA, boils down to whether the agency should regulate carbon dioxide emitted by new cars in an effort to curb global climate change. In 2003, a band of 12 states, most of them from the Northeast and the West Coast, asked the EPA to regulate the gases under the federal Clean Air Act.

The EPA refused, and the states, which claim they face real threats, including the flooding of coastal areas, sued.

Carbon dioxide is a "major contributor to climate change globally and locally," said John Nielsen-Gammon, the state climatologist for Texas and a professor of meteorology at Texas A&M University. Emissions of carbon dioxide are "a legitimate cause of concern."

Texas decided not to stay out of the case — as a bunch of others did — and signed onto a brief circulated by the State of Michigan, the home of U.S. automakers, which argues that the Clean Air Act should not address carbon dioxide emissions because much of the gas is emitted by foreign nations.

The Clean Air Act, the nine states argue in the amicus brief, does not "authorize EPA to set emission standards that will not meaningfully address an air quality issue like global climate change," which is caused primarily by "CO2 and other greenhouse gas emissions from outside of the United States."

"Instead, the Act is designed to actually achieve air quality goals that will effectively protect public health and welfare through U.S. emission reductions."

Regulation of carbon dioxide emissions would put industry — especially the auto industry — at a competitive disadvantage, said Rusty Hills, a spokesman for the Michigan attorney general's office.

"The developed world already has more pollution controls than the Second World or Third World," Hills said. "If industry needed to do more to comply, it could further adversely affect industries in competition."

The Bush administration is committed to reducing greenhouse gas emissions, EPA spokeswoman Jennifer Wood said.

But the White House prefers voluntary actions by industry rather than federal regulation to curtail emissions.

Although the case is strictly about vehicle emissions, it could have implications for other industries if carbon dioxide is found to be a chemical the EPA should regulate.

Texas has gained national attention, for instance, for plans by utility companies to build coal-fired power plants, which would add about 115 million tons of carbon dioxide annually into the atmosphere. The carbon dioxide emissions from 11 of the new plants, proposed by TXU Corp., would be the equivalent of adding 10 million Cadillac Escalades on the road, according to the nonprofit Environmental Defense.

Texas Gov. Rick Perry has supported the plant proposals and has been routinely attacked by environmentalists because of it, despite the state's taking a lead in renewable energy generation.

"Texas is one of the few places that refuses to be part of the discussion in how to limit emissions," said Colin Rowan, a spokesman for Environmental Defense. "We should hold ourselves accountable to how much we emit."