DALLAS, Texas (Legal Newsline) - Environmentalists in Texas this week sued in an effort to force the state to regulate carbon dioxide and other greenhouse gas emissions.

The lawsuit against the Texas Commission on Environmental Quality asks a Travis County judge to bar the state from approving coal-fired power plants until the state starts regulating greenhouse gases, which some scientists blame for global warming.

The lawsuit by Public Citizen said the state should be limiting emissions. The group points to a 2007 U.S. Supreme Court decision that classified carbon dioxide as an air pollutant under the federal Clean Air Act.

"Scientists, governments and regulatory agencies in other states, at the federal level, and internationally recognize that CO2 emissions contribute to global warming, thereby causing significant impacts from climate change," the lawsuit says. "Indeed, for many years, the likelihood of such harms has been ever increasingly documented, to the point that CO2 now is recognized to be a very harmful air contaminant and pollutant."

The lawsuit seeks specifically to affect five coal- and petroleum coke-fired plants awaiting permit hearings in the state. The projects are in Nolan, Limestone, Matagorda, Goliad and Nueces counties.

"Texas leads the nation in the emissions of global warming gases. If we were a nation, we would rank seventh in emissions among the countries on earth," said Tom "Smitty" Smith, director of Public Citizen's Texas office. "The time has come for the TCEQ to take its head out of the sand and begin the process to regulate CO2 emissions from Texas sources."

In a statement, TCEQ chairman Bryan Shaw said the jury is still out on the dangers of climate change.

"The science on global warming is far from settled," Shaw said in a statement. He noted that unnecessary state regulations would "impose great costs on Texas, without any guarantee of a measurable environmental benefit. Reducing CO2 in Texas will do nothing to lower CO2 globally, but will have the effect of sending U.S. jobs to China and India."