PROVIDENCE, R.I. – Rhode Island has adopted new standards to cut vehicle emissions of greenhouse gases, which are believed to be a leading cause of global warming.

The new amendments filed Thursday by the state Department of Environmental Management mean that beginning with the 2009 model year, cars sold in Rhode Island will need to adhere to rules that aim to reduce emissions of carbon dioxide and other pollutants by increasing fuel efficiency. The updated regulations take effect in 20 days.

Under the federal Clean Air Act, California is allowed to set pollution standards for cars and trucks that are more stringent than federal standards. Other states can choose either California’s standards or the looser federal rules.

Gov. Don Carcieri, in announcing Rhode Island’s adoption of the California rules, said motor vehicles constitute the largest source of greenhouse gas emissions in the state.

“This will improve the air quality for all Rhode Islanders,” Carcieri said in a statement.

Connecticut, Maine, New Jersey, New York and Vermont have already adopted the standards, while Massachusetts is expected to finalize the regulations on Dec. 30, according to the Rhode Island Public Interest Research Group.

Environmental groups applauded Carcieri for adopting the rules, but rapped the governor for not joining a multistate agreement to reduce carbon dioxide emissions from power plants in the Northeast.

“These new car standards are a big step forward, but the fight against global warming is a zero-sum game,” said Matt Auten of RIPIRG.

“If power plant emissions continue to rise then the gains these new standards create won’t mean much at the end of the day,”

Carcieri spokesman Jeff Neal has said the governor will continue to work with the other states on the power plant emissions initiative, but he wants more time to study whether it would drive up already high energy prices.