The suit comes one year to the day after the Supreme Court required the EPA to decide how to regulate greenhouse gas emissions from cars under the federal Clean Air Act.

Katherine Kennedy, Deputy Attorney General for Environmental Protection, says the first step for the EPA needs to be "endangerment determination."

KENNEDY: Which is an acknowledgment that global warming poses dangers for the public health and welfare. After that initial step, the EPA should go through the process of figuring out what standards should apply.

REPORTER: A spokesperson for the EPA says they're reviewing the petition. And they'll take into account all sources of emissions to find the best approach for dealing with climate issues.