While statewide estimates have been made, Leiter said that to his knowledge, no one has quantified the San Diego region's total carbon dioxide emissions. The agency is working with the nonprofit San Diego Foundation on the study, which is expected to be completed in a few months.

SANDAG, however, has quantified emissions from transportation, believed to be the largest source of greenhouse gas emissions.

Leiter said the 2030 regional transportation plan that the association board approved in November estimated that the county's cars, buses and delivery trucks now cough up 17.4 million tons of carbon dioxide a year.

That total is expected to rise by about 30 percent, to 22.7 million tons, annually by 2030, under the new $57 billion blueprint for freeway lanes, railroad tracks and bus lines.

What is unclear is what the region's total is, and what proportion of the total the transportation sector accounts for, Leiter said. State officials estimate that statewide, cars and trucks account for 40 percent of the total, with power plants generating 25 percent and industry producing 20 percent.

But Leiter said the mix very likely is different for San Diego County, given that it doesn't have the massive ports Los Angeles and San Francisco do, or the intense industrial development of other urban regions.

SANDAG didn't take action, but is devoting a day at its annual winter retreat in Borrego Springs next week to discuss ways to curb emissions. Local officials have been feeling political heat since Attorney General Jerry Brown sent them a letter in late November highly critical of the transportation plan, saying it fails to address global warming. The agency invited Brown to speak at the retreat but he isn't expected to attend.