There is an article in the Seattle Times that reviews a study done in 2005 which states Seattle-Tacoma-Bellevue is ranked number six as lowest carbon emissions per capita. I’m not sure why the study is three years old and just being released now.
The article goes on to state that “Seattle draws its energy primarily from essentially carbon-free hydropower” and has a carbon footprint which is 10 times less than Washington DC’s carbon footprint.
“The authors [of the study] offer a partial portrait of overall emissions, concentrating on residential electricity and fuel use and the mileage traveled by cars and trucks, factors that contribute about half of overall carbon emissions. The calculations do not include industrial emissions, those from commercial or government structures and those from air, rail or sea transportation.”
It would be interesting to see how much these figures would change if the study actually included commercial structures. Cities like Los Angeles, which is ranked #2 on this list would probably not stay ranked at #2.
“The Honolulu area, with the smallest carbon footprint, ranked No. 1 in the study, from the Brookings Institution, followed by the area including Los Angeles and Orange counties in California, the Portland-Vancouver area, the New York metropolitan area and the Boise-Nampa, Idaho, area.”
The list of 10 smallest and largest metropolitan cities carbon footprints can be found on the Seattle-PI website.  Here the link to the Seattle Times article titled: “Study: Seattle area No. 6 on list of smallest carbon footprint“.