On December 3, 2007, the City Council, adopted Ordinance 122574 that requires City departments that perform environmental review under the State Environmental Policy Act (SEPA) to evaluate greenhouse gas (GHG) emissions when reviewing permit applications for development. King County already started to do this evaluation in October 2007, becoming the first local government in the nation to officially add GHG emissions to the environmental review of construction projects. Seattle will be one of the first cities in the country to require such a review.

The City Council also adopted Comprehensive Plan goals and policies in 2007, Ordinance 122610, related to achieving reductions in GHG emissions. To carry out these goals and policies, assessment of greenhouse gas emissions from proposed development will be required beginning March 31, 2008. Under this assessment, project proponents for development that triggers environmental review will be required to identify the climate change impact of their proposal as captured through quantification of GHG emissions. At this point, the legislation does not require changes in the development proposals as a result of the review. Instead, the requirement is a first step toward limiting the potential negative effects of construction projects on the environment by disclosing emissions.

The Department of Planning and Development (DPD) is now working to develop procedures for carrying out the directive.