SFLCV worked with Livable City and Supervisor Ross Mirkarimi to draft a Climate Change Goals and Action Plan ordinance. The ordinance was approved in committee on April 17th, 2008, and will go before the full board on April 29th, 2008. This overall goals of the ordinance are to reduce greenhouse gases 25% below 1990 levels by 2017, 40% below 1990 levels by 2025, and 80% below 1990 levels by 2050. The City would adopt specific reduction targets for each year. Every city department would create a departmental action plan to achieve its goals.
You can read more detail about the ordinance on the Livable City site, with information about what is already on San Francisco's books, and what some other cities are doing.