This paper describes the methodology and data used to determine greenhouse gas (GHG) emissions attributable to ten cities or city-regions: Los Angeles County, Denver City and County, Greater Toronto, New York City, Greater London, Geneva Canton, Greater Prague, Barcelona, Cape Town and Bangkok. Equations for determining emissions are developed for contributions from: electricity; heating and industrial fuels; ground transportation fuels; air and marine fuels; industrial processes; and waste. Gasoline consumption is estimated using three approaches: from local fuel sales; by scaling from regional fuel sales; and from counts of vehicle kilometres travelled. A simplified version of an intergovernmental panel on climate change (IPCC) method for estimating the GHG emissions from landfill waste is applied. Three measures of overall emissions are suggested: (i) actual emissions within the boundary of the city; (ii) single process emissions (from a life-cycle perspective) associated with the city's metabolism; and (iii) life-cycle emissions associated with the city's metabolism. The results and analysis of the study will be published in a second paper.