The quantification of greenhouse gases (GHGs) emissions is a prerequisite for understanding and managing urban emissions in an effective way. Measuring emissions enables cities to identify sources and sectors with the most emissions reduction potential, to set up appropriate reduction strategies and targets accordingly and to monitor the performance of emission reductions. Despite the important role of cities and their emissions in climate change, however, only a handful of research studies on city-wide emissions have been conducted, mainly due to the lack of handful of research studies on city-wide emissions have been conducted, mainly due to the lack of available data and appropriate methodologies at the city level, while a number of studies have examined emissions from a single sector such as energy, transportation and building or at the country level.
Currently, there is no single international standard protocol available for measuring urban emissions, which makes it difficult to estimate and compare emissions between cities or over time in a consistent and meaningful way. How to define a system boundary and what emission factors and calculation methods to be applied in quantifying urban emissions can significantly alter the level of estimated emissions for one city. Against this backdrop, the research started from a question whether the conventional measurement method of urban emissions, which is based on a production-based approach, truly represents the low-carbon characteristic of a city. The research aims to review conventional methods used to quantify urban emissions, to analyze the compare GHG emissions of metropolitan cities in Korea using different methods, and to draw policy implications for urban emission.
Preliminary results for the case of Seoul show two distinctive features of its emission trend over time: a decrease in direct emissions and a rapid increase in indirect emissions. The decrease in the direct emissions is primarily attributable to the decline in the demand for petroleum, coal and city gas in the city, which has been replaced by electricity instead. On the other hand, the rapid increase in indirect emissions is an outcome of the increased demand for electricity, accounting for 90% of the total indirect emissions. The comparisons of the estimates under different approaches further verity the significant contribution of indirect emissions associated with end-use activities in Seoul.