The study compared the environmental sustainability of 30 major cities in 30 European countries. The cities were evaluated in eight categories: CO2 emissions; energy; buildings; transportation; water; air quality; waste and land use; and environmental governance.

Oslo was the best city in the CO2 emissions category, emitting only 2.5 tons of CO2 per capita/per year compared to the EU average of 8.5 tons. Oslo also topped the energy category, but lost out to Copenhagen and Stockholm in the overall score.

The Economist Intelligence Unit developed the index and wrote the report in cooperation with Siemens.

- As far as possible, the research is based on data from official sources, such as municipal statistics departments and city governments, said  James Watson, managing editor at the Economist Intelligence Unit and the editor of the study.

The study also includes in-depth city portraits that reveal the strengths and weaknesses of each urban center, while also highlighting initiatives and projects from which other cities can learn.

More information about the study is available on Siemen’s website.

The ranking results of the European Green City Index: