Athens is one of the least green major cities in Europe, according to a new study presented yesterday at the United Nations Climate Change Conference in Copenhagen by the Economist Intelligence Unit (EIU) and German electronics and engineering giant Siemens. Athens ranked 22nd, according to a study of the environmental sustainability of 30 European cities. Copenhagen is the greenest city, followed by Stockholm, Oslo and Vienna. The study evaluates the cities in eight categories: C02 emissions, energy, buildings, transportation, water, air quality, waste and land use, and environmental governance. «All of the cities face formidable challenges. For example, renewable sources of energy currently account for only about 7 percent of these cities’ energy supply, which is significantly under the target of 20 percent set by the EU for 2020,» said James Watson, managing editor at the EIU.