What is the climate record in German big cities compared to other international metropolises? Which parks and green areas reduce the CO2 footprint? In the future, a 3D map will show where high carbon-dioxide emissions arise in cities and where it is worth cutting costs. To this end, the Helmholtz Centre Potsdam - German Research Centre for Geosciences GFZ and international partners from business, industry, and cities is integrating statistical data into three-dimensional models. The basis, for example, are energy consumption and the CO2 emission factor, which indicates the climate compatibility of electricity and heat generation.