Cities that accumulate more than 55% of the world’s population always were and still are the centers of the most powerful transformation of the natural environment. They change natural and produce artificial matter and energy flows including those of water, food, wastes, etc. Our study is based on the data for the largest cities of the European region with the population numbers over 1 mln inhabitants. First of all we evaluated human-related flow of energy against the natural flow represented by the radiation balance. The indicator of anthropogenic energy flow was the consumption of energy by urban dwellers. Correlation of radiation balance and energy consumption allows identifying the groups of major European cities according to the degree of the natural energy flow transformation. The anthropogenic energy load within the urban territories of Europe averages 30–40% of the natural radiation balance being even higher in the largest cities, such as London or Moscow. We also analyzed climate changes within urban areas against the rural background. The rise of annual temperatures in European cities is extremely diversified. The maximum changes are in the cities of Denmark, southern Finland and Romania. If compared with temperature changes over the rural areas the most pronounced correlation is also for Denmark and Finland. Despite certain fluctuations the general trend of urban air temperature increase is obvious since the 1950s.