It is always hotter in towns by 2°C on average and sometimes, by more than that. This is because of the concentration of human activity but also because of city structures, asphalt on the ground, big walls, etc. However, this is not why towns are contributing to global warming.
The main factor is indeed energy consumption, especially in buildings. This alone accounts for almost 8% of the world’s anthropogenic greenhouse gas emissions. A third of these emissions is linked to heating in winter and then to cooling in the summer, in countries like the United States. We must remember that air conditioners make the problem they are supposed to be solving three times worse. They consume a lot of energy and are therefore responsible for greenhouse gas emissions. They also release hot air and use powerful greenhouse effect for cooling.
Street lighting and lighting in buildings are responsible for the emission of 1.9 billion tons of CO2 every year. This figure could be considerably reduced with new energy- saving bulbs. In a country like France, fridges and freezers, lighting and audio-visual equipment monopolise a third and a quarter of electricity consumption each respectively.
Higher standards of living, larger populations and the increase in the numbers and sizes of houses mean that more energy is needed. The tertiarisation of the economy also plays a big part in this as services, trade and information technology require large amounts of energy.
But, paradoxically, high density in towns helps save energy. Buildings are usually easier to heat and better insulated than insulated houses. The latter need their own roads, their own piping, their own electricity cables, etc that require as much energy and as many building materials each time.