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The average temperature of regions with high urbanization rate is 1-3° C higher than that of rural areas around them. At night, this difference can reach 12° C. This phenomenon, first recorded in 1818 by the English scientist Luke Howard, is called the heat island.
Some of the radiation energy that reaches the Earth from the Sun is absorbed by the atmosphere, some of it is reflected back into space directly by the atmosphere, and the rest is absorbed by the surface of the earth. The surface of the Earth loses heat by radiation, convection and evaporation. The balance between the energy it receives and gives constitutes the energy "budget" of the Earth.
The main reason why the average temperature of the cities is higher than the rural areas is thought to be the decrease in evaporation and cooling in the cities. In addition to cooling by evaporation, trees and other plants contribute to the cooling process with the shadow effect they create.
Trees and other plants also contribute to cooling by evaporation. Plants that convert water and carbon dioxide into food through photosynthesis take the water in the soil with their roots. They release some of the water they take from the soil through their leaves and stems through sweating and dripping. In order for it to evaporate from liquid state to gas, water must take heat from outside. Therefore, evaporation helps to reduce the air temperature. Moisture in the soil also contributes to cooling by evaporation.