Megacities heated air within a thousand kilometers

Large cities have giant "stove", able to increase the average temperature of one degree Celsius in the remote rural areas, even at a distance of several thousand miles away, indicating that the underestimation of the role of cities in climate change, climate scientists say in a paper published in the journal Nature Climate Change.

"We found that the lost heat from the major cities, can heat up the atmosphere in remote regions from them. This phenomenon is due to changes in the circulation of air masses, which causes the release of excess heat in homes and other parts of the cities," — said the head of a group of scientists Guan Zhang (Guang Zhang) from the University of California, San Diego (USA).

Zhang and his colleagues came to this conclusion by estimating the amount of thermal energy that emit large cities in North America, Europe and China to the environment. As noted by the authors, the global contribution of the residual heat in the climate change itself is small — the most common calculations, they increase the average temperature of the earth by only 0.01 degrees.

However, in reality the situation is quite different, since the general climate models do not account for the fact that this heat is not evenly distributed, but is concentrated in the large urban areas.

According to calculations of Zhang and his colleagues, half of the global "excess" heat — about 6.7 TWh of energy — was produced by large metropolitan areas, is a relatively small part of the land. Thanks to this, each square meter of a typical metropolis accounted for 0.4 watts of residual heat. According to the researchers, this is sufficient for the emergence of significant changes in the circulation of winds in the cities themselves, and at a great distance from them.

As an example of these changes lead researchers, two phenomena — increasing average annual temperatures in the provincial areas of the U.S. by 1 degree at a distance of several thousand kilometers, and their decrease by 1 degree in Europe. Believe Zhang and his colleagues, as a major change in annual average temperatures should be taken into account in the simulation of how the Earth's climate will change in the future.

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