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A new study has found that the waste heat generated by cities could affect temperatures over a thousand miles away. The heat produced through transportation, heating and cooling units and other sources within major cities in the North Hemisphere causes winter warming across large areas of northern Asia and North America. According to researchers from the University of California, Florida State University and National Center for Atmospheric Research, some remote areas have experienced temperature increases of one degree Celsius (1.8 degrees Fahrenheit).
The waste heat examined in the study differs from the so-called “heat island effect”. While the latter refers to waste heat release produced by re-radiation from pavements and buildings, the new findings are related to heat produced through transportation, heating and cooling units and other direct sources within urban areas.
“The burning of fossil fuel not only emits greenhouse gases but also directly affects temperatures because of heat that escapes from sources like buildings and cars,” says NCAR scientist and study co-author Aixue Hu. “Although much of this waste heat is concentrated in large cities, it can change atmospheric patterns in a way that raises or lowers temperatures across considerable distances.”
“What we found is that energy use from multiple urban areas collectively can warm the atmosphere remotely, thousands of miles away from the energy consumption regions,” says study lead author Guang Zhang. “This is accomplished through atmospheric circulation change.”
Metropolitan areas on the east and west coasts of North America and in northern Asia are located beneath major “hot spots” of atmospheric circulation. The waste heat from these cities builds up and forms thermal mountains which cause air jets moving eastward to deflect northward and southward. This results in widening of the jet stream on higher altitudes, which brings hot air from the south and warms territories far from the urban areas. This, in turn, causes cooling in other areas.
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