Waste Heat from Cities Changes Weather Thousands of Miles Away: Study

Large cities can affect the weather of local regions located thousands of miles away, according to a new study.

It is known that the heat generated due to human activities in big cities influences the atmosphere and causes the urban areas to be warmer by several degrees than the surrounding countryside.

But a new study by atmospheric researchers has discovered that the "waste heat" generated by buildings, cars and other sources alters the regional climate around them, raising temperatures of remote locations by as much as 1.8 degrees F. Even if you live more than 1,000 miles from the nearest large city, it could affect the weather.

Researcher Aixue Hu, of the National Center for Atmospheric Research, and his colleagues examined the effects of "waste heat" generated in major Northern Hemisphere urban areas on local temperatures, using computer models. They found that the "waste heat" causes winter warming across large areas of northern North America and northern Asia.

In some remote areas, the temperatures increased by as much as 1.8 degrees Fahrenheit. However, the research team noticed that the changes to atmospheric circulation caused by the waste heat cooled the areas of Europe by as much as 1.8 degrees F, with the temperature decrease mostly occurring in the fall.

"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," lead author Guang Zhang of the Scripps Institute of Oceanography, said in a statement. "This is accomplished through atmospheric circulation change."

The research team found that the heat generated by everyday activities in urban cities alters the air circulation patterns and other major atmospheric systems, including the character of the jet stream. A significant amount of heat is lifted up into the jet stream, which causes the fast moving current of air to widen. This, in turn, causes the average temperatures to rise during winter in most parts of North America and Asia, while some parts of Europe cool off a bit during fall, according to a report in Smithsonian.

The impact of urban heat on global mean temperatures is nearly negligible, as the total human-produced waste heat is only about 0.3 percent of the heat transported across higher latitudes by atmospheric and oceanic circulations, according to the researchers. But the waste produced by the burning of fossil fuel still has a significant impact on the weather conditions in surrounding local regions, they conclude.

The findings of the study, "Energy consumption and the unexplained winter warming over northern Asia and North America", are published in the journal Nature Climate Change.