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Cities, with their chaotic traffic and polluted air, don't just harm the health of the city-folk, but also cause changes in weather patterns in places that are thousands of miles away, according to a new study.

Researchers found that "waste heat" generated from cars and buildings in cities across the Northern Hemisphere are making parts of Northern America and Asia experience warm weather during winters.

The same waste heat cools many parts of Europe. Researchers estimate that the waste heat decreases winter temperatures by 1 degree C (1.8 degrees F). According to the researchers, this variation in temperature occurs due to changes in atmospheric circulation. However, globally the increase in temperature will be about 0.01 degrees C (about 0.02 degrees F), as waste heat makes just 0.3 percent of all heat that's passed through oceanic currents around the world.

"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. 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," said Aixue Hu, a co-author of the study in a news release.

Researchers say that their study isn't based on the urban heat island effect, where the urban areas experience warm weather due to heat reflected by the buildings and pavements. In the present study, researchers examined the direct effects of heat from cars and buildings on the environment.

The heat from the sun is the main source of heat on earth and it is this heat that is transported through oceanic currents across regions. And although human activity contributes very little to this global heat distribution, researchers say that certain areas of the world may be directly influenced by the changes in the jet streams.

"The world's most populated and energy-intensive metropolitan areas are along the east and west coasts of the North American and Eurasian continents, underneath the most prominent atmospheric circulation troughs and ridges. The release of this concentrated waste energy causes the noticeable interruption to the normal atmospheric circulation systems above, leading to remote surface temperature changes far away from the regions where waste heat is generated," said Ming Cai of Florida State University, one of the study authors.