By Ariel Schwartz

Anyone who lives 1,000 miles away from a major city probably thinks they're immune to all the side effects--positive and negative--of city life. They're wrong. A study published in Nature Climate Change recently found that waste heat from cars, buildings, and other heat sources in cities across the Northern Hemisphere trigger high winter temperatures, even in remote areas.

You've probably heard of the urban heat island effect--a phenomenon that occurs when retained heat is re-radiated by buildings and pavements. This is different. The study, which comes from researchers at University of California, San Diego; Florida State University; and the National Center for Atmospheric Research, looks at heat emitted directly from cars and other sources.

PhysOrg explains how the scientists conducted their research:

[The authors] analyzed the energy consumption--from heating buildings to powering vehicles--that generates waste heat release. The world's total energy consumption in 2006 was equivalent to a constant-use rate of 16 terawatts (one terawatt, or TW, equals 1 trillion watts). Of that, an average rate of 6.7 TW was consumed in 86 metropolitan areas in the Northern Hemisphere. Using a computer model of the atmosphere, the authors found that the influence of this waste heat can widen the jet stream.

That means waste heat from urban energy consumption can spread far and wide. So if humanity wants to curb the disturbing recent patterns of winter warming--and all the cascading problems throughout the year that occur because of it--we need to focus on urban energy consumption. Slowing energy consumption won't make a big dent in global climate change (an average worldwide temperature increase of 0.02 degrees F is from waste heat), but it will make a difference regionally.

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