Waste Heat From Cities Has Global Climate Effects

New York
New York City (Photo by Dominick Zarillo)


SAN DIEGO, California, February 5, 2013 (ENS) – The waste heat generated by everyday energy consumption in urban areas is influencing major atmospheric circulation systems and causing continental-scale surface warming in high latitudes, new research has found.

Led by Guang Zhang, a research meteorologist at Scripps Institution of Oceanography at the University of California, San Diego, the scientists report that waste heat released in major cities in the Northern Hemisphere causes as much as one degree Celsius (1.8 degrees F) of winter warming in high latitudes of the North America and Eurasian continents.

“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,” Zhang said. “This is accomplished through atmospheric circulation change.”

Climate scientists, from left, Guang Zhang, Ming Cai, Aixue Hu

The study, “Energy Consumption and the Unexplained Winter Warming Over Northern Asia and North America,” appears in the current online edition of the journal “Nature Climate Change.” The study was funded in part by the National Oceanic and Atmospheric Administration’s Climate Program Office.

The trio of climate researchers includes Ming Cai, a professor in Florida State University’s Department of Meteorology and Aixue Hu of the National Center for Atmospheric Research in Boulder, Colorado.

“The burning of fossil fuel not only emits greenhouse gases but also directly effects temperatures because of heat that escapes from sources like buildings and cars,” Hu said.

Cai said, “The world’s most populated metropolitan areas, which also have the highest rates of energy consumption, are along the east and west coasts of the North American and Eurasian continents, underneath the most prominent atmospheric circulation troughs and ridges.”

New York
New York City (Photo by Dominick Zarillo)

“The concentrated and intensive release of waste energy in these areas causes a noticeable interruption to normal atmospheric circulation systems, leading to remote surface temperature changes far away from the regions where the waste heat is generated,” said Cai.

The world’s total energy consumption in 2006 was 16 terawatts – one terawatt equals one trillion watts. Of that, 6.7 terawatts were consumed in the 86 metropolitan areas considered in this study.

The release of waste heat is different from energy that is naturally distributed in the atmosphere, the researchers explained.

The largest source of heat, solar energy, warms the Earth’s surface. Atmospheric circulations distribute that energy from one region to another.

Human energy consumption distributes energy that remained dormant and sequestered for millions of years, mostly in the form of oil or coal. Though the amount of human-generated energy is a small portion of that transported by nature, it is highly concentrated in urban areas.

The authors report that the influence of urban heat can widen the jet stream in areas outside the tropics. They add that the heating is not uniform. Partially counterbalancing it, the changes in major atmospheric systems cool areas of Europe by as much as one degree Celsius, with much of the temperature decrease occurring in the fall.

The effect of waste urban heat helps to explain the difference between actual observed warming in the last 50 years and the amount of warming predicted by computer models that only include anthropogenic greenhouse gases and aerosols, the authors said.

The study does not address whether the urban heating effect disrupts atmospheric weather patterns or plays a role in accelerating global warming, though Zhang said drawing power from renewable sources such as solar or wind provides a societal benefit in that it does not add net energy into the atmosphere.

Zhang said the climate impact this research studied is distinct from the so-called urban heat island effect, an increase in the warmth of cities compared to unpopulated areas caused by land use changes. Such island effects are mainly a function of the heat collected and re-radiated by pavement, buildings and other urban features.

The researchers suggest that the influence of energy consumption should be considered, in addition to heat-trapping gases and aerosols, as human-caused factors in computer models to predict the future climate.

Copyright Environment News Service (ENS) 2013. All rights reserved.

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