Satellite Data Show Higher Surface Temperatures Near Wind Farms

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SAN FRANCISCO — A study billed as the first to use satellite observations to explore the environmental impact of large wind farms found that a high concentration of wind turbines in Texas produced a significant increase in nearby surface temperatures.

The study, published April 29 in the journal Nature Climate Change, focused on an area of west-central Texas featuring four of the world’s largest wind farms with a total of 2,358 turbines. Using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments flying onboard NASA’s Terra and Aqua Earth observing satellites, researchers discovered that surface temperatures near the wind farms warmed more rapidly, at a rate of approximately 0.72 degrees per decade, than nearby areas without wind turbines.

Scientists attributed the warming to the presence of wind turbines because the higher surface temperatures correlated precisely with the location of the turbines. In addition, researchers noted that surface temperatures near the wind farms continued to rise from 2000 to 2011, a period when wind turbines were being built in the area.

The warming trend was most noticeable at night. In the evening, the ground tends to cool more rapidly than the air, which results in layers of cooler air near the surface and warmer air at higher altitudes. The air turbulence caused by the wind turbines stirred up the atmospheric layers, which brought warmer air closer to the ground and helped to raise land surface temperatures, Liming Zhou, a professor in the Department of Atmospheric and Environmental Sciences at the University of Albany, part of the State University of New York, said in a May 14 email.

Researchers stressed that the study and its findings in no way undercut arguments in favor of wind energy. The results simply underscore the need for scientists to conduct further research to determine how wind turbines affect weather and climate, since wind is the world’s most rapidly growing source of energy.

“We are committed to wind and other renewable energy,” SomnathBaidya Roy, one of the study’s co-authors and an assistant professor in the University of Illinois’ Department of Atmospheric Sciences, said in a May 10 email. “Understanding the impacts of wind farms will help us develop strategies to manage or mitigate the impacts and thus make informed choices.”

The researchers also pointed out that wind farms are not likely to produce any overall atmospheric warming. The surface temperature increases detected in the study were small and limited to the area near the wind turbines. In all likelihood, the wind turbines create no net warming of the air but simply redistribute heat in the atmosphere by bringing it closer to the surface. That redistribution is “fundamentally different from the large-scale warming effect caused by increasing atmospheric concentrations of greenhouse gases due to the burning of fossil fuels,” Zhou said.

Zhou conceived the idea for the Texas wind farm study last summer while reading a newspaper article describing the growing use of wind power in the United States. U.S. wind energy production increased tenfold between 2001 and 2011. By 2011, wind farms produced 46,919 megawatts, or nearly 3 percent, of the nation’s electrical power, according to a report released in January by the American Wind Energy Association.

While scientists had previously conducted studies exploring the relationship between wind energy and temperature, those studies relied on more-limited data. In 2010, Roy published a report in the online journal Proceedings of the National Academy of Sciences that used computer models and a six-week record of temperatures around a single wind farm in San Gorgonio, Calif., to show that the area near the wind turbines was slightly warmer at night and cooler during the day than comparable areas without wind turbines. The new study, which relies on 10 years of data related to four large wind farms, is important because it offers a much more comprehensive look at wind turbines and their impact, Roy said.

Interestingly, the Texas and San Gorgonio studies showed different results related to daytime temperatures. While Roy noted that surface temperatures near wind turbines in San Gorgonio were cooler during the day than surrounding areas, the Texas study found that wind turbines had little if any impact on daytime temperatures.

Zhou and his colleagues plan to conduct further research on how wind farms affect their surroundings, although they have not yet selected one or more regions to study. “We are likely to start with the biggest wind farms in the Great Plains and Midwest states which have experiencing rapid growth in wind energy installations,” Zhou said.