The headlines that started appearing on April 30 were alarming: "New research shows wind farms cause global warming," proclaimed Fox News and Reuters. "Wind farms may be warming the planet," said New Jersey's Star Ledger. "Wind farms can cause climate change, finds new study," announced The Telegraph. The Daily Mail even shouted in all caps in its headline, "Wind farms make climate change WORSE."
Too bad they all got it wrong.
The articles were all referring to a paper, "Impacts of wind farms on land surface temperature," published online April 29 in the journal Nature Climate Change. The study, conducted by scientists from the University of Albany and other institutions, looked at four wind farms in west-central Texas between 2003 and 2011. Using satellite data, the researchers found that the surface temperature around these wind farms rose "up to 0.72°C per decade, particularly at night-time."
What this actually suggests is that the surface temperature around wind farms rises slightly due to the atmospheric turbulence created by the moving blades of the wind turbines. As the authors explained in a Q&A document (pdf) that accompanied their paper, "This warming effect is most likely caused by the turbulence in turbine wakes acting like fans to pull down warmer near surface air from higher altitudes at night."
Going into more detail, the authors wrote: "Enhanced vertical mixing mixes warm air down and cold air up, leading to a warming near the surface at night." That effect occurs more naturally during the day, when the sun heats up and mixes the air.
The authors attributed the 0.72 degree temperature rise over the eight-year period to the more than 20-fold increase in the number of wind turbines in the region, from 111 in 2003 to 2,358 in 2011. They also wrote that the warming effect was very specific to the regions in which the wind farms were located and did not have a global effect.
They also concluded that it was likely that the wind turbines "do not create a net warming of the air and instead only redistribute the air's heat near the surface (the turbine itself does not generate any heat) which is fundamentally different from the large-scale warming effect caused by increasing atmospheric concentrations of greenhouse gases due to the burning of fossil fuels."
Interestingly, this actually supports a 2010 study which had similar findings. That study, published in Proceedings of the National Academy of Sciences, examined a wind farm near Palm Springs, Calif., (one of the country's oldest wind-energy sites) and also found that temperatures were slightly warmer at night and cooler during the day. Co-author Somnath Baidya Roy of the University of Illinois at Urbana-Champaign told Scientific American that the same principle has long been put to good use in agriculture. "Orange farmers in Florida use giant fans to protect their crops from frost. Just like wind turbines, these fans generate turbulence and mixing, producing a warming near the surface at night."
Reuters wrote that this study casts "a shadow over the long-term sustainability of wind power." The science tells a different story.