"Researchers at the State University of New York at Albany analysed the satellite data of areas around large wind farms in Texas, where four of the world's largest farms are located, over the period 2003 to 2011.The 0.72 degree Celsius warming is significant considering that "[s]cientists say the world's average temperature has warmed by about 0.8 degrees Celsius since 1900, and nearly 0.2 degrees per decade since 1979." So, the warming in Texas in areas with wind farms is almost equal in a decade to average global warming in the last four decades. That's a 4x multiplier.
"The results, published in the journal Nature Climate Change, showed a warming trend of up to 0.72 degrees Celsius per decade in areas over the farms, compared with nearby regions without the farms.
"'We attribute this warming primarily to wind farms,' the study said. The temperature change could be due to the effects of the energy expelled by farms and the movement and turbulence generated by turbine rotors, it said.
"'These changes, if spatially large enough, may have noticeable impacts on local to regional weather and climate,' the authors said."
Apparently the culprit is that the air turbulence caused by the wind turbines keeps the surrounding ground area warmer than in areas without wind turbines.
"The Texas study found the temperature around wind farms rose more at night, compared with nearby regions. This was possibly because while the earth usually cools after the sun sets, bringing the air temperature down, the turbulence produced by the farms kept the ground in their area warm."H/T William Jacobson