Carbon dioxide produced by burning fossil fuels has been linked to rising global temperatures in a number of studies.
As such, many countries are moving toward cleaner sources of renewable energy like wind turbines, which creates no emissions, uses no water and is considered green.
However, a recent study by University of Albany researchers and other scientists indicate that large wind farms in certain areas of the US may be affecting local land surface temperature.
To understand the potential impact of wind farms on local weather and climate, Professor Liming Zhou and his team analyzed NASA satellite-derived land surface temperatures of regions around large wind farms in Texas during 2003–2011.
The researchers found a nighttime warming effect over wind farms of up to 0.72 °C per decade over the nine years in which data was collected. Since the spatial pattern of warming mirrors the geographic distribution of wind turbines, they attribute the warming primarily to wind farms.
Interesting enough, the year-to-year land surface temperature over wind farms also showed a persistent upward trend from 2003 to 2011 - consistent with the increasing number of operational wind turbines with time.
"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," explained Professor Somnath Baidya Roy at University of Illinois, Urbana-Champaign, a co-author of the study.
Overall, while the reported warming effect is local and rather insignificant compared to the strong background year-to-year land surface temperature variation, the authors believe the phenomenon requires further investigation.
"The unit of the estimated warming effect (°C per decade) is just one simple way to quantify the wind farm impacts while reducing the year-to-year data noise," said Zhou.
"The estimated warming trends only apply to the study region and to the study period, and thus should not be interpolated linearly into other regions (e.g., globally) or over longer periods (e.g., for another 20 years). For a given wind farm, once there are no new wind turbines added, the warming effect may reach a stable level."
Several recent studies of the impact of wind farms on weather and climate have utilized numerical models due to the lack of observations over wind farms. As numerical models are computationally intensive and have uncertainties in simulating regional and local weather and climate, the authors believe remote sensing is likely the most efficient and effective way to study wind farm impacts over larger spatial and longer temporal scales.
"The study presents the first observational evidence of wind farm impacts on land surface temperature with spatial detail using satellite data. It represents a first step in exploring the potential of using satellite data to quantify the possible impacts of the development of big wind farms on weather and climate," said Prof. Chris Thorncroft.
"We are now expanding this approach to other wind farms and building models to understand the physical processes and mechanisms driving the interactions of wind turbines and the atmosphere boundary layer near the surface."